JP2007303583A - Servo valve control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a servo valve control device having a control property for smoothing and stabilizing the controlled variable of a servo valve applied for position control. <P>SOLUTION: The servo valve control device comprises the servo valve, a setting part for inputting a target value for the controlled variable of the servo valve, generating a predetermined reference input signal from the target value, and outputting it, a detection part mounted to the servo valve for detecting the controlled variable of the servo valve and outputting a feedback amount, a comparison part for comparing the reference input signal outputted by the setting part with the feedback amount outputted by the detection part, and outputting a deviation therebetween, and an adjustment part for outputting an operation amount given to the servo valve after receiving the deviation outputted by the comparison part. The comparison part is provided with an amplitude restricting part connected to a signal line which gives the deviation to the adjustment part for restricting the deviation outputted by the comparison part in a predetermined level range. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a servo valve, and more particularly to a control device for a servo valve that is hydraulically controlled and variably controls its control amount.

  Conventionally, hydraulic control widely used in industrial devices and the like is servo valve control by a closed loop system (feedback control system), and the drive is controlled by this feedback control system. In the servo valve control, the output flow rate of the servo valve is applied to the hydraulic cylinder to actuate the piston, and its position is electrically detected to perform feedback control. Specifically, in this control, a deviation is obtained by comparing with a command signal corresponding to the target value, a signal that reduces this deviation is given to the control mechanism to control the servo valve, and the flow rate is adjusted and controlled to load. It is comprised so that the position of may be adjusted.

  For example, as shown in FIG. 4, the feedback control device used for such an application is directly input to the control target 1 (for example, a servo valve) or the feedback loop which forms the whole or a part of the control target device. A setting unit 2 that generates a reference input signal for operating the feedback control system with a value set from the outside as a target value so that the control amount of the control target 1 takes a set value, and takes out a signal necessary for control from the control target 1 The detection unit 3 including a sensor that converts the physical value into the same type as the target value and outputs it, and compares the reference input signal with the signal output from the detection unit 3 to generate a deviation as an operation signal that causes a control operation. The comparator 4 that receives the deviation output from the comparator 4 generates a signal necessary for the feedback control system to perform a desired function and sends the signal to the operation unit. Adjust unit 5, and an operation portion 6 to be applied to the controlled object is converted into an operation amount for controlling the controlled object by receiving a signal output from the adjusting unit 5.

Incidentally, the comparison unit 4, the adjustment unit 5, and the operation unit 6 often have a unit configuration integrated as a servo amplifier module, for example.
In addition, this kind of feedback control apparatus is widely applied to various plant control, general industrial measurement, etc. (for example, refer patent documents 1 thru | or 3).
Incidentally, when the position of a cylinder such as an actuator is controlled using a servo valve, generally an operation close to linear is executed. The setting signal of the feedback control device that performs such position control mainly changes gradually over time or changes stepwise in a short time.
JP-A-9-291902 JP-A-8-144709 JP-A-57-176406

  However, when the target value changes stepwise in a short time or suddenly changes in the feedback control device that performs the position control described above, the deviation signal given to the adjusting unit 5 changes abruptly. The operation amount given to the servo valve 1 to be controlled also changes abruptly. As a result, there is a problem in that overshoot and undershoot occur in the control amount of the servo valve 1 and so-called hunting occurs in a cylinder such as an actuator.

  The present invention has been made in consideration of such conventional circumstances, and the object of the present invention is to make the controlled amount of a servo valve applied to the position control of a cylinder such as an actuator smooth and stable. It is an object of the present invention to provide a servo valve control device capable of obtaining the controlled characteristics.

In order to achieve the above-described object, a servo valve control device according to the present invention receives a servo valve and a target value of a control amount for the servo valve, generates a predetermined reference input signal from the target value, and outputs it. A setting unit that is attached to the servo valve, detects a control amount of the servo valve and outputs a feedback amount, and outputs the reference input signal output from the setting unit and the detection unit. A servo valve control device comprising: a comparison unit that compares the feedback amount and outputs the deviation; and a control unit that receives the deviation output from the comparison unit and outputs an operation amount applied to the servo valve. Because
An amplitude limiting unit that is connected between the comparison unit and the adjustment unit and limits the deviation output from the comparison unit to a predetermined level range is provided.

Generally, the adjusting unit includes a proportional operation (P operation) and an integration operation (I operation). If necessary, the adjusting unit further includes a differential operation (D operation).
The servo valve is configured to variably control the control amount of hydraulic pressure with current.

  In the servo valve control device of the present invention described above, the amplitude limiter controls the level of the amplitude of the deviation (signal) output from the comparison unit and applied to the adjustment unit, so that it falls within a predetermined level range. Even if there is a sudden change in the target value, the control amount of the servo valve can be controlled smoothly, and an excellent effect can be obtained that stable control characteristics can be obtained.

  A servo valve control apparatus according to an embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of a main part of a control apparatus for a servo valve according to an embodiment of the present invention. In this figure, the parts denoted by the same reference numerals as those in FIG. 4 represent the same components, and the basic configuration is the same as that of the conventional one shown in FIG. 1 to 3 are diagrams for explaining a servo valve control apparatus according to an embodiment of the present invention, and the present invention is not limited to these drawings.

  In FIG. 1, reference numeral 20 denotes a deviation (signal) connected between the comparison unit 4 and the adjustment unit 5 (point b) constituting a feedback control device (servo amplifier) for controlling the servo valve and output from the comparison unit 4. ) Is an amplitude limiter (limiter) that limits the amplitude so that the level signal is within a predetermined range. In this limiter 20, the signal output from the setting unit 2 changes in a sine wave shape, and the deviation (signal) output from the comparison unit 4 changes in a sine wave shape on the basis of 0V as indicated by a broken line in FIG. As shown by the solid line in FIG. 2, the amplitude of the deviation (signal) exceeding the predetermined positive level limit value (+ ΔV) and the negative level limit value (−ΔV) is limited. It plays a role to suppress.

More specifically, the limiter 20 includes four operational amplifiers (op-amps) OP _{1 to} OP ₄ as shown in FIG. The first operational amplifier OP ₁ and the second operational amplifier OP _2, respectively constitute a non-inverting amplifier circuit, the role of the level limiting circuit to reduce the positive level of the deviation beyond the positive level of the limit value (+ [Delta] V) (signal) Bear. The third operational amplifier OP ₃ and the fourth operational amplifier OP _4, respectively constitute an inverting amplifier non-inverting amplifier circuit, suppress the negative level of the deviation beyond the negative level of the limit value (- [Delta] V) (signal) Plays the role of a level limiting circuit.

Both ends of two resistors R ₁ and R ₂ connected in series are connected to a constant voltage DC power supply (not shown), and a positive input terminal of the first operational amplifier OP ₁ is connected from a connection portion of these resistors R ₁ and R _2. And a predetermined voltage is applied via the resistor R _i1 . Further, the first output and the negative input terminal of the operational amplifier OP _1, is connected to the feedback resistor R _f1 determines the amplification degree of the operational amplifier OP _1. The first output terminal of the operational amplifier OP ₁ is grounded through a fixed resistor R _G1 and the variable resistor R _G2 connected in series. Inverting amplifier according to the first operational amplifier OP ₁ generates a reference voltage for operating the next stage second operational amplifier OP ₂ (positive voltage).

On the other hand, the positive input terminal of the second operational amplifier OP ₂ is connected to the sliding terminal of the variable resistor R _G2 through a resistor R _i3. Also in the second output terminal and the negative input terminal of the operational amplifier OP _2, a capacitor C ₁ and diode D ₁ are connected in parallel. The anode of the diode D ₁ is the second negative input terminal of the operational amplifier OP _2, the cathode is connected to the second output terminal of the operational amplifier OP _2.

The non-inverting amplifier including the operational amplifier OP _2, the level of the signal a second operational amplifier OP ₂ is that which exceeded through the diode D ₁ when the level of the deviation output from the comparison unit 4 exceeds a predetermined level ( It plays the role of a limiter that absorbs a positive voltage signal.
The voltage applied to the second positive input terminal of the operational amplifier OP ₂ is resistor by a voltage output from the first operational amplifier OP _1, by adjusting the variable resistor R _G2 are adjusted partial pressure as [+ [Delta] V] _Is given via R _i3 . Therefore, when the second voltage exceeding the voltage given to the positive input terminal of the operational amplifier OP ₂ is given to the second negative input terminal of the operational amplifier OP _2, via the diode D ₁ positive exceeding [+ [Delta] V] the deviation of the voltage levels (signal) by absorbing from the second output terminal of the operational amplifier OP ₂ is limited to a certain level.

On the other hand, to the negative input terminal of the third operational amplifier OP _3, a predetermined voltage is applied from the two connection portions of the resistor R _1, R ₂ connected in series through the resistor R _i2, the positive input terminal Is grounded. Also between the third negative input terminal and the output terminal of the operational amplifier OP _3, feedback resistor R _f2 determines the third amplification degree of the operational amplifier OP ₃ is connected. The output terminal of the third operational amplifier OP ₃ is grounded through a fixed resistor R _G3 and variable resistor R _G4 connected in series.

Inverting amplifier according to the third operational amplifier OP ₃ generates a reference voltage (negative voltage) for operating the fourth operational amplifier OP ₄ of the next stage.
The positive input terminal of the fourth operational amplifier OP ₄ is connected to the sliding terminal of the variable resistor R _G4 via a resistor R _i4. This fourth output terminal and the negative input terminal of the operational amplifier OP _4, a capacitor C ₂ and the diode D ₂ are connected in parallel. The anode of the diode D ₂ is the output terminals of the fourth operational amplifier OP _4, a cathode connected to the negative input terminals of the fourth operational amplifier OP _4. The non-inverting amplifier comprised of the fourth operational amplifier OP ₄ is a fourth operational amplifier OP ₄ when the level of the deviation output from the comparison unit 4 exceeds a predetermined level that exceeded through the diode D ₂ It plays the role of a limiter that absorbs the level signal (negative voltage signal).

The voltage applied to the positive input terminal of the fourth operational amplifier OP _4, the resistance by the voltage outputted from the third operational amplifier OP _3, by adjusting the variable resistor R _G4 is adjusted partial pressure as [- [Delta] V] _Is provided via the device R _i4 . Thus a negative voltage level of deviations above the [- [Delta] V] given to the positive input terminal of the fourth operational amplifier OP ₄ (signal) is applied to the negative input terminal of the fourth operational amplifier OP _4, a diode D ₂ absorb deviation of a large negative voltage level (signal) from the output terminal of the second operational amplifier OP ₄ through to be limited to a certain level.

Thus it is connected to the second operational amplifier OP ₂ and the fourth operational amplifier OP ₄ of the respective output terminals connected with each other to provide a difference (signal) to the adjusting unit 5 from the comparison unit 4 signal lines (b point) . The level of the deviation (signal) can be set as a voltage signal within a predetermined range (+ ΔV to −ΔV) by adjusting the variable resistors R _G2 and R _G4 , respectively.

Thus, according to the servo valve control device of the present invention, the comparison unit 4 constituting the feedback control device (servo amplifier) connects the amplitude limiting unit 20 to the signal line that gives a deviation to the adjustment unit 5, so that the target value When there is a sudden change, the deviation can be limited to be within a predetermined level.
More specifically, in the displacement control using the servo valve 1, the amount of oil necessary for the displacement is sent from the servo valve 1 to the cylinder for controlling the displacement. The oil feed amount is determined by the opening degree of the servo valve 1 per hour. Therefore, the pressure applied to the cylinder may be proportional to the force required to displace the cylinder.

  Therefore, even if a large deviation is output from the comparison unit 4, the servo valve control device of the present invention controls the deviation so as not to exceed a predetermined level by the amplitude limiting unit 20. Therefore, the above-described servo valve control device can limit the oil feed speed to the cylinder within a predetermined range while restricting the opening per hour of the servo valve 1 within a certain range. For this reason, it becomes possible to suppress the inertia of a cylinder and to suppress so-called hunting.

As described above, the servo valve control apparatus of the present invention described above limits the amplitude of the deviation (signal) output from the comparison unit 4 and applied to the adjustment unit 5 by the amplitude limiting unit 20 so as to be within a predetermined level range. Therefore, even if there is a sudden change in the target value, the control amount of the servo valve 1 can be controlled smoothly, and stable control characteristics can be obtained.
The servo valve control apparatus according to the present invention is a control to which a PI controller or a PID controller configured to include a proportional operation and an integral operation, and further a differential operation, which are generally used as process control in the adjusting unit 5 is applied. Even in the system, it is only necessary to connect the amplitude limiting unit 20 to a signal line that gives a deviation from the comparison unit 4 to the adjustment unit 5, and the control amount of the servo valve 1 can be made smooth without changing the existing servo amplifier. An excellent effect can be obtained that control can be performed and stable control characteristics can be obtained. Therefore, the servo valve control device of the present invention is particularly suitable as a control device for a hydraulic servo valve that controls displacement of a cylinder by hydraulic pressure.

  The servo valve control device of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

The block diagram which shows the principal part schematic structure of the control apparatus of the servo valve which concerns on one Embodiment of this invention. The graph which shows an example of the deviation signal which restricted the change of the deviation signal shown in FIG. 1, and the amplitude of the deviation by an amplitude limitation part. The figure which shows an example of the circuit which comprises the amplitude limiting part shown in FIG. The block diagram which shows the principal part schematic structure in the control apparatus of the conventional servo valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control object 2 Setting part 3 Detection part 4 Comparison part 5 Adjustment part 6 Operation part 20 Amplitude restriction part

Claims (4)

A servo valve;
A setting unit that receives a target value of a control amount for the servo valve, generates a predetermined reference input signal from the target value, and outputs the reference input signal.
A detection unit that is attached to the servo valve, detects a control amount of the servo valve, and outputs a feedback amount;
A comparison unit that compares the reference input signal output from the setting unit and the feedback amount output from the detection unit and outputs the deviation;
In response to the deviation output by the comparison unit, the servo valve control device includes an adjustment unit that outputs an operation amount to be given to the servo valve.
The servo valve control device, wherein the comparison unit is connected to a signal line that gives the deviation to the adjustment unit, and includes an amplitude limiting unit that limits the deviation output from the comparison unit to a predetermined level range. .   The servo valve control device according to claim 1, wherein the adjustment unit includes a proportional operation and an integral operation.   3. The servo valve control apparatus according to claim 2, wherein the adjustment unit further includes a differential operation.   4. The servo valve control device according to claim 1, wherein the servo valve variably controls a control amount by hydraulic pressure.

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