JP2724054B2 - Positioning 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 positioning control device for a robot, an NC machine tool, and the like, and more particularly to a positioning control device for realizing high-precision positioning in a short time.

[0002]

2. Description of the Related Art As shown in FIG. 4, when a position of a control target 2 is controlled using a speed control means 1, a position detection means 3 is used.
The output of the position-speed function generating means 4 is given to the position detected by using the speed control means 1 as a speed command. Therefore, the speed of the electric motor is controlled by the speed command according to the current position, and the control target 2 is positioned. Since the position-speed function is set to be zero at the target position, the motor eventually stops.

[0003]

The position control device constructed as described above has a delay as shown in FIG. 5 even when a required speed command is given to the position due to the delay of the loop transfer function of the position control system. Since the response of the motor speed 5 at each position is delayed as compared with the speed command 6, the required speed cannot be obtained at that position, and a large position error occurs. This error has a negative value during acceleration and a positive value during deceleration. However, the acceleration / deceleration response is affected by the load, so that the positive / negative cannot be canceled, which is a major cause of generating a large positional error.

In order to solve the above problem, the present invention does not use only the feedback loop of the position control system. When a moving position is given, a time-speed function that can achieve the movement of the given position is calculated. Generated and given as a speed command of the speed control system, which responds faster than the position control system, feeds back the resulting position error, and corrects the deviation from the position detected value against the position reference value calculated from the time-speed function. Accordingly, an object of the present invention is to provide a positioning control device capable of reducing a position error.

[0005]

FIG. 1 is a block diagram showing the overall configuration of the present invention. In the figure, reference numeral 7 denotes a speed control means which controls the speed based on a speed reference value 8 and outputs the speed. Reference numeral 9 denotes a control object, which inputs speed and outputs position. Numeral 10 is a time-speed function generating means, which inputs a moving distance as a reference value and outputs a speed command 8 with respect to time. Numeral 11 is a time-position function generating means for integrating the speed command 8 to generate a position command. Numeral 12 denotes a position detecting means for obtaining a difference from the abutting point 13 and giving the difference to the speed reference value 8 as a speed correction signal. As described above, when the moving distance is given, the positioning proceeds by the time-speed function,
The correction operation by the feedback position loop is controlled so that the difference between the reference position and the actual position is eliminated.

[0006]

When the moving distance is given, the time-speed function 1 shown in FIG.
4 is generated by the time-speed function generator 10. This speed function is given and controlled as a speed reference value 8 of the speed control means 7, and the control object 9 moves. In this case, due to a response delay of the speed control means, an error occurs in the actual position with respect to the instantaneous position reference value 8 as shown in a response of 15 in FIG. Therefore, the position reference value is generated with respect to time by the time-position function generation means 11 from the integration of the speed command, and is compared with the position signal of the position detection means 12 by the abutting point 13. As a result, the speed command value 8 is corrected based on the obtained position error signal. As is clear from FIG. 2, the errors-and + during acceleration and deceleration are canceled, and the position error can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 3 is a block diagram of one embodiment of the present invention. In the figure, reference numeral 16 denotes a time-speed function generating means for generating a time-speed function that satisfies a given travel distance. Table 1 shows the time-speed functions in the acceleration, constant speed, and deceleration periods in the case of constant torque linear acceleration.

[Table 1]

[0008]

The speed control system comprises a speed feedback system comprising a speed control means 17, a power converter 18, an electric motor 19, a rotation pulse generator 20, a position control object 21, and a speed detection means 22. The speed is controlled according to a speed reference value generated by the time-speed function generating means 16. In this case, as shown in FIG. 2, compared with the time-speed function, that is, the speed reference value 14, the actual motor speed 15 has a delay in response, causing a position error. Therefore, as shown on the right side of Table 1, a time-position function is generated by the time-position function generating means 23 in FIG.
Using this as a reference value, it is compared with the position feedback value obtained by the position detection means 24, and the resulting position error signal is given as a correction signal for the speed reference value of the speed control system.
In this case, since the detection signal of the position detecting means 24 has a relatively large response delay, by giving it through the advance compensating means 25, the correction delay of the position error is compensated, which is extremely effective in reducing the position error.

In the above description, the current position of the position control object 21 is detected by the position detecting means 24. Instead of this method, the number of pulses of the rotational position pulse generator is integrated by using a counter or the like, and FIG. Even when used as a position detection signal as indicated by the dotted line 3, substantially the same control can be performed.

[0011]

As described above, according to the present invention,
Based on the movement distance, the time-speed function generator gives the speed reference value to the speed control system, so that the speed can be controlled with good responsiveness and the positioning accuracy is improved. Besides, time-
Since the position reference value is generated by the position function generation means, and the deviation from the actual position is corrected as it is or after the advance is compensated, the speed reference value is corrected, so that extremely high positioning accuracy can be obtained. Actually, as a result of experimentally producing a control device and conducting experiments, the correction amount by the position detection means is 2 to 3%. This means that positioning based on the time-speed function generating means 16 is mainly performed, and positioning with good responsiveness can be performed.
The method using the pulse integration of the rotation pulse generator 20 as an input to the position detecting means 24 eliminates the need for a position detector, which is economically advantageous.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the principle of the present invention.

FIG. 2 is a diagram showing a time-speed function and a response.

FIG. 3 is a block diagram showing one embodiment of the present invention.

FIG. 4 is a block diagram of a conventional positioning control system.

FIG. 5 is a diagram showing a position-velocity function and a response of a conventional positioning control system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Speed control means 2 Control object 3 Position detection means 4 Position-speed function generation means 5 Motor speed response 6 Position-speed function 7 Speed control means 8 Speed reference value 9 Control object 10 Time-speed function generation means 11 Time-position function Generating means 12 position detecting means 13 butting point 14 time-speed function 15 motor speed response 16 time-speed function generating means 17 speed control means 18 power converter 19 variable speed motor 20 rotation pulse generator 21 position control object 22 speed detecting means 23 time-position function generating means 24 position detecting means 25 advance compensating means

Claims (2)

(57) [Claims] An object to be controlled which is driven and moved by an electric motor is
In a positioning control device that performs positioning control, when a movement distance of the control target is given, the movement distance is required.
Necessary time-time to generate speed command which is speed function-speed
Degree function generating means, and position detection for detecting a moving distance, that is, a position of the control object.
Output means and the generated time-velocity function,
Time-position function generating means for generating a position command which is a number
And the detected position output by the position detecting means, and the time-position
Using the deviation from the position command output by the
The speed command output from the time-speed function generating means is supplemented.
A correcting means for correcting the speed of the electric motor and a deviation from the corrected speed command.
Speed control means for adjusting the speed of the motor using the difference . 2. The positioning control apparatus according to claim 1, wherein said correction means includes a compensation means having a lead compensation characteristic for compensating for a time delay caused by a loop transfer function of a position control system.