JPH01108608A - Position controller for servomotor - Google Patents

Abstract

PURPOSE:To obtain control with high accuracy by switching the control system of a speed loop to PI control and first-order lag/first-order lead control corresponding to the deviation of a position. CONSTITUTION:The title device is operated in such a way that two systems of the PI control and the first-order lag/first-order lead control are provided at a speed control part and the control is switched to the PI control or the first-order lag/first-order lead control based on the deviation of the position after a position command is inputted. The switching of the control is performed by employing the PI control in which a current is increased integrally until it overcomes statical friction. In such a way by employing the first-order lag/ first-order lead control in which no accumulative feeding is generated and the position command coincides with position feedback or lowers torque steeply after friction is reduced, it is possible to prevent overshoot from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a speed loop control method in a precision position control device for machine tools and similar machines.

[Conventional technology]

FIG. 4 shows a control method that is currently often used as a position control device. (1) is the position control section, (2) is the speed control section, (8) is the current control section, (4) is the servo motor, (
5) shows the mechanical system.

Also, the symbols in the figure are as follows.

[θ*: Position command, θ: Position feedback, (:: Speed command, ω: Speed feedback, D = Position deviation, ■*: Current command, ■: Current feedback, KT: Motor torque constant, J: Motor deviation, S nila plus operator]

Conventionally, P control was used as the position control section, and PI control was used as the speed control section.
P control is often used as the control and current control section, and the position and speed control section in this case is shown in FIG. 5, and its Bode diagram is shown in FIG. In addition, in the figure, Kp is the position p-gain,
Kv is the velocity harp gain, and Kv is the velocity μmm backward compensation time constant.

When the speed control section is configured in this way, the mechanical system (5) in Fig. 4 generates a nonlinear friction component, such as static friction Fs and dynamic friction S, for the speed ω as shown in Fig. 9, for example. If it is included, an overshoot error may occur in θ relative to θ. That is, in the timing chart of Fig. 10, θ'' is input, a positional deviation occurs, and it is multiplied by Kp to become ω, and ω
8 increases with respect to the difference between Since it has exceeded mft, θ has exceeded θ''. At this time, the paper begins to decrease, and since there is only a screw between the motor and the mechanical system, a current of 1 m is equivalent to the dynamic friction Fm.
When the temperature falls below f, θ1 and θ match and the motor stops.

Another conventional method includes first-order lag and first-order advance control as a speed control section, and the Bode diagrams of the position and speed control sections in this case are shown in FIG. 7 and FIG. 8, respectively.

Note that in the figure, TD is a speed loop delay compensation time constant, and the others are the same as in FIG. 5.

If configured in this way, θ may not be able to follow θ8, which may cause accumulation of feed. In other words, in the timing chart of Fig. 11, θ8 is input, a positional deviation occurs, and K
It is multiplied by p and becomes ω, and - increases with respect to the difference between ω and ω, but if ω is not fed back, PI
In the case of sub-control, compared to the integral action, in this case it is a -th lag action, and there is saturation, so if the position deviation is small, the static friction of the machine part F
Is corresponding to s is not reached, and θ does not move. When θ is further input, D increases, and ■ reaches work 8, θ starts to move for the first time, so if commands are input little by little, positional deviation accumulates to a certain extent and the movement repeats, resulting in storage feed. .

[Problem that the invention seeks to solve]

Conventional position control devices are configured as described above, so overshoot and feed are likely to occur, and even if they can be adjusted well, adjustment is difficult and delicate.
When the static and dynamic friction of a mechanical system changes due to aging, etc., overshoot and feed will occur.

This research was carried out in order to solve the above-mentioned problems, and to create a positioning control device that is easy to adjust, can be controlled without overshoot or accumulating feed, and is resistant to changes in the mechanical system. aim at something.

[Means for solving problems]

The position control device according to the present invention includes two systems of PI sub-control first-order lag first-order advance control in the speed control section, and after a position command is input, υPI control or -second lag first-order advance control is performed according to the position deviation. [Operation] The control switching in this invention uses the PI sub-control, which increases the current integrally until static friction is overcome, so that no storage feed occurs, and the position Overshoot does not occur by fully adopting first-order delay and first-order advance control that rapidly reduces torque after the command and position feedback match or decrease.

[Embodiments of the invention]

Hereinafter, all the drawings of a simple embodiment of this invention will be explained. 1st
In the figure, (1) is the position control section, (2) is the speed control section, (3) is the current control section, (4) is the motor, (5) is the mechanical system, and (6) is the switching judgment. Department. Figure 2 is (
The details of 1) the position control section, (2) the speed control section, and (6) the switching determination section, and the reference numerals in the drawings are the same as those in FIG. 5 and FIG. 6.

Further, FIG. 8 shows a switching determination section. (7), (8)
is a comparator, (9) is a rising differential circuit, and α is a flip-flop circuit.

To explain the operation of the switching determination section, the position command θ8 is (
8) When input to the comparator, (8) the output of the comparator changes from 0 to 1, 9) rises, passes through the differentiation circuit, and (10)
The flip-flop circuit is reset, the output becomes 0, and PI sub-control is selected. When the position feedback θ moves and matches θ, the position error becomes 0, so (7) O is input to the comparator and the output changes from 0 to 1, so (10
) The flip-flop output is 1, and the 9th-order delay-advance control is selected, and this state is maintained until the next 05 manual input is applied.

Next, in the overall control operation, until 08 is input in the timing chart of Fig. 12, it is first-order delay and first-order advance control, and when r is input, a position error occurs, and it is multiplied by Kp and becomes ω. , - increases with respect to the difference between ω and ω, but at this time, since the PI sub-control has been switched, it increases integrally, and when it reaches Is, θ starts to move and θ matches r. Since the instantaneous position deviation becomes 0, the PI sub-control is switched to first-order delay/first-order advance control, and the work 8 is rapidly reduced.

Therefore, θ matches θ4 without overshooting.

Here, the time constant W for the -next advance is set to a small value to the extent that the servo system does not become unstable in terms of control theory, and the time constant TD for the -next lag is set to a large value to the extent that oversheet does not occur. There is no need to make delicate adjustments to the mechanical system.

3. In the above embodiment, in (6) the switching determination section, after the position command is input, the Pi control is performed until the position feedback matches the command, and then the first-order delay and first-order advance control is performed. In an actual machine, the same effect can be obtained even if the control is quickly switched to -next lag one-in advance control, such as switching when the feedback reaches the command overlapping μm.

〔Effect of the invention〕

As described above, according to the present invention, since the servo motor position control device is configured so that the speed control part and the PI sub-control are switched to primary lag primary advance control, highly accurate control can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a position control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a position and speed control section, and a switching determination section, and FIG. 3 is a detailed diagram of the switching determination section. Fig. 4 is a block diagram showing a conventional position control device, Fig. 5 is the prologue of the position/speed control section when the speed control section is P1 control, Fig. 6 is its Bode diagram, and Fig. 7 is the speed A block diagram of the position/speed control unit in the case of first-order delay first-order advance control, Fig. 8 is its Bode diagram, Fig. 9 is a characteristic diagram of the simple vibration included in the mechanical system, and Fig. 10 is the conventional Position command when P system t1 is adopted in the speed control section. Feedback current command timing chart, 11th
12 is a timing chart for the conventional first-order lag/first-order advance control, and FIG. 12 is a timing chart for an embodiment of the present invention. (1) Position control section, (2) Speed control section, (8) Current control section, (4) Servo motor, (5) Mechanical system, (6) Switching judgment section, (7) Comparator, (8) Comparison (9) rising differential circuit, (10) flip-flop circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Q- 1 (Figure 10 Time Figure 11 Clearance Figure 12 @Dark A Knee Next Delayed First Way tSe 1 #p B: PI Sub-Wholesale Procedure Amendment (Method) % Formula % 2, Name of Invention Servo Motor Position control device 3, Representative of the person making the amendment Moriya Shiki I Date of amendment order January 26, 1988 (shipment date) 6. Column for a brief explanation of the drawings in the specification subject to amendment. 7. Amendment "11th wa" on page 8, line 12 of the description of contents is amended to ``Fig. 11 wa''.

Claims (1)

[Claims] In a position control device that has a speed control section as a minor loop, the control method of the speed loop is set to P according to the position deviation.
A servo motor position control device characterized by switching between I control and first-order lag/first-order advance control.