JP2002149204A - Control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a control device that the correspondence relation among parameters to be adjusted for multiple control specifications can be easily recognized and the response waveform of a controlled system can be easily and visually adjusted. SOLUTION: This control device is equipped with a target signal generator 11 which generates a target signal, a feedback compensator 15 which computes a first manipulated variable according to the deviation of the output signal S of the controlled system from the target value signal, and a feedforward compensator 14 which computes a second manipulated variable according to the target value signal branched off from the target value signal generator 11 and performs two-degree-of-freedom control so that the first and second manipulated variables are added to obtain a manipulated variable of the controlled system and the output of the controlled system is made to coincide with the target value signal; and the target value signal is inputted to the feedback compensator 15 and feedforward compensator 14 via different filters 12 and 13, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a two-degree-of-freedom control device provided with a feedback compensator and a feedforward compensator.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a conventional two-degree-of-freedom control apparatus provided with a feedback (FB) compensator and a feedforward (FF) compensator. The target value signal generator 101 gives a signal corresponding to the target value of the control target 104 to the control device. For example, in the case of position control, the control target 104
A signal corresponding to the target position is generated, and in the case of speed control, a signal corresponding to the target speed is generated. The output of the controlled object is detected by a sensor (not shown) and fed back to calculate a deviation from a target value, and a feedback (FB) compensator 1
Enter 03. Feedback (FB) compensator 103
Calculates an operation amount (correction amount) based on the deviation signal.

The control device shown in FIG. 1 is called a feed-forward type two-degree-of-freedom control device and has a feedback (F
B) In addition to the compensator 103, a feedforward (FF) compensator 102 that calculates a signal from the target value signal generator as a forward manipulated variable is provided. The feedforward (FF) compensator 102 calculates an operation amount based only on the target value signal. Then, a result calculated based on both operation amounts of the feedback (FB) compensator 103 and the feedforward (FF) compensator 102 is input as an operation amount of the control target 104.

[0004] The use of a deviation signal and a target value as state quantities for calculating the manipulated variable is called two-degree-of-freedom control. Generally feedforward (FF) compensator 1
It is known that the response of the control target is improved by adding 02.

[0005] As specifications required when controlling the controlled object 104, there are cases where a plurality of specifications such as a steady speed, an overshoot amount, and a settling time of the controlled object 104 must be simultaneously achieved. When such a plurality of control specifications are required, if the correspondence of the parameters to be adjusted to a certain specification is clear, the adjustment of the parameters becomes very simple. Further, it becomes easy to shape the response waveform of the control target by adjusting the parameters.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is easy to understand the correspondence between parameters to be adjusted with respect to a plurality of control specifications, and at the same time, to visualize the response waveform of a control object. It is an object of the present invention to provide a control device which can be easily adjusted.

[0007]

According to a first aspect of the present invention, there is provided a target value signal generator for generating a target value signal, and a deviation between the target value signal and an output signal of a control object. And a feed-forward compensator for calculating a second operation amount based on a target value signal branched from the target value signal generator. In a control device that adds two operation amounts to obtain an operation amount of a control object and controls the two-degree-of-freedom control so that an output of the control object coincides with a target value signal, the target value signal is feedback-compensated through different filters. And a feed-forward compensator.

[0008] By inputting the target value signal to the feedback compensator and the feedforward compensator through different filters as described above, the parameters of each filter can be independently adjusted, and the response speed of the controlled object, That is, the speed of convergence with respect to acceleration / deceleration at the start and stop of the operation and fluctuations in the system can be determined independently.

The invention described in claim 2 is the first invention.
The control device according to the above, further comprising a ramp shaper for converting the step-like waveform into a ramp-like waveform between the target value signal generator and the filter.

As described above, since the ramp shaper is provided between the target value signal generator and the filter, the steady speed of the controlled object is first determined by the parameters of the ramp shaper, and then the operation at the start of operation is performed by the parameters of each filter. The acceleration and deceleration at the time of stop can be determined, and the waveform of the target trajectory can be easily shaped.

The invention described in claim 3 is the same as the claim 2
The feedback compensator is P
An ID (proportional-integral-derivative) controller is used, and the feedforward compensator is a PD (proportional-derivative) controller.

As described above, the feedback compensator is PI
By using a D controller and a feedforward compensator as a PD controller, the parameter adjustment procedure first creates a target value trajectory to be controlled, and feeds an operation amount that approaches the trajectory without feedback compensation. Convergence by feedback compensation,
Disturbance suppression and the like can be performed. For this reason, the feedforward compensator and the feedback compensator can be easily handled independently, and a strong feedback characteristic can be obtained at the same time while obtaining a fast response by the feedforward compensator. Further, since the number of parameters handled for realizing this is small, adjustment is easy, and the role of the parameters is very clear, so that the response waveform can be easily shaped visually.

The invention described in claim 4 is the first invention.
Wherein the control target is a control system that controls the position or speed of the hydraulic actuator with a control valve.

The invention described in claim 5 is the same as the claim 4.
Wherein the hydraulic actuator is a single-rod hydraulic cylinder, the feedforward compensator includes a differential element, and a switch that switches a differential coefficient of the differential element according to a target value signal of the hydraulic cylinder. It is characterized by having.

As described above, the feedforward compensator includes a differential element and is provided with a switch that switches according to the target value signal of the hydraulic cylinder. Positioning control can be realized.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. Here, a case where the control object is a hydraulic cylinder and the control device of the present invention is applied to cylinder positioning control by a control valve will be described as an example. FIG. 2 is a diagram showing a configuration of a hydraulic cylinder system to which the control device according to the present invention is applied. The hydraulic cylinder system includes a high-pressure fluid generator 20 for supplying high-pressure fluid, a hydraulic cylinder 3
0, a control valve 40 for controlling the supply and discharge of the high-pressure fluid to the hydraulic cylinder 30; a displacement signal S of the hydraulic cylinder 30 is input to the control device 10; The control valve 40 is controlled via 50.

The high-pressure fluid generator 20 comprises a pump 21, an electric motor 22 for driving the pump 21, a filter 23, a cooler 24, a tank 25 and the like.

The hydraulic cylinder 30 is arranged vertically, and a load 33 is applied to the piston 32 of the cylinder 31. By controlling the supply amount and pressure of the fluid from the high-pressure fluid generator 20 to the hydraulic cylinder 30 by the control valve 40, the position of the piston of the hydraulic cylinder 30 is controlled. The position of the piston 32 of the hydraulic cylinder 30 is detected by a displacement sensor 34, and a displacement signal S is fed back to the control device 10. The control device 10 calculates an operation amount serving as an input signal of the control valve based on the feedback signal and a target position signal generated inside the control device 10. The calculated operation amount is input as a voltage value to the amplifier 50 that drives the control valve 40, and drives the control valve 40.

FIG. 3 is a block diagram of a control device according to the present invention. A target value signal generator 1 for generating a target position signal
1 generates a target position signal (voltage value) So corresponding to the cylinder position signal. The voltage value of the signal So changes stepwise when the target position is changed. The target position signal So branches to the feed-forward compensator 14 and the feedback compensator 15 and is divided into the filters 12 and 13.
Is input to The filters 12 and 13 have a low-pass filter characteristic given by, for example, the following equation. The filters 12 and 13 are independent of each other. That is, the parameters ω _n and ζ that determine the characteristics can be adjusted independently of each other.

G _R (s) = ω _n ² / (s ² + ζω _n s + ω _n ² )

This transfer function converts a step-like input signal Si into signals Sf ₁ , Sf ₂ and Sf ₃ as shown in FIG. The input signal Si that changes stepwise from 0 (V) to 1 (V) at time 0 second is input to the filters 12 and 13. In FIG. 4, when ω _n is increased in the order of ω ₁ , ω ₂ , ω ₃ , the response becomes faster.

[0022] Although the waveform of the output signal Sf ₁₃ of the output signal Sf ₁₂ and filter 13 of the filter 12 can be changed in omega _n and ζ for the transfer function, the target trajectory actually asks the control object without overshoot In many cases, it is not necessary to change ζ to “1” or the like because it is often a waveform. The waveform shown in FIG. 4 is obtained when ζ = 1. In this filter element, only ω _n is used as a parameter for waveform shaping. ω _n is the response speed of the output signal waveform, and ζ is a parameter that determines the attenuation.

The output signal Sf ₁₂ of the filter 12 is sent to the feedforward (FF) compensator 14, and the output signal Sf ₁₃ of the filter ₁₃ is sent to the displacement sensor 34 of the cylinder 30.
Is calculated and then input to the feedback (FB) compensator 15. The output signals S _FF and S _FB calculated by the feed forward (FF) compensator 14 and the feedback (FB) compensator 15 are added, and the added value (S _FF + S _FB ) is used as an operation amount to drive the cylinder system 60. I do. A block shown as a cylinder system 60 in FIG. 3 indicates a portion from an input end to the control valve 40 to an output end of the displacement sensor 34 of the hydraulic cylinder 30 in FIG. That is, the calculated operation amount becomes an input to the control valve 40, and the hydraulic cylinder 30 is displaced based on the signal,
The position is detected by the displacement sensor 34 and the position signal is fed back.

FIG. 5 is a block diagram of a control device in which a ramp shaper 16 for converting the step-like target position signal So from the target value signal generator 11 into a ramp shape is disposed after the target value signal generator 11. . By arranging the ramp shaper 16 after the target value signal generator 11, the steady-state speed of the response can be defined. FIG. 6 shows the output signal waveform of the ramp shaper 16 and the output signal waveforms of the filters 12 and 13.

As shown in FIG. 6, a step-like input signal Si from the target value signal generator 11 is input to the ramp shaper 16 and has a predetermined slope as shown by Sl ₁ , Sl ₂ and Sl ₃ . After the conversion into the ramp waveform, the waveforms Sf ₁ , S
The waveform is shaped into f ₂ and Sf ₃ . The setting parameter of the ramp shaper 16 is only the slope of the waveform and is set to Sm. S in FIG.
l ₁ , Sl ₂ , and Sl ₃ are waveforms when the parameter Sm is sequentially increased.

FIG. 7 shows a parameter Sm of the ramp shaper 16.
FIG. 9 is a diagram showing output waveforms of the filters 12 and 13 when the parameter ω _n is changed while the value of ω is fixed.
Output waveform Sf when _n is increased in the order of ω ₁ , ω ₂ , ω _3
1 , Sf ₂ and Sf ₃ are shown. By placing the lamp shaper 16 in front of the filters 12 and 13,
First, the steady speed of the controlled object is determined by the parameter Sm of the ramp shaper 16, and the filter 12 and the filter 1 are controlled.
3 parameters ω and the start operation by _n can determine the acceleration and deceleration at the time of stopping, it is possible to easily shape the waveform of the target trajectory.

FIG. 8 is a block diagram specifically showing the feedforward (FF) compensator 14 and the feedback (FB) compensator 15. The feedforward (FF) compensator 14 is an element having a differential element s and multiplied by a differential coefficient β to obtain an operation amount, and a feedback (FB) compensator 15
Is a PI (proportional integration) controller including a proportional coefficient Kp and an integrator 1 / s, and Ti is an integral coefficient. A switch 15-1 is provided immediately before the integral element Ti / s, and when the deviation between the target value and the cylinder position becomes smaller than a predetermined value, a switch is connected to activate the integral element (integrator) Ti / s. It is supposed to. This is the integral element (integrator)
The switch is provided to prevent saturation of Ti / s, and is called an anti-windup switch.

FIG. 9 is a diagram showing an output waveform of the feedforward (FF) compensator 14 when the target value is switched stepwise. An example is shown in which the parameter ω _{n of the} filter 12 is changed and ω ₁ , ω ₂ , and ω ₃ are increased in this order.

FIG. 10 is a diagram showing a response waveform of the control target when the output of the feedforward (FF) compensator 14 is directly input to the control target, that is, when the feedback control is not performed and the control is performed in an open loop. is there. Note that the vertical axis represents the cylinder position as 0 (V) to 1 (V) in order to correspond to the input signals 0 (V) to 1 (V). As explained in the parameter adjustment procedure described later, feedforward (FF) without feedback control
The ω _n and differential coefficient β of the filter 12 are adjusted so that the response waveform is close to the target value trajectory only by the output (manipulation amount) of the compensator 14. Then, the feedback (FB) compensator 15 corrects the error from the target value trajectory for which the waveform has been previously determined. The feed forward (FF) compensator 14 and the feedback (FB) compensator 15 are provided with the filters 12 and 13 independently of each other in order to perform this adjustment independently.

Next, the procedure of parameter adjustment will be described. Procedure 1. The steady speed of the controlled object is determined by the parameter Sm of the ramp shaper 16.

Procedure 2. The parameter ω _{n of the} filter 13
Thus, the target value waveforms at the start and stop of the operation are shaped.

Procedure 3. Feedback (FB) compensator 1
With the proportional coefficient Kp of 5 as zero and the parameter ω _n as the initial parameter of the filter 12, the differential coefficient β of the feedforward (FF) compensator 14 is determined while actually operating the controlled object.

Procedure 4. Adjusting the parameters omega _n of the filter 12 so as to approximate the actual start and stop time of the waveform and desired trajectory determined in the above procedure 1-2.

Procedure 5 Feedback (FB) compensator 1
The proportional coefficient Kp and the integral coefficient Ti on the fifth side are determined from the viewpoint of convergence with respect to the target value and disturbance suppression.

As is clear from the above-described parameter adjustment procedure, the control device according to the present invention first creates a target value trajectory to be obtained for the control object, and gives an operation amount approaching the trajectory without feedback compensation by a feedforward element. In addition, convergence, disturbance suppression, and the like are performed by feedback compensation. Therefore, the feed forward (F
F) The compensator 14 and the feedback (FB) compensator 15 can be easily handled independently, and the feedforward (FF)
With the compensator 14, a strong feedback characteristic can be obtained at the same time while obtaining a fast response. Further, adjustment is easy because the number of parameters handled to realize this is small, and the role of the parameters is very clear, so that it is easy to visually shape the response waveform.

The parameters to be adjusted and their roles are as follows. Sm: Steady speed ω _n (Filter 13): Acceleration / deceleration at start / stop of target value operation ω _n (Filter 12): Acceleration / deceleration at start / stop of operation of controlled object β: Feed forward Input gain (differential coefficient) ・ Kp: Feedback gain (proportional coefficient) ・ Ti: Integration constant

FIG. 11 is a block diagram of a control device according to the present invention. In particular, FIG. 11 is a block diagram of a control device suitable for controlling a single rod cylinder to be controlled. Since the single rod cylinder has a different pressure receiving area depending on the moving direction and a different flow rate of supply to the cylinder when moving at a constant speed, it is necessary to consider that the control target is different in the expansion and contraction direction of the piston. For this purpose, a switch 14-1 for switching the differential coefficient is provided on the input side of the feedforward (FF) compensator 14. The switch 14-1 switches by determining in which direction the cylinder moves by comparing the current position with the target position signal generated by the target value signal generator 11.

In the above parameter adjustment procedure 3, each differential coefficient β is determined according to the direction of expansion and contraction of the cylinder. That is, the derivative β ₁ is adjusted in the direction in which the cylinder extends, and the derivative β ₂ is adjusted in the direction in which the cylinder contracts. As described above, in the case of the single rod cylinder, the control target differs depending on the moving direction, but since the basic system structure is the same, only switching the differential coefficient (gain) β of the feedforward (FF) compensator 14 is sufficient. Positioning control can be realized.

FIG. 12 is a diagram showing an example of the result of controlling the hydraulic cylinder system having the structure shown in FIG. 2 by the control device according to the present invention. The position when the piston 32 of the hydraulic cylinder 30 is at the lower end is 0 mm, and the position is 5 mm to 105 mm.
Is displaced 100 mm to the position shown in FIG.
Although the input signal Si changes stepwise, the input signal Si is converted into a smooth target trajectory by the ramp shaper 16 and the filter 13, and the output signal Sf _{13 of the} filter 13 is obtained.
Is controlled as the target trajectory. It accelerates and decelerates at the start and stop of the operation, giving a smooth response. FIG.
At the same time, the deviation from the target value is shown. It can be seen that the positioning is performed at the target position without a steady deviation.

FIG. 13 is a diagram showing an example of the result of controlling the hydraulic cylinder system having the configuration shown in FIG. 2 by the control device according to the present invention. The piston 32 of the hydraulic cylinder 30 descends from the 105 mm position to the 5 mm position. This is a case in which control is performed to perform This is the time of descent is switched in the direction of the differential coefficient beta ₂ of hydraulic cylinder 30 retracts the switch 14-1.

FIG. 14 is a diagram showing the results of tests performed to confirm the convergence to the target value when the hydraulic cylinder system having the configuration shown in FIG. 2 is controlled by the control device according to the present invention. 3 shows a deviation signal when the neutral position of the control valve 40 that controls the hydraulic cylinder 30 is intentionally shifted and positioning control is performed using the same parameters. The waveform shown as 0% does not shift the neutral position. The case where the neutral position is shifted by ± 5% for every 1% with respect to the rated input of the control valve 40 is also shown. In practice, it is unlikely that system fluctuations will change so much. This result indicates that the control device has a strong feedback characteristic with respect to system fluctuation.

In the above example, the example of positioning control of the hydraulic cylinder has been described, but the control target of the control device according to the present invention is not limited to this. For example, it can be used for speed control of a hydraulic motor, position control of an electric motor, and the like.

[0043]

As described above, according to the invention described in each claim, the following excellent effects can be obtained.

In the parameter adjustment procedure, first, a target value trajectory to be obtained for the controlled object is created, and an operation amount approaching the trajectory without feedback compensation is given by a feedforward element, and convergence and disturbance suppression are performed by feedback compensation. Therefore, the feedforward compensator and the feedback compensator can be easily handled independently, and a strong feedback characteristic can be obtained at the same time while obtaining a fast response by the feedforward compensator.

Further, since the number of parameters handled for realizing this is small, adjustment is easy, and the role of the parameters is very clear, so that it is easy to visually shape the response waveform.

According to the fifth aspect of the present invention, the feedforward compensator further includes a differentiating element and is provided with a switch that switches according to a target value signal of the hydraulic cylinder. Only by switching the differential coefficient, good positioning control can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a conventional control device.

FIG. 2 is a diagram showing a configuration of a hydraulic cylinder system to which a control device according to the present invention is applied.

FIG. 3 is a block diagram of a control device according to the present invention.

FIG. 4 is a diagram illustrating an example of conversion of a step-like input signal waveform by a filter of the control device according to the present invention.

FIG. 5 is a block diagram of a control device according to the present invention.

FIG. 6 is a diagram showing an output signal waveform of a ramp shaper of the control device according to the present invention.

FIG. 7 is a diagram showing an output signal waveform of a filter of the control device according to the present invention.

FIG. 8 is a block diagram of a control device according to the present invention.

FIG. 9 is a diagram showing an output waveform of a feedforward compensator of the control device according to the present invention.

FIG. 10 is a diagram showing a response waveform when the output of the feedforward compensator of the control device according to the present invention is directly input to the control target.

FIG. 11 is a block diagram of a control device according to the present invention.

FIG. 12 is a diagram showing a result of controlling the hydraulic cylinder system shown in FIG. 2 by the control device according to the present invention.

FIG. 13 is a diagram showing a result of controlling the hydraulic cylinder system shown in FIG. 2 by the control device according to the present invention.

FIG. 14 is a diagram showing test results for confirming convergence when the hydraulic cylinder system shown in FIG. 2 is controlled by the control device according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 control device 11 target value signal generator 12 filter 13 filter 14 feed forward (FF) compensator 15 feedback (FB) compensator 16 ramp shaper 20 high-pressure fluid generator 30 hydraulic cylinder 40 control valve 50 amplifier 60 cylinder system

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H001 AA01 AA03 AA06 AB06 AC03 AD04 AE12 AE14 AE23 5H004 GA27 GA30 GB20 HA07 HB07 KB02 KB04 KB06 KB13 KB22 KB32 LB04 MA12 5H303 AA30 BB01 BB06 BB11 DD06 KK02 KK03 KK04

Claims (5)

[Claims] A target value signal generator for generating a target value signal; a feedback compensator for calculating a first manipulated variable based on a deviation between the target value signal and an output signal of a control target;
A feedforward compensator for calculating a second operation amount based on a target value signal branched from the target value signal generator, and adding the first and second operation amounts as an operation amount of a control target; In a control device for controlling two degrees of freedom so that an output of the controlled object coincides with a target value signal, the target value signal is input to a feedback compensator and a feedforward compensator through respective different filters. Control device. 2. The control device according to claim 1, further comprising a ramp shaper for converting a step-like waveform into a ramp-like waveform between the target value signal generator and the filter. . 3. The control device according to claim 2, wherein the feedback compensator is a PID (proportional integral derivative) controller, and the feedforward compensator is a PD (proportional derivative) controller. apparatus. 4. The control device according to claim 1, wherein the control target is a control system that controls a position or a speed of a hydraulic actuator with a control valve. 5. The control device according to claim 4, wherein the hydraulic actuator is a one-rod hydraulic cylinder, the feedforward compensator includes a differential element, and a differential coefficient of the differential element is determined by the hydraulic cylinder. A control device comprising a switch that switches according to a target value signal.