JPH0540521A - Controller for servo-motor - Google Patents

Abstract

(57) [Abstract] [Purpose] To be able to set the timing of giving correction data over a wide speed range with high accuracy. [Structure] A first-order delay circuit (21) having a time constant substantially the same as the time constant of the position control loop of the servomotor is provided. The position command (E0) is input to the primary delay circuit (21),
The timing for giving the lost motion correction command (E9) is set based on the obtained output signal (E2). [Effect] The timing of giving the correction data can be set with high accuracy over a wide speed range. Therefore, highly accurate arcuate cutting is possible in a wide speed range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo motor control device, and more specifically, it is capable of properly compensating for the following delay of rotation even when the rotation direction of the servo motor is reversed at extremely low speed. The present invention relates to a servo motor control device.

[0002]

2. Description of the Related Art When a feed axis of a machine tool is controlled by a servomotor, when the direction of rotation of the servomotor is reversed, the inertia of the mechanical system of the machine tool or lost motion causes a delay in tracking the rotation. Therefore, when the rotation direction of the servo motor is reversed, it is necessary to correct the command sent from the control device to compensate for this tracking delay. To this end, it is necessary to comprehend the required drive torque value as accurately as possible immediately after the rotation direction is reversed to create correction data, and to input the correction data at an appropriate timing and in an appropriate method. Is.

When machining with a machine tool, arc-shaped cutting is representative of machining in which the rotation direction of the servo motor is reversed during processing. When the quadrants are switched during the arcuate cutting, the rotation of the servomotor is not immediately reversed even if a command for reversing at the quadrant switching point is input, and there is a slight delay. Therefore, an arc-shaped projection is generated near the quadrant switching point, and there is a problem that the machining accuracy cannot be said to be sufficient.
Therefore, in order to improve the processing accuracy of such arcuate cutting, various proposals have been conventionally made.

FIG. 3 is a block diagram of a conventional servo motor control device disclosed in Japanese Patent Laid-Open No. 63-308613. This conventional servomotor control device holds backlash correction data and backlash acceleration data in a data holding unit, and when it determines that the mechanical system has reached the position where backlash correction should be performed, the backlash correction data is returned. Is added to the position command, and backlash acceleration data is added to the speed command. To determine whether the mechanical system has reached the position where backlash correction should be performed,
The error counter monitors the deviation between the position command and the position feedback amount, and it is determined whether or not the deviation becomes zero.

[0005]

In recent years, the speed and accuracy of NC machine tools have been increasing. Therefore, in order to improve machining accuracy such as arcuate cutting, not only the accuracy of the correction data but also the correction data It is also necessary to improve the accuracy of the timing of giving the.

In the above-mentioned conventional servo motor control device, the timing for adding the backlash correction data is determined by determining the time when the servo motor position deviation becomes zero using the actual measurement data of the servo motor position. ing. Since the unit of position deviation, LSB (Least Signal Bits), is usually in the unit of submicron, the position deviation fluctuates even by a slight change in the state of the sliding surface of the machine tool, and the time when it becomes zero easily shifts. I will end up. This is especially noticeable when the servo motor reverses at an extremely low speed. Therefore, the timing of adding the backlash correction data is likely to be deviated, and it is difficult to make the addition timing of the backlash correction data highly accurate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a servo motor control device capable of highly accurately setting the timing of giving correction data over a wide speed range.

[0008]

A servomotor control apparatus according to the present invention corrects a command for controlling a servomotor when the direction of rotation of the servomotor is reversed to compensate for a delay in following the rotation of the servomotor. The servo motor control device is equipped with a primary delay element having a time constant almost the same as that of the position control loop of the servo motor, and the position command for servo motor control is input to the primary delay element to obtain It is characterized in that the timing for giving a correction command is set based on the output signal thus obtained.

In the servo motor control device of the present invention,
It is preferable to set the timing for reading the torque command immediately before reversal based on the output signal of the first-order lag element.

[0010]

In the servo motor control device of the present invention, a primary delay element having a time constant substantially the same as the time constant of the position control loop of the servo motor is provided, and a position command for servo motor control is provided to the primary delay element. As input, the first-order lag element serves as a model for theoretically grasping the position of the servo motor.

Therefore, if the reversal position in the rotation direction of the servo motor is calculated based on the output of the first-order lag circuit, the optimum timing for giving the correction command can be known. Therefore, for example, even if the position deviation varies due to load fluctuation during deceleration at an extremely low speed, the correction command can always be given at the optimum timing.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of essential parts showing a servo amplifier of an embodiment of a servo motor control device of the present invention.

Referring to FIG. 1, a servo motor control apparatus according to the present invention includes a servo amplifier (10), a servo motor (not shown) controlled based on a command sent from the servo amplifier (10), and a servo motor (not shown). A mechanical system (not shown) driven by a servo motor is provided.
A movement command is sent from the NC device to the servo amplifier (10) every predetermined sampling period.

The servo amplifier (10) includes a position deviation calculator (11), a multiplier (12), a speed deviation calculator (13),
Adder (14), multiplier (15), multiplier (16), integral term (delay element) (17), adder (18), lost motion correction unit (19), and inverted signal generation unit (2)
0).

The position deviation calculator (11) calculates the position deviation (E1) from the position command (E0) sent from the NC unit and the position feedback amount (Ep) sent from the mechanical system, and the multiplier (12). To send to. This position deviation (E1)
Is also sent to the lost motion correction section (19). The position command (E0) sent from the NC device is also sent to the primary delay circuit (21) of the inverted signal generator (20).

The multiplier (12) multiplies the position deviation (E1) by the gain K1 and sends it as a speed command (E2) to the speed deviation calculator (13). This speed command (E2) is also sent to the lost motion correction section (19).

The speed deviation calculator (13) has a speed command (E
2) and the speed feedback amount (Ev) sent from the mechanical system
Then, the speed deviation (E3) is calculated from the above and sent to the adder (14). The speed deviation (E3) is also sent to the adder (18).

The adder (14) adds the speed deviation (E3) and the correction signal (E7) sent from the multiplier (16), and the speed deviation (E4) thus corrected is added to the multiplier (1).
5).

The multiplier (15) multiplies the corrected speed deviation (E4) by the gain K3 and sends it to the servo motor as a torque command (E5). K3 = T, where Tp is the time constant of the position control loop and T is the sampling period.
There is a / TP relationship.

The multiplier (16) multiplies the addition result (E6) of the adder (18) by a constant TK2 and sends the correction signal (E7) obtained as a result to the adder (14). In addition, K2
Is the frequency at which the integration effect appears, and T is the sampling period.

The integral term (delay element) (17) is a correction command (E) sent from the lost motion correction section (19).
9) is added to the operation result (E8) of the adder (18) and integrated, and the result (E8) is sent to the adder (18).

The adder (18) adds the speed deviation (E3) and the calculation result (E8) of the integral term (17), and sends the result (E6) to the multiplier (16). Addition result (E6)
Is also sent to the integral term (17).

A lost motion correction unit (19) calculates lost motion correction data and outputs an inverted signal generation unit (2).
0) The inversion signal (E14) sent from 0) recognizes the inversion of the servomotor, and outputs the correction command (E9) to the integral term (17).
To send to. This correction command (E9) corrects the torque command (E5) immediately after the servo motor reverses, and is given to the speed control circuit as an initial value immediately after the servo motor rotation reverses. In addition,
The calculation of the lost motion correction data is performed by a known method.

In this embodiment, when the correction command (E9) is sent, the polarity of the polarity inversion signal (E14) based on the speed deviation signal (E12) output from the primary delay circuit (21) decreases first and then the polarity is first obtained. When is changed, that is, the inverted signal (E14)
It is assumed that the value has changed from plus (minus) to minus (plus) by one unit LSB. By doing this, even when the vehicle is gradually decelerating at an extremely low speed, variations in the mechanical load, etc. do not cause variations in the determination of the reversal timing, and it is possible to more stably grasp the proper reversal timing. There are advantages.

The inverted signal generator (20) includes a primary delay circuit (21), an adjustment signal generator (22), and an adder (2).
3) is provided. The inversion signal generator (20) monitors the position command (E0), creates an inversion signal (E14) based on the speed deviation signal (E12) calculated by the primary delay circuit (21), and the lost motion correction unit. (19).
The lost motion correction unit (19) determines that the rotation direction of the servo motor is reversed when the polarity of the input inversion signal (E14) first changes, and the correction command (E9) is given to the integral term (17). Send out.

The first-order delay circuit (21) has the same time constant as the time constant of the position control loop of the servo motor, and serves as a model of the operation of the servo motor being controlled. The first-order delay circuit (21) includes an adder (21a), an adder (21b), a multiplier (21c), and an integral term (delay element) (21d), and has only a loop corresponding to a position control loop. is doing. This is because the servomotor used in a machine tool usually has a speed control loop whose response is sufficiently higher than that of the position control loop, and therefore it is considered that only the loop corresponding to the position control loop is sufficient. is there. A loop corresponding to the speed control loop may be provided.

The adder (21a) adds the position deviation (E0) sent from the NC unit and the feedback signal (E13) output from the multiplier (21c) to the position deviation signal (E).
11) is calculated and sent to the adder (21b).

The adder (21b) outputs a position deviation signal (E1
1) and the output (E14) of the integral term (21d) are added to calculate the speed deviation signal (E12), which is sent to the multiplier (21c). The velocity deviation signal (E12) is also sent to the integral term (21d) and the adder (23).

The multiplier (21c) outputs a velocity deviation signal (E1
2) is multiplied by a constant K4 and the result (E13) is added to the adder (2
Give feedback to 1a).

The integral term (21d) is the velocity deviation signal (E1
2) is integrated and the result (E14) is sent to the adder (21b).

The adjustment signal generator (22) generates an adjustment signal (E13) to be added to the speed deviation signal (E14) and sends it to the adder (23). By adding the adjustment signal (E13),
The inverted signal (E14) sent to the lost motion correction section (19) is increased or decreased. As a result, the timing at which the polarity of the inversion signal (E14) changes changes, so that the timing at which the lost motion correction unit (19) sends the correction command (E9) can be shifted.

Depending on the mechanical system to be controlled, if the speed deviation signal (E12) calculated by the first-order delay circuit (21) is used as it is as the inversion signal (E14), the timing may become improper. In many cases, the speed deviation signal (E1
It is preferable to delay 2) as it is, rather than to use it as an inverted signal (E14). Therefore, in such a case, the adjustment signal (E13) is generated to delay or accelerate the timing.

Further, in consideration of the fact that it may be preferable to change the above timing by changing the polarity (+ → − or − → +) of the rotation speed of the servo motor at the time of quadrant switching, in this embodiment, adjustment is performed. The signal generator (22) is used to change the polarity of the rotation speed of the servo motor (+ → − or − →
The adjustment signal (E13) can be set independently according to (+).

The adder (23) outputs a speed deviation signal (E12).
The adjustment signal (E13) is added to and the result is sent to the lost motion correction section (19) as an inverted signal (E14).

Next, the correction data created by the lost motion correction section (19) will be described. As the correction data for lost motion correction, a method of giving a fixed value in advance and reading it out as needed, a method of measuring the torque value immediately before reversing the rotation direction of the servo motor and using that value, etc. There is. When the torque value immediately before reversal is used, it is preferable to read and use the torque command (E5) at a time as close as possible to reversal, but it is necessary that accurate correction data can be obtained by the torque command value.

Normally, no large fluctuation (variation) of the torque command value occurs except when the servo motor reverses at an extremely low speed, so the torque command (E
5) should be read. However, when the servo motor reverses at an extremely low speed, the fluctuation (variation) of the torque command value is very large, so even if the torque command (E5) is read at a predetermined reading time, that value is accurate. It does not always indicate the load torque value. Therefore, it is necessary to set a signal indicating the read timing of the torque command (E5) and read the torque command (E5) by the signal.

FIG. 2 is an explanatory diagram showing the relationship between the feedback pulse, the command pulse and the torque command at the time of extremely low speed inversion. As is clear from FIG. 2, in extremely low speed reversal, the number of revolutions (speed) is very low, so the command pulse becomes the deviation amount as it is. Therefore, when one command pulse is input, the torque command value increases by one unit. start. Next, when one feedback pulse is input, the deviation becomes 0, so the torque command value decreases and goes toward zero. This phenomenon is repeated. For this reason, the speed becomes intermittent, and the variation in the torque command value becomes extremely large. Therefore,
Even if the torque command (E5) is read in this state, it cannot be considered that the value indicates an accurate load torque value.

Therefore, in this embodiment, the torque command (E
The speed deviation signal (E12) calculated by the primary delay circuit (21) is used as a signal indicating the reading timing of 5),
The torque command (E5) is read at the time when the speed deviation signal (E12) decreases and first becomes zero. By doing so, it is possible to read the torque command (E5) before the intermittent speed starts and at the closest time of reversal.

As described above, when the torque command (E5) immediately before reversal is read using the speed deviation signal (E12) to create the lost motion correction data, an accurate torque value can be stably obtained. Therefore, the accuracy of the lost motion correction data is improved. Therefore, the effect of the lost motion correction can be remarkably improved in combination with the fact that the timing of giving the correction data becomes appropriate. In FIG. 2, the torque command (E5) is given at time t0.
Of the servo motor, and time t1 indicates the time of reversal of the servo motor.

Speed deviation signal (E12) output from the primary control circuit (21) which is a model of the servo motor being controlled
Can be used for applications other than the inversion signal and the torque command read signal. For example, when the position of the servo motor deviates from the theoretical position, the speed deviation signal (E12) can be used to correct the operation of the servo motor.

[0041]

As described above, the servo motor control device of the present invention can set the timing for giving the correction data over a wide speed range with high accuracy. Therefore, highly accurate arcuate cutting is possible in a wide speed range. Further, if the timing for reading the torque command immediately before reversal is set based on the output signal of the first-order lag element, the accuracy of the correction data is improved, so that the correction effect is provided in combination with the higher accuracy of the timing for giving the correction data. It can be significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts of a servo amplifier of an embodiment of a servo motor control device of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a feedback pulse, a position command pulse, and a torque command when reversing at an extremely low speed.

FIG. 3 is a block diagram showing an example of a conventional servo motor control device.

[Explanation of symbols]

 10 Servo Amplifier 11 Position Deviation Calculator 12 Multiplier 13 Speed Deviation Calculator 14 Adder 15 Multiplier 16 Multiplier 17 Integral Term (Delay Element) 18 Adder 19 Lost Motion Corrector 20 Inverted Signal Generator 21 Primary Delay Circuit 21a Adder 21b Adder 21c Multiplier 21d Integral term (delay element) 22 Adjustment time generator 23 Adder

[Procedure amendment]

[Submission date] December 18, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

FIG. 5 is a block diagram of a conventional servo motor control device disclosed in Japanese Patent Laid-Open No. 63-308613. This conventional servomotor control device holds backlash correction data and backlash acceleration data in a data holding unit, and when it determines that the mechanical system has reached the position where backlash correction should be performed, the backlash correction data is returned. Is added to the position command, and backlash acceleration data is added to the speed command. To determine whether the mechanical system has reached the position where backlash correction should be performed,
The error counter monitors the deviation between the position command and the position feedback amount, and it is determined whether or not the deviation becomes zero.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

The multiplier (15) multiplies the corrected speed deviation (E4) by the gain K3 and sends it to the servo motor as a torque command (E5) .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction content]

In this embodiment, when the correction command (E9) is sent, the polarity of the polarity inversion signal (E14) based on the speed deviation signal (E12) output from the primary delay circuit (21) decreases first and then the polarity is first obtained. When is changed, that is, the inverted signal (E14)
There has been and when it becomes plus (minus) or Lama Inasu (plus). By doing this, even when the vehicle is gradually decelerating at an extremely low speed, variations in the mechanical load, etc. do not cause variations in the determination of the reversal timing, and it is possible to more stably grasp the proper reversal timing. There are advantages. 3 and 4 show arcuate movement and midway movement, respectively.
Time change such as position command when performing reverse movement including stop
In both figures, (a) is a position command,
(B) is the position feedback amount, (c) is the speed command and position
The positional deviation, (d), shows the time change of the torque command.
In (c), the speed command and the position deviation change at the same rate of change.
It is drawn as something to do. FIG. 3C and FIG.
As is clear from (c), the speed command is slightly delayed after reversing.
Since it starts to increase to the negative side,
As shown, the position deviation (E1) sharply decreases after reversal.
Is increasing to the side. Therefore, the speed of the servomotor,
Even if the position deviation is small, the variation becomes large.
I understand. On the other hand, an ideal servo mode without the influence of load
If you use the output of the behavior model of
The speed command and position deviation change linearly before and after reversing.
Can be made. Therefore, send the correction command (E9).
As the timing signal that indicates when the
Servo motor operation rather than using position deviation
It is clear that it is better to use the model.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

FIG. 2 is an explanatory diagram showing the relationship between the feedback pulse, the command pulse and the torque command at the time of extremely low speed inversion. As apparent from FIG. 2, in the very low speed reversal, since the rotational speed (speed) is very low, the command pulse as it becomes deviation, therefore, the torque command value when the command pulse enters one begins to increase. Next, when one feedback pulse is input, the deviation becomes 0, so the torque command value decreases and goes toward zero. This phenomenon is repeated. For this reason, the speed becomes intermittent, and the variation in the torque command value becomes extremely large. Therefore, even if the torque command (E5) is read in this state, it cannot be considered that the value indicates an accurate load torque value.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a time variation such as a position command when performing an arcuate movement .
2A is a position command, and FIG.
Feedback amount, (c) is speed command and position deviation, (d)
Indicates the time change of the torque command.

[Procedure Amendment 6]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Added

[Correction content]

FIG. 4 is an explanatory diagram showing a time change of a position command or the like when performing a reversal movement including a halfway stop.
(B) shows the position feedback amount, (c) shows the speed command and position deviation, and (d) shows the time change of the torque command.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 5

[Correction method] Added

[Correction content]

FIG. 5 is a block diagram showing an example of a conventional servo motor control device.

[Procedure Amendment 8]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Added

[Correction content]

[Figure 4]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Added

[Correction content]

[Figure 5]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Torao Takeshita 5-14 Yada Minami, Higashi-ku, Nagoya City Mitsubishi Electric Corporation Nagoya Works (72) Inventor Yoshio Shinohara 5-14 Yada Minami, Higashi-ku, Nagoya Mitsubishi Electric Corporation Nagoya Works

Claims (2)

[Claims] 1. A servomotor control device for compensating a delay in following a rotation of a servomotor by compensating a command for controlling the servomotor when the direction of rotation of the servomotor is reversed. Equipped with a primary delay element that has a time constant almost the same as the time constant of the position control loop, and sets the timing to give a correction command based on the output signal obtained by inputting the position command for servo motor control to the primary delay element. Servo motor control device characterized by being. 2. The servo motor control device according to claim 1, wherein the timing for reading the torque command immediately before reversal is set based on the output signal of the first-order lag element.