JPH01191908A - Positioning controller - Google Patents

Abstract

PURPOSE:To ensure the smooth acceleration and deceleration by using a soft limiter to gradually saturate the feedforward output and switching the control of the feedforward mainbody to the control of the feedback main body. CONSTITUTION:The function of a soft limiter 16 is provided to a position control part 10 of a positioning controller. The limiter 16 is used for a saturation element which controls the output of a feedforward. The part 10 consists of a waste time element transmission function 13 which supplies a position command signal P1(S), a subtractor 11a which uses the output P'1(S) of the function 13 as a single input, a positio control transmission function 12, a speed feedforward transmission function 14, the limiter 16, and an addition part 11b. While a speed control part 20, a speed detecting part 40 and a position detecting part 50 contains a speed control system transmission function 21, a transmission function 41 and a position feedback transmission function 51 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a positioning control device, and particularly to a positioning control device that is effective when applied to a drive unit of a robot or the like.

B9 Summary of the Invention The present invention provides a positioning control device comprising a position control section that receives a position command signal as input and outputs a speed command signal, and a speed control section that receives the speed command signal as input and outputs a control signal to a motor. By inputting a position command signal and limiting the feed forward output using a soft limiter that has the characteristic of gradually becoming saturated, a positioning control device is obtained that is capable of smooth speed control even in the high speed rotation range of the motor. .

C0 Prior Art Generally, a positioning control device has a configuration as shown in FIG. That is, in FIG. 5, IO is a digital position control unit which inputs and binds a position command signal Sl and outputs an analog speed command signal S2.

20 is a speed control section which receives an analog speed command signal S2 from the position control section 10 and outputs a current signal as a speed control signal S3. 30 is a servo motor, and speed control section 2
Rotation operation is performed based on the speed control signal S3 from 0. 4
0 is a speed detector that detects the rotational speed of the servo motor 30. 50 is a position detector, which detects 30 rotational positions by a servo motor.

According to the positioning control device shown in FIG. 5, a current feedback signal S4 is fed back to the speed control section 20 based on the speed control output signal S3 of the speed control section 20. Further, the speed detection signal S5 from the speed detector 40 is transmitted to the speed control unit 2.
It is fed back to 0. Furthermore, the position detection signal S6 is fed back from the position detector 50 to the position control section 10.

That is, the digital position control section 10 inputs the position command signal s1 and the position feedback signal S6, and outputs the analog speed command signal S2.

The speed control unit 20 receives an analog speed command signal S2, a current feedback signal S4, and a speed feedback signal S.
5 as an input and outputs a speed control signal S3.

In the positioning control device shown in FIG. 5, the speed control section 20 and the servo motor 30 may be a combination of a DC servo amplifier and a DC servo motor, or a combination of an AC servo amplifier and an AC servo motor. Furthermore, the position detector 50 may also be used as the speed detector 40.

Positioning control includes an FTP operation in which the object is simply positioned by moving from the current position to the target point, and a CP operation in which the object is positioned by moving along a predetermined path from the current position to the target point.

In industrial robots, etc., it is used when performing the following operations. In other words, FTP operation is used when changing the posture significantly or when moving at high speed to reach the target point in the shortest possible time.

The CP operation is a case of tracking a determined path (trajectory).

Conventionally, the positioning control device having the configuration shown in FIG.
If tracking accuracy during CP operation is to be improved, the block diagram shown in FIG. 7 will be used.

In FIG. 6, tta is a subtraction section, 12 is a position control transfer function, and these comparison section 11a and position control transfer function 12 correspond to the position control section 10. Reference numeral 21 denotes a speed control system transfer function, which corresponds to the speed control section 20. 41 is a transfer function that converts speed into position, and corresponds to the speed detector 40.

5I is a position feedback transfer function and corresponds to the position detector 50.

Further, in FIG. 6, constants and variables are defined as follows.

S nira plus calculation factor.

Pt(S): Position command signal.

p, (s): position output.゛Tdl: Delay time of dead time element.

T6. : Servo amplifier response time.

K FF: Feed forward constant.

KL: Position deviation control gain.

Kv: Speed constant of speed control system.

KP: Constant that converts velocity to position.

K FB: Position feedback constant.

In FIG. 7, Ia is a dead time element transfer function, 11b
is a comparator and adds these functions to the position control section 10.

Figure 9 shows the response characteristics of the control device shown in the block diagram of Figure 6 obtained through simulation, and Figure 1 shows the response characteristics of the control device shown in the block diagram of Figure 7.
This is figure 0. The conditions for the simulation are as follows:
The resolution of the position detector 50 per motor rotation is 400
0 pulse, and 3(v
) is input, the motor rotates at 101000 (rp).

D1 Problem to be Solved by the Invention As is clear from the response characteristics shown in FIGS. 9 and 10,
The advantages and disadvantages of the device that performs only simple feedback control as shown in the figure and the device that performs feed forward control as shown in FIG. 7 are as follows.

[Positioning control device shown in Fig. 6] (Ia) Advantages: When performing acceleration/deceleration control as shown in Fig. 9, the acceleration/deceleration is smooth in the rotation range of the motor;
For example, the arm of the robot body is caused by vibrations caused by the mechanical mass spring system.

(1b) Disadvantages: As shown in FIG. 9, the position deviation pulse becomes large and the tracking accuracy is poor.

[Positioning control device shown in FIG. 7] (2a) Advantages: As shown in FIG. 10, the tracking accuracy during CP operation is greatly improved. If about 90% of the feed forward compensation is performed, the positional deviation l pulse will be about 1/10.

(2b) Disadvantages: As shown in FIG. 10, the acceleration and deceleration of the motor in the high-speed rotation range changes rapidly, so that, for example, the arm of the robot body tends to vibrate due to the mechanical mass spring system.

In addition, for example, in industrial robots, - inside the shell,
The motor rotation speed in FTP operation and CP operation is FT
More than several hundred (rpm) for P operation, O(rpm) for cp operation
m) to several hundred (rpm). Therefore, in view of the above points, the digital position control unit 10 is provided with the following characteristics to achieve feedback control and feed
Improved the shortcomings of forward control.

(i) When the rotation of the motor is relatively small, such as in CP operation, the operation is performed mainly through feed forward control.

(ii) When the rotational speed of the motor is high, such as in PTP operation, the operation is performed mainly through feedback control.

In order to realize the operations (i) and (ii) above, the eighth
As shown in Figure (A), a hard limiter 15 is added to the position control unit 10, and the feed-forward output is limited by the saturation element by the hard limiter 15, so that when the motor rotation speed is large, the feed-forward effect is reduced. has been lowered so that it becomes the operation of the feedback control itself.

However, with this method, when accelerating or decelerating the motor,
The response becomes the response waveform shown in Fig. 8 (B), and at the point when the feed forward output begins to be saturated by the hard 1 luminaire 15, the speed command changes rapidly and becomes disordered as shown in Fig. 11. It wasn't on point.

The present invention has been made in view of the problems of the prior art as described above, and its purpose is to provide a feed forward loop in the positioning control loop, and to gradually control the output of the feed forward loop. An object of the present invention is to provide a highly accurate positioning control device that enables smooth speed control using a soft limiter that saturates.

Means for Solving the E0 Problem In order to achieve the above object, the positioning control device of the present invention uses a dead time element transfer function that receives a position command signal as an input, and an output signal of this dead time element transfer function. The position control unit 10 is composed of a position control transfer function of the subtraction unit 1 as an input, a speed/feed-forward transfer function that receives a speed command signal as input, a soft limiter having smooth saturation characteristics such as a sine wave characteristic, and an addition unit. However, a speed control section is configured by a speed control system transfer function, a speed detection section is configured by a transfer function that converts speed into position, and a position detection section is configured by a position feedback transfer function.

The output of F1 action feed forward is limited by a soft limiter that gradually saturates, and feedback is generated from feed forward-based control when the motor is accelerated from a stopped state to high speed rotation of several thousand rpm. There is a smooth switch to main control, and acceleration and deceleration change smoothly in the high-speed rotation range.

G. Examples Examples of the present invention will be described below with reference to FIGS. 1 to 5.

In this embodiment, as shown in FIG.
The function of a soft limiter 16 is further added to the position control section 10 shown in FIG. The soft limiter 16 is a saturation element soft limiter that limits the feed forward output, and has a sine wave curve (s) shown in FIG. 2(A).
In curve), a polygonal line as shown in FIG. 2(B), or any other type having input/output characteristics that gradually saturate may be used.

In the positioning control device according to this embodiment, as shown in FIG. 1, a dead time element transfer function 13. A subtraction unit 1 which receives the output signal p', (S) of this dead time element transfer function 13 as a negative input.
1a, position control transfer function 12. Speed command signal p, (s
) as an input velocity-feed-forward transfer function 14. A position control section 10 is configured by the soft limiter 16 and the addition section 11b.

Also, the speed control unit 20 is controlled by the speed control system transfer function 21.
A transfer function 41 that converts speed to position constitutes a velocity detection section 40, and a position feedback transfer function 51 constitutes a position detection section 50.

According to the positioning control device shown in FIG. 1, the input position command signal P t (s) is delayed for a certain period of time by the dead time element 13 to generate a signal p', (s), and Pl(
A position deviation signal (deviation pulse) is obtained by subtracting the position feedback signal pr(s) from S), and a position control signal V is obtained by multiplying the position deviation signal by a gain constant KL.

seek. Also, differentiate the position command signal p, (s) and multiply the value by the feed forward constant KFF,
The value of the feed forward signal vtr is set to V'rr(S) by limiting the value of Vrr(S) using a soft limiter 16 which has a characteristic that the output gradually saturates depending on the input.
, and add the previous values of t(S) and v'rr(s) to obtain the command V,(S) to the speed control unit 20. From this, if the rotation speed of the servo motor 30 is small, Limits the feed forward effect and switches to feed forward control (deviation control)-based operation.

Therefore, the servo motor 30 is changed from O (rpm) to 20
The response when accelerating and decelerating to 0.00 (rpm) in 0.5 seconds is shown in Figure 3, and compared to the conventional feed forward control shown in Figure 10. , the acceleration/deceleration changed smoothly in the motor's high-speed rotation range.

In addition, as shown in Fig. 4, when the motor rotation speed is relatively low such as in CP operation, from O (rpm) to 666 (rpm).
When accelerating and decelerating to pm) at 0.5 (seconds), feed forward control is sufficiently effective, and the speed is 1/20 to 1/30 compared to when no feed forward control is performed.
This resulted in a deviation pulse of

H1 Effects of the Invention Since the present invention is configured as described above, it produces the following effects.

(i) In a range where the motor rotation speed is relatively small, such as in CP operation, feed forward works sufficiently.
The deviation pulse becomes extremely small and the tracking accuracy is greatly improved.

(ii) When the rotation speed of the motor is relatively large, such as in FTP operation, the feedforward-based operation
Since the operation is gradually switched to feedback-based operation, changes in acceleration/deceleration of the motor in the high-speed rotation range become smoother, and the driven body becomes less likely to vibrate.

(iii) The soft limiter that limits the feed forward output may be of any type as long as it has the characteristic of gradually becoming saturated, or may be a function based on polygonal line approximation, and calculation is simple.

[Brief explanation of the drawing]

FIG. 1 is a transfer function block diagram of a positioning control device according to an embodiment of the present invention, and FIGS. 2(A) and 2(B) are characteristic diagrams of a soft limiter used in the block diagram of FIG. Figures 3 to 4 are operational characteristic diagrams based on the transfer function block diagram of Figure 1, Figure 5 is a block diagram of the positioning control device, and Figures 6 to 8 are transfer functions of the conventional positioning control device. In the block diagram, FIG. 9 is an operational characteristic diagram of the apparatus shown in FIG. 6, FIG. 10 is an operational characteristic diagram of the apparatus shown in FIG. 7, and FIG. 11 is an operational characteristic diagram of the apparatus shown in FIG. lO...Position control section, 20...Speed control section, 30.
...Servo motor, 40...Speed detection section, 50...
Position detection section, lla... Subtraction section, ttb... Addition section, 12... Gain constant transfer function, 13... Dead time element transfer function, 14... Feed forward constant transfer function, 16. ... Soft limiter, 21 ... Speed control system transfer function, 41 ... Speed position conversion transfer function, 51
...Position feedbank transfer function.

Claims (1)

[Claims] (1) A position control unit that receives a position command signal and a position feedback signal from a position detection unit that detects the position of the motor, and outputs a speed command signal, and detects the speed command signal of this position control unit and the speed of the motor. In a positioning control device that includes a speed control section that receives a speed feedback signal from a speed detection section and outputs a control signal to the motor, a position command signal (P_i) is delayed by a certain period of time due to a dead time element (P'_i). ), and the signal (P'
The position feedback signal (P_f) is subtracted from the position feedback signal (P_f) to obtain the position deviation signal, and a gain constant (K
_L) to obtain the position control signal (V_ε), and a means for differentiating the position command signal (P_i) and feeding that value.
A feed forward signal (V_f_f) is obtained by multiplying by a forward constant (K_F_F), and the value of the feed forward signal (V_f_f) is limited by a soft limiter whose output gradually saturates depending on the input. (V'f_f), a means for determining the value of the position control signal (V_ε) and a feed forward signal (V_f
The command (V_i) to the speed control unit is obtained by adding the value of
), and when the motor rotation speed is small, feed forward is applied to reduce the position deviation, and when the motor rotation speed is large, the feed forward effect is limited and the operation is based on feedback control. A positioning control device characterized in that the position control section is constituted by switching means.