JP2002157018A - Position control device for full-closed loop - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detector capable of keeping high position detecting precision even with large backlash and stabilizing the positioning precision over a long period while wrong positional information is outputted in a conventional position detector when exceeding the tolerance of backlash, resulting in a wrong positioning. SOLUTION: A third differential device 43 calculates the difference between the positional information after outputted by a position composition part 37 and the positional information after correction outputted last time by a position correction part 38 to directly determine speed information V2 for a position detector 11 side. A fourth differential device 44 calculates the difference V3 between speed information V1 obtained by differentiating the positional information inputted from a position detector 7 on a servo motor 5 side and the speed information V2. The position correction part 38 corrects positional information after composition P3 based on the difference V3 of speed information and outputs positional information after correction P4.

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 for controlling the position of a feed shaft of a machine tool or the like, and more particularly to a position of a fully closed loop with respect to a shaft having a large backlash using a gear reduction mechanism. It relates to a control device.

[0002]

2. Description of the Related Art A conventional position control device will be described with reference to FIG. A conventional position control device includes an N (not shown)
Based on the NC program unit 1 read and interpreted by the C program reading unit and the NC program interpreting unit, the function generating unit 2 calculates the movement information (target position, speed, etc.) of the axis, and the axis control unit 3 To transfer the position command. As shown in FIG. 4, the axis control unit 3 includes a position loop operation unit 31, a speed loop operation unit 32, an output unit 33, a first input unit 34, a second input unit 35, a differential operation unit 36, and a position synthesis unit 37. The position synthesizing unit 37 includes a position detection value P1 of the motor position detector 7 that detects the rotor position of the servo motor 5 input through the first input unit 34,
A position detection value P2 of a direct position detector 11 such as an inductosin which detects the position of the circular table 12 input through the second input unit 35 is combined and output as a position detection value P3. The differential operation unit 36 calculates the rotation speed of the motor by differentiating the position P1 on the motor detector side obtained from the first input unit 34. Then, the synthesized position detection value P
3 and a position loop calculator 31 based on the motor rotation speed.
And a speed loop calculation unit 32 performs a position loop calculation and a speed loop calculation, respectively, and outputs the results as a current command value via an output unit 33. The power amplifier 4 performs a PWM process by a known technique from a current command value (PWM command) received via the output unit 33 to generate each phase voltage to be applied to the servomotor 5. By applying this voltage, a driving torque is generated in the servo motor 5, and the driving load system including the worm 8, the disc gear 9, the jig 10, and the circular table 12 is relayed to a desired position and speed through the coupling 6. Drive.

Conventionally, as the direct position detector 11, one having a limited absolute range because of its low cost has been used. For this reason, there is an allowable value of the backlash amount, and if it exceeds this, control becomes impossible. For example, when a 720-pole inductosin is used for the direct position detector 11, the range of 1 degree can be detected by absolute. That is, the position detection value P output from the second input unit 35
2 is 0 to 0.999 when the rotary table 12 makes one rotation.
It changes 360 cycles in the range of 9 degrees. On the other hand, the position detector 7 on the side of the servo motor 5 is an absolute encoder having an absolute range of 100 rotations, and is constituted by a reduction mechanism such that the disk gear 9 makes one rotation when the worm 8 makes 100 rotations. Then, the first input unit 34
The position detection value P1 output by the unit changes within a range of 0 to 359.9999 degrees in units of the circular table when the circular table 12 makes one rotation. Here, the position detection value P3 after the synthesis
Is obtained by the following equation.

[0004]

X = INT (P1 + 0.5) (1) where INT () is a function that returns the largest integer not exceeding the numerical value of the number in parentheses. (Eg INT (1.9) = 1, IN
T (-1.9) =-2) Y = P1 + 0.5-X (2) Z = Y-P2 (3) If Z ≧ 0, P3 = X + P2 (4) Z <0 Then P3 = X + P2-1 (5)

That is, according to this, the servo motor 5
The integer part of the position detection value P1 obtained by the side position detector 7 and the part below the decimal point of the directly detected position detection value P2 are synthesized. By obtaining the position detection value P3 after the combination in this way, the influence of the backlash can be tolerated to some extent, and the position can be directly determined with the accuracy of the position detector 11. The amount of backlash that can be tolerated by this method is ± 0.
If it is less than 5 degrees, if it exceeds it, it will be positioned once in the wrong position.

[0006]

Therefore, in the conventional position control device, if the amount of backlash increases due to wear of the gears or the like, the position of the position control device exceeds the allowable amount of backlash and is positioned at an incorrect position. was there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a fully closed loop capable of maintaining high positioning accuracy even when the backlash amount is large and performing stable position control for many years. It is an object to provide a position detecting device.

[0008]

SUMMARY OF THE INVENTION In order to solve the problems of the prior art, the present invention provides a first position detector for detecting a rotational position of a motor, and a first position detector for directly detecting a position of an object to be driven by the motor. A position control device that includes a two-position detector and a position combining unit that combines information on the positions detected by the first position detector and the second position detector, and that directly performs positioning with the accuracy of the position detector. A first differential calculator for calculating first speed information by differentiating the position information output by the first position detector, and a first differential calculator for differentiating the position information output by the position synthesizer. A second differential operation unit that calculates the second speed information; a difference device that calculates a difference between the first speed information and the second speed information; and a combining unit that combines the position information based on a value output by the difference unit. To correct the incorrect location information It is characterized in that it comprises a position information correcting unit.

Thus, the change of the position information after the combination
The change in the rotational position information of the motor is compared, and the combined position information is corrected based on the change. Even if the backlash amount is large by using the corrected position information,
High positioning accuracy can be maintained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A position detecting device according to an embodiment of the present invention will be described with reference to the drawings. The position detecting device according to the embodiment of the present invention has the same configuration as the conventional one shown in FIG. 3, but differs in the internal configuration and operation of the axis control unit 3 from the conventional one. That is, as shown in FIG. 1, the axis control unit 3 of the present embodiment includes a position loop operation unit 31, a speed loop operation unit 32, and an output unit 33.
, A first input unit 34, a second input unit 35, a differentiation operation unit 36, a position synthesis unit 37, a position correction unit 38,
It comprises the fourth difference units 41 to 44. FIG.
FIG. 2 is a block diagram illustrating an example of an axis control unit of the full rose loop position control device according to the present invention. Here, components having the same configuration as the conventional one are denoted by the same reference numerals, and description thereof is omitted. FIG. 2 is an explanatory diagram showing the operation of the block diagram of FIG.

The position corrector 38 differentiates the position information output from the position synthesizer 37 with the position information output from the position detector 7 (the first position detector of the present invention) on the servo motor 5 side. The correction based on the comparison between the result and the difference between the combined position information is performed, and the corrected position information P4 is output.
The third differentiator 43 subtracts the corrected position information P4 (n-1) previously output by the position correcting unit 38 from the position information P3 output by the position synthesizing unit 37, and performs the following (6). The speed information V2 (the second speed information of the present invention) on the side of the position detector 11 (the second position detector of the present invention) is calculated as in the equation.
The third differentiator 43 corresponds to a second differential operation section of the present invention.

[0012]

V2 = P3-P4 (n-1) (6)

Further, the differential operation unit 36, which is the first differential operation unit of the present invention, differentiates the position information from the position detector 7 on the servo motor 5 side to obtain the speed information V1 (the first differential operation unit of the present invention).
The speed information V2 is subtracted from the speed information by the fourth differentiator 44, and is output as a difference value V3 of the speed information as in the following equation (7). The fourth differentiator 44 corresponds to a differentiator according to the present invention.

[0014]

V3 = V1-V2 (7)

The position correcting section 38 corrects the position information P3 obtained by the position synthesizing section 37 by calculation of the following equation (8) to obtain corrected position information P4 (n).

[0016]

P4 (n) = P3 + INT (V3 + 0.5) (8)

As described above, according to the present embodiment, the speed V1 obtained from the position information on the position detector 7 side of the servomotor 5 and the speed V2 obtained from the direct position detector 11 side are used. Since the position corrector 38 corrects the error of the position information P3 calculated by the position synthesizer 37, the position detection accuracy is maintained even for a large backlash, thereby achieving high-precision positioning for many years. Becomes possible.

Next, the operation of the position detecting device of this embodiment will be described with reference to specific numerical examples. FIG. 2 shows that the backlash of the direct position detector 11 as viewed from the position detector 7 is ± 0.6 °, and after n = 1, only 0.3 ° per sampling time of the axis control unit 3, 8 shows calculation results of equations (1) to (8) when the servo motor 5 rotates.

At the time of n = 3, since the backlash exceeds the allowable value ± 0.5 ° of the conventional system, the detection position P3 of the position synthesizing section 37 is an incorrect calculation result. Here, assuming that the rotary table 12 does not move much beyond the rotation speed of the servo motor 5, the difference between the two speeds is outside the range of the reference value (-0.5 to +0.5). It can be determined that the combination of the positions is incorrect.
Therefore, the position can be corrected by evaluating the difference V3 between the two velocities as shown in Expression (8).

[0020]

According to the present invention, an error in the position information synthesized by the position synthesizing unit is corrected based on the difference between the speed obtained from the motor-side detector and the speed obtained directly from the position detector. Since the position detecting device is modified by the method described above, high position detection accuracy can be maintained even if the backlash increases due to aging or the like, thereby enabling high-precision positioning for many years.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing an example of an axis control unit of a full-rose loop position control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of the position control device according to the embodiment of the present invention.

FIG. 3 is a configuration block diagram illustrating an example of a conventional full-rose loop position control device.

FIG. 4 is a configuration block diagram showing an example of an axis control unit of a conventional full-rose loop position control device.

[Explanation of symbols]

1 NC program section, 2 function generation section, 3 axis control section, 4 power amplifier, 5 servo motor, 6 coupling, 7 position detector, 8 worm, 9 disc gear, 10 jig, 11 direct position detector, 12 circle table, 31 position loop calculation, 32 speed loop calculation,
33 output section, 34 input section, 35 input section, 36 differential operation section, 37 position synthesis section, 38 position correction section, 4
1, 42, 43, 44 Differentiator.

Claims (2)

[Claims] 1. A first position detector for detecting a rotational position of a motor, a second position detector for directly detecting a position of an object to be driven by the motor, and a first position detector and a second position detector. A position combining unit that combines information of the detected positions;
A position control device that performs positioning with the accuracy of a direct position detector, wherein a first differential operation unit that calculates first speed information by differentiating position information output by the first position detector; A second differential calculator for calculating second speed information by differentiating the position information output by the position synthesizer; a differentiator for calculating a difference between the first speed information and the second speed information; A position information correction unit for correcting an error in the information of the position synthesized by the position synthesis unit based on the value output by the difference unit; and a position control device for a fully closed loop. 2. The second differential operation unit subtracts the information on the position after the previous position correction from the information on the position output from the position synthesizing unit, and obtains the information based on the information on the position output from the second position detector. 2. The full-closed loop position control device according to claim 1, wherein information on the speed obtained is calculated.