JPH0738127B2 - Robust controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device that controls a controlled variable of a controlled object to a predetermined value, and more particularly to a robust control device that suppresses fluctuation occurring in the controlled object as a disturbance. Is.

[Prior art and its problems]

(Prior Art) Conventionally, a control device used in a field related to FA, such as an articulated robot arm, requires a control device for controlling each motor provided at each joint of the arm. However, various parameters such as the moment of inertia change depending on the weight and rotation speed of the object gripped at the tip of the arm. In addition to this, nonlinear torque disturbance during motor control is added. Then, in order to eliminate the interference of each joint of the robot arm, it is necessary to reduce the sensitivity to the fluctuation of the parameter and the disturbance. Conventionally, in order to control such a controlled object, a method of deriving a controlled variable based on a mechanical system equation of each joint and performing feedforward compensation has been used.

(Problems to be Solved by the Invention) However, according to such a feedforward control, the fluctuation of the parameters must be completely expressed by the mechanical system equation. As a result, the system configuration becomes extremely complicated, and it takes time to perform the compensating operation due to the time delay of each system, etc., and there is a problem that the followability to changes is poor.

[Object of the Invention]

The present invention is a control device for such a complicated controlled object, and a compensating means for inputting a manipulated variable by inputting a deviation between a controlled object model and a controlled variable of an actual controlled object into a high frequency region differential compensation element It is a technical subject to suppress the influence of parameter fluctuations and disturbances by adding it to the device and to enable control with a fast response speed.

[Constitution and effect of the invention]

(Means for Solving Problems) The present invention is a control device for controlling a controlled variable of a controlled object to a predetermined value. As shown in FIG. 1, the controlled variable and the controlled target value obtained from the controlled object 1 are controlled. And a first adding means 3 for adding the operation amount generated by the control unit and the steady-state deviation compensation operation amount.
The model 4 of the controlled object, which has the same transfer function as the controlled object and to which the addition operation amount of the first addition means is given, and the deviation of the controlled variable obtained when the operation amount is given to the controlled object and the model. The deviation detecting means 5 has a transfer function represented by the product of the deviation detecting means 5 for detecting and the inverse system of the transfer function indicating the model and the high-frequency cutoff filter of the first-order lag system, that is, 1 / F (s). A high-frequency differential compensation element 6 that gives a compensation operation amount obtained by giving the detected deviation to the first adding means, and a compensation operation amount obtained from the high-frequency differential compensation element are amplified to reduce the influence of disturbance. The amplifying unit 7 for converting into a signal, the second addition unit 8 for adding the operation amount of the first adding unit and the compensation operation amount given by the amplifying unit to give the output to the control target, and the control amount of the control target are detected. And control unit and deviation detection Controlled variable-detecting means provided to the stage 9
And are provided.

(Operation) According to the present invention having such a feature, the control amount obtained from the controlled object and the target value are given to the control unit which has been conventionally used to obtain the operation amount, and the operation amount is subjected to the deviation operation. In addition to the amount, the operation amount is given to the model of the controlled object in addition to the first adder. Then, the deviation between the control amount obtained from the model and the control amount obtained from the controlled object is detected, and the compensation operation amount is obtained in addition to the high-frequency differential compensation element. Further, the compensation operation amount is given to the first adding means, amplified and given to the second adding means, and the outputs of the first adding means are added and given to the controlled object.

In this way, when deviations in the control amount occur due to parameter fluctuations and disturbances that occur in the controlled object, such as fluctuations in the load and moment of inertia, etc., those effects are adjusted according to the amplification factor by the compensation operation amount amplified by the amplification means. The sensitivity can be lowered, and the compensation operation amount is added to the control target so as to suppress the deviation of the remaining control amount by adding the compensation operation amount to the first adding means.

(Effect of the invention) Therefore, according to the present invention, various control devices that are conventionally used to match the control amount with the target value, such as PI control device and PID control device, are used as they are. The output is added to the model of the controlled object, and the amount of compensation operation is added to the model of the controlled object to give it to the controlled object.
Therefore, the output fluctuation can be reduced and the output deviation can be canceled even when the controlled object has a parameter fluctuation or a disturbance. Therefore, it is possible to configure a control device that is not easily affected by parameter fluctuations and disturbances in a steady state and a transient state. Therefore, even if the control target is a multi-joint type robot arm and there is interference between the joints, the fluctuation can be suppressed for each joint. Therefore, each joint can be treated as a non-interference system and each motor can be independently controlled. Furthermore, since the model to be controlled, the high frequency differential compensation element, etc. can be configured with a relatively simple electronic circuit, there is almost no time delay, and the excellent effect that control with high response speed can be realized is obtained. .

[Explanation of Examples]

FIG. 2 is a block diagram showing the configuration of the robust control device of the present invention. In this figure, the same parts as those in FIG. 1 are designated by the same reference numerals. Now, the controlled object 1 is, for example, a motor,
The transfer function is P (s). The control amount Y (s), which is the rotation speed signal obtained from the controlled object 1, is given to the control unit 2 together with the target value W (s) of the rotation speed. Control unit 2
Is a normal control device that controls the controlled variable Y (s) to match the target value W (s). The manipulated variable U (s) obtained from the control unit 2 is the first addition means 3, that is, the addition point 11
Given to. The addition output is given to the second addition means 8, that is, the addition point 12, and the model 4 of the controlled object 1 is further added.
Given to. Here, P which is the transfer function of the controlled object 1
The model 4 of the controlled object 1 is configured by an electronic circuit so as to have the nominal transfer function of (s), and its transfer function is P _m (s). Since the manipulated variable U (s) is added to the model 4 from the addition point 11, the control amount obtained as its output is in principle the same as the control amount Y (s) obtained from the controlled object 1. . Then, these control amounts are added to the addition point 13 which is the deviation detecting means 5. The addition point 13 gives the deviation of these control amounts to the high frequency differential compensation element 6. The high-frequency differential compensation element 6 is the product of the inverse system of P _m (s) of the model 4, that is, the inverse system represented by the transfer function P _m ^-1 (s), and the high-frequency cutoff filter, 1 / F (s). ^Is an element having a transfer function P _m ⁻¹ (s) / F (s) represented by The output of the high-frequency differential compensation element 6 is added to the amplification means 7 as a compensation operation amount. The amplifying means 7 is an amplifier having a compensation gain β, the output of which is applied to the second summing point 12. Here, the loop given from the high-frequency differential compensation element 6 to the second addition point 12 via the amplifying means 7 constitutes a low-sensitivity compensation loop A for reducing the sensitivity of the influence of parameter fluctuation and disturbance. The output of the high frequency differential compensation element 6 is given to the first addition point 11 as it is. The addition point 11 is for adding the operation amount U (s) and the compensation operation amount. The loop from the high frequency differential compensation element 6 to the first addition point 11 constitutes a complete suppression loop B that completely suppresses the deviation due to the parameter fluctuation and the disturbance remaining after the sensitivity reduction. The compensation operation output of the high-frequency differential compensation element 6 is given to the second addition point 12 and the model 4 to be controlled. The second addition point 12 is the compensation operation amount with the reduced sensitivity and the first addition point.
The operation amount U (s) obtained from 11 is added, and its output is given to the addition point 14. The addition point 14 indicates the disturbance D (s) applied to the controlled object 1 as an addition point on the block diagram.

Next, FIG. 3 is a circuit diagram showing an embodiment in which the control device shown in the block diagram of FIG. 2 according to the present invention is constituted by an analog circuit. In the figure, the controlled object 1 is, for example, a motor 21 of a robot arm, and a control amount obtained by the motor 21, for example, a rotation speed is detected by a speed detector 22. The output of the speed detector 22 is given to the non-inverting input terminal of the operational amplifier 23 which is the deviation detecting means 5. This motor 21
Is assumed to have a transfer function k / (1 + τ ₀ s) represented by, for example, a first-order delay system, and the operational amplifier 24
The circuit realized by is a circuit showing the first-order lag system model 4. Then, the output of the operational amplifier 24 is given to the inverting input terminal of the operational amplifier 23 which constitutes the subtractor. The output of the subtractor 23 is given to the input terminals of the operational amplifiers 25 and 26. The circuit constituted by the operational amplifiers 25, 26 and 27 is a circuit that realizes the high frequency differential compensation element 6 having the transfer function represented by the product of the inverse system of the model and the reciprocal of the filter, the output of which is the amplifying section. 7 is provided to the operational amplifier 28 and the adding means 3 is provided to the operational amplifier 29. Further, the operation output of the PID control device 31 constituting the control unit 2 is given to the input terminal of the operational amplifier 29. The operational amplifier 29 adds these, and the output terminal thereof is provided with a filter composed of the amplifier 30, and the output of the operational amplifier 29 further constitutes one input terminal of the operational amplifier 32 which constitutes the second adding means 8. Given to. Further, the amplified output of the operational amplifier 28 is similarly applied to the other input terminal. Adder 32
Is output to the motor 21 via the operational amplifier 33 which constitutes an inverter, and constitutes a robust control device.

Next, the relationship between the manipulated variable U (s) and the controlled variable Y (s) generated from the control unit 2 of the robust control device of this embodiment is expressed by the following equation.

here Further, the following equation holds between the disturbance D (s) and the control amount Y (s).

By transforming the equation (1), the following equation is obtained.

Here, 1 / F (s) is a filter element of a first-order lag system, and the following equation holds.

Therefore, F (s) is expressed by the following equation.

F (s) = τs + 1 (4) Here, 1 / F (s) is a high-frequency cutoff filter of the first-order lag element system that becomes 1 in the steady state. That is, the gain is almost 1 in the low frequency region, and the gain becomes smaller than 1 in the high frequency region, and the transfer characteristic is attenuated. Also, in the equation (3), the term of {1-1 / F (s)} of the denominator is close to 1 for high frequency components, smaller than 1 for low frequency components, and has a frequency of 0 (DC component). On the other hand, it is completely 0. Therefore, the following equation holds.

That is, since {1-1 / F (s)} is 0 in the steady state, the transfer function P _m (s) of the model is the transfer function P _m of the controlled object 1 from the equation (3) in the steady state where no disturbance is applied.
It matches with (s). Therefore, δ
(S) becomes 0 completely. Also, until {1 / F (s)} reaches a steady state, parameter fluctuation δ (s) and disturbance input D
In order to reduce the influence of the output on (s), the loop by the low sensitivity compensation loop A works. For example, [1 / {1 in equation (3)
+ Β / F (s)}], if β has a value of about 10 to 100, the influence on the parameter variation δ (s) is about 1/10 to 1/100 corresponding to the value of β. Become. That is, the low-sensitivity compensation loop can reduce the influence of the parameter variation on the output.

Further, by modifying the equation (2), the following equation can be obtained as the relation between the disturbance input and the manipulated variable.

In this equation as well, the effect of suppressing the parameter variation δ (s) on the output is reduced, and the 1 / (1 + β / F (s)) suppressing effect is generated by the low-sensitivity loop by the amplifying unit 7. . Therefore, if β has a value of 10 to 100,
The influence on the output is reduced to about 1/10 to 1/100 according to the value of β, and the influence of disturbance can be reduced. In the steady state, 1-1 / F (s) becomes 0, and the remaining deviation can be canceled by the complete suppression loop.

Next, the operation of this embodiment will be described. FIG. 4 is a time chart showing temporal changes in the controlled variable and manipulated variable of the controlled object and the output of each block. If the target value changes at times t ₁ and t ₂ , the target amount is significantly different from the control amount. Therefore, as shown in FIG. 4 (a), the target value (W (s)) having a large level is PID. Input to the control device 31. The waveform shown by the solid line in FIG. 4 (b) is the speed detector 22 which is the detecting means.
It is a figure which shows the speed signal (control amount Y (s)) obtained more, and the waveform shown with a broken line is the response obtained from the model 4 of the motor 21. Therefore, this deviation is obtained from the operational amplifier 23, which is the deviation detecting means 5, as shown in FIG. Therefore, the compensation operation amount having a waveform as shown in FIG. 4 (d) can be obtained from the high frequency range differential compensation element 6. Then, this signal is added to the manipulated variable (U (s)) from the PID control device 3 by the operational amplifier 29 which is the first adding means 3 to output the signal shown in FIG. 4 (e). That is, the manipulated variable U (s)
Is obtained by subtracting the waveform of FIG. 4 (d) from the waveform of FIG. 4 (e). The output signal of the first adding means 3 and this signal and the amplified output of the amplification section 7 for the compensation operation amount are added as shown in FIGS. 4 (f) and 4 (g) and added as an operation amount for the motor 21. . Therefore, as shown in FIG. 4 (b), the deviation obtained from the actual motor 21 can be controlled so that it converges without overshoot within an extremely short time and coincides with the target value. Further even if the disturbance is caused by conditions such as to other joints is driven to rotate the robot arm at time t ₃ in the same manner, the control amount of the actual controlled object and the controlled variable obtained from the model 4 is different Therefore, the compensation is performed by giving the deviation to the high-frequency differential compensation element 6 for compensation. Since such compensation operation is performed in an extremely short time, the original control amount is restored in a short time. When control is performed only by the control unit 2 without performing such control, overshoot occurs and the control amount gradually matches the target value. On the other hand, in the control device according to the present invention, the control amount can reach the target value in an extremely short time.

Although the present embodiment describes the PID control device as the control unit, the present invention provides various other control devices, such as PI or IP, that provide an operation output for making the control unit match the control amount with the target value. It can be applied to various control devices such as a control device and an optimum control device. The control target is not limited to the robot arm, and the present invention can be applied to various control targets having a large number of disturbance generating elements.

[Brief description of drawings]

FIG. 1 is a block diagram of a robust control device showing a configuration of the present invention, FIG. 2 is a block diagram of a robust control device according to an embodiment of the present invention, and FIG. 3 is an electronic diagram of its model and high frequency differential compensation element. FIG. 4 is a circuit diagram of an embodiment constructed by a circuit, and FIG. 4 is a time chart showing the manipulated variables and controlled variables and the output of each block in this embodiment. 1 ... Control object, 2 ... Control unit, 3 ... First adding means, 4 ... Model of control object, 5 ... Deviation detecting means, 6
…… High frequency differential compensation element, 7 …… Amplifier, 8 …… Second
Addition means, 9 ... Detection means, 21 ... Motor, 22 ... Speed detector, 23-30, 32, 33 ... Operational amplifier, 31 ... PID control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-3716 (JP, A) JP-A-59-208615 (JP, A)

Claims (1)

[Claims] 1. A control unit, which is provided with a control amount and a control target value obtained from a controlled object and performs an operation to bring the control amount close to the target value, and an operation amount generated by the control unit and a steady deviation compensation operation amount. A first addition means, a model of a control object having the same transfer function as that of the control object, to which the addition operation amount of the first addition means is given, and an operation amount given to the control object and the model Deviation detection means for detecting the deviation of the control amount obtained at times, and a transfer function represented by the product of the inverse system of the transfer function showing the model and the high-frequency cutoff filter of the second-order lag system, and the deviation detection A high-frequency differential compensation element that gives the first addition means a compensation operation amount obtained by giving the deviation detected by the means, and a compensation operation amount obtained from the high-frequency differential compensation element is amplified to An amplification unit for reducing the sensitivity of the sound, a second addition unit for adding an operation amount of the first addition unit and a compensation operation amount given by the amplification unit to give an output to a control target, and the control target A control amount detecting means for detecting the control amount of the control means and supplying the control amount to the control part and the deviation detecting means.