WO1988003676A1

WO1988003676A1 - Digital servo system

Info

Publication number: WO1988003676A1
Application number: PCT/JP1987/000859
Authority: WO
Inventors: Masatoyo Sogabe; Kanemasa Okuda; Shunsuke Matsubara
Original assignee: Fanuc Ltd
Priority date: 1986-11-06
Filing date: 1987-11-06
Publication date: 1988-05-19

Abstract

A digital servo system which is featured by improved precision in the ''halt'' position. A position detection means (1) counts +1 or -1 every time when an object is moved by a predetermined distance, and sends the position of the object to a position error detection means (2). The error relative to a position command value obtained by the position error detection means (2) is sent to a velocity command generation means (3), where it is processed into velocity command. To the velocity command is added by a velocity command offset addition means (8) an offset value having an absolute value smaller than a minimum velocity command value. A motor (40) is driven on the velocity command that is added to the offset value.

Description

Description Digital '' Servo System Technical Field

The present invention relates to a digital 'servo' system for a motor. Background art

Fig. 1 shows the general configuration of a conventional digital servo system for a motor.

1 is that the position of the object is calculated by counting +1 or -1 each time the object passes through a predetermined position set at equal intervals, depending on the direction of the passage. 2 is a position deviation detecting means for detecting a deviation of the output of the position detecting means 1 from a predetermined position (position command value) specified separately, and 3 is a position deviation detecting means 2 Speed command generating means for outputting a speed command value for moving the object in accordance with the output of the object, 4 speed detecting means for detecting the moving speed of the object, and 5 moving speed of the object A speed deviation detecting means for detecting a deviation from the speed command value, a torque command generating means for outputting a torque command value to a motor in accordance with an output of the speed deviation detecting means, The object is moved according to the torque command value. It is over motor drive means.

In the above configuration, speed detection means 4, speed deviation detection means 5, The torque command generating means 6 and the motor driving means 7 form a motor speed control driving means 10, and receive the speed command to control and drive the motor speed.

FIG. 2 shows an example of a hard disk configuration of the digital servo system shown in FIG.

Basically, the microcomputer 100 performs the numerical control and control, and the ball-screw coder 50, together with the counter function (not shown) inside the micro-computer 100, performs the speed detection shown in FIG. Means 4 and position detection means 1 are realized respectively. The speed detecting means 4 obtains speed information by counting the output of the pulse encoder 50 at every clock cycle of the microcomputer. The switching amplifier 30 of FIG. 2 realizes the motor driving means 7 of FIG. Blocks other than the above in FIG. 1 are all digital numerical value generating means realized by the micro-computer 100.

In the above configuration, the position command value input to the position deviation detecting means 2 is one count of the position detecting means based on the output (position feedback) of the position detecting means 1. When min larger, the positional deviation Ken岀means outputs + 1, which is output as a constant kappa _[rho times toying with velocity command value V _cm d (= K _P) in the speed command generating means 3. This is input to the motor speed control driving means 10 so that the motor is driven to move the object linked to the motor. The object linked to the motor moves and the position detecting means 1 When the position reaches +1 counted position, the counted value of the position detecting means 1 which is incremented by 1 is input to the position deviation detecting means 2, where the counted value is compared with the position command value. Is done. At this time, since the count value is equal to the position command value, the output of the position deviation detecting means 2 becomes 0, and the output of the speed command generating means 3 also becomes 0. By inputting the speed command value that has become 0, the motor speed control driving means 10 controls the speed to become 0, and the motor and the object interlocked therewith are decelerated, and the speed is reduced by frictional resistance or the like. Stopped. However, in the position detecting means 1, since the position of the object is detected at intervals of the "equal intervals", the object stops at any position between the positions detected at the intervals. I don't know. That is, the positioning accuracy of the stop position has a limit determined by the resolution (for example, 1 m) of the position detecting means 1 (actually, the pulse coder 50). Disclosure of the invention

An object of the present invention is to provide a servo system capable of positioning near a scale position set at an interval determined by the resolution of a position detecting means that outputs an incremental output. The digital servo system according to the present invention counts +1 or -1 each time the object passes through a position set at a predetermined interval, depending on the direction of the passage, and counts the object. Position detecting means for detecting the position of the object; and a deviation of the position of the object detected by the position detecting means from a position command value separately commanded. Position deviation detecting means for detecting, speed command generating means for outputting a speed command value for moving the object according to the output of the position deviation detecting means,

A motor speed control driving means for controlling the speed of the motor in accordance with the speed command value and driving the motor;

Speed command offset adding means for adding a constant offset value to the speed command value, and the absolute value of the offset value is determined by the output of the position deviation detecting means corresponding to one count in the position detecting means. Accordingly, the absolute value of the speed command value output from the speed command generating means is smaller than the absolute value of the speed command value. BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 shows the basic configuration of a conventional motor digital 'servo' system.

Fig. 2 shows an example of hardware configuration of the digital servo system.

FIG. 3 is a diagram showing a basic configuration of a digital * servo 'system according to the present invention, and

FIG. 4 is an explanatory diagram of the position of an object in the digital * servo system according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

The basic configuration of the present invention is shown in FIG. A speed command offset adding means 8 is provided on the output side of the speed command generating means 3. The other configuration is exactly the same as the configuration shown in FIG.

The speed command offset adding means 8 adds a fixed offset value to the speed command value output from the speed command generating means 3. Here, the absolute value of the offset value is determined when the output of the position deviation detecting means 2 is a deviation corresponding to one count in the position detecting means, and the speed command is generated accordingly. It shall be smaller than the absolute value of the speed command value output from the means.

In the present invention, the provision of the above-mentioned speed command offset adding means 8 allows the object driven by the motor to move in the direction opposite to the traveling direction every time it passes through the position of the scale determined by the position command value. When a small speed command value to be driven in the direction is received, a small vibration is generated around the position command value around the position command value.

Hereinafter, the function of the speed command offset adding means 8 will be described more specifically.

Assuming that the position command value input to the position deviation detecting means 2 is larger than the value of the output (position feedback) of the position detecting means 1 by one count of the position detecting means, the position the deviation detecting means outputs + 1, which is outputted as the speed command value is a constant K _P times in the speed command generating means 3 V c ni d (== Κ Ρ).

Here, according to the present invention, the speed command value V c ni d = K p is fixed. • Add the offset value of (C). As described above, IC0 is IKpI.

Thus, when the motor speed control driving means 10 is used, Κ ρ +

Co is input as a speed command value with an offset value added. Thus, the motor is driven to move the object. When the object linked to the motor moves and reaches a position where the position detecting means 1 counts +1 (this point is a point on the scale 0), the position detecting means 1 increases by one. The count value is input to the position deviation detecting means 2, where the count value is compared with the position command value. At this time, since the count value is equal to the position command value, the output of the position deviation detecting means 2 becomes 0, and the output of the speed command generating means 3 also becomes 0. As a result, the output of the speed command offset adding means 8 inputted to the motor speed control driving means 10 is the offset value C. Becomes

For example, K _P > 0, C. Consider the case <0,

K p + C. Speed command of opposite sign. Then, the motor speed control means 10 controls the speed to rotate the motor in the reverse direction. In this way, the object linked to the motor returns to the point of the above-mentioned mega 0 again and passes there. At this time, 11 is counted in the position detecting means 1 and this is again input to the position deviation means and compared with the position command value. Here, the position command value becomes larger by +1 count again, so that the motor is reversed in the same manner as described above, and the object returns to the direction of point 0. Pass through the point of Hyakumori 0.

The target linked to the motor in this way corresponds to the position command value The moving direction is reversed in response to a speed command to move in the opposite direction every time a point on the scale 0 is passed, and a small vibration is made around the point on the scale 0 around the point on the scale 0. This is shown in Figure 4.

Offset value C. The same applies to the case of <0. Similarly, as shown in FIG. 4, the count value of the position detecting means 2 slightly vibrates around the scale 1 at which the force changes from 0 to 1. In this case, when the position of the object is in the range of the count value 0, the output of the position deviation detecting means 2 is 0 as described above, and the output of the speed command generating means 3 derived from this is also 0. Powerful, offset value according to the present invention

When C ₀ (> 0) is added to the speed command value, the object moves in the positive direction and eventually exceeds scale 1. Then the count value of the position detecting means 1 is 1, as an output one K _P of the speed command generating hand stage 3 in response thereto, offset value C. according to the present invention this value (J.> 0, IC. | K | K _P i) plus negative speed command-K _P + C. Is issued. When the speed command is issued in the negative direction, the position of the target object goes over the scale 1 position again and enters the range of the numerical value 0. Therefore, every time the position of the object exceeds the position of the scale 1, the object receives a speed command in the opposite direction and vibrates slightly around the position of the scale 1.

Thus, the object vibrates slightly around the position command value near the position of the scale determined by the position command value, and the positioning accuracy is improved.

The offset value c described above. The minimum value that can be detected and output by the position deviation detecting means 2 is 1, and the speed command When the gain of generating means 3 is Kp, for example,

1 1

C o =-K or C 0 K p

twenty two

Can be.

Further, in the example in which the present invention is applied to a 1 μm resolution ball (inclined output signal bit) as the position detecting means 1, the positioning accuracy has been improved to about 0.2 m. .

As described above, in the digital servo system for a motor according to the present invention, positioning can be performed with higher accuracy than the resolution of the position detecting means that outputs incrementally. Industrial applicability

The digital servo system according to the present invention is particularly useful in a system that determines the position of an object with a motor with high accuracy, such as an NC machine tool.o

Claims

The scope of the claims

1. Each time an object passes a position set at a predetermined interval, a position detecting means (1) which counts +1 or -1 according to the direction of the passage to detect the position of the object. ,

Position deviation detecting means for detecting a deviation of the position of the object detected by the position detecting means from a separately instructed position command value

(2) and

Speed command generating means for outputting a speed command value for moving the object in accordance with the output of the position deviation detecting means (2)

(3) and

A motor speed control drive means (10) for controlling and driving the speed of the motor in accordance with the speed command value, wherein:

A speed command offset adding means (8) for adding a constant offset value to the speed command value, and an absolute value of the offset value is determined by an output of the total position deviation detecting means (2). Is smaller than the absolute value of the speed command value output from the speed command generating means (3) when the value is one count in the position detecting means (1). Digital 'servo' system.

2. The motor speed control comb driving means (10) includes: speed detecting means (4) for detecting a moving speed of the object;

Speed deviation detecting means (5) for detecting a deviation of the moving speed of the object from a speed command value to which the offset value has been added; Torque command generating means (6) for outputting a torque command value to the motor according to the output of the speed deviation detecting means (5);

2. The digital servo system according to claim 1, further comprising: motor driving means (7) for moving said object in accordance with said torque command value.

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