JP2007140950A - Digital servo control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital servo control device which suppresses vibration of a control object by smoothing a torque feedforward signal and minimizing abnormal noise. <P>SOLUTION: This device comprises: a delay device 64 storing a current multiplication value obtained by multiplying a differential signal of an instruction signal or an output signal of a speed feedforward controller 5 by a torque feedforward gain TFF; and a torque feedforward controller 6 generating the torque feedforward signal, based on either the current multiplied value or a previous multiplied value of the previous sampling. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a digital servo controller that improves positioning performance during digital control.

A conventional digital servo control device differentiates a position command to obtain a speed feedforward signal, differentiates it again to create a torque feedforward signal, and uses it as it is (see, for example, Patent Document 1).
FIG. 9 is a block diagram of a conventional servo control device. In the figure, Kp is a position loop proportional gain, K1 is a speed loop integral gain, K2 is a speed loop proportional gain, 36 is a current loop circuit, 38 is an electric part of the servo motor, R is a winding resistance, and L is a winding. 40 is a mechanical part of the servo motor, Kt is a torque constant, Jm is an inertia, and 42 is a transfer function for integrating the rotational speed of the servo motor and calculating the position. 44 is a position feedforward term, and α1 is a position feedforward coefficient. 46 is a speed feedforward term, and α2 is a speed feedforward coefficient. The speed feedforward coefficient α2 is normally a value close to the value of Jm / Kt (Jm: inertia, Kt: torque constant). Note that the value of the feedforward coefficient α1 of the position feedforward term 44 is experimentally determined according to the motor characteristics and the like (ideally 1 is good).

  In the conventional control, the position command α is differentiated, and the position feedforward coefficient α1 is multiplied by the differential value to obtain a position feedforward control amount, and the normal position loop control, that is, the current position P of the motor is determined from the position command α. The position deviation ε is subtracted to obtain a normal speed command by multiplying it by the position loop proportional gain Kp. Then, the position feedforward control amount is added to the normal speed command to obtain the speed command Vc. On the other hand, the position feedforward control amount is differentiated and multiplied by the speed feedforward coefficient α2 to obtain the speed feedforward control amount, and the speed loop control (IP control), that is, the speed command Vc is used to calculate the servomotor. The speed deviation is obtained by subtracting the actual speed V, and the conventional current command value obtained by subtracting the value obtained by integrating the speed deviation and multiplying the integral gain K1 by the value obtained by multiplying the actual speed V of the servo motor by the proportional gain K2. The current command Ic is obtained by adding the speed feedforward control amount.

  If the value of the position command α changes, the position deviation ε also increases, and the speed command output in the normal position loop process also changes greatly, but there is a delay in the position loop. However, the position feedforward control increases the position feedforward control amount in accordance with the amount of change in the position command α and adds it to the speed command, resulting in a feedforward controlled speed command. Compensated. The same applies to the speed loop, and the current command by the normal speed loop process also changes according to the change in the speed command, but there is a delay due to the integral term. However, also in this case, since the current command is obtained by adding the speed feedforward control amount by the speed feedforward control, the delay of the speed loop is also compensated, and the response of the servo system is improved as a whole. As a result, the followability of the servo motor with respect to the position command α is improved, and the undulation of the position deviation is reduced.

The following method has been adopted when realizing the conventional digital control.
The position and speed loop processing cycle is TP, and the position command in each position and speed loop processing is a (n) (n = 1, 2, 3. Then, the differential value b (n) of the position command a (n) is actually calculated as a difference by the calculation of equation (1).

  b (n) = {a (n) -a (n-1)} / TP (1)

  The position feedforward signal is obtained by multiplying the value of b (n) by the position feedforward coefficient α1 to obtain a feedforward control amount c (n).

  c (n) = α1 · b (n) (2)

  The feedforward control amount d (n) of the speed is obtained by subtracting the feedforward control amount c (n−1) at the position of the previous period from the position feedforward control amount c (n) as shown in the equation (3). The value obtained was multiplied by (α2 / TP).

  d (n) = α2 · {c (n) −c (n−1)} / TP (3)

In this way, in the conventional feedforward control device, the position command is simply differentiated (the difference between the current value and the previous value divided by the sampling period) and multiplied by α1 to obtain the velocity feedforward signal and differentiated again. A procedure has been taken in which a product of α2 multiplied by α2 is used as a current (or torque) feedforward signal.
JP-A-3-015911 (page 4-7, FIGS. 1 and 8)

  In the conventional servo control device, the torque feedforward signal is generated by further differentiating the signal obtained by differentiating the position command (the difference between the current value and the previous value divided by the sampling period). There was a problem that it became dirty and abnormal noise was generated during motor operation. There is also a problem that the controlled object vibrates for the same reason.

  The present invention has been made in view of such problems, and when the signal obtained by further differentiating the torque feedforward signal is larger than a set threshold value, the torque feedforward signal before one sampling is used, thereby providing torque feed. It is an object of the present invention to provide a digital servo control device that can smooth forward signals, reduce abnormal noise during motor operation, and suppress vibrations to be controlled.

  In order to solve the above problem, the present invention is configured as follows.

According to the first aspect of the present invention, in the digital servo control device that performs speed feedforward control or torque feedforward control, the command signal or the differential signal of the output signal of the speed feedforward controller is multiplied by the torque feedforward gain. A delay unit that stores a value, and a torque feedforward controller that generates a torque feedforward signal based on one of the current multiplication value and the previous multiplication value one sampling before;
According to a second aspect of the present invention, the differential signal according to the first aspect of the invention is a position command two-time differential signal, a speed command one-time differential signal, or a speed feedforward signal one time. It is a differential signal.
According to a third aspect of the present invention, the torque feedforward controller according to the first aspect of the present invention includes a selector that selects either the current multiplication value or the previous multiplication value, and a switching signal that switches the selector. Has a differentiator or an averaging circuit.
According to a fourth aspect of the invention, the differentiator according to any of the first to third aspects of the invention further differentiates the differential signal once and compares the differentiated signal with a preset threshold value. When the threshold value is larger than the preset threshold value, the switching signal is output so as to select the previous multiplication value.
According to a fifth aspect of the present invention, the averaging circuit according to the first or third aspect of the invention calculates an average value of the multiplication values before N sampling (N is a natural number) of the current multiplication value, An absolute value of a difference between the current multiplication value and the average value is calculated, and the absolute value is compared with a preset threshold value. When the absolute value is larger than the preset threshold value, the previous multiplication value is selected. The switching signal is output.
According to a sixth aspect of the invention, an arbitrary low-pass filter is provided at the output of the speed feedforward controller or the torque feedforward controller according to the first aspect of the invention.

According to the first to sixth aspects of the present invention, the speed command, the speed feedforward signal, or the differential torque feedforward signal that is the differential signal of the position command differential signal can be smoothed, and the motor is in operation. No abnormal noise or vibration of the controlled object, and good control performance can be realized at the time of positioning.
According to invention of Claim 2, it can apply to various uses and can improve the versatility of a control apparatus.
According to the third to fifth aspects of the present invention, when the torque feedforward signal becomes dirty due to a difference calculation error that is a differential signal, the previous torque feedforward signal can be used. Can be. Further, only when the torque feed forward signal becomes dirty, the best torque feed forward signal can be easily switched.
Since the signal obtained by filtering the speed feedforward signal or the torque feedforward signal according to the sixth aspect of the invention is used as the speed feedforward signal or the torque feedforward signal, there is no abnormal noise during motor operation or vibration of the controlled object. Therefore, good control performance (high accuracy, high speed, etc.) can be realized during positioning.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a digital servo control apparatus showing a first embodiment of the present invention. In the figure, the digital servo control device of the present invention includes a position controller 1, a speed controller 2, a speed feedforward controller 5, a torque feedforward controller 6, and a differentiator 7, and controls a control object 3. To do. Reference numeral 4 denotes a detector that detects the position of the control target 3.
The position controller 1 inputs a position deviation between the position command and the motor position that is the output of the detector 4 and outputs a speed command. The differentiator 7 inputs the motor position, which is the output of the detector 4, performs a differentiation operation, calculates and outputs the motor speed. The speed feedforward controller 5 includes a differentiator 51 and a multiplier 52. The position feed command is input, the differentiator 51 performs a differentiation operation, and the multiplier 52 multiplies the speed feedforward gain VFF. Output speed feed forward signal. The differentiation operation by the differentiator 51 is expressed by the following equation (4), where IN (n) is the current input, IN (n-1) is the previous input, Ts is the sampling period, and OUT (n) is the output of the differentiator 51. Calculated by
OUT (n) = {IN (n) −IN (n−1)} / Ts (4)

  The speed controller 2 adds the speed command that is the output of the position controller 1 and the speed feedforward signal that is the output of the speed feedforward controller 2, and subtracts the motor speed that is the output of the differentiator 7. To output a torque command. The torque feedforward controller 6 includes differentiators 61 and 62, a multiplier 63, a delayer 64, and a selector 65. The torque feedforward controller 6 receives a speed feedforward signal and performs a differentiation operation in the differentiator 61. At 63, the torque feed forward gain TFF is multiplied to generate a torque feed forward signal.

The delay unit 64 stores the generated torque feed forward signal. Here, the output of the differentiator 61 is further differentiated by the differentiator 62. When the output of the differentiator 62 is larger than a preset threshold value, the selector 65 is stored in the delay unit 64. Outputs the previous value of torque feed forward signal. The operations of the differentiators 61 and 62 are the same as the operation of the differentiator 51, assuming that the current input is IN (n), the previous input is IN (n-1), the sampling period is Ts, and the output is OUT (n). OUT (n) = {IN (n) −IN (n−1)} / Ts (5)
It becomes.

Then, a signal obtained by adding the output of the speed controller 2 and the torque feedforward controller 6 is applied to the controlled object 3 to control the controlled object 3.
The part where the present invention differs from Patent Document 1 is a part provided with a differentiator 62, a delayer 64, and a selector 65 in the torque feedforward controller 6.
As described above, the digital servo control device of the present invention uses the torque feedforward signal generated last time when the torque feedforward signal output from the torque feedforward controller 6 has an error due to the difference calculation of the differentiator 61. Thus, a smooth torque feed forward signal can be obtained.

Further, the torque feedforward controller of the digital servo control device of the present invention may be a torque feedforward controller having another configuration.
For example, FIG. 2 shows a second embodiment of the present invention, and a block of a torque feedforward controller showing another configuration that can be used in the servo control apparatus showing the first embodiment of the present invention. FIG. In the figure, a torque feedforward controller 106 receives a speed feedforward signal, performs a differentiation operation by a differentiator 61, and multiplies a torque feedforward gain TFF by a multiplier 63 to generate a torque feedforward signal.

The delay unit 64 stores the generated torque feed forward signal. Here, the output of the multiplier 63 is input to the averaging circuit 67. In the averaging circuit 67, the difference between the output of the multiplier 63 and the average value of the output of the multiplier 63 before n sampling (n is a natural number). Is larger than the threshold value set in advance, the selector 65 outputs the previous value of the torque feed forward signal stored in the delay unit 64. The operation of the differentiator 61 is similar to the operation of the differentiator 51, assuming that the current input is IN (n), the previous input is IN (n-1), the sampling period is Ts, and the output is OUT (n). OUT (n) = {IN (n) −IN (n−1)} / Ts (6)
It becomes.
The present embodiment is different from the first embodiment in that an averaging circuit 67 in the torque feedforward controller 106 is provided instead of the differentiator 62 in the torque feedforward controller 6 in FIG. .

FIG. 3 is a block diagram of a digital servo control apparatus showing a third embodiment of the present invention. In the figure, components having the same reference numerals as those in FIG. 1 showing the first embodiment of the present invention perform the same operations, and thus description thereof will be omitted.
The torque feedforward controller 206 includes differentiators 61, 62, and 66, a multiplier 63, a delayer 64, and a selector 65. The position command is input and the differentiators 61 and 66 perform two differentiation operations. And the multiplier 63 multiplies the torque feed forward gain TFF to generate a torque feed forward signal. The delay unit 64 stores the generated torque feed forward signal. Here, the output of the differentiator 61 is further differentiated by the differentiator 62, and when the output signal of the differentiator 62 is larger than a preset threshold value, the selector 65 saves the torque stored in the delay device 64. Output the previous value of the feed forward signal.
Differentiating operations of the differentiators 61 and 62 are expressed by equation (7) where IN (n) is the current input, IN (n-1) is the previous input, Ts is the sampling period, and OUT (n) is the output. Calculated.
OUT (n) = {IN (n) −IN (n−1)} / Ts (7)

Then, a signal obtained by adding the output of the speed controller 2 and the torque feedforward controller 206 is applied to the controlled object 3 to control the controlled object 3.
Note that this embodiment differs from the first embodiment in that a position command is sent to the torque feed instead of the speed feedforward signal via the speed feedforward controller 5 which is the input of the torque feedforward controller in FIG. This is a point that is used as an input of the forward controller 206 and is passed through a differentiator 66 in the torque feedforward controller 206.

Further, the torque feedforward controller of the digital servo control device of the present invention may be a torque feedforward controller having another configuration.
For example, FIG. 4 shows a fourth embodiment of the present invention, and a block of a torque feedforward controller showing another configuration that can be used in the servo control apparatus showing the third embodiment of the present invention. FIG. In the figure, a torque feedforward controller 306 receives a position command, performs differentiation operation twice by differentiators 61 and 66, and multiplies a torque feedforward gain TFF by a multiplier 63 to generate a torque feedforward signal. To do.

The delay unit 64 stores the generated torque feed forward signal. Here, the output of the multiplier 63 is input to the averaging circuit 67. In the averaging circuit 67, the difference between the output of the multiplier 63 and the average value of the output of the multiplier 63 before n sampling (n is a natural number). Is larger than the threshold value set in advance, the selector 65 outputs the previous value of the torque feed forward signal stored in the delay unit 64. The differential operation of the differentiator 61 is calculated by the equation (8) where IN (n) is the current input, IN (n-1) is the previous input, Ts is the sampling period, and OUT (n) is the output. The
OUT (n) = {IN (n) −IN (n−1)} / Ts (8)
Note that this embodiment differs from the third embodiment in that an averaging circuit 67 in the torque feedforward controller 306 is provided instead of the differentiator 62 in the torque feedforward controller 206 in FIG. .

In the first to fourth embodiments, the invention related to the digital servo control device related to position control has been described. In the fifth and sixth embodiments, the invention related to the digital servo control device related to speed control will be described. That is, the first to fourth embodiments are cases of position command input, and the fifth and sixth embodiments are cases of speed command input.
FIG. 5 is a block diagram of a digital servo control apparatus showing a fifth embodiment of the present invention. In the figure, components having the same reference numerals as those in FIG. 1 showing the first embodiment of the present invention perform the same operations, and thus description thereof will be omitted. Reference numeral 406 denotes a torque feedforward controller.
Note that this embodiment differs from the first embodiment in that a speed command is input instead of a position command, and this is an example applied to a digital servo control device related to speed control.

Further, the torque feedforward controller of the digital servo control device of the present invention may be a torque feedforward controller having another configuration.
For example, FIG. 6 shows a sixth embodiment of the present invention, and a block of a torque feedforward controller showing another configuration that can be used in the servo control apparatus showing the fifth embodiment of the present invention. FIG.
Note that this embodiment is different from the fifth embodiment in that an averaging circuit 67 in the torque feedforward controller 506 is provided instead of the differentiator 62 in the torque feedforward controller 406 in FIG. .

The speed feedforward signal of the present invention may be a speed feedforward signal obtained by filtering the output of the speed feedforward controller with an arbitrary low-pass filter.
For example, FIG. 7 shows a seventh embodiment of the present invention, and is a block diagram for filtering the output of the speed feedforward controller. In the figure, a signal obtained by filtering the output of the speed feedforward controller 5 by an arbitrary low-pass filter 53 is used as a speed feedforward signal. This can be applied instead of the velocity feedforward signal in the first and third embodiments.

Further, the torque feedforward signal of the present invention may be a torque feedforward signal obtained by filtering the output of the torque feedforward controller using an arbitrary low-pass filter.
For example, FIG. 8 shows an eighth embodiment of the present invention and is a block diagram for filtering the output of the torque feedforward controller. In the figure, a signal obtained by filtering the output of the torque feedforward controller 6 by an arbitrary low-pass filter 68 is used as a torque feedforward signal. This can be applied instead of the toll feed forward signal in the first to sixth embodiments.

1 is a block diagram of a digital servo control apparatus showing a first embodiment of the present invention. FIG. 9 is a block diagram of a torque feedforward controller showing another configuration that can be used in the servo control device showing the second embodiment of the present invention and showing the first embodiment of the present invention. It is a block diagram of the digital servo control apparatus which shows the 3rd Example of this invention. FIG. 10 is a block diagram of a torque feedforward controller showing another configuration that can be used in the servo control device showing the fourth embodiment of the present invention and showing the third embodiment of the present invention. It is a block diagram of the digital servo control apparatus which shows the 5th Example of this invention. It is a block diagram of the torque feedforward controller which shows the 6th Example of this invention and shows the other structure which can be used with the servo control apparatus which shows the 5th Example of this invention. FIG. 10 is a block diagram illustrating a seventh embodiment of the present invention and filtering an output of a speed feedforward controller. FIG. 10 is a block diagram illustrating an eighth embodiment of the present invention and filtering the output of a torque feedforward controller. It is a block diagram which shows the conventional digital servo control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Position controller 2 Speed controller 3 Control object 4 Detector 5 Speed feedforward controller 6, 106, 206, 306, 406, 506 Torque feedforward controller 7, 51, 61, 62, 66 Differentiator 52, 63 Multiplier 53 Filter 64 Delay device 65 Selector 67 Averaging circuit 68 Filter

Claims (6)

In a digital servo controller for speed feedforward control or torque feedforward control,
A delay unit that stores the current multiplication value obtained by multiplying the differential signal of the command signal or the output signal of the speed feedforward controller by the torque feedforward gain, and either the current multiplication value or the previous multiplication value before one sampling; A digital servo control device comprising: a torque feedforward controller that generates a torque feedforward signal based on one of them.   2. The digital servo control device according to claim 1, wherein the differential signal is a position command double differential signal, a speed command single differential signal, or a speed feed forward signal single differential signal. . The torque feedforward controller selects either the current multiplication value or the previous multiplication value;
2. The digital servo control apparatus according to claim 1, further comprising a differentiator or an averaging circuit that outputs a switching signal for switching the selector. The differentiator differentiates the differential signal once more,
2. The switching signal is output so as to select the previous multiplication value when the first differentiated signal is compared with a preset threshold value and is larger than the preset threshold value. 3. The digital servo control device according to 3. The averaging circuit calculates an average value of the multiplication values up to n samplings (n is a natural number) of the current multiplication value,
Calculate the absolute value of the difference between the current multiplication value and the average value,
4. The switching signal is output so as to select the previous multiplication value when the absolute value is compared with a preset threshold value and is larger than the preset threshold value. Digital servo controller.   2. The digital servo control device according to claim 1, further comprising an arbitrary low-pass filter at an output of the speed feedforward controller or the torque feedforward controller.

Images