WO2009080122A1 - A control arrangement, a controle device, a method, a computer program and a computer readable medium - Google Patents

A control arrangement, a controle device, a method, a computer program and a computer readable medium Download PDF

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Publication number
WO2009080122A1
WO2009080122A1 PCT/EP2007/064496 EP2007064496W WO2009080122A1 WO 2009080122 A1 WO2009080122 A1 WO 2009080122A1 EP 2007064496 W EP2007064496 W EP 2007064496W WO 2009080122 A1 WO2009080122 A1 WO 2009080122A1
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WO
WIPO (PCT)
Prior art keywords
power
electrical
control
control arrangement
modifier
Prior art date
Application number
PCT/EP2007/064496
Other languages
French (fr)
Inventor
Roger Mellander
Xiaolong Feng
Yang Gao
Original Assignee
Abb Research Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Abb Research Ltd. filed Critical Abb Research Ltd.
Priority to PCT/EP2007/064496 priority Critical patent/WO2009080122A1/en
Publication of WO2009080122A1 publication Critical patent/WO2009080122A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/003—Load forecast, e.g. methods or systems for forecasting future load demand
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/10—Constant-current supply systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/31—From computer integrated manufacturing till monitoring
    • G05B2219/31414—Calculate amount of production energy, waste and toxic release
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/32—Operator till task planning
    • G05B2219/32021—Energy management, balance and limit power to tools
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/39—Robotics, robotics to robotics hand
    • G05B2219/39407—Power metrics, energy efficiency
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P80/00—Climate change mitigation technologies for sector-wide applications
    • Y02P80/10—Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications

Definitions

  • the present invention relates to a control arrangement adapted for controlling at least one electrical appliance arranged to use electrical power to perform a task.
  • the control arrangement comprises a power input modifier adapted to receive electrical power from a power source and at least one power output modifier adapted to supply electrical power to the electrical appliance.
  • the invention also relates to a control device adapted to control a power input modifier and to a method for controlling a power input modifier.
  • the electricity carried by power grids is in most countries high voltage alternating currents, which are controlled to always have the same characteristics. Close to the end user, the high voltage alternating current is transformed into a lower voltage alternating current, for households typically around 230 V. Other characteristics of the current, however, such as frequency, still remain unchanged.
  • modification devices In many applications, in particular applications concerning manufacturing tasks in manufacturing plants or factories, the machinery demands electrical power having different characteristics. In these and other cases it is known to use some kind of electrical power modification in order to change the characteristics of the electrical power to fit the machinery.
  • modification devices comprise AC/DC-converters, AC/AC- transformers and DC/AC-inverters.
  • Other examples of modification devices also comprise frequency modulators, and voltage- and/or current-generators.
  • One such application relates to the power supply for an industrial robot, in which the robot is controlled by supplying electricity to the electrical engines, which are coupled to and drives the robot.
  • the engines are controlled by supplying them with electri- cal power having different frequency depending on the desired engine speed. Since the power supplied by the power grid usually have a set frequency the control arrangement for controlling the engines of the robot usually comprises a power input modifier in the form of an AC/DC-converter, transforming the alter- nating current into direct current, coupled to a power output modifier in the form of a DC/AC-inverter adapted to supply the engine with an alternating current with controllable frequency.
  • AC/DC-converters have historically been constructed by a col- lection of diodes. In later years however the diodes have been replaced by transistors, making it possible to control the conver- sion from alternating current into direct current.
  • patent document US 5,373,223 shows a power supply system arranged to avoid voltage fluctuations in the part following the AC/DC-converter. By calculating the power at the output from the system and controlling the AC/DC-converter so that the calculated power and the power in the converter are balanced such fluctuations are decreased.
  • Other examples of uses of controlled AC/DC-converters are shown in for example patent documents US2007/0223258 and US2006/0077602.
  • One object of the present invention is to indicate a control ar- rangement adapted to receive and supply electrical power to an electrical appliance, which decreases the energy losses in the system.
  • control arrangement according to the preamble of claim 1 , which is characterized in that the control device is adapted to predict the future expected power need for at least one electrical appliance, to estimate the buildup of energy in the control arrangement and/or in the electrical appliance, and to control the power input modifier to transfer an electrical power into the control arrangement based on the predicted power need and built-up energy.
  • control device is adapted to control the power input modifier to transfer an electrical power into the control arrangement, so that at least a part of the built-up energy is used for powering the at least one electrical appliance.
  • Energy may build up both in the control arrangement, for example as electric charge in capacitors or as magnetic energy in solenoids, or as electrical or mechanical energy in the electrical appliance that is to be controlled.
  • the invention it is possible to decrease the power input so that at least a part of the stored energy can be used for driving the electrical appliance.
  • the invention gives the advantage of a smaller energy loss.
  • the total energy input over time may be decreased, since the power input may be decreased during periods when less power is needed, which decreases the power losses in the control arrangement.
  • the stored energy may become released and suddenly fed into the system causing voltage spikes that may damage the components in the system, unless consumed in a safety circuit, such as a resistor or bleeder.
  • the input power may be controlled so that the maximum voltage in the system remains low.
  • the invention also gives the advantage that the components used in the control arrangement may be adapted for lower voltages, meaning that the cost for the components is decreased.
  • the prediction of the future power need may be based on a pre- execution of a control program for the appliance or appliances.
  • the prediction may also be based on a possible cyclic behaviour for the appliance, which may be the case in a manufacturing process that repeats itself endlessly.
  • the estimation may be based on calculations, on measurements, on simulations of the appliance or on the experience from previous runs. The estimation may also be based on the knowledge of the useful energy stored during normal operation of the appliance, or for different power levels for the appliance. The estimation may also be based on a simulation of the stored energy departing from a model of the control arrangement and the appliance. It is not necessary that all the built-up energy in the control arrangement and/or appliance is estimated in order to achieve the invention. It is sufficient that the level of stored energy that can be used, useful stored energy, is estimated. The estimation of stored energy may be made during the operation of the appliance, either continuously or at certain intervals, or the estimation may be made beforehand.
  • the control based on the predicted future power need and esti- mated stored energy may also be based on experience from previous runs, so that the energy losses are minimised.
  • the energy losses for the appliances can be measured by measurements of the current through an energy sink, and the power input decreased before a peak in energy loss in the next corresponding cycle.
  • the control arrangement may comprise control circuits in hardware and/or control modules in software.
  • the control arrangement may be adapted to control one or several appliances of the same or different types.
  • the control arrangement may also be adapted to control various components pertaining to the functioning of the appliance, including components within the control arrangement itself.
  • the control arrangement may also be constituted by several physically distinct or separated units, as well as being constituted by only one unit.
  • a power input modifier is a device that receives electrical power or electricity from a source and modifies the characteristics of the electricity before forwarding the electricity.
  • the modifier may be adapted to modify any of the characteristics of the electric current, such as the nature of the current (AC/DC), the shape of the current (square, sinus form), frequency, voltage, and size of the current (ampere).
  • the power input modifier is adapted to control the amount of electric power allowed to pass through the power input modifier and into the control arrangement.
  • control arrangement comprises at least one power output modifier adapted to receive the modified electrical power from the power input modifier, to further modify the received electrical power and to supply the modified electrical power to the electrical appliance.
  • the at least one power output modifier is adapted to receive electrical power from the at least one appliance and to return the electrical power into the control arrangement.
  • energy delivered and stored in an appliance can be returned to the control arrangement and stored for use at a later time.
  • Such energy from the appliance may be kinetic energy, which may be returned due to a reduction of the speed of the appliance.
  • control device is adapted to control at least one function of the at least one electrical appliance.
  • control device is adapted to control at least one electrical appliance to perform a task.
  • the prediction of future power need can be more accurate.
  • control device is adapted to calculate a desired behaviour for the electrical appliance in advance, and to predict the power need departing from the desired behaviour.
  • control device is adapted to control the function of the at least one electrical appliance by controlling the at least one power output modifier, wherein the at least one power output modifier is adapted to control the at least one electrical appliance by supplying a modified electrical power to the electrical appliance.
  • the electrical appliance is controlled by the amount of power supplied to the appliance it is easy to achieve the advantages of the invention. Furthermore, there is usually a higher gain in saved energy when using the control arrangement according to the invention.
  • control device is adapted to control the power input modifier to input a higher power than the present power need when the control device predicts an expected higher power need in the future for the at least one appliance.
  • control device is adapted to cause a higher power input than the present power need for the appli- ance, when the control device predicts an expected high power need in the near future.
  • control device is adapted to control the power input modifier to input lower power than the present power need when the control device predicts an expected lower power need in the future for the at least one appliance. Then built-up energy is consumed by the appliance for performing the task in advance of the appliance entering a low power state, meaning that any stored energy will be used for performing the task rather than being consumed in the safety circuit.
  • control arrangement is adapted to control at least two appliances, wherein the control device is adapted to predict the collected power need for both appliances together. It is advantageous to input power to the control ar- rangement based on the sum of the power need for the two appliances, since the sum is more likely to be smooth with smaller relative power changes. Furthermore, it is possible to redirect power from one appliance to the other appliance, when one of the appliances needs high power and the other appliance needs lower power. Furthermore, if energy has been stored in one appliance during a high power work phase, the stored energy may be returned into the control arrangement and transferred to the other appliance, when the first appliance enters a low power task, making even larger energy savings possible.
  • the control arrangement comprises at least one energy storage.
  • the energy storage comprises a capacitor and/or a battery.
  • the en- ergy storage is arranged electrically connected between the power input modifier and the appliance.
  • the energy storage is arranged electrically connected between the power input modifier and the power output modifier.
  • the energy storage is adapted to store energy and preferably is also adapted to transform the stored energy back into electrical power. Hence energy may be stored in the energy storage and then reduced by being transferred to the electrical appliance and used for performing a task.
  • the energy storage and the control arrangement are adapted to allow disconnection of the energy storage from the control arrangement.
  • the energy storage and the control arrangement are also adapted to allow reconnection of the energy storage.
  • the control arrangement comprises at least two energy storages, wherein it is possible to change the active, connected, energy storage. This is advantageous if one of the energy storages is filled during a low power need phase, or correspondingly, empty of energy during a high power need phase for the appliance.
  • control arrangement is adapted to supply power to and control an electrical appliance adapted to perform manufacturing tasks.
  • the energy consumption for automation equipment is very high and the power need also varies greatly over time, meaning that large savings can be made by supplying the electrical appliances by power with a control arrangement according to the invention.
  • the power input modifier may be a converter, preferably an AC/DC-converter.
  • the power output modifier may in turn be an inverter transforming DC current into AC current.
  • the power output modifier is adapted to supply a frequency modulated alternating current.
  • the power from the power output modifier may be used for controlling for example an electrical engine and the engine speed of the engine.
  • control arrangement is arranged to supply power to and control an electrical appliance in the form of an industrial robot.
  • An industrial robot is moved by use of electrical engines controlled by being supplied with alternating current with various frequency.
  • the input alternating current needs to be modified twice, first into a DC-current and then into an AC-current with varying frequency.
  • the engines automatically produces electricity during deceleration, wherein the generated energy may be stored in the control arrangement and reused during acceleration.
  • the industrial robot may also store energy itself in the form of kinetic energy.
  • the invention also relates to a method for controlling the modification of electrical power in a power input modifier and to a control device adapted to control the modification of electrical power in a power input modifier.
  • the invention also relates to a computer program directly downloadable into the internal memory of a computer for controlling a control arrangement to perform the steps according to the invention.
  • Fig. 1 shows one example of a control arrangement for three electrical appliances according to one example of the invention.
  • Fig. 2 a-c shows a method for controlling a power input modifier and two appliances according to one example of the invention.
  • a system adapted for performing a task comprising three electrical appliances 9a, 9b, 9c and a control arrangement 1 adapted to control and supply power to the three electrical appliances 9a, 9b, 9c according to one example of the invention is shown.
  • the control arrangement 1 comprises a control device 3 adapted to control the electrical appliances 9a, 9b, 9c.
  • the control arrangement 1 further comprises a power input modifier 5 adapted to receive electrical power from a power source 1 1 and to modify the characteristics of the received electrical power.
  • the power input modifier 5 is adapted to forward the modified electrical power to at least one, in this example three, power output modifiers 7a, 7b, 7c.
  • the power output modifiers 7a, 7b, 7c are adapted to further modify the characteristics of the received electrical power and to forward and supply the electrical power to the three appliances.
  • the power input modifier may instead be adapted to forward and supply the electrical power to the electrical appliances directly.
  • the control device 3 is adapted to predict the future expected power need for the electrical appliances controlled by the control arrangement.
  • the control device 3 is adapted to predict the future expected power need based on the execu- tion of a control program 25 containing control instructions for causing the electrical appliances to perform a desired task or tasks.
  • the control device 3 is also adapted to estimate the buildup of energy in the control arrangement and/or in the electrical appliances.
  • the built-up energy may for example be energy stored in the electrical circuits of the control arrangement or electrical appliances, for example as electrical energy in capacitors or as magnetic energy in solenoids.
  • the built-up energy may also be mechanical energy such as kinetic energy or potential energy, or any other form of energy stored during the func- tion of the electrical appliances.
  • the power input modifier 5 is adapted to modify the electrical power in such a way that the power input modifier 5 may controls the amount of power that is fed into the control arrangement.
  • the control device 3 is adapted to control the power input modifier 5 to feed an electrical power into the control arrangement 1 based on the predicted power need and the built-up energy. In so doing it is possible to decrease the total energy input over time, since the power input may be decreased during periods when less power is needed, which in turn decreases the power losses in the control arrangement.
  • the control device is adapted to predict the collective power need for both appliances together.
  • the control device is adapted to control the power input modifier to input a lower power than the present power need when the control device predicts an expected lower power need in the future for the two appliances. Since the power input is lower than the power need stored, built-up energy is consumed by the appliance for performing the task. Hence the stored energy will be used for doing work instead of creating an over-voltage in the control arrangement, which might lead to power losses. Hence the power usage of the control arrangements and appliances is reduced.
  • the input power may be controlled so that the maximum voltage in the system remain within a desired limit, so that the components used in the control arrangement may be adapted for lower voltages, meaning that the cost for the components is decreased.
  • the control device 3 is further adapted to control the power in- put modifier 5 to input a higher power than the present power need for the two electrical appliances, when the control device predicts an expected higher power need in the future for the at least one appliance. In this manner it is possible to increase the energy stored within the control arrangement and the electrical appliances. Hence it is possible to generate a higher power level output for the electrical appliances than the power levels that the power input modifier can deliver. Hence it is possible to increase the efficiency of a control arrangement while decreasing the installation costs.
  • the power input modifier 5 is adapted to receive electrical power from a power source 1 1 , in this example from the power grid.
  • the received electrical power is thus an alternating current having a fixed frequency and fixed voltage.
  • the power input modifier is provided with a power input connection 13, which may be electrical conductors, cables, contactors or similar.
  • the power input modifier 5 is adapted to modify the characteristics of the received electrical power from the power source 1 1 .
  • the power input modifier 5 is an AC/DC- converter, wherein the received alternating current is modified into a direct current.
  • the power input modifier 5 comprises a circuit containing four transistors 15, which in this example are connected to function as controllable diodes.
  • the circuit shown in the figure is one of the most basic forms of controllable AC/DC-converters, chosen for the sake of clarity. In practice the AC/DC-converter may of course be any kind of simple or advanced controllable AC/DC-converter.
  • the power input modifier may also be any other form of modifier, in- eluding for example being a transformer, an inverter, a frequency modulator, or a voltage or current feeder.
  • the power output modifiers 7a-c are DC/AC- invertors adapted to receive the modified electrical power from the power input modifier 5 via the internal connection 17, to modify the received electrical power into an alternating current, and to supply the modified alternating current to the electrical appliances.
  • the first and second electrical appliances 9a, 9b are engines which are frequency controlled, wherein the power output modifiers 7a, 7b may control the engine speed of the electrical appliances 9a, 9b by changing the frequency of the alternating currents.
  • the power output modifiers 7a-c are therefore also adapted to control the voltage output to each engine. Hence the voltage output will correspond to the resistance ex- perienced by each engine.
  • the third electrical appliance 9c is in this example an industrial robot, showing the arbitrariness of the term electrical appliance.
  • the electrical appliance may in practice be any kind of electrical appliance adapted to perform a task, alone or in conjunction with other appliances.
  • the electrical appliance is adapted to perform a manufacturing task, and most preferably the electrical appliance is an industrial robot or an engine for driving an industrial robot.
  • the control device 3 comprises a main control device 23 adapted to execute a robot program 25.
  • the robot program 25 comprises instructions for operating the main control device and also control instructions for instructing the robots controlled by the control arrangement to perform their tasks.
  • the main control device 23 comprises an internal memory and a processor adapted to perform the execution of the robot program.
  • the main control device 23 is further adapted to predict the future expected power need for the industrial robots departing from the execution of the robot program.
  • the main control device 23 is usually adapted to execute the robot program and the robot instructions for controlling the robots in advance of issuing the control signals to the robots. This is due to that heavy computations are needed before the correct control signals can be supplied to the robots.
  • the main control device 23 is further adapted to supply the control signals to the power output modifiers 7a-c.
  • the control de- vice 23 is adapted to control the function of the industrial robots by providing control signals to the power output modifiers 7a-c, wherein the power output modifiers are adapted to control the appliances 9a-b and the industrial robot 9c by supplying a modified electrical power to the appliances and the industrial robot.
  • the electrical engines are controlled by supplying an alternating current having different frequency to achieve different engine speeds.
  • the control arrangement 1 further comprises a power input modifier control circuit 27 adapted to receive the control signals from the main control device 23 and control the function of the power output modifier.
  • the power input modifier control circuit 27 is adapted to provide control signals for controlling the transistors in the power input modifier, so that the terminals are switched from a non-conducting state into a conducting state.
  • the level of power allowed to pass through the power input modifier depends on the conductivity of the transistors.
  • the control arrangement further comprises an energy storage 29 adapted for storing energy within the control arrangement.
  • the energy storage is in this example adapted to a function as a buffer for the electrical current to reduce variations, such as ripple.
  • the energy storage comprise a capacitor 31 adapted to smooth out possible oscillations in the direct current.
  • the energy storage 29 further comprises a rechargeable battery 33 adapted to smooth out larger and slower fluctuations in the current.
  • the energy storage and the control arrangement are adapted to allow disconnection of the energy storage 29 from the control arrangement 1 .
  • the energy storage 29 and the control arrangement 1 are also adapted to allow reconnection of the energy storage 29 to the control arrangement 1 .
  • the power output modifiers 7a-c are further adapted to receive electrical power from the electric appliances 9a-c and to return the electrical power into the control arrangement 1 .
  • the appliances 9a-c are arranged to generate electricity during a deceleration phase of the industrial robots, wherein kinetic energy from the moving members of the robot is transformed into electricity in said engines 9a-b and industrial robot 9c, and returned to the power output modifiers 7a-c.
  • the generated, previously stored, energy is returned to the control arrangement, and may either be instantaneously used by another appliance or be stored in the energy storage 29.
  • the control arrangement 1 further comprises an energy sink 35 adapted to decrease the energy in the system, for example in the event of to high voltage in this system.
  • the energy sink comprises a transistor 37, which is controlled to al- low a current through the transistor when the voltage in the control arrangement 1 is higher than a desired voltage.
  • the energy sink may comprise a zener diode adapted to allow a current through the diode when the voltage is higher than a desired voltage.
  • the energy sink 35 further comprises a resistor 39 coupled in series with the transistor 37. The resistor 39 transforms any current flowing through the resistor into heat.
  • the method comprises controlling at least one electrical appliance, in this example two electrical appliances, to perform a task by the use of a control arrangement.
  • the electrical appliances are arranged to use electrical power in order to perform the task, which in this example is a manufacturing task.
  • the control arrangement comprises a control device and the method comprises controlling the function of the at least one electrical appliance with use of the control device.
  • the method comprises controlling electrical appliances adapted to perform manufacturing tasks.
  • the method further comprises controlling electrical appliances in the form of electrical engines driving at least one in- dustrial robot.
  • the method further comprises controlling at least all engines belonging to the same industrial robot.
  • the electrical appliances are arranged to be controlled by the power level with which they are supplied.
  • the invention comprises controlling the function of the at least one electrical appliance, by controlling at least one power output modifier supply power to, and to control the at least one electrical appliance, by supplying a modified electrical power to the electrical appliance.
  • the power output modifier is thus controlled by the control device to modify the electrical power in accordance with desired performance.
  • the method comprises receiving electrical power from a power source, and modifying the characteristics of the electrical power in a power input modifier.
  • the method also comprises modifying the electrical power so that different levels of electrical power is allowed into the control arrangement by the power input modifier.
  • the method comprises controlling the modification of the electrical power in the power input modifier with the control device.
  • the method further comprises receiving the modified electrical power from the power input modifier in a power output modifier, modifying the received electrical power in the power output modifier, and supplying the modified electrical power to the electrical appliance for controlling the appliance.
  • the method comprises supplying a frequency modulated alternating current.
  • the method comprises predicting the future expected power need for the at least one electrical appliance, and estimating the build-up of energy in the control arrangement and/or in the electrical appliance by use of the control device.
  • the control device also performs predicting of the collective power need for both appliances together.
  • the method may also comprise running an appropriate control program for the electrical appliances in a processor within the control device.
  • a fourth step 46 the method comprises controlling the power input modifier to transfer an electrical power into the control arrangement based on the predicted power need and the built-up energy.
  • the power fed into the control arrangement will be dependent on both the present power need and on possibly stored energy within the arrangement or the appliances. Hence differences in stored energy in the system can be taken into account, so that the energy losses for the control arrangement and appliances are decreased.
  • the method also comprises controlling the power input modifier to transfer an electrical power into the control arrangement, so that at least a part of the built-up energy is used for powering the at least one electrical appliance.
  • the method may also comprise controlling the power input modifier to input a higher power than the present power need when the control device predicts an expected higher power need in the future for the at least one appliance. Hence the stored energy within the control arrangement and the appliances is increased so that more power is available for an expected demanding task.
  • the method may also comprise controlling the power input modifier to input a lower power than the present power need when the control device predicts an expected lower power need in the future for the at least one appliance. In this manner, since the input power is lower than the used power, built-up, stored energy is consumed by the appliance for performing the task.
  • the method may also comprise receiving electrical power from the at least one appliance in the power output modifier, and returning the electrical power to the control arrangement.
  • the method then also comprises storing the energy in at least one energy storage.
  • the returned energy may then be used at a later time and is not lost.
  • the returned power may be instantaneously used by another appliance connected with the same control arrangement, and used for performing a task.
  • FIG. 2b-d one example of a power management while controlling a power input modifier and two appliances according to the method described in relation to fig. 2a is shown.
  • fig. 2b the variation in power need for the two appliances is shown. The need for power is dependent on the work task the appliances are to perform, and is calculated beforehand in accordance with the method in fig. 2a.
  • fig. 2c the stored energy in the control arrangement and in the two appliances is shown. The stored en- ergy may be estimated from measurements, or be based on the predicted power need and knowledge of the power input, or in some other appropriate manner.
  • fig. 2d the power input made by the power input modifier according to the invention is shown. The diagrams are divided into different work phases labelled by the letters A-F.
  • a first work phase A the appliances are accelerated into motion.
  • the power need is high since energy must be added to increase the velocity of a movable member belonging to each ap- pliance.
  • the power input modifier is controlled to supply a high power into the control arrangement to allow the acceleration, and the stored energy is increasing, since energy is transformed into kinetic energy for the movable members and possible circuits are energized.
  • the movable members In a second work phase B, the movable members have constant velocity.
  • the power need is low and constant, since the power is only needed to overcome friction and possibly to perform work in relation to the desired work task.
  • the power supplied by the power input modifier is correspondingly low and constant as is the stored energy.
  • the power need for the appliances is predicted before hand. In this case it is predicted that the movable members are to be decelerated during the next work phase C, wherein the power need for the appliances will be lower, in this case negative.
  • the power input modifier is controlled to input a lower power than the pre- sent power need in a second sub-phase B 2 , occurring before the lower power need phase.
  • the power input during the second sub-phase B 2 is nearly zero, and that the stored energy in the control arrangement and appliances is decreased.
  • the stored energy reduced during the second sub- phase B 2 is mostly energy built-up in the circuits of the control arrangement and appliances, such as energy stored in capacitors and solenoids.
  • the movable members are deceler- ated.
  • the power need is negative since energy is released as the kinetic energy of the movable members is transformed into electric energy and returned to the control arrangement. Since the capacitors and solenoids in the control arrangement have been emptied from energy the released kinetic energy can be stored within the control arrangement. Before the invention such released energy would have been consumed in an energy sink and would constitute a power loss. The kinetic energy is also reduced due to friction, which in any event will constitute a power loss. In the event that only one appliance is decelerated the released energy can also be redirected to another appliance instead.
  • a fourth work phase D the movable members are to remain at rest, wherein the power need is zero.
  • the power input modifier is therefore controlled to input a very low power into the system.
  • the stored energy also remains constant at a low level.
  • the power need in the near future is predicted ac- cording to the method according to the invention.
  • the power need is predicted to increase during the next phase E, when the movable members are once again to be accelerated.
  • the power input modifier is therefore controlled to input a higher power into the control arrange- ment.
  • the power input during D 2 is however not as high as during an acceleration phase.
  • the stored energy is increased slightly since capacitors and solenoids are energized.
  • the movable members are accel- erated.
  • the power need is high since kinetic energy is to be built up for the movable members.
  • the power input modifier is consequently controlled to input a high power into the control arrangement. Since the power input modifier has already been controlled to energize the control arrangement there is also stored energy available to power the appliance. Hence the appliance may be powered with a higher power than what is provided by the power input modifier.
  • a sixth work phase F the movable members are again to be held at constant velocity, wherein the power need and the power input by the power input modifier are low and mostly equal, while the stored energy in the form of kinetic energy and energy in the electric circuits of the control arrangement and appliances is constant.
  • the power input modifier and the power output modifier may be arranged within the same unit or be arranged separately at a distance apart from each other.
  • the control arrangement may be constituted by several or only one unit.
  • the power source may be a local power generator, for example the emergency power for a facility.

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Abstract

The present invention relates to acontrol arrangement (1) adapted for controlling at least one electrical appliance (9a-c) arranged to use electrical power to perform a task. The invention also relates to a control device (23) for controlling a power input modifier (85), a method for controlling a power input modifier (5), a computer program (25), and a computer readable medium (25). The control device is adapted to predict the future expected power need for the at least one electrical appliance, to estimate the accumulated energy in the control arrangement and/or in the electrical appliance and to control the power input modifier to transfer an electrical power into the control arrangement based on the predicted power need and the built-up energy.

Description

A CONTROL ARRANGEMENT, A CONTROL DEVICE, A METHOD, A COMPUTER PROGRAM AND A COMPUTER READABLE MEDIUM
TECHNICAL FIELD
The present invention relates to a control arrangement adapted for controlling at least one electrical appliance arranged to use electrical power to perform a task. The control arrangement comprises a power input modifier adapted to receive electrical power from a power source and at least one power output modifier adapted to supply electrical power to the electrical appliance. The invention also relates to a control device adapted to control a power input modifier and to a method for controlling a power input modifier.
PRIOR ART
The electricity carried by power grids is in most countries high voltage alternating currents, which are controlled to always have the same characteristics. Close to the end user, the high voltage alternating current is transformed into a lower voltage alternating current, for households typically around 230 V. Other characteristics of the current, however, such as frequency, still remain unchanged.
In many applications, in particular applications concerning manufacturing tasks in manufacturing plants or factories, the machinery demands electrical power having different characteristics. In these and other cases it is known to use some kind of electrical power modification in order to change the characteristics of the electrical power to fit the machinery. Examples of such modification devices comprise AC/DC-converters, AC/AC- transformers and DC/AC-inverters. Other examples of modification devices also comprise frequency modulators, and voltage- and/or current-generators.
One such application relates to the power supply for an industrial robot, in which the robot is controlled by supplying electricity to the electrical engines, which are coupled to and drives the robot. The engines are controlled by supplying them with electri- cal power having different frequency depending on the desired engine speed. Since the power supplied by the power grid usually have a set frequency the control arrangement for controlling the engines of the robot usually comprises a power input modifier in the form of an AC/DC-converter, transforming the alter- nating current into direct current, coupled to a power output modifier in the form of a DC/AC-inverter adapted to supply the engine with an alternating current with controllable frequency.
One problem with this application is that in some cases when the engine speed is slowed down a high voltage is created over the power modifiers, which may damage the power supply system. The system has therefore been provided with a resistor connected with the earth, known as a bleeder, adapted to receive a current from the system and transform it into heat in or- der to protect the system. This solution however gives large energy losses in the bleeder, which costs money and is environmentally unfriendly. Furthermore, these systems usually also comprises at least one capacitor in order to smooth out oscillations in the direct current formed by the AC/DC-converter. This capacitor must have a very high capacitance due to the hazard of being fed high voltage from the engines, which makes the capacitor very expensive.
AC/DC-converters have historically been constructed by a col- lection of diodes. In later years however the diodes have been replaced by transistors, making it possible to control the conver- sion from alternating current into direct current. One example of the use of such an AC/DC-converter is shown in patent document US 5,373,223, which shows a power supply system arranged to avoid voltage fluctuations in the part following the AC/DC-converter. By calculating the power at the output from the system and controlling the AC/DC-converter so that the calculated power and the power in the converter are balanced such fluctuations are decreased. Other examples of uses of controlled AC/DC-converters are shown in for example patent documents US2007/0223258 and US2006/0077602.
SUMMARY OF THE INVENTION
One object of the present invention is to indicate a control ar- rangement adapted to receive and supply electrical power to an electrical appliance, which decreases the energy losses in the system.
This object is achieved with the control arrangement according to the preamble of claim 1 , which is characterized in that the control device is adapted to predict the future expected power need for at least one electrical appliance, to estimate the buildup of energy in the control arrangement and/or in the electrical appliance, and to control the power input modifier to transfer an electrical power into the control arrangement based on the predicted power need and built-up energy. Preferably the control device is adapted to control the power input modifier to transfer an electrical power into the control arrangement, so that at least a part of the built-up energy is used for powering the at least one electrical appliance.
Energy may build up both in the control arrangement, for example as electric charge in capacitors or as magnetic energy in solenoids, or as electrical or mechanical energy in the electrical appliance that is to be controlled. With the invention it is possible to decrease the power input so that at least a part of the stored energy can be used for driving the electrical appliance. Hence the invention gives the advantage of a smaller energy loss. Yet a further advantage with the invention is that the total energy input over time may be decreased, since the power input may be decreased during periods when less power is needed, which decreases the power losses in the control arrangement.
Furthermore, in control arrangements according to the prior art, the stored energy may become released and suddenly fed into the system causing voltage spikes that may damage the components in the system, unless consumed in a safety circuit, such as a resistor or bleeder. With the invention the input power may be controlled so that the maximum voltage in the system remains low. Hence the invention also gives the advantage that the components used in the control arrangement may be adapted for lower voltages, meaning that the cost for the components is decreased.
The prediction of the future power need may be based on a pre- execution of a control program for the appliance or appliances. The prediction may also be based on a possible cyclic behaviour for the appliance, which may be the case in a manufacturing process that repeats itself endlessly.
The estimation may be based on calculations, on measurements, on simulations of the appliance or on the experience from previous runs.. The estimation may also be based on the knowledge of the useful energy stored during normal operation of the appliance, or for different power levels for the appliance. The estimation may also be based on a simulation of the stored energy departing from a model of the control arrangement and the appliance. It is not necessary that all the built-up energy in the control arrangement and/or appliance is estimated in order to achieve the invention. It is sufficient that the level of stored energy that can be used, useful stored energy, is estimated. The estimation of stored energy may be made during the operation of the appliance, either continuously or at certain intervals, or the estimation may be made beforehand.
The control based on the predicted future power need and esti- mated stored energy may also be based on experience from previous runs, so that the energy losses are minimised. In a cyclic program for the appliances the energy losses for the appliances can be measured by measurements of the current through an energy sink, and the power input decreased before a peak in energy loss in the next corresponding cycle.
The control arrangement may comprise control circuits in hardware and/or control modules in software. The control arrangement may be adapted to control one or several appliances of the same or different types. Furthermore, the control arrangement may also be adapted to control various components pertaining to the functioning of the appliance, including components within the control arrangement itself. The control arrangement may also be constituted by several physically distinct or separated units, as well as being constituted by only one unit.
A power input modifier is a device that receives electrical power or electricity from a source and modifies the characteristics of the electricity before forwarding the electricity. The modifier may be adapted to modify any of the characteristics of the electric current, such as the nature of the current (AC/DC), the shape of the current (square, sinus form), frequency, voltage, and size of the current (ampere). Preferably the power input modifier is adapted to control the amount of electric power allowed to pass through the power input modifier and into the control arrangement.
According to one embodiment the control arrangement comprises at least one power output modifier adapted to receive the modified electrical power from the power input modifier, to further modify the received electrical power and to supply the modified electrical power to the electrical appliance. By modifying the electricity twice before supplying the electricity to the appliance it is easier to control the storage of energy in between the modifiers, since it is possible to control the power flow in two locations. Furthermore, the control arrangement according to the invention may be used for a wider selection of appliances, since greater changes in the characteristics of the electricity can be made.
According to one embodiment the at least one power output modifier is adapted to receive electrical power from the at least one appliance and to return the electrical power into the control arrangement. Hence, energy delivered and stored in an appliance can be returned to the control arrangement and stored for use at a later time. Such energy from the appliance may be kinetic energy, which may be returned due to a reduction of the speed of the appliance.
According to one embodiment the control device is adapted to control at least one function of the at least one electrical appliance. Preferably the control device is adapted to control at least one electrical appliance to perform a task. Hence the prediction of future power need can be more accurate. Preferably the control device is adapted to calculate a desired behaviour for the electrical appliance in advance, and to predict the power need departing from the desired behaviour.
Preferably the control device is adapted to control the function of the at least one electrical appliance by controlling the at least one power output modifier, wherein the at least one power output modifier is adapted to control the at least one electrical appliance by supplying a modified electrical power to the electrical appliance. In applications in which the electrical appliance is controlled by the amount of power supplied to the appliance it is easy to achieve the advantages of the invention. Furthermore, there is usually a higher gain in saved energy when using the control arrangement according to the invention.
According to a further embodiment the control device is adapted to control the power input modifier to input a higher power than the present power need when the control device predicts an expected higher power need in the future for the at least one appliance. Preferably the control device is adapted to cause a higher power input than the present power need for the appli- ance, when the control device predicts an expected high power need in the near future. Hence it is possible to store energy in the control arrangement and/or in the appliance beforehand, which means that the stored energy can be used as an extra power boost for the electrical appliance. This may for example be advantageous at the start-up of the electrical appliance, when the energy stored in the control arrangement and in the appliance is lower at the beginning than during normal use. Hence the time for energizing the control arrangement and appliance is decreased. It may also be advantageous in the event that very energy demanding or heavy work is expected for the appliance.
According to a further embodiment the control device is adapted to control the power input modifier to input lower power than the present power need when the control device predicts an expected lower power need in the future for the at least one appliance. Then built-up energy is consumed by the appliance for performing the task in advance of the appliance entering a low power state, meaning that any stored energy will be used for performing the task rather than being consumed in the safety circuit.
In one embodiment the control arrangement is adapted to control at least two appliances, wherein the control device is adapted to predict the collected power need for both appliances together. It is advantageous to input power to the control ar- rangement based on the sum of the power need for the two appliances, since the sum is more likely to be smooth with smaller relative power changes. Furthermore, it is possible to redirect power from one appliance to the other appliance, when one of the appliances needs high power and the other appliance needs lower power. Furthermore, if energy has been stored in one appliance during a high power work phase, the stored energy may be returned into the control arrangement and transferred to the other appliance, when the first appliance enters a low power task, making even larger energy savings possible.
According to one embodiment the control arrangement comprises at least one energy storage. Preferably the energy storage comprises a capacitor and/or a battery. Preferably, the en- ergy storage is arranged electrically connected between the power input modifier and the appliance. Preferably, the energy storage is arranged electrically connected between the power input modifier and the power output modifier. The energy storage is adapted to store energy and preferably is also adapted to transform the stored energy back into electrical power. Hence energy may be stored in the energy storage and then reduced by being transferred to the electrical appliance and used for performing a task.
According to one embodiment the energy storage and the control arrangement are adapted to allow disconnection of the energy storage from the control arrangement. Preferably the energy storage and the control arrangement are also adapted to allow reconnection of the energy storage. Hence, it is possible to fill the energy storage with energy during a low power need phase for the appliance, and then disconnect the energy storage for future use. During a high power need phase it is then possible to reconnect the energy storage to allow an extra power boost. Preferably the control arrangement comprises at least two energy storages, wherein it is possible to change the active, connected, energy storage. This is advantageous if one of the energy storages is filled during a low power need phase, or correspondingly, empty of energy during a high power need phase for the appliance.
According to a further embodiment the control arrangement is adapted to supply power to and control an electrical appliance adapted to perform manufacturing tasks. The energy consumption for automation equipment is very high and the power need also varies greatly over time, meaning that large savings can be made by supplying the electrical appliances by power with a control arrangement according to the invention.
In one embodiment the power input modifier may be a converter, preferably an AC/DC-converter. The power output modifier may in turn be an inverter transforming DC current into AC current. Preferably the power output modifier is adapted to supply a frequency modulated alternating current. Hence the power from the power output modifier may be used for controlling for example an electrical engine and the engine speed of the engine.
Preferably the control arrangement is arranged to supply power to and control an electrical appliance in the form of an industrial robot. An industrial robot is moved by use of electrical engines controlled by being supplied with alternating current with various frequency. Hence the input alternating current needs to be modified twice, first into a DC-current and then into an AC-current with varying frequency. Furthermore, the engines automatically produces electricity during deceleration, wherein the generated energy may be stored in the control arrangement and reused during acceleration. The industrial robot may also store energy itself in the form of kinetic energy.
According to a further aspect the invention also relates to a method for controlling the modification of electrical power in a power input modifier and to a control device adapted to control the modification of electrical power in a power input modifier. The invention also relates to a computer program directly downloadable into the internal memory of a computer for controlling a control arrangement to perform the steps according to the invention.
DESCRIPTION OF ATTACHED DRAWINGS
The invention is now to be described as a number of non-limiting examples of the invention with reference to the attached draw- ings.
Fig. 1 shows one example of a control arrangement for three electrical appliances according to one example of the invention.
Fig. 2 a-c shows a method for controlling a power input modifier and two appliances according to one example of the invention.
DETAILED DESCRIPTION
In Fig. 1 a system adapted for performing a task comprising three electrical appliances 9a, 9b, 9c and a control arrangement 1 adapted to control and supply power to the three electrical appliances 9a, 9b, 9c according to one example of the invention is shown. The control arrangement 1 comprises a control device 3 adapted to control the electrical appliances 9a, 9b, 9c. The control arrangement 1 further comprises a power input modifier 5 adapted to receive electrical power from a power source 1 1 and to modify the characteristics of the received electrical power. In this example the power input modifier 5 is adapted to forward the modified electrical power to at least one, in this example three, power output modifiers 7a, 7b, 7c. The power output modifiers 7a, 7b, 7c are adapted to further modify the characteristics of the received electrical power and to forward and supply the electrical power to the three appliances. In another example the power input modifier may instead be adapted to forward and supply the electrical power to the electrical appliances directly.
The control device 3 is adapted to predict the future expected power need for the electrical appliances controlled by the control arrangement. In this example the control device 3 is adapted to predict the future expected power need based on the execu- tion of a control program 25 containing control instructions for causing the electrical appliances to perform a desired task or tasks. The control device 3 is also adapted to estimate the buildup of energy in the control arrangement and/or in the electrical appliances. The built-up energy may for example be energy stored in the electrical circuits of the control arrangement or electrical appliances, for example as electrical energy in capacitors or as magnetic energy in solenoids. The built-up energy may also be mechanical energy such as kinetic energy or potential energy, or any other form of energy stored during the func- tion of the electrical appliances. The power input modifier 5 is adapted to modify the electrical power in such a way that the power input modifier 5 may controls the amount of power that is fed into the control arrangement. In this example the control device 3 is adapted to control the power input modifier 5 to feed an electrical power into the control arrangement 1 based on the predicted power need and the built-up energy. In so doing it is possible to decrease the total energy input over time, since the power input may be decreased during periods when less power is needed, which in turn decreases the power losses in the control arrangement.
In this example, the control device is adapted to predict the collective power need for both appliances together. The control device is adapted to control the power input modifier to input a lower power than the present power need when the control device predicts an expected lower power need in the future for the two appliances. Since the power input is lower than the power need stored, built-up energy is consumed by the appliance for performing the task. Hence the stored energy will be used for doing work instead of creating an over-voltage in the control arrangement, which might lead to power losses. Hence the power usage of the control arrangements and appliances is reduced. Furthermore, the input power may be controlled so that the maximum voltage in the system remain within a desired limit, so that the components used in the control arrangement may be adapted for lower voltages, meaning that the cost for the components is decreased.
The control device 3 is further adapted to control the power in- put modifier 5 to input a higher power than the present power need for the two electrical appliances, when the control device predicts an expected higher power need in the future for the at least one appliance. In this manner it is possible to increase the energy stored within the control arrangement and the electrical appliances. Hence it is possible to generate a higher power level output for the electrical appliances than the power levels that the power input modifier can deliver. Hence it is possible to increase the efficiency of a control arrangement while decreasing the installation costs.
The power input modifier 5 is adapted to receive electrical power from a power source 1 1 , in this example from the power grid. The received electrical power is thus an alternating current having a fixed frequency and fixed voltage. For receiving the electrical power the power input modifier is provided with a power input connection 13, which may be electrical conductors, cables, contactors or similar.
The power input modifier 5 is adapted to modify the characteristics of the received electrical power from the power source 1 1 . In this example the power input modifier 5 is an AC/DC- converter, wherein the received alternating current is modified into a direct current. For this purpose the power input modifier 5 comprises a circuit containing four transistors 15, which in this example are connected to function as controllable diodes. The circuit shown in the figure is one of the most basic forms of controllable AC/DC-converters, chosen for the sake of clarity. In practice the AC/DC-converter may of course be any kind of simple or advanced controllable AC/DC-converter. Furthermore, the power input modifier may also be any other form of modifier, in- eluding for example being a transformer, an inverter, a frequency modulator, or a voltage or current feeder.
The power input modifier is connected to an internal connection 17 connecting the power input modifier with the three power output modifiers 7a-c. The internal connection may be any form of electrical conductor connecting the power modifiers, and may also constitute an internal connection if a power input modifier and a power output modifier are arranged within the same unit. In this preferred example, in which the power input modifier and the power output modifiers are separated, and the power input modifier modifies the receive electrical power into a direct cur- rent, the internal connection 17 comprises a first electrical conductor 19, constituting a positive voltage conductor, and a second electrical conductor 21 , constituting a negative voltage conductor. Thus electricity will tend to flow in the direction from the first electrical conductor 19 towards the second electrical conductor 21 .
In this example the power output modifiers 7a-c are DC/AC- invertors adapted to receive the modified electrical power from the power input modifier 5 via the internal connection 17, to modify the received electrical power into an alternating current, and to supply the modified alternating current to the electrical appliances. In this example the first and second electrical appliances 9a, 9b are engines which are frequency controlled, wherein the power output modifiers 7a, 7b may control the engine speed of the electrical appliances 9a, 9b by changing the frequency of the alternating currents. When transforming the electrical power from the power output modifiers into mechanical motion the engines 9a, 9b will experience a resistance against movement. Depending on the magnitude of the resistance more or less power will be needed to drive the motion of the engines. In this example the power output modifiers 7a-c are therefore also adapted to control the voltage output to each engine. Hence the voltage output will correspond to the resistance ex- perienced by each engine.
Two of the electrical appliances, 9a, 9b, are in this example electrical engines for driving the movement of a movable member of an industrial robot. The third electrical appliance 9c is in this example an industrial robot, showing the arbitrariness of the term electrical appliance. The electrical appliance may in practice be any kind of electrical appliance adapted to perform a task, alone or in conjunction with other appliances. Preferably the electrical appliance is adapted to perform a manufacturing task, and most preferably the electrical appliance is an industrial robot or an engine for driving an industrial robot. The control device 3 comprises a main control device 23 adapted to execute a robot program 25. The robot program 25 comprises instructions for operating the main control device and also control instructions for instructing the robots controlled by the control arrangement to perform their tasks. The main control device 23 comprises an internal memory and a processor adapted to perform the execution of the robot program. The main control device 23 is further adapted to predict the future expected power need for the industrial robots departing from the execution of the robot program. In the application of industrial robots, the main control device 23 is usually adapted to execute the robot program and the robot instructions for controlling the robots in advance of issuing the control signals to the robots. This is due to that heavy computations are needed before the correct control signals can be supplied to the robots.
The main control device 23 is further adapted to supply the control signals to the power output modifiers 7a-c. The control de- vice 23 is adapted to control the function of the industrial robots by providing control signals to the power output modifiers 7a-c, wherein the power output modifiers are adapted to control the appliances 9a-b and the industrial robot 9c by supplying a modified electrical power to the appliances and the industrial robot. In this example the electrical engines are controlled by supplying an alternating current having different frequency to achieve different engine speeds.
The control arrangement 1 further comprises a power input modifier control circuit 27 adapted to receive the control signals from the main control device 23 and control the function of the power output modifier. In particular the power input modifier control circuit 27 is adapted to provide control signals for controlling the transistors in the power input modifier, so that the terminals are switched from a non-conducting state into a conducting state. The level of power allowed to pass through the power input modifier depends on the conductivity of the transistors.
The control arrangement further comprises an energy storage 29 adapted for storing energy within the control arrangement. The energy storage is in this example adapted to a function as a buffer for the electrical current to reduce variations, such as ripple. To this end the energy storage comprise a capacitor 31 adapted to smooth out possible oscillations in the direct current. The energy storage 29 further comprises a rechargeable battery 33 adapted to smooth out larger and slower fluctuations in the current.
In this example the energy storage and the control arrangement are adapted to allow disconnection of the energy storage 29 from the control arrangement 1 . The energy storage 29 and the control arrangement 1 are also adapted to allow reconnection of the energy storage 29 to the control arrangement 1 . Hence, it is possible to fill the energy storage with energy during a low power need phase for the appliance, and then disconnect the energy storage for future use.
The power output modifiers 7a-c are further adapted to receive electrical power from the electric appliances 9a-c and to return the electrical power into the control arrangement 1 . In particular the appliances 9a-c are arranged to generate electricity during a deceleration phase of the industrial robots, wherein kinetic energy from the moving members of the robot is transformed into electricity in said engines 9a-b and industrial robot 9c, and returned to the power output modifiers 7a-c. The generated, previously stored, energy is returned to the control arrangement, and may either be instantaneously used by another appliance or be stored in the energy storage 29. The control arrangement 1 further comprises an energy sink 35 adapted to decrease the energy in the system, for example in the event of to high voltage in this system. In this example the energy sink comprises a transistor 37, which is controlled to al- low a current through the transistor when the voltage in the control arrangement 1 is higher than a desired voltage. Alternatively, the energy sink may comprise a zener diode adapted to allow a current through the diode when the voltage is higher than a desired voltage. The energy sink 35 further comprises a resistor 39 coupled in series with the transistor 37. The resistor 39 transforms any current flowing through the resistor into heat.
In fig. 2a-c one example of a method for controlling a power input modifier and two electrical appliances is shown. Since the method concerns a control method, the steps described are in most cases performed continuously and collectively. Some of the steps may be performed only during a short period, while other steps may be performed repeatedly during the entire use of the method.
In a first, general step 40, the method comprises controlling at least one electrical appliance, in this example two electrical appliances, to perform a task by the use of a control arrangement. The electrical appliances are arranged to use electrical power in order to perform the task, which in this example is a manufacturing task. In this example the control arrangement comprises a control device and the method comprises controlling the function of the at least one electrical appliance with use of the control device.
In this example the method comprises controlling electrical appliances adapted to perform manufacturing tasks. In this example the method further comprises controlling electrical appliances in the form of electrical engines driving at least one in- dustrial robot. In order to achieve an efficient control of the ro- bot the method further comprises controlling at least all engines belonging to the same industrial robot.
In this particular example, the electrical appliances are arranged to be controlled by the power level with which they are supplied. Hence the invention comprises controlling the function of the at least one electrical appliance, by controlling at least one power output modifier supply power to, and to control the at least one electrical appliance, by supplying a modified electrical power to the electrical appliance. The power output modifier is thus controlled by the control device to modify the electrical power in accordance with desired performance.
In a second step 42 the method comprises receiving electrical power from a power source, and modifying the characteristics of the electrical power in a power input modifier. The method also comprises modifying the electrical power so that different levels of electrical power is allowed into the control arrangement by the power input modifier. In this example the method comprises controlling the modification of the electrical power in the power input modifier with the control device.
In this example the method further comprises receiving the modified electrical power from the power input modifier in a power output modifier, modifying the received electrical power in the power output modifier, and supplying the modified electrical power to the electrical appliance for controlling the appliance. In one example the method comprises supplying a frequency modulated alternating current.
In a third step 44 the method comprises predicting the future expected power need for the at least one electrical appliance, and estimating the build-up of energy in the control arrangement and/or in the electrical appliance by use of the control device. The control device also performs predicting of the collective power need for both appliances together. The method may also comprise running an appropriate control program for the electrical appliances in a processor within the control device.
In a fourth step 46 the method comprises controlling the power input modifier to transfer an electrical power into the control arrangement based on the predicted power need and the built-up energy. Thus the power fed into the control arrangement will be dependent on both the present power need and on possibly stored energy within the arrangement or the appliances. Hence differences in stored energy in the system can be taken into account, so that the energy losses for the control arrangement and appliances are decreased. The method also comprises controlling the power input modifier to transfer an electrical power into the control arrangement, so that at least a part of the built-up energy is used for powering the at least one electrical appliance.
The method may also comprise controlling the power input modifier to input a higher power than the present power need when the control device predicts an expected higher power need in the future for the at least one appliance. Hence the stored energy within the control arrangement and the appliances is increased so that more power is available for an expected demanding task.
Correspondingly the method may also comprise controlling the power input modifier to input a lower power than the present power need when the control device predicts an expected lower power need in the future for the at least one appliance. In this manner, since the input power is lower than the used power, built-up, stored energy is consumed by the appliance for performing the task.
In this example the method may also comprise receiving electrical power from the at least one appliance in the power output modifier, and returning the electrical power to the control arrangement. Preferably the method then also comprises storing the energy in at least one energy storage. The returned energy may then be used at a later time and is not lost. Alternatively the returned power may be instantaneously used by another appliance connected with the same control arrangement, and used for performing a task.
Turning to fig. 2b-d one example of a power management while controlling a power input modifier and two appliances according to the method described in relation to fig. 2a is shown. In fig. 2b the variation in power need for the two appliances is shown. The need for power is dependent on the work task the appliances are to perform, and is calculated beforehand in accordance with the method in fig. 2a. In fig. 2c the stored energy in the control arrangement and in the two appliances is shown. The stored en- ergy may be estimated from measurements, or be based on the predicted power need and knowledge of the power input, or in some other appropriate manner. In fig. 2d the power input made by the power input modifier according to the invention is shown. The diagrams are divided into different work phases labelled by the letters A-F.
In a first work phase A, the appliances are accelerated into motion. The power need is high since energy must be added to increase the velocity of a movable member belonging to each ap- pliance. Correspondingly, the power input modifier is controlled to supply a high power into the control arrangement to allow the acceleration, and the stored energy is increasing, since energy is transformed into kinetic energy for the movable members and possible circuits are energized.
In a second work phase B, the movable members have constant velocity. The power need is low and constant, since the power is only needed to overcome friction and possibly to perform work in relation to the desired work task. In a first sub-phase B1 of the second work phase B, the power supplied by the power input modifier is correspondingly low and constant as is the stored energy.
According to the method, the power need for the appliances is predicted before hand. In this case it is predicted that the movable members are to be decelerated during the next work phase C, wherein the power need for the appliances will be lower, in this case negative. Hence, according to the method, the power input modifier is controlled to input a lower power than the pre- sent power need in a second sub-phase B2, occurring before the lower power need phase. In fig. 2d it is shown that the power input during the second sub-phase B2 is nearly zero, and that the stored energy in the control arrangement and appliances is decreased. The stored energy reduced during the second sub- phase B2 is mostly energy built-up in the circuits of the control arrangement and appliances, such as energy stored in capacitors and solenoids.
In the third work phase C, the movable members are deceler- ated. The power need is negative since energy is released as the kinetic energy of the movable members is transformed into electric energy and returned to the control arrangement. Since the capacitors and solenoids in the control arrangement have been emptied from energy the released kinetic energy can be stored within the control arrangement. Before the invention such released energy would have been consumed in an energy sink and would constitute a power loss. The kinetic energy is also reduced due to friction, which in any event will constitute a power loss. In the event that only one appliance is decelerated the released energy can also be redirected to another appliance instead.
In a fourth work phase D, the movable members are to remain at rest, wherein the power need is zero. During a first sub-phase D1 the power input modifier is therefore controlled to input a very low power into the system. The stored energy also remains constant at a low level.
As before, the power need in the near future is predicted ac- cording to the method according to the invention. In this case the power need is predicted to increase during the next phase E, when the movable members are once again to be accelerated. During a second sub-phase D2 the power input modifier is therefore controlled to input a higher power into the control arrange- ment. The power input during D2 is however not as high as during an acceleration phase. The stored energy is increased slightly since capacitors and solenoids are energized.
During the fifth work phase E, the movable members are accel- erated. The power need is high since kinetic energy is to be built up for the movable members. The power input modifier is consequently controlled to input a high power into the control arrangement. Since the power input modifier has already been controlled to energize the control arrangement there is also stored energy available to power the appliance. Hence the appliance may be powered with a higher power than what is provided by the power input modifier.
During a sixth work phase F the movable members are again to be held at constant velocity, wherein the power need and the power input by the power input modifier are low and mostly equal, while the stored energy in the form of kinetic energy and energy in the electric circuits of the control arrangement and appliances is constant.
The invention is not limited to the embodiments described above, but may be varied freely within the framework of the attached claims. In particular, the power input modifier and the power output modifier may be arranged within the same unit or be arranged separately at a distance apart from each other. Similarly, the control arrangement may be constituted by several or only one unit. The power source may be a local power generator, for example the emergency power for a facility.

Claims

1 . A control arrangement (1 ) adapted for controlling at least one electrical appliance (9a-c) arranged to use electrical power to perform a task, the control arrangement comprising a power input modifier (5) adapted to receive electrical power from a power source (1 1 ) and to modify the characteristics of the electrical power, and a control device (23) adapted to control the modification of the electrical power in the power input modifier (5), characterized in that the control device is adapted to predict the future expected power need for the at least one electrical appliance (9a-c), to estimate the build-up of energy in the control arrangement (1 ) and/or in the electrical appliance (9a-c), and to control the power input modifier (5) to transfer an electri- cal power into the control arrangement (1 ) based on the predicted power need and the built-up energy.
2. The control arrangement according to claim 1 , characterized in. that the control device (23) is adapted to control the power input modifier to transfer an electrical power into the control arrangement, so that at least a part of the built-up energy is used for powering the at least one electrical appliance.
3. The control arrangement according to claim 1 or 2, character- ized in that the control device (23) is adapted to control the power input modifier (5) to input a higher power than the present power need when the control device predicts an expected higher power need in the future for the at least one appliance.
4. The control arrangement according to any of the claims 1 -3, characterized in that the control device (23) is adapted to control the power input modifier (5) to input a lower power than the present power need when the control device predicts an expected lower power need in the future for the at least one appli- ance (9a-c).
5. The control arrangement according to any of the claims 1 -4, characterized in that the control arrangement (1 ) comprises at least one power output modifier (7a-c) adapted to receive the modified electrical power from the power input modifier, to fur- ther modify the received electrical power and to supply the modified electrical power to the electrical appliance (9a-c).
6. The control arrangement according to claim 5, characterized in. that the at least one power output modifier (7a-c) is adapted to receive electrical power from the at least one appliance (9a-c) and to return the electrical power into the control arrangement
(1 )-
7. The control arrangement according to any of the claims 1 -6, characterized in that the control device (23) is further adapted to control the function of the at least one electrical appliance.
8. The control arrangement according to claim 5 and 7, characterized in that the control device (23) is adapted to control the function of the at least one electrical appliance by controlling the at least one power output modifier (7a-c), wherein the at least one power output modifier is adapted to control the at least one electrical appliance (9a-c) by supplying a modified electrical power to the electrical appliance.
9. The control arrangement according to any of the claims 1 -8, characterized in that the control arrangement (1 ) is adapted to control at least two appliances, wherein the control device is adapted to predict the collective power need for both appliances together.
10. The control arrangement according to any of the claims 1 -9, characterized in that the control arrangement comprises at least one energy storage (29) electrically connected between the power input modifier and the appliance.
1 1 . The control arrangement according to any of the claims 1 - 10, characterized in that the control arrangement (1 ) is adapted to supply power to and control an electrical appliance adapted to perform manufacturing tasks.
12. A control device (23) adapted to control the modification of electrical power in a power input modifier (5) adapted to receive electrical power from a power source, to modify the characteristics of the electrical power and to supply the modified electrical power to a control arrangement (1 ) adapted to supply electrical power to at least one electrical appliance (9a-c) arranged to use electrical power to perform a task, characterized in. that the control device (23) is adapted to predict the future expected power need for the at least one electrical appliance, to estimate the build-up of energy in the control arrangement (1 ) and/or in the electrical appliance (9a-c), and to control the power input modifier (5) to transfer an electrical power into the control arrangement based on the predicted power need and the built-up energy.
13. A method for controlling the modification of electrical power in a power input modifier (5) adapted to supply electrical power to a control arrangement and at least one electrical appliance (9a-c) adapted to perform a task, the method comprising receiving electrical power from a power source (1 1 ) and modifying the characteristics of the electrical power with the power input modifier, and controlling the modification of the electrical power in the power input modifier with a control device (23), characterized in that the method comprises predicting the future expected power need for the at least one electrical appliance (9A-C), estimating the build-up of energy in the control arrangement (1 ) and/or in the electrical appliance (9a-c), and controlling the power input modifier to transfer an electrical power into the control arrangement based on the predicted power need and the built-up energy.
14. A method according to claim 13, characterized in that the method comprises controlling the power input modifier (5) to transfer an electrical power into the control arrangement, so that at least a part of the built-up energy is used for powering the at least one electrical appliance.
15. A method according to claim 13 or 14, characterized in that the method comprises controlling the power input modifier (5) to input a higher power than the present power need when predict- ing a higher expected power need in the future for the at least one appliance.
16. A method according to any of the claims 13-15, characterized in that the method comprises controlling the power input modifier to input a lower power than the present power need when predicting a lower expected power need in the future for the at least one appliance.
17. A method according to any of the claims 13-16, character- ized in that the control arrangement comprises at least one power output modifier, and the method comprises receiving the modified electrical power from the power input modifier with the at least one power output modifier, further modifying the received electrical power and supplying the modified electrical power to the electrical appliance.
18. A method according to claim 17, characterized in that the method comprises receiving electrical power from the at least one appliance in the power output modifier and returning the electrical power into the control arrangement.
19. A method according to any of the claims 13-18, characterized in that the method comprises controlling the function of the at least one electrical appliance.
20. A method according to claim 17 and 19, characterized in that the method comprises controlling the function of the at least one electrical appliance by controlling the at least one power output modifier, and controlling the at least one electrical appliance by supplying a modified electrical power to the electrical appliance with the at least one power output modifier.
21 . A method according to any of the claims 13-20, characterized in that the method comprises controlling at least two appli- ances, and predicting the collective power need for both appliances together.
22. A method according to any of the claims 13-23, characterized in that the method comprises supplying power to and con- trolling an electrical appliance adapted to perform manufacturing tasks.
23. A computer program (25) directly downloadable into the internal memory of a control device (23), characterized in that the computer program comprises software for inducing the control device to perform the steps in any of the claims 13-23.
24. A computer readable medium (25), having a computer program written thereon, characterized in that the program is de- signed to induce a control device (23) to perform the steps in any of the claims 13-23.
PCT/EP2007/064496 2007-12-21 2007-12-21 A control arrangement, a controle device, a method, a computer program and a computer readable medium WO2009080122A1 (en)

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Application Number Priority Date Filing Date Title
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Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2007/064496 WO2009080122A1 (en) 2007-12-21 2007-12-21 A control arrangement, a controle device, a method, a computer program and a computer readable medium

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030040847A1 (en) * 2001-05-18 2003-02-27 Jonah Tsui System and method for managing utility power use
US20030163224A1 (en) * 2002-01-16 2003-08-28 Juergen Klaar Energy supply network and method for operating an energy supply network
US20040260489A1 (en) * 2003-05-13 2004-12-23 Ashmin Mansingh Energy management system in a power and distribution system
US20060276938A1 (en) * 2005-06-06 2006-12-07 Equinox Energy Solutions, Inc. Optimized energy management system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030040847A1 (en) * 2001-05-18 2003-02-27 Jonah Tsui System and method for managing utility power use
US20030163224A1 (en) * 2002-01-16 2003-08-28 Juergen Klaar Energy supply network and method for operating an energy supply network
US20040260489A1 (en) * 2003-05-13 2004-12-23 Ashmin Mansingh Energy management system in a power and distribution system
US20060276938A1 (en) * 2005-06-06 2006-12-07 Equinox Energy Solutions, Inc. Optimized energy management system

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