JPH06250740A - Digital positioning controller - Google Patents

Abstract

PURPOSE:To provide stable positioning control at all times by providing a control system which is hardly influenced by disturbance variation. CONSTITUTION:This controller is equipped with a controlled system 9, an observation device which observes the controlled variable and state of the controlled system 9, and a subtracter 2 which calculates the deviation of the controlled variable, observed by the observation device, from a command, and controls the controlled system the deviation signal outputted by the subtracter 2. A digital control system which has an integral element is provided as the controller and the observation device observes the behavior of the controlled system which is converged on the command; and it is decided whether or not the behavior is within a previously set convergence behavior area and the value of the integral element is adjusted independently of integrating operation to converge the behavior of the controlled system into the area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital controller for positioning or the like.

[0002]

2. Description of the Related Art When controlling an object to which a steady disturbance is applied, a feedback control system including an integral element in a predistorter is often applied. However, the steady disturbance often fluctuates in a strict sense, and has an influence such as causing an overshoot in the response of the control system or lengthening the settling time. As an example, positioning control is taken as an example. When performing positioning control of a moving body such as an XY stage for the purpose of high-speed and highly accurate positioning, generally, the moving body is ideally rigid (mass system) or has a primary or secondary delay during large displacement. A speed control system designed as a system is applied to follow the target speed pattern, and the positioning is often settled by switching to a positioning control system that includes an integral element that compensates for friction that is a steady disturbance near the target value. . However, friction changes depending on the position and aging, so the speed of the moving body may vary when switching from the speed control system to the position control system,
It was difficult to keep the amount of overshoot and the settling time constant because of the influence of disturbance fluctuations on the integral operation of the positioning control system.

As a conventional method for solving this problem,
For example, there is JP-A-62-106510. In this conventional example, a constant velocity movement section is provided near the target value to stabilize the switching to the positioning control system and reduce the amount of overshoot, and further adjust the deceleration start position in the velocity pattern. By adding a learning function that keeps the length of the moving section constant, the influence of characteristic changes of the controlled object such as changes in friction is reduced.

[0004]

In the above-mentioned conventional example, since the constant velocity section is provided in the target velocity pattern, there is a problem that the positioning settling time becomes longer than in the case of the trapezoidal pattern. Also, if the fluctuations such as friction are large, the learning function may not converge, and even if it converges, a certain number of trials is required, and detailed learning data for moving distance, place, etc. is created. In order to do so, there is also a problem that a huge memory is required.

An object of the present invention is to realize a control system that is not easily affected by disturbance fluctuations. Taking positioning control as an example, this problem is solved by compensating for fluctuations in friction and the like, and it is always stable. It is to realize positioning control.

[0006]

The above object is to provide an observing device for observing a controlled variable and a state of a controlled object, a subtractor for calculating a deviation between a controlled variable and a target value observed by the observing device, and the subtractor. In a control device that controls a controlled object based on an output deviation signal, a digital control system having an integral element is provided as a control device, and the behavior of the controlled object converging to a target value is observed by an observation device, and the behavior is preset. It is achieved by determining whether or not it is in the convergent behavior region, adjusting the value of the integral element separately from the integral action, and constraining the behavior of the controlled object within the preset convergent behavior region. When this means is applied to positioning control, a moving body that performs positioning, a position measuring device that measures the position of the moving body,
A subtracter that calculates the deviation between the output of the position measuring device and the target position, a control device that controls the moving body based on the deviation signal of the subtractor output, and a drive that drives the moving body based on the manipulated variable that is the output of the control device. In the device, a digital control system having an integral element is provided as a control device, and it is determined whether or not the behavior of the controlled object converging to the target position is within a preset converging behavior region, and the value of the integral element is set separately from the integral operation. Is adjusted and the behavior of the moving body is restricted within the convergence behavior region.

[0007]

By performing the control using the above means, it is possible to solve the problems in the prior art, compensate for the fluctuation of the disturbance applied to the controlled object, and always keep the convergent behavior of the controlled object constant.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a control system showing an embodiment of the present invention in positioning control of a moving body. In FIG. 1, the target value and the position of the moving table, which is the control amount, are simultaneously sampled by the sampler 1 and the sampler 10, respectively, and the subtractor 2 calculates the deviation between the target value and the moving body position. The deviation is input to the digital integrator 3, the integrated value which is the output of the digital integrator 3 is multiplied by the integration gain 4, and the adder 5 adds the deviation and the deviation. The output of the adder 5 is multiplied by the loop gain 6 and then the zero-order hold 7
Is added as an operation amount to the controlled object 9 via. Here, the controlled object 9 includes the moving body and its drive device, and the influence of friction is considered as an equivalent disturbance applied to the adder 8. The determiner 11 is an area in which the convergence of the velocity of the moving body, which is the state variable of the controlled object, and the deviation, which is the output of the subtractor 2, to the target value of the moving body is preset on the phase plane of the deviation-velocity. It is determined whether or not there is a transition (described later with reference to FIG. 2). If the result of determination is that the convergence behavior is outside the region, the switch 12 is switched to the terminal 12b side, and the integral value is multiplied by ρ and updated. At this time, if the switch 14 is turned off, the integration operation is completely stopped, the switch 14 is turned on, and the switch 12 is switched to the terminal 12a side in synchronization with the sampler 1 and the sampler 10, and then switched to the 12b side. For example, the integral value can be updated by multiplying by ρ while performing the integral operation. Here, in FIG. 1, the digital integrator is realized as a backward difference method, but it may be realized by using a method of bilinear conversion or matching Z conversion. It is also conceivable that the state variable to be controlled may be estimated using an observer, or the speed may be obtained from the position signal using an approximate differentiation method such as backward difference.

2 and 3 show typical behaviors on the phase surface to be controlled. The convergence behavior of a linear first-order lag system is a first-order straight line that passes through the origin on the phase plane because the velocity and the deviation have a proportional relationship of the natural angular frequency times. In addition, the convergence behavior of the second-order lag system having the real root as the representative root becomes similar. However, in the conventional method, the behavior as shown in FIG. 3 may occur due to overshoot due to the fluctuation of the disturbance applied to the system. Therefore, in the present invention, as shown in FIG. 2, the maximum value ωmax and the minimum value ωmin of the natural angular frequency are set, and a region sandwiched by straight lines having these two values as slopes is set as a set convergence behavior region and the actual convergence is performed. If the behavior is below a straight line with ω min as the slope, the integral value is multiplied by ρ (ρ> 1). If the actual convergence behavior exceeds the straight line with ω max as the slope, the integral value is ρ (ρ <1 1) By doubling, the behavior of the controlled object is restrained within the set convergence behavior region.

4 and 5 show typical time responses of the controlled object. FIGS. 4 and 5 correspond the behaviors on the phase planes of FIGS. 2 and 3 to the time domain, and schematically show that the present invention prevents the occurrence of overshoot due to disturbance fluctuations and the like.

FIG. 6 shows an ideal target velocity pattern when moving a fixed distance to perform positioning. In FIG. 6, a section 60a is a maximum acceleration section, a section 60b is a maximum speed section, and a section 60c is a maximum deceleration section, which moves a fixed distance in the shortest time. Depending on the moving distance, the section 60b may not exist. After moving a certain distance using this ideal target speed pattern and speed control system, when switching is performed to the positioning control system including the integral element in the section 60d near the target value and positioning is performed, friction fluctuations and the like from the speed control system When switching to the position control system, the speed and the integral operation of the position control system are affected, and overshoot often occurs.
Therefore, for example, in the conventional example of Japanese Patent Laid-Open No. 62-106510, as shown in FIG.
By setting 0, the speed of the moving body at the time of switching from the speed control system to the position control system is made constant. This stabilizes the switching to the positioning control system, reduces the amount of overshoot, further adjusts the deceleration start point 71 in the speed pattern, and provides a learning function for keeping the length of the constant velocity movement section 70 constant. By adding them, the influence of the characteristic variation of the controlled object such as the friction variation is reduced. However, by providing the constant velocity movement section 70, the positioning time may be extended as compared with the case where the velocity pattern shown in FIG. 6 is used. On the other hand, according to the present invention, the section 60
The convergence behavior to the target value in the positioning control system used in d is
Since it is constrained within the preset convergence behavior region, the constant velocity section 70 for stabilizing the switching to the positioning control system and reducing the overshoot amount becomes unnecessary, and the ideal velocity pattern shown in FIG. 6 is used. The positioning time can be shortened.

[0012]

According to the present invention, the behavior of the controlled object can be constrained within a preset convergence region, and the influence of fluctuations of disturbance such as friction can be suppressed, so that a digital positioning control device that is always constant is provided. can do.

[Brief description of drawings]

FIG. 1 is a block diagram of a control system according to the present invention.

FIG. 2 is a characteristic diagram showing a behavior of a controlled object on a phase surface according to the present invention.

FIG. 3 is a characteristic diagram showing a behavior of a controlled object on a phase surface by a conventional method.

FIG. 4 is a characteristic diagram of a time response of a controlled object according to the present invention.

FIG. 5 is a characteristic diagram of a time response of a control target according to a conventional method.

FIG. 6 is an explanatory diagram of an ideal target speed pattern.

FIG. 7 is an explanatory diagram of a target speed pattern according to a conventional method.

[Explanation of symbols]

1 ... Sampler, 2 ... Subtractor, 3 ... Digital integrator, 4
... integral gain, 5 ... adder, 6 ... loop gain, 7 ... 0
Next hold, 8 ... Adder, 9 ... Control object, 10 ... Sampler, 11 ... Judgment device, 12 ... Switching device, 13 ... Integral value update gain, 14 ... Switch.

Claims (1)

[Claims] 1. A controlled object, an observing device for observing a controlled variable and a state of the controlled object, a subtractor for calculating a deviation between the controlled variable and the target value observed by the observing device, and a subtracter for the subtractor. In a control device for controlling the controlled object based on an output deviation signal, as the control device, a digital control system having an integral element is provided, and the behavior of the controlled object converging to the target value is observed by the observation device, It is determined whether or not the convergence behavior is within a preset convergence behavior region, the value of the integration element is adjusted separately from the integration action, and the convergence behavior of the controlled object is constrained within the convergence behavior region. Digital positioning control device.