JP2017016391A - Control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that in the case of finite time settling control in homogenous control, oscillation is deteriorated when an error is small or follow-up performance is deteriorated when an error is 1 or greater.SOLUTION: A control device 3 comprises: an error calculation unit 31 for calculating an error in the present value of a control object with respect to a host command value; a homogenous order acquisition unit 33 for acquiring a homogenous order in accordance with the error; an arithmetic unit 34 for performing an exponential arithmetic on the error that corresponds to the homogenous order so that homogenous control is achieved; and a command value calculation unit 36 for calculating a low-order command value from the arithmetic result. The homogenous order is set to 0 in a small range and a large range of errors. As a result, it is possible to suppress an increase in oscillation in the small range of errors, as compared with finite time settling control, and to improve convergence in the large range of errors.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a control device that controls a control target as a homogeneous system.

  Conventionally, a control method using the homogeneity of a system is known (Non-Patent Documents 1 and 2). Further, such a homogeneous system is applied to P-PI control in which the position is controlled by P control to generate a speed command, and the speed is controlled by PI control to generate a current command. A control method called control is also known (Non-Patent Document 3).

V. T. Haimo, "Finite time controllers", SIAM Journal on Control and Optimization, Volume 24 Issue 4, pp. 760-770, 1986 A. Bacciotti, L. Rosier, "Liapunov Functions and Stability in Control Theory", Springer-Verlag, 2005 Naoki Nishida, Toshiaki Matoba, Bunichi Nakamura, Nami Nakamura, “Highly Accurate Control of Robot Manipulators Using Homogeneous P-PI Control”, 55th Annual Conference of the Institute of Systems, Control and Information Engineers, 2011

However, in the conventional homogeneous system, the homogeneous order is fixed. In particular, in the case of finite time settling control in which the homogeneity order is fixed to a negative value, there is a possibility that vibration will increase in a small error state, that is, in a system stop state, or follow in a large error state. There were problems such as performance degradation.
Generally speaking, there has been a desire to be able to perform more appropriate control in the control by the conventional homogeneous system.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device capable of performing more appropriate control in the control by the homogeneous system.

In order to achieve the above object, a control device according to the present invention includes an error calculation unit that calculates an error between a higher-order command value and a current value of a control target, a homogeneous order acquisition unit that acquires a homogeneous order, In order to be controlled, an arithmetic unit that performs an exponential operation according to the order of the error is provided, and a command value calculation unit that calculates a lower order command value from a calculation result by the arithmetic unit.
With such a configuration, the homogeneous order changes in the homogeneous system, so that, for example, the homogeneous degree acquisition unit can appropriately control the homogeneous order to perform more appropriate control. It becomes like this.

The control device according to the present invention further includes a scaling unit that multiplies the error by a scaling factor that is a positive real number, and an inverse scaling unit that multiplies the operation result of the operation unit by the reciprocal of the scaling coefficient. Further, the error multiplied by the scaling factor may be exponentially calculated, and the command value calculation unit may calculate the lower command value from the calculation result obtained by multiplying the inverse of the scaling factor.
In the homogeneous system, the result of the exponent operation changes depending on whether the error to be calculated is larger than 1. Therefore, with such a configuration, it is possible to make the error that is the object of calculation fall within an appropriate value range in which the effect of exponential calculation can be obtained.

In addition, the control device according to the present invention may further include a changing unit that changes the scaling coefficient used by the scaling unit and the inverse scaling unit based on the current value related to the control target.
With such a configuration, for example, by changing the scaling coefficient according to the current value or the like, the error to be calculated can be dynamically changed to a range where a more appropriate effect can be obtained.

In the control device according to the present invention, the homogeneity order acquisition unit may acquire the homogeneity order based on an error multiplied by the scaling coefficient.
With such a configuration, it is possible to make the error used for obtaining the homogeneous order within an appropriate range.

In the control device according to the present invention, the homogeneity order acquisition unit may acquire a homogeneity order of 0 in a range where the absolute value of the error is smaller than a threshold value smaller than 1.
With such a configuration, it is possible to suppress an increase in vibration in a state where an error is small.

In the control device according to the present invention, the homogeneous order acquisition unit may acquire a homogeneous order that is less than 0 in a range where the absolute value of the error is larger than the threshold value and smaller than 1.
With such a configuration, the error convergence performance can be improved in a range where the absolute value of the error is larger than the threshold value and smaller than 1.

In the control device according to the present invention, the homogeneity order acquisition unit may acquire a homogeneity order that is 0 or more in a range where the absolute value of the error is 1 or more.
With such a configuration, the followability in a state with a large error can be improved.

In the control device according to the present invention, the control target may be a motor.
With such a configuration, for example, in a robot operated by a motor, it is possible to improve the control performance of both a high-speed operation that can increase the error and a fine operation that can reduce the error.

Further, a control device according to the present invention includes a position error calculation unit that calculates a position error between a position command and a current position of a motor to be controlled, a homogeneous order acquisition unit that acquires a homogeneous order, and homogeneous control, A first calculation unit that performs exponential calculation according to the order of the position error, a speed command calculation unit that calculates a speed command by performing proportional control on the calculation result by the first calculation unit, A speed error calculation unit that calculates a speed error between the speed command and the current speed of the motor, a second calculation unit that performs exponential operation on the speed error in accordance with the order of homogeneity so as to perform homogeneous control, A current command calculation unit that calculates a current command from a calculation result of the two calculation units, and the homogeneity order acquisition unit acquires the homogeneity order using at least one of the position error and the speed error, and the second The calculation unit of The first and second exponent operation units that perform numerical operations are provided, and the current command calculation unit performs proportional control on the operation result of the first exponent operation unit, and performs integral control on the operation result of the second exponent operation unit. To do.
With such a configuration, the homogeneous order can be changed in the homogeneous P-PI control. For example, the homogeneous degree acquisition unit appropriately acquires the homogeneous order to perform more appropriate control. Will be able to.

  According to the control device of the present invention, the homogeneous order can be changed in the homogeneous system. For example, more appropriate control can be performed by acquiring an appropriate homogeneous order.

The block diagram which shows the structure of the control apparatus by embodiment of this invention Graph showing an example of correspondence between error and same order in the embodiment Graph showing an example of the relationship between the error and the result of exponentiation in the embodiment The flowchart which shows operation | movement of the control apparatus by the embodiment Graph for comparing the error of the control device according to the embodiment and the error of the conventional example The block diagram which shows another example of a structure of the control apparatus in the embodiment The block diagram which shows another example of a structure of the control apparatus in the embodiment

  Hereinafter, a control device according to the present invention will be described using embodiments. Note that, in the following embodiments, the components given the same reference numerals are the same or equivalent, and repetitive description may be omitted. The control device according to the present embodiment constitutes a homogeneous system capable of changing the homogeneous order.

  FIG. 1 is a block diagram showing a configuration of a control device 1 according to the present embodiment. The control device 1 according to the present embodiment includes a position error calculation unit 11, a scaling unit 12, a homogeneous order acquisition unit 13, a first calculation unit 14, an inverse scaling unit 15, and a speed command calculation unit 16. , A speed error calculation unit 17, a scaling unit 18, a second calculation unit 19, an inverse scaling unit 20, and a current command calculation unit 21. The second computing unit 19 includes a first exponent computing unit 19a and a second exponent computing unit 19b. Moreover, the current command calculation unit 21 includes a proportional control unit 21a, an integration control unit 21b, and an adder 21c. For example, the control device 1 uses a position detected by a position detection unit (encoder) without using a special sensor to control a drive unit (AC motor and DC motor) that drives a moving object. In addition, the control may be performed so that the starting position and speed are followed with high accuracy. The control by the control device 1 is P-PI control, and the P-PI control is a homogeneous system. That is, the control by the control device 1 according to the present embodiment is homogeneous P-PI control. For the homogeneous system, see Non-Patent Documents 1 to 3 above.

  The position error calculation unit 11 calculates a position error between the position command and the current position of the motor to be controlled. The motor to be controlled may be, for example, a motor that operates each axis of an industrial robot, a motor that feeds a welding wire, or another motor. The position error calculation unit 11 may be, for example, a subtracter that subtracts the current position of the motor from the position command. The position command may be, for example, a position command value calculated based on the taught position. The current position of the motor may be, for example, the position (angle) of the motor measured by an encoder.

  The scaling unit 12 multiplies the position error calculated by the position error calculation unit 11 by a scaling coefficient that is a positive real number. The scaling factor may be a preset value, or may be a value that is dynamically changed, as will be described later. Here, the former case will be mainly described. In the acquisition of the homogeneity order and the exponent operation described later, the result varies depending on whether or not the absolute value of the error is smaller than 1. Further, depending on the situation, the absolute value of the error may be less than 1. For example, when a position that is an integer value, such as a pulse value, is used, the position error is also an integer, and the absolute value of the error never becomes a value other than 1 other than 0. Thus, for example, the scaling factor may be set such that the maximum absolute value of error after multiplying by the scaling factor is less than 1, or many of the absolute values of error after multiplying by the scaling factor are The scaling factor may be set to be less than 1. In the latter case, for example, the maximum absolute value of the error after multiplying by the scaling factor may be 1 or more. Note that the scaling factor is preferably set so that the absolute value of the error after multiplying by the scaling factor changes in as many ranges as possible in the range of 0 to 1.

  The homogeneous order acquisition unit 13 acquires the homogeneous order (τ). The homogeneous order is a parameter that determines the homogeneity of the control device 1. Here, the case where the homogeneity order acquisition unit 13 acquires the homogeneity order using the position error multiplied by the scaling coefficient will be described, but the homogeneity order may be acquired by other methods. For example, the homogeneity order acquisition unit 13 may acquire the homogeneity order using at least one of a position error and a velocity error. The homogeneity order acquisition unit 13 may acquire the homogeneity order using, for example, at least one of a position error and a speed error and the current speed. Note that the position error and the velocity error may be independently multiplied by a scaling factor, or may not be so. The homogeneous order acquired by the homogeneous order acquisition unit 13 is used in each of the first calculation unit 14 and the first and second exponent calculation units 19a and 19b of the second calculation unit 19. . That is, when control using the homogeneous order is performed in the control device 1, control using the same homogeneous order is performed in each of the one or more arithmetic units.

Here, the relationship between the homogeneous order τ and the control in the homogeneous system will be described.
(1) Finite time settling control (τ <0)
Control by a homogeneous system in which the homogeneous order τ is negative is called finite time settling control. In the finite time settling control, it is theoretically guaranteed to converge to the target in a finite time. In addition, the finite time settling control is theoretically guaranteed to converge faster than the exponential stability control and the rational stability control. In the finite time settling control, high error convergence performance is exhibited when the error is less than 1. However, it is known that when the error is 1 or more, the error convergence performance is degraded. In a system with many disturbances, even if the input is theoretically appropriate in a region where the error is small, a large input causes performance degradation due to the influence of the disturbance.

(2) Rational stability control (τ> 0)
Control by a homogeneous system in which the homogeneous order τ is positive is called rational stability control. Since the rational stable control requires an infinitely long time to converge to the target, if the error is less than 1, the error convergence performance is degraded. On the other hand, when the error is 1 or more, high error convergence performance is exhibited. For this reason, even in a system with many disturbances, if the error is small, the input is also small compared to other control modes, so that performance degradation is unlikely to occur.

(3) Exponential stability control (τ = 0)
Control by a homogeneous system in which the homogeneous order τ is 0 is called exponential stability control. The exponential stability control is the same as the conventional control that is not a homogeneous system. For example, when τ = 0 in homogeneous P-PI control, P-PI control is performed.

For example, the homogeneity order acquisition unit 13 may acquire a homogeneity order that is 0 in a range where the absolute value of the error is smaller than the threshold value e _TH1 . Further, the homogeneity order acquisition unit 13 may acquire a homogeneity order that is less than 0 in a range where the absolute value of the error is larger than the threshold value e _{TH1 and} smaller than 1. If the absolute value of the error is equal to the threshold value e _TH1 , a homogeneous order that is 0 may be acquired. Further, the homogeneity order obtaining unit 13 may obtain a homogeneity order of 0 or greater than 0, that is, a homogeneity order of 0 or more, in a range where the absolute value of the error is 1 or more. It is assumed that the threshold value e _TH1 is a positive value smaller than 1. Further, when the homogeneity order obtaining unit 13 obtains the homogeneity order using an error, the homogeneity order corresponding to the error is obtained using a predetermined relationship between the error and the homogeneity order. May be. The relationship between the error and the homogeneous order may be a relationship between the absolute value of the error and the homogeneous order. The relationship between the two may be indicated by a function, or may be indicated by a correspondence relationship such as a table. FIG. 2 is a graph showing an example of the relationship between the absolute value of such an error and the homogeneous order. In FIG. 2, when the absolute value of the error is x, the homogeneous order τ is as follows. Note that a is a negative real number.
τ = 0 (0 ≦ x ≦ e _TH1 )
τ = a (x−e _TH1 ) ² (2x + e _TH1 −3e _TH2 ) / (e _TH1 −e _TH2 ) ³ (e _TH1 <x <e _TH2 )
τ = a (e _TH2 ≦ x <1)
τ = 0 (x ≧ 1)

  As shown in the graph of FIG. 2, it is preferable that the homogeneous order τ that changes in accordance with the absolute value of the error continuously changes in places where the absolute value of the error is other than 1. By doing so, the three control modes of finite time settling control, rational stability control, and exponential stability control are continuously connected and changed. Note that when the absolute value of the error is 1, the result of exponential calculation, which will be described later, is the same as the error to be calculated, so that even if the homogeneous order τ is discontinuous, the control is not discontinuous. Absent. As described above, when the homogeneity order is discontinuous at a position where the absolute value of the error is 1, it is preferable that the homogeneity order is 0 at the discontinuous position. By doing so, exponential stability control is performed at locations where the homogeneous orders are discontinuous, and the calculation results by the first and second calculation units 14 and 19 are continuous. Further, at a place where the absolute value of the error is other than 1, the homogeneous order τ may be a smooth function with respect to the absolute value of the error. Further, in the range where the absolute value of the error is 1 or more, as described above, the homogeneous order may be a positive value. Therefore, for example, in the range where the absolute value of the error is 1 or more, the homogeneous order may change as indicated by the broken line in the graph of FIG.

The first computing unit 14 performs exponential computation on the position error according to the homogeneous order so as to achieve homogeneous control. The position error is a position error multiplied by the scaling coefficient by the scaling unit 12. It should be noted that performing the exponent operation so as to achieve homogeneous control means performing the exponent operation so that the control device 1 becomes a homogeneous system. The exponent operation is to raise to the power of r while maintaining the sign of the operation target. That is, the following equation is calculated. This also applies to other exponent operations. Note that r is a function of the homogeneous order τ. Therefore, the value of r is determined according to the homogeneous order τ acquired by the homogeneous order acquisition unit 13. The first calculation unit 14 calculates an index r using the value of τ acquired by the homogeneous order acquisition unit 13 and a function of the homogeneous order τ, and performs an exponent operation using the calculated r. Also good. The function of τ will be described later.
| Computation Target | ^r xsgn (Computation Target)

Here, sgn (z) is the following sign function.
sgn (z) = 1 (z> 0)
sgn (z) = 0 (z = 0)
sgn (z) =-1 (z <0)

  As can be seen from the above equation, the absolute value of the calculation result increases or decreases with respect to the absolute value of the calculation target with the absolute value of the error being the calculation target = 1. Will be switched. For example, when r> 1, the absolute value of the calculation result is smaller than the absolute value of the calculation target in a range where the absolute value of the calculation target is smaller than 1, and in the range where the absolute value of the calculation target is larger than 1, The absolute value of the calculation result is larger than the absolute value of the calculation target. Therefore, the range of the calculation target is determined by the unit system of error (for example, meter, centimeter, radian (rad), degree (deg), meter / second, centimeter / second, radian / second, degree / second, etc.) In other words, when the error is directly subject to calculation, appropriate control may not be possible. Specifically, when the encoder pulse value is used as a value indicating the angle of the motor, the absolute value of the error does not take a value smaller than 1 other than 0. Therefore, as described above, it is preferable to scale the error scale to an appropriate range (for example, a range of 1 or less) by multiplying by a scaling factor.

  The inverse scaling unit 15 multiplies the calculation result by the first calculation unit 14 by the inverse number of the scaling coefficient. That is, the calculation result by the first calculation unit 14 is divided by the scaling coefficient. The scaling coefficient is the same as the scaling coefficient used in the scaling unit 12.

  The speed command calculation unit 16 calculates a speed command by performing proportional control on the calculation result of the first calculation unit 14. The calculation result is a calculation result obtained by multiplying the inverse of the scaling coefficient by the inverse scaling unit 15. The proportional control may be performed by multiplying the calculation result by a proportional gain. The result of the proportional control becomes the speed command value.

  The speed error calculation unit 17 calculates a speed error between the speed command calculated by the speed command calculation unit 16 and the current speed of the motor. The motor is the same motor as the motor from which the current position is acquired. The speed error calculation unit 17 may be, for example, a subtracter that subtracts the current speed of the motor from the speed command. The current speed of the motor may be, for example, a speed (angular speed) obtained by time-differentiating the position of the motor measured by the encoder.

  The scaling unit 18 multiplies the speed error calculated by the speed error calculation unit 17 by a scaling factor that is a positive real number. The scaling factor may be a preset value, or may be a value that is dynamically changed, as will be described later. Here, the former case will be mainly described. The reason for multiplying the speed error by the scaling factor and the setting of the scaling factor are the same as the description of the scaling unit 12 except that the scaling factor is to be multiplied. Note that the scaling factor used by the scaling unit 18 may be the same as or different from the scaling factor used by the scaling unit 12. Usually, the scaling coefficient is set independently in each of the scaling units 12 and 18. The scaling unit 18 passes the result obtained by multiplying the speed error by the scaling coefficient to each of the first and second exponent operation units 19a and 19b. Therefore, for example, the scaling unit 18 may perform one multiplication process and pass the result to the first and second exponent operation units 19a and 19b, respectively, or the first and second exponents. Multiplication processing may be performed for each of the arithmetic units 19a and 19b.

The second computing unit 19 performs exponential computation according to the homogeneity order for the speed error so as to achieve homogeneous control. Since the exponent calculation is performed in the first and second exponent calculation units 19a and 19b, the first and second exponent calculation units 19a and 19b respectively perform exponent calculations according to the homogeneous orders for the speed errors. Do. The speed error is a speed error multiplied by the scaling coefficient by the scaling unit 18. The exponent calculation by the first and second exponent calculation units 19a and 19b is the same as the exponent calculation by the first calculation unit 14. Here, the index r used in the exponent calculation will be described. In order for the control device 1 to be a homogeneous system, the exponents used in the first arithmetic unit 14 and the first and second exponent arithmetic units 19a and 19b cannot be arbitrarily taken. Specifically, in the case of P-PI control, the operation is as follows. R ₁ can be arbitrarily set in a range where each r is larger than 0. For example, r ₁ = 1 may be set. Further, the range of τ is limited in order to make each r positive according to the determination of r ₁ .
First computing unit 14: r = (r ₁ + τ) / r ₁
First exponent operation unit 19a: r = (r ₁ + 2τ) / (r ₁ + τ)
Second exponent operation unit 19b: r = (r ₁ + 3τ) / (r ₁ + τ)

  The inverse scaling unit 20 multiplies the calculation result by the second calculation unit 19 by the inverse number of the scaling coefficient. That is, the inverse scaling unit 20 multiplies each of the calculation results by the first and second exponent operation units 19a and 19b by the inverse of the scaling coefficient. The scaling coefficient is the same as the scaling coefficient used in the scaling unit 18. Note that the homogeneity is not lost even if the scaling factor multiplication and the inverse scaling factor multiplication are performed before and after the exponent operation on the error. Therefore, when the exponent operation according to the acquired homogeneous order is performed so that the first and second arithmetic units 14 and 19 perform the homogeneous control, the scaling units 12 and 18 and the inverse scaling unit The control device 1 having 15 and 20 is also a homogeneous system.

  The current command calculation unit 21 calculates a current command from the calculation result of the second calculation unit 19, that is, the calculation result of the first and second exponent calculation units 19a and 19b. Specifically, the proportional control (proportional operation) is performed on the calculation result by the first exponent calculation unit 19a by the proportional control unit 21a, and the integration control unit 21b performs integration control on the calculation result by the second exponent calculation unit 19b. Integration operation) is performed, and the result of the proportional control and the result of the integration control are added by the adder 21c, whereby the current command value is calculated. Note that the calculation results by the first and second exponent calculation units 19 a and 19 b are calculation results obtained by multiplying the inverse of the scaling coefficient by the inverse scaling unit 20. Here, the operation result obtained by multiplying the operation result of the first exponent operation unit 19a by the reciprocal of the scaling coefficient is the target of proportional control, and the operation result of the second exponent operation unit 19b is multiplied by the reciprocal of the scaling coefficient. It is assumed that the calculated result is the target of integration control. The proportional control may be performed by multiplying the calculation result by a proportional gain. Further, the integral control may be performed by multiplying the integral value of the calculation result by an integral gain.

Here, the relationship between the error and the result of the exponent operation will be described with reference to FIG. In the graph of FIG. 3, the relationship between the absolute value of the error and the absolute value of the exponent operation is shown by a thick solid line corresponding to the case where the relationship between the absolute value of the error and the homogeneous order is shown in FIG. Yes. Further, in the graph of FIG. 3, the relationship between the absolute value of the error and the absolute value of the exponent operation result corresponding to the case where the homogeneity order is a negative fixed value, that is, the case of finite time settling control, is one point. Shown with a chain line. In the case of the conventional P-PI control that is not a homogeneous system, the exponent calculation is not performed, so the error and the value corresponding to the calculation result are equal. In the graph of FIG. 2, since the absolute value of the error is τ = 0 in the range where the absolute value of the error is less than or equal to the threshold value e _TH1 and in the range of 1 or more, the result of the exponent operation is the same as in the P-PI control. Further, since τ <0 in the range where the absolute value of the error is larger than the threshold value e _{TH1 and} less than 1, the result of the exponent operation is larger than that in the P-PI control. As a result, it converges faster within that range. Thus, in the minute range where the error is close to 0, it becomes the same as the P-PI control, and the increase in vibration in the stopped state can be suppressed more than the finite time settling control (τ <0). On the other hand, when the error exceeds the threshold value e _TH1 , the tracking error can be controlled so as not to increase. Further, when the error is in the range of 1 or more, it becomes the same as the P-PI control, so that the convergence is faster than the finite time settling control (τ <0). In the range where the absolute value of the error is greater than 1, the absolute value of the calculation result corresponding to the case where the homogeneous degree (τ) is set to a value greater than 0 (in the case of the broken line in FIG. 2) is shown in FIG. -It exists above the PI control. Therefore, in that case, the convergence performance can be improved over the P-PI control in the range where the absolute value of the error is larger than 1. As described above, the control device 1 according to the present embodiment has a problem in the finite-time settling homogeneous P-PI control. In this case, it is possible to avoid the deterioration of the follow-up performance. As a result, for example, when performing a high-speed movement such as an operation of moving the hand position of the robot from one position to another at the highest speed, that is, when the error can be large, on the contrary, a certain limited range In the case where a fine movement is performed at a high speed, that is, even when the error can be reduced, more accurate control can be realized. Thus, according to the control device 1, highly accurate and stable control can be realized in a wider range requiring the follow-up control.

Next, operation | movement of the control apparatus 1 is demonstrated using the flowchart of FIG.
(Step S101) The position error calculation unit 11 calculates a difference between the position command and the current position of the motor, and outputs a position error that is a subtraction result.

  (Step S102) The scaling unit 12 multiplies the position error by a scaling coefficient.

  (Step S103) The homogeneous order obtaining unit 13 obtains a homogeneous order corresponding to the position error multiplied by the scaling coefficient.

  (Step S <b> 104) The first calculation unit 14 performs exponential calculation according to the homogeneous order acquired in Step S <b> 103 on the position error multiplied by the scaling coefficient.

  (Step S105) The inverse scaling unit 15 multiplies the result of the exponent operation by the inverse of the scaling coefficient.

  (Step S106) The speed command calculation unit 16 calculates a speed command using a calculation result obtained by multiplying the inverse of the scaling coefficient.

  (Step S107) The speed error calculation unit 17 calculates a difference between the calculated speed command and the current speed of the motor, and outputs a speed error that is a subtraction result thereof.

  (Step S108) The scaling unit 18 multiplies the speed error by a scaling coefficient. The scaling unit 18 outputs the multiplication result to each of the first and second exponent operation units 19a and 19b.

  (Step S109) The first exponent computing unit 19a of the second computing unit 19 performs exponential computation according to the homogeneity obtained in step S103 on the speed error multiplied by the scaling coefficient. In addition, the second exponent calculation unit 19b of the second calculation unit 19 performs exponent calculation according to the homogeneous order acquired in step S103 on the speed error multiplied by the scaling coefficient.

  (Step S <b> 110) The inverse scaling unit 20 multiplies the result of the exponent operation by the first exponent operation unit 19 a by the inverse number of the scaling coefficient, and outputs the result to the proportional control unit 21 a of the current command calculation unit 21. The inverse scaling unit 20 multiplies the result of the exponent operation by the second exponent operation unit 19b by the inverse of the scaling coefficient and outputs the result to the integration control unit 21b of the current command calculation unit 21.

(Step S <b> 111) The proportional control unit 21 a of the current command calculation unit 21 performs proportional control on the calculation result obtained by multiplying the inverse of the scaling coefficient by the inverse scaling unit 20. The integration control unit 21 b of the current command calculation unit 21 performs integration control on the calculation result obtained by multiplying the inverse of the scaling coefficient by the inverse scaling unit 20. Further, the adder 21c of the current command calculation unit 21 adds the result of the proportional control and the result of the integration control, and outputs a current command that is the addition result.
Note that a series of processing shown in the flowchart of FIG. 4 is repeated to control the motor to be controlled.

  Next, experimental results using the control device 1 according to the present embodiment will be described. In this experiment, the hand of a robot having a vertical 6-axis manipulator was moved in an arc. And the control apparatus 1 by this Embodiment was compared with the control apparatus which performs the conventional P-PI control about three motors near the installation part of a robot. In this experiment, the same control gain is used in the proportional control and the integral control in the control according to the present embodiment and the conventional P-PI control. In addition, the scaling coefficient was set so that a value slightly larger than the maximum value of the position error and the speed error becomes 1 using the result of performing the same operation by P-PI control in advance. FIG. 5A to FIG. 5C are graphs showing temporal changes in angle tracking errors with respect to the J1 axis to the J3 axis in this experiment, respectively. In each figure, “P-PI control” is a graph showing the result of conventional P-PI control, and “homogeneous P-PI control” shows the result of control of the control device 1 in the present embodiment. It is a graph. The graph shows values after multiplication by a scaling coefficient. From the graphs of FIG. 5, it can be seen that the control error by the control device 1 is generally improved over the conventional P-PI control. It can also be seen that the error convergence time is also shortened.

In the following table, the maximum absolute value of the error in the control by the control device 1, the maximum absolute value of the error in the conventional P-PI control, and the error reduction rate for the J1 axis to the J3 axis are shown. Yes. From the table, it can be seen that the angle tracking error can be reduced by up to 51%. Further, since the error reduction rate of the J3 axis having the largest error is the largest, it can be seen that the error can be reduced more effectively as the error after multiplication of the scaling coefficient is larger.

As described above, according to the control device 1 according to the present embodiment, in the control device 1 that performs the homogeneous control in the classical control system, more appropriate control is realized by changing the homogeneous order according to the error. Will be able to. Specifically, in the range where the error is smaller than the threshold value e _TH1 , the increase in vibration in the stopped state can be suppressed as compared with the finite time settling control by making the homogeneity order 0. In addition, in the range where the error is 1 or more, by setting the homogeneity degree to 0, convergence can be improved as compared with the finite time settling control. Further, in the range where the error is 1 or more, the convergence degree can be improved as compared with the finite time settling control or the conventional P-PI control by making the homogeneous order larger than 0. Further, in the range where the error is larger than the threshold value e _{TH1 and} smaller than 1, the convergence degree can be improved as compared with the conventional P-PI control by making the homogeneous order negative. In addition, the finite time settling control, rational stability control, and exponential stability control are continuously switched by making the relationship between the absolute value of the error and the homogeneous order τ continuous in the range where the error absolute value is other than 1. Therefore, it is possible to suppress vibration that may occur when switching the control mode. Further, when the relationship between the absolute value of the error and the homogeneous degree τ is continuous and smooth in the range where the absolute value of the error is not 1, the control mode can be switched more smoothly. . Conventionally, for example, when switching the control gain discontinuously between a precise operation and a high-speed operation, vibration may occur at the time of switching, so it was necessary to perform the switching at a low-speed operation. In the case of the control device 1, the occurrence of such vibration can be suppressed as described above. Further, since the vibration at the time of switching the control mode can be suppressed as described above, the control gain can be set to a large value. As described above, when the control gain is set to a large value, the operation can be performed at a higher speed and the tact time can be reduced. Also, depending on the control system, the control performance deteriorates due to changes in physical parameters due to changes over time, so that maintenance for changing the control parameters is required. On the other hand, by performing control so that the tracking error does not easily increase as in the control device 1, it is possible to extend the period until the maintenance is required.

In the present embodiment, the case where the homogeneity order obtaining unit 13 obtains the homogeneity order based on the position error multiplied by the scaling coefficient has been described. However, as described above, this need not be the case. It is. For example, the homogeneity order acquisition unit 13 may acquire the homogeneity order based on the speed error multiplied by the scaling factor, and the position error multiplied by the scaling factor, the speed error multiplied by the scaling factor, The homogeneity order may be acquired based on both. In that case, for example, the homogeneous order τ may be determined as follows. However, the absolute value of the position error is x, and the absolute value of the speed error is y. The threshold value e _{TH1_1} is a threshold value of the position error corresponding to the threshold value e _TH1 , and the threshold value e _{TH1_2} is a threshold value of the speed error corresponding to the threshold value e _TH1 , both of which are smaller than 1.
τ = 0 (0 ≦ x ≦ e _{TH1_1} or 0 ≦ y ≦ e _{TH1_2} )
τ <0 (e _{TH1_1} <x <1 and e _{TH1_2} <y <1)
τ ≧ 0 (x ≧ 1 and y> e _{TH1_2} , or y ≧ 1 and x> e _{TH1_1} )
In this case as well, it is preferable that the homogeneous order τ continuously changes in places other than x = 1 or y = 1. In the place where x = 1 or y = 1, the homogeneous order τ may not be continuous, but in that case, as described above, the homogeneous order τ is preferably 0 in a non-continuous place. It is.

  Moreover, although this Embodiment demonstrated the case where the scaling factor used in the scaling parts 12 and 18 and the inverse scaling parts 15 and 20 was decided beforehand, it may not be so. For example, as illustrated in FIG. 6, the control device 1 may further include a changing unit 22 that changes the scaling coefficient. The changing unit 22 changes the scaling coefficient used in the scaling unit 12 and the inverse scaling unit 15 and the scaling coefficient used in the scaling unit 18 and the inverse scaling unit 20. When the scaling coefficients used in the scaling units 12 and 18 and the inverse scaling units 15 and 20 are the same, the changing unit 22 may change one scaling coefficient. The change may be made according to the current speed, for example. For example, when the absolute value of the current speed is large, the changing unit 22 changes so that the scaling factor becomes smaller, and when the absolute value of the current speed is small, the changing unit 22 changes so as to become a larger scaling coefficient. May be performed. The change may be made according to a history of errors multiplied by a scaling factor. For example, when the situation where the absolute value of the error multiplied by the scaling factor is smaller than a predetermined threshold (<< 1) continues, the changing unit 22 changes the scaling factor to be large, When the situation where the absolute value of the error multiplied by the scaling factor is larger than a predetermined threshold (> 1) continues, the scaling factor may be changed to be small. The increase or decrease of the scaling factor may be performed, for example, by multiplying the current scaling factor by a predetermined value or by adding / subtracting.

  Further, in the present embodiment, a case has been described in which homogeneous control for changing the homogeneous order is performed in P-PI control. However, control other than P-PI control, for example, P-PID control, Needless to say, in the P control, the PI control, the PID control, etc., the homogeneous control for changing the homogeneous order may be performed. Even in such a case, it is assumed that an exponent operation according to the same order is performed on the calculated error before the P control, the PI control, the PID control, and the like. The exponent operation is performed to achieve homogeneous control. In addition, before and after the exponent operation, multiplication of the scaling coefficient and multiplication of the inverse of the scaling coefficient may be performed. In addition, the homogeneous order used to determine the exponent of the exponent operation may be calculated from the error multiplied by the scaling factor. FIG. 7 is a block diagram showing an example of such a control device 3. The control device 3 includes an error calculation unit 31, a scaling unit 32, a homogeneous order acquisition unit 33, a calculation unit 34, an inverse scaling unit 35, and a command value calculation unit 36.

  The error calculation unit 31 calculates an error between the upper command value to be controlled and the current value to be controlled. The higher order command value and the current value may be, for example, a position, a speed, or other values. The higher order command value may be calculated based on, for example, teaching information, or may be a command value calculated by a higher order command value calculation unit. The error calculation unit 31 corresponds to, for example, the position error calculation unit 11 and the speed error calculation unit 17.

  The scaling unit 32 multiplies the error by a scaling coefficient that is a positive real number. The scaling unit 32 corresponds to, for example, the scaling units 12 and 18.

  The homogeneous order acquisition unit 33 acquires the homogeneous order. For example, the homogeneity order acquisition unit 33 acquires the homogeneity order using at least one of the error corresponding to the upper command value, that is, the error calculated by the error calculation unit 31 and the error corresponding to the lower command value. Alternatively, the same order may be obtained using other errors. The error may be an error multiplied by a scaling factor. FIG. 7 shows a case where the homogeneity order is obtained using a result obtained by multiplying the error corresponding to the upper command value by the scaling coefficient. As described above, the acquisition of the homogeneous order is τ = 0 when the absolute value of the error is smaller than the threshold (<1), and τ ≧ 0 when the absolute value of the error is larger than 1, so that the absolute error When the value is in the range between them, it is preferable to obtain such that τ <0. Further, it is preferable that the homogeneous order is continuous at a place where the absolute value of the error is other than 1. It should be noted that the homogeneous order τ does not have to be continuous at a location where the absolute value of the error is 1, but in that case, the homogeneous order τ may be 0 at a location that is not continuous as described above. Is preferred. Further, the homogeneity order acquisition unit 33 may acquire the homogeneity order using the current value (for example, the current speed) of the control target. The homogeneous order acquisition unit 33 corresponds to, for example, the homogeneous order acquisition unit 13.

  The computing unit 34 performs exponential computation according to the homogeneity order on the error so as to achieve homogeneous control. The error may be an error obtained by multiplying the scaling coefficient by the scaling unit 32. The exponent operation is as described above, and is to be raised to the power of r while maintaining the sign of the operation target. As described above, the index r is a function of the homogeneous order τ, so that the control device 3 becomes a homogeneous system, or the control system including the control device 3 becomes a homogeneous system. Suppose that the function is determined. Therefore, homogeneous control is realized by performing exponential computation using the exponent r determined according to the acquired τ. The calculation unit 34 corresponds to, for example, the first calculation unit 14 or the second calculation unit 19. Accordingly, two or more calculations may be performed in the calculation unit 34 as in the second calculation unit 19.

  The inverse scaling unit 35 multiplies the calculation result by the calculation unit 34 by the inverse number of the scaling coefficient. The scaling factor is the same as the scaling factor used in the scaling unit 32. The inverse scaling unit 35 corresponds to, for example, the inverse scaling units 15 and 20. Therefore, in the inverse scaling unit 35, similarly to the inverse scaling unit 20, each of two or more calculation results may be multiplied by the inverse of the scaling coefficient.

  The command value calculation unit 36 calculates a lower command value from the calculation result obtained by the calculation unit 34. The calculation result may be a calculation result obtained by multiplying the inverse of the scaling coefficient. The calculation of the lower order command value may be performed by, for example, P control, PI control, PID control, or other control. As a method for calculating the lower order command value according to the error of the upper order command value, a known method can be used. The lower order command value may be used for controlling the control target, and may be used for generating a lower order command value. The command value calculation unit 36 corresponds to, for example, the speed command calculation unit 16 or the current command calculation unit 21. Accordingly, the command value calculation unit 36 may calculate the lower command value using two or more calculation results, as in the current command calculation unit 21.

  Note that the control target of the control device 3 may be a motor or another control target. That is, the control by the control device 3 may be servo control, process control, or other control. When the control is servo control, the motor to be controlled may be used in, for example, an industrial robot or a welding apparatus, or may be used in another apparatus or the like. When the control performed by the control device 3 is process control, the control target may be, for example, a power generation amount of a plant. In this case, for example, the upper command value may be the amount of power generated by the plant, and the lower command value may be the gas pressure of the fuel of the gas turbine.

  In addition, for example, another control loop may exist inside the control loop corresponding to the control device 3, or another control loop may exist outside the control loop corresponding to the control device 3. Good. In such a case, the entire control system may be a homogeneous system, or only the control device 3 may be a homogeneous system.

  Moreover, the control apparatus 3 may be provided with the change part which changes the scaling factor which the scaling part 32 and the inverse scaling part 35 use based on the present value regarding a control object. Note that the current value related to the control target used for changing the scaling coefficient may be the current value used in the error calculation by the error calculation unit 31, or may be another current value. For example, when the current value used in the error calculation by the error calculation unit 31 is the current position of the motor, the changing unit may change the scaling coefficient based on the current position of the motor, or the current value of the motor The scaling factor may be changed based on the speed.

  In the present embodiment, the case where the multiplication of the scaling coefficient and the multiplication of the reciprocal of the scaling coefficient are performed before and after the exponent operation, respectively, is not necessary. For example, if the error range is appropriate without performing multiplication of the scaling factor, multiplication of the scaling factor or the like may not be performed. In the case where the multiplication of the scaling coefficient is not performed, for example, the control device 1 may not include the scaling units 12 and 18 and the inverse scaling units 15 and 20, and the control device 3 includes the scaling unit 32, and The inverse scaling unit 35 may not be provided.

  In the above embodiment, each process or each function may be realized by centralized processing by a single device or a single system, or may be distributedly processed by a plurality of devices or a plurality of systems. It may be realized by doing.

  In the above embodiment, the information exchange between the components is performed by one component when, for example, the two components that exchange the information are physically different from each other. It may be performed by outputting information and receiving information by the other component, or when two components that exchange information are physically the same, one component May be performed by moving from the phase of the process corresponding to to the phase of the process corresponding to the other component.

  In the above embodiment, information related to processing executed by each component, for example, information received, acquired, selected, generated, transmitted, or received by each component In addition, information such as threshold values and mathematical formulas used by each constituent element in processing may be temporarily or over a long period of time in a recording medium (not shown), even if not specified in the above description. Further, the storage of information on the recording medium (not shown) may be performed by each component or a storage unit (not shown). Further, reading of information from the recording medium (not shown) may be performed by each component or a reading unit (not shown).

  Also, in the above embodiment, when the information used by each component etc., for example, information such as the threshold used by each component in the process, various setting values, etc. may be changed by the user, Even if not specified, the user may be able to change the information as appropriate, or may not be so. If the information can be changed by the user, the change is realized by, for example, a not-shown receiving unit that receives a change instruction from the user and a changing unit (not shown) that changes the information in accordance with the change instruction. May be. The change instruction received by the receiving unit (not shown) may be received from an input device, information received via a communication line, or information read from a predetermined recording medium, for example. .

  In the above-described embodiment, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component can be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. At the time of execution, the program execution unit may execute the program while accessing the storage unit or the recording medium. The program may be executed by being downloaded from a server or the like, or may be executed by reading a program recorded on a predetermined recording medium (for example, an optical disk, a magnetic disk, a semiconductor memory, or the like). Good. Further, this program may be used as a program constituting a program product. Further, the computer that executes the program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed.

  Further, the present invention is not limited to the above-described embodiment, and various modifications are possible, and it goes without saying that these are also included in the scope of the present invention.

  As described above, according to the control device of the present invention, it is possible to obtain an effect that more accurate control can be realized.

DESCRIPTION OF SYMBOLS 1, 3 Control apparatus 11 Position error calculation part 12, 18, 32 Scaling part 13, 33 Homogeneous degree acquisition part 14 1st calculating part 15, 20, 35 Inverse scaling part 16 Speed command calculation part 17 Speed error calculation part 19 Second calculation unit 19a First exponent calculation unit 19b Second exponent calculation unit 21 Current command calculation unit 21a Proportional control unit 21b Integration control unit 21c Adder 22 Change unit 31 Error calculation unit 34 Calculation unit 36 Command value calculation unit

Claims (9)

An error calculation unit for calculating an error between the upper command value and the current value of the control target;
A homogeneous order acquisition unit for acquiring a homogeneous order;
An arithmetic unit that performs exponential operation according to the homogeneity order for error so as to be homogeneous control;
And a command value calculation unit that calculates a lower command value from a calculation result of the calculation unit. A scaling unit that multiplies the error by a scaling factor that is a positive real number;
An inverse scaling unit that multiplies the operation result of the operation unit by the inverse of the scaling coefficient, and
The arithmetic unit performs an exponential operation on the error multiplied by the scaling factor,
The control device according to claim 1, wherein the command value calculation unit calculates a lower command value from a calculation result obtained by multiplying a reciprocal of the scaling coefficient. The control device according to claim 2, further comprising: a changing unit that changes the scaling coefficient used by the scaling unit and the inverse scaling unit based on a current value related to the control target. 4. The control device according to claim 2, wherein the homogeneous order acquisition unit acquires the homogeneous order based on an error multiplied by the scaling coefficient. 5. The control device according to claim 1, wherein the homogeneous order acquisition unit acquires a homogeneous order that is 0 in a range where an absolute value of an error is smaller than a threshold smaller than 1. 5. The control device according to claim 5, wherein the homogeneous order obtaining unit obtains a homogeneous order that is less than 0 in a range in which an absolute value of an error is larger than the threshold and smaller than 1. The control device according to any one of claims 1 to 6, wherein the homogeneity order obtaining unit obtains a homogeneity order that is 0 or more in a range where the absolute value of the error is 1 or more. The control device according to claim 1, wherein the control target is a motor. A position error calculation unit that calculates a position error between the position command and the current position of the motor to be controlled;
A homogeneous order acquisition unit for acquiring a homogeneous order;
A first calculation unit that performs exponential calculation according to the homogeneous degree for the position error so as to achieve homogeneous control;
A speed command calculation unit that calculates a speed command by performing proportional control on a calculation result by the first calculation unit;
A speed error calculator that calculates a speed error between the speed command and the current speed of the motor;
A second computing unit that performs exponential computation according to the homogeneous order for the speed error so as to achieve homogeneous control;
A current command calculation unit that calculates a current command from a calculation result by the second calculation unit,
The homogeneous order acquisition unit acquires the homogeneous order using at least one of a position error and a velocity error,
The second computing unit includes first and second exponent computing units that perform exponential operations according to the homogeneous orders, respectively, for speed errors,
The current command calculation unit is a control device that performs proportional control on a calculation result of the first exponent calculation unit and performs integral control on a calculation result of the second exponent calculation unit.

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