JPH06100201B2 - Electro-hydraulic servo controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is not affected by the characteristics of the mechanical system to be controlled,
Moreover, the present invention relates to an electro-hydraulic servo control device that operates stably and with high response.

The electro-hydraulic servo control device is used in a vibration testing machine, various simulators, and a drive unit of industrial machines such as rolling mills and robots. FIG. 1 is an example thereof, which is an electrohydraulic servo control device of a trumpet roll 1 which is provided in a down coiler for winding a strip and presses around the strip wound on a mandrel 1a. The trumpet roll 1 is attached to the tip of a swing frame 3 that swings around a pivot 2, and its position is controlled by a hydraulic cylinder 4 that swings the frame 3. In the figure, a spring designated by reference numeral 5 is an oil column spring due to the rigidity of the oil in the cylinder. The amount of pressure oil supplied to the hydraulic cylinder 4 is controlled by the servo valve 6.

When this device is modeled, as shown in FIG. 2, the movable parts such as the frame 3 and the trumpet roll 1 are moved through the spring 5 of the oil column to perform the positioning. The spring constant of the oil column spring 5 is k, and the mass of the movable portion is m. Also,
The movable part receives a braking action when the piston 7 moves in oil. This is represented by a dashpot in the figure, and its viscous damping coefficient is c.

By the way, in order to improve the responsiveness and accuracy of positioning of the controlled object, that is, the trumpet roll 1, the following matters are important.

 The mass m of the moving part is small.

 The spring constant k is large.

Appropriate braking works, in other words viscous damping coefficient c
Takes an appropriate value.

That is, even if the piston 7 of the hydraulic cylinder 4 is displaced by x, the response becomes slow if the heavy moving part is pushed by the soft spring, and if the braking does not work, the vibration continues until the position reaches the target value. Takes a long time. FIG. 3 shows an example of a response waveform when the response is poor. In the figure, t _R is the response time.

In order to meet the above requirements, the following are required.

′ Make the machine lighter and give it the necessary strength.

′ Increase the diameter of hydraulic cylinder 4 and shorten the stroke.

'Provide a damping mechanism such as a damper.

However, for ', it is difficult to achieve both weight reduction and strength, and for', increasing the diameter increases the amount of oil required for control and increases the cost, and the stroke is determined by the use of the machine. However, there is a problem that the cost cannot be shortened, and the cost of ′ is increased.

In order to solve the above problems by control, a phase lead circuit is often used in conventional classical control theory. However, in order to realize the phase lead circuit characteristics for completely compensating for the characteristics of the controlled object, it is necessary to realize the characteristics that exist only in the mathematical definition of pure differentiation, which is impossible at all. is there. Therefore, a kind of pseudo-derivative is used to perform compensation to the extent that the characteristic of the controlled object is replaced by the improved characteristic of the compensation element.

There is an inverse function compensation method as a way of thinking that has advanced the compensation by such a phase advance circuit. This inverse function compensation method will be described in association with the control device of FIG. The control device shown in FIG. 1 has the configuration shown in FIG. 4, and is represented by a block diagram handled in control engineering as shown in FIG. A configuration in which inverse function compensation is added is shown in the block diagram of FIG. First, the fourth
In FIGS. 5 and 5, reference numeral 8 is a mechanical element such as the trumpet roll 1 and the swing frame 3. The displacement amount y of the trumpet roll 1 in the machine 8 is detected by the displacement meter 9,
And it is fed back. The displacement y is compared with the set value r, and the deviation is ε. In FIG. 5, KA is a gain, S is a Laplace operator, and 1 / S means integration. T in the transfer function of the servo valve 6 is the servo valve time constant, A in the transfer function of the hydraulic cylinder 4 is the cylinder-effective area, and a, b, c in the transfer function of the machine 8 are the weight of the machine and the hydraulic cylinder. Is a characteristic function based on the spring constant and viscous damping of
If a differential equation is set up in the model shown in the figure, m '+ c' + k (x'-x) = 0 m '+ c' + kx '= kx (= F) (1) is obtained. When this is Laplace transformed, x '= k / (ms ² + cs + k) × x (2), and if m / k = a, c / k = b, 1 = c, x' = y The transfer function 8 of the block diagram shown in FIG. 6 is obtained. Displacement meter 9
T _{L in} the transfer function of is the displacement meter time constant. Then, i is the servo current, Q is the output flow rate of the servo valve 6, and x is the piston displacement of the hydraulic cylinder 4.

FIG. 6 shows a block diagram in which the inverse function compensating element 10 is added in FIG. 5, and the same reference numerals as those in FIG. 5 represent the same elements as in FIG. If the inverse function compensation element 10 is added after the mechanical system 8 to be controlled, it becomes 1 / (as ² + bs + c) × (as ² + bs + c) = 1 (3), and it is as if the characteristics of the machine 8 do not exist. Be compensated as if. As described above, if the inverse function compensating element 10 can be completely realized instead of approximation, it is possible to design a control system having a necessary response and accuracy with respect to a control target without considering the above-mentioned constraints. However, the input / output relationship of the inverse function compensating element 10 becomes a '+ b' + cx '= y (4) from FIG. 6, and the first-order differential value (speed) and second-order differential value (acceleration) of the input x It turns out that it cannot be realized without asking.

However, it is impossible to realize a circuit that completely performs such differentiation, as described above, and normally, the circuit shown in FIG.
As shown in (b), a resistor R, a capacitor C, and a coil L are used, and a circuit having an approximate differential characteristic in a frequency region required for compensation is used. In FIG. 7, ei is an input,
eo represents the output.

The circuits of FIGS. 7 (a) and 7 (b) are expressed by the following equations.

G (S) = TS / (TS + 1) (5) When Tε << 1 (S = jε), this has the differential characteristic of the following equation.

G (S) ≈TS (6) However, in FIG. 7A, T = RC, and in FIG. 7B, T = L / R.

However, such a pseudo differentiating circuit is only an approximation circuit that holds when ε <1 / T, and the inverse function compensating element configured by using this pseudo differentiating circuit shows the characteristic of the machine 8 by the equation (3). So it was insufficient to compensate.

The present invention has been made in consideration of the above circumstances, and is an electrohydraulic servo control device using an inverse function compensation element,
An object of the present invention is to provide an electrohydraulic servo control device in which characteristics of a controlled object are compensated in a wide frequency band.

In order to achieve such an object, the first invention of the present application is an electrohydraulic servo control device in which an inverse function compensating element for compensating for a characteristic of a controlled object is inserted in a control loop to detect a displacement of the controlled object. Displacement meter, a speedometer for detecting the speed of the controlled object, an accelerometer for detecting the acceleration of the controlled object, the displacement detected by the displacement meter, the speed detected by the speedometer and the accelerometer The inverse function compensating element is constituted by means for multiplying the detected accelerations by a predetermined gain and adding the results, and outputting the result to the control loop.

Further, a second invention of the present application is an electrohydraulic servo control device in which an inverse function compensating element for compensating for a characteristic of a controlled object is inserted in a control loop, and a displacement gauge for detecting a displacement of the controlled object, An accelerometer that detects the acceleration of the controlled object, an integrating unit that integrates the acceleration detected by the accelerometer, a displacement detected by the displacement meter, an integration result by the integrating unit, and an acceleration detected by the accelerometer. Is multiplied by a predetermined gain and added, and the result is output to the control loop to form the inverse function compensating element.

According to these inventions, a differentiation circuit that causes a problem in frequency characteristics is not used, and a physical quantity directly detected by an accelerometer or the integrated value thereof is multiplied by a predetermined gain and added to obtain an inverse function compensation element. Since it is output to the control loop as a function value, the characteristics of the controlled object can be completely compensated over a wide frequency band.

An embodiment of the present invention will be described below with reference to FIGS. Incidentally, the same parts as those of the conventional one described above are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 8 is a block diagram of the control device according to the present invention, and the position of the trumpet roll 1 in the device of FIG. In this example, a displacement meter 9, a speedometer 11, and an accelerometer 12 are provided as detectors for detecting the state quantity of the trumpet roll 1 to be controlled.
Tv in the transfer function of the speedometer 11 is the speedometer time constant and the accelerometer 12
Ta in the transfer function of is an accelerometer time constant. The time delay due to the specific numbers TL, Tv, and Ta of the displacement gauge 9, the speedometer 11, and the accelerometer 12 is two to three orders of magnitude lower than the delay of the machine 8 and can be ignored here.

Then, the displacement meter 9, speedometer 11, and accelerometer 12 are
Displacement x ', velocity', and acceleration'of are detected moment by moment. These detected values are multiplied by c times, b times, and a times by gain circuits 9 ', 11', and 12 ', respectively, and added by an adder circuit 20. As a result, as seen from x to y in FIG. 8, since the expression (4) is realized, the relationship of the expression (3) is satisfied from the input x of the machine 8 to the output y of the inverse function compensation element. Completely approved.

Therefore, apparently, the characteristics of the machine 8 are compensated as if they do not exist, and there is no output delay.

FIG. 9 shows a configuration example of the present electro-hydraulic servo control device for position control of the trumpet roll 1 similar to FIG. In this example, a swing displacement fulcrum portion of the swing arm 3 is provided with a rotary displacement gauge 9, and the swing arm 3 is also provided.
An accelerometer 12 is provided in the middle part of the. Then, the displacement x'and the acceleration 'by the displacement gauge 9 and the accelerometer 12
The detection signal of is input into the control device 13, and control by the above-mentioned inverse function compensation method is performed here. In this example, only the displacement meter 9 and the accelerometer 12 are provided as state quantity detectors, and no speedometer is provided. This is because the speed can be obtained without degrading the accuracy by integrating the acceleration detected by the accelerometer 12, and of course, a speed detector may be separately provided to directly detect the speed. Needless to say. Such control is performed by four swing arms 3 around the down coiler for winding the strip.
Is similarly performed for each hydraulic cylinder 4.

FIG. 10 shows an example of the configuration of the present electro-hydraulic servo control device for controlling a hydraulic pressure rolling mill. This rolling mill is equipped with a hydraulic reduction cylinder 14 on the lower backup roll R ₁ side and a reduction screw on the upper backup roll R ₂ side.
15 is provided, by the control of the servo valve 16 for the reduction cylinder 14 and the control of the reduction screw drive motor 17,
The rolling force of the rolled material w by the upper and lower work rolls R ₃ R ₄ is adjusted. The rolling mill is equipped with a reduction screw position detector 18, a load cell 19, and a cylinder.
It has a hydraulic pressure reduction cylinder position detector (displacement meter) 9 and an accelerometer 12 which are arranged on 14 movable parts. These detection signals are input into the control device 13, and the servo control by the above-mentioned inverse function compensation method is performed here.

The electro-hydraulic servo control device of the present invention can be applied to various hydraulic devices other than the hydraulic down coiler and the hydraulic pressure rolling mill described above, and the applicable range is wide. The inverse function compensating element may be composed of either hardware such as an electronic circuit or software using a computer.

As described above, according to the electrohydraulic servo control device of the present invention, the inverse function compensating element is configured without using the differentiating circuit, so that the characteristics of the controlled object can be completely compensated over a wide frequency band. Therefore, it is possible to realize servo control which is not affected by the characteristics of the controlled object.

In the above description, for the sake of convenience, the case where the position of the controlled object is controlled has been taken up, but it should be pointed out that the present invention can also be applied to the case where speed and force are controlled.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a position control mechanism portion of a trumpet roll in a down coiler, FIG. 2 is a diagram showing the mechanism portion of FIG. 1 as a model, and FIG. 3 is a response when position control response is poor. FIG. 4 is a block diagram of a hydraulic servo control system, FIG. 5 is a diagram showing the configuration of FIG. 4 as a model, and FIG. 6 is a block diagram of an inverse function compensation control system. 7 (a) and 7 (b) are circuit diagrams showing different examples of an approximate differentiating circuit constituting a conventional inverse function compensation control element,
FIG. 8 is a diagram showing a model of a control system in an embodiment of the present invention, FIG. 9 is a schematic configuration diagram of a down coiler having a control device of the present invention, and FIG. 10 is a control device of the present invention. It is a schematic block diagram of a hydraulic rolling mill. 1 ... Lubber roll, 4 ... Hydraulic cylinder, 6 ... Servo valve, 8 ... Machine, 9 ... Displacement meter, 10 ... Inverse function compensation element, 11 ... Speedometer, 12 ... Accelerometer.

Claims (2)

[Claims] 1. An electrohydraulic servo control device having an inverse function compensating element for compensating the characteristic of a controlled object inserted in a control loop, comprising: a displacement gauge for detecting displacement of the controlled object; and a speed of the controlled object. A speedometer for detecting, an accelerometer for detecting the acceleration of the controlled object, a displacement detected by the displacement gauge, a speed detected by the speedometer and an acceleration detected by the accelerometer, each having a predetermined gain. The electro-hydraulic servo control device is characterized in that the inverse function compensating element is constituted by means for multiplying by and adding and outputting the result to the control loop. 2. An electrohydraulic servo control device having an inverse function compensating element for compensating the characteristic of a controlled object inserted in a control loop, comprising: a displacement gauge for detecting a displacement of the controlled object; and an acceleration of the controlled object. An accelerometer for detecting, an integrating means for integrating the acceleration detected by the accelerometer, a displacement detected by the displacement gauge, an integration result by the integrating means, and an acceleration detected by the accelerometer. An electrohydraulic servo control device characterized in that the inverse function compensating element is constituted by means for multiplying and adding a gain and outputting the result to the control loop.