JP3269198B2 - Position control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control device applied to machine tools, industrial robots and the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional position control apparatus uses position and velocity feedback. That is, in order to position the detection position x of the object having the mass M at the target position r, the detection position x is negatively fed back (negative feedback) before the position loop gain K _p 8, and the detection position x is differentiated by the differentiator 7. speed determined Te is (in a system with a speed detector that detects speed) is negatively fed back to the preceding stage of the speed loop gain K _v 6. Since it is position control, it is considered that negative feedback of speed is unnecessary, but it is practically essential for stabilizing the system (adding viscosity). If there is no negative feedback of the velocity and the remaining S ² in the denominator of the block 1,
The vibration system has no damping.

[0003]

However, in the prior art, in a system having only a position detector and no speed detector,
It is necessary to obtain the speed from the position by a difference calculation, and there is a problem that the resolution of the speed is coarser than the resolution of the position. Therefore, there is a problem that only the position control that is coarser than the resolution of the position sensor can be performed. Accordingly, it is an object of the present invention to provide a position control device capable of performing stable and high-speed response position control by using only position feedback without using speed.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a negative position error.
Feedback loop and position positive feedback loop
Providing the door, the position control device for controlling the positioning to the target position of the object without providing a speed loop, and the
The position negative feedback loop can be
Provided before the position controller consisting of the proportional-integral controller
The position is fed back to the input terminal of the subtractor, and the target
Subtract the position from the position and input to the position controller
And the positive feedback loop at the position
To the input terminal of the adder provided after the
Feedback the position through the filter,
The output of the position controller and the low-pass filter
Add position and input to positive feedback controller
And was, it is characterized in.

[0005]

Since the present invention is realized by feedback of only the position, the same control accuracy as the resolution of the position sensor can be realized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the present invention will be described. FIG. 1 is a transfer function of an object having a mass M to be controlled, in which an input is a force f and an output is a position x. FIG. 2 is a block diagram of the present invention for controlling the position of an object having a mass M of FIG.
In this embodiment, three position feedback loops A to C
There is. A is a position negative feedback proportional control loop. The block 5 of this loop is a proportional control (proportional gain K ₂ ), but may be a proportional integral control. B is a position positive feedback proportional control loop in which the feedback signal passes through a first-order lag filter 4. K _pf 3 is the proportional gain of positive feedback,
T is a time constant of the first-order lag filter. C is block 1
With localization (the transfer function G (S) = 1 / S ² is a non-localization system, but the transfer function G (S) = ω ² / S ² + ω ² is a localization system) This is a minor loop for converting to However, since the effect of providing the loop A results in a localization system, the loop C is not necessarily required.

The operation of the control system shown in the block diagram of FIG. 2 will be described. FIG. 4 shows a pole-zero arrangement of a control target. The proportional control of C loop, as shown in the root locus of Fig. 5, the origin of the polar moves on the imaginary axis with gain, when the gain K _1, natural frequency (K ₁ / M) ^1/2 free It becomes a damped oscillation root. Incidentally, this is the same as in the case where there is no negative feedback at the speed described in the related art. Further, the root locus when the positive feedback of the B loop is also performed is shown in FIG.
Becomes By this positive feedback, the oscillation root is stabilized as poles P ₂ and P ₃ , and the first-order lag pole moves to the slower first-order lag pole P ₁ . The resulting poles and zeros of the input and output transfer functions are as shown in FIG. FIG. 8 shows a root locus when the proportional control of the A loop is further performed. By setting an appropriate proportional gain K _2, poles of the closed loop control can all stable roots as shown by _{P 1, P 2, P 3} , P 4. Finally, the transfer function of the closed loop control system is as shown in FIG.

Hereinafter, specific embodiments of the present invention will be described.
FIG. 10 shows an embodiment of the present invention. This is an example in which the control means 12 controls the position x of the motor 10 detected by the position detector 11 so as to follow the position command r. Instead of the motor 10, the position detector 11 may be of a linear type attached to a driven side (not shown), for example, a table driven by a ball screw. In this example, since the force f is proportional to the motor current i _M, position controller 12 outputs a current command i _r. The current amplifier 13 outputs the current command i _r
To a motor current i _M. FIG. 11 shows a block diagram of this embodiment corresponding to FIG. The control means 12 corresponds to blocks 3, 4, and 5. Block 2 (proportional gain K ₁ ) in FIG.

[0009]

As described above, according to the present invention, since position control can be realized only by position feedback without using speed, the accuracy of the speed information can be obtained by calculating the speed by the difference calculation from the position. It is possible to eliminate the deterioration and, consequently, the deterioration of the accuracy of the position control, to perform the position control with the accuracy of the position sensor, and to improve the accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control target.

FIG. 2 is a block diagram illustrating the concept of the present invention.

FIG. 3 is a block diagram of a conventional position control system.

FIG. 4 shows pole-zero arrangement and root locus for explaining the behavior of the control system of the present invention.

FIG. 5 shows a pole-zero arrangement and a root locus for explaining the behavior of the control system of the present invention.

FIG. 6 shows pole-zero arrangement and root locus for explaining the behavior of the control system of the present invention.

FIG. 7 shows pole-zero arrangement and root locus for explaining the behavior of the control system of the present invention.

FIG. 8 shows pole-zero arrangement and root locus for explaining the behavior of the control system of the present invention.

FIG. 9 shows a closed loop transfer function of the position control system of the present invention.

FIG. 10 is a diagram showing an embodiment of the present invention.

11 is a block diagram corresponding to FIG. 10 corresponding to FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transfer function of a mass object 2 Proportional control gain 3 Positive feedback proportional control gain 4 First order lag filter 5 Proportional control gain 6 Proportional control gain 7 Differentiation (difference) calculator 8 Proportional control gain 10 Motor 11 Position detector 12 Control means 13 Current amplifier A Negative feedback proportional control loop of position B Positive feedback proportional control loop of position C Minor loop of position for conversion to system with localization

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G05D 3/00-3/20 G05B 11/00-13/04

Claims (1)

(57) [Claims] 1. A position negative feedback loop and a position
Provide a positive feedback loop and set a speed loop.
In a position control device that controls the positioning of an object at a target position without moving the object, the negative feedback loop of the position is controlled by proportional control.
Installed before the position controller consisting of a controller or a proportional-integral controller.
Feedback the position to the input terminal of the subtracted
Subtract the position from the target position and set the position controller
As input, positive feedback loop of the position is the position system
The low-pass filter is connected to the input terminal of the adder provided after the controller.
Feedback the position through the filter,
Controller output and said position through said low pass filter
Is added to the input of the positive feedback controller.
A position control device, characterized in that: