JP4658181B2 - Servo control device - Google Patents

Description

  The present invention relates to a servo control device that drives a load machine such as a feed axis of a machine tool or an arm of an industrial robot with a motor, and more particularly to a servo control device that performs trajectory control in a machine having two or more axes. Is.

As a conventional servo control device, feedforward control is performed in order to compensate for a response delay with respect to a command value of a controlled amount such as position and speed. For example, the position command is differentiated to obtain the position feedforward control amount, the feedforward control amount is added to the control amount obtained by the position loop control to obtain a speed command, and the speed obtained by differentiating the position feedforward control amount The position control responsiveness is improved by adding the feedforward control amount to the value obtained by the speed loop control and performing servo control as a current command (for example, FIG. 1 of Patent Document 1 below). .
In addition, a simulation control circuit for a mechanical system model configured by approximating a mechanical system composed of a torque transmission mechanism, a load machine, and an electric motor as a two-inertia resonance system is configured, and the simulated motor position, speed, and torque of the simulation control circuit are determined. By adding to the value obtained by position loop control and speed loop control as feedforward control amount, the rigidity of the controlled object is low, and even if it has resonance characteristics, the responsiveness of position control is enhanced without exciting vibration There is one (for example, FIG. 25 of the following patent document 2).

Japanese Patent No. 2762364 JP 2000-92882 A

Since the conventional servo control device is configured as described above, the servo control device described in Patent Document 1 has sufficient performance when the control object has high rigidity and can be regarded as a rigid body. However, if the rigidity of the control object is low and the resonance characteristic is present and this method is implemented to increase the responsiveness, mechanical resonance causes vibration at the controlled position and speed, and FIG. As shown in FIG. 1, there is a problem that positioning accuracy and trajectory accuracy are lowered.
Further, in the servo control device described in Patent Document 2, when the controlled object can be regarded as a two-inertia resonance system, the position of the controlled object always follows the position of the simulated control circuit completely and excites vibration. However, the simulated control circuit constitutes a feedback control system, and the impulse response is not symmetrical. Therefore, even if a symmetrical trajectory is given as a command trajectory, the response trajectory of the controlled object is not symmetric. Therefore, when a command locus having the same shape is reciprocated while changing the traveling direction as shown in FIG. 14, an error occurs between the reciprocal response locus. This has caused problems such as causing damage to the processed surface when reciprocating the mold.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a servo control device that reduces vibrations caused by mechanical characteristics and matches the reciprocal trajectories.

The servo control device according to the present invention performs position control on a signal obtained by subtracting the motor position signal from the position feedforward signal among the position feedforward signal, speed feedforward signal, and torque feedforward signal calculated from the position command signal. And a speed controller that adds a speed feedforward signal to the output of the position controller and performs speed control on the signal obtained by subtracting the motor speed signal, and provides torque feedforward to the output of the speed controller. By outputting a signal obtained by adding the signals as a motor torque command signal, the drive has two or more shafts and the rigidity between the motor and the motor mounting base is lower than the rigidity between the motor and the load. in the servo controller for trajectory control by driving the objective machine, the rate of by differentiating the position command signal A differentiator for computing a I over-forward signal, as an operator and an output signal of the feed-forward signal of the torque calculation value as the input signal by the arithmetic unit for multiplying the total inertia of the driven machine along with differentiating the calculated value by the differentiator A vibration suppression filter configured to calculate and set the gain of the output signal with respect to the input signal to decrease with respect to the resonance frequency component of the driven machine and to increase with respect to the anti-resonance frequency component of the driven machine ; It is equipped with.

According to the present invention, in the vibration suppression filter, it calculates a feedforward signal of the torque calculation value by the arithmetic unit as the input signal as an output signal, the gain of the output signal to the input signal, to the resonance frequency component of the driven machine Therefore, a high vibration suppression effect can be obtained with a simple configuration by setting to decrease and to increase to the anti-resonance frequency component of the driven machine . In particular, when vibration occurs due to low rigidity between the motor of the machine and the motor installation base, the vibration of the machine can be suppressed.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a servo control device according to Embodiment 1 of the present invention. In the figure, the servo control device 1 drives and controls a machine (drive target machine) 2 in accordance with a position command signal. .
In the servo control device 1, an FIR (Finite Impulse Response) filter unit 3 corrects a position command signal, and a mechanical characteristic compensation unit 4 determines a predetermined frequency corresponding to the characteristic of the machine 2 from the corrected position command signal. The components are attenuated to calculate position, speed and torque feedforward signals, and the feedback compensator 5 drives the machine 2 in accordance with the calculated position, speed and torque feedforward signals. .
The FIR filter unit 3 includes an FIR filter 6.

  Further, in the mechanical characteristic compensator 4, the position command calculator 7 attenuates the anti-resonance frequency component of the machine 2 from the position command signal to calculate a position feedforward signal, and the differentiator 8 calculates the position command signal. The speed command calculator 9 attenuates the anti-resonance frequency component of the machine 2 from the value calculated by the differentiator 8 and calculates a speed feedforward signal. The calculator 10 calculates the value calculated by the differentiator 8. The torque command calculator 11 attenuates the resonance frequency component of the machine 2 from the value calculated by the calculator 10 and calculates the torque feedforward signal.

Further, in the feedback compensation unit 5, the subtractor 12 subtracts the motor position signal from the position feedforward signal and outputs it to the position controller 13, the position controller 13 obtains the speed control signal, and the adder / subtractor 14 The speed feedforward signal and the speed control signal are added and the motor speed signal is subtracted and output to the speed controller 15. The speed controller 15 obtains a torque control signal, and the adder 16 receives the torque feedforward signal. And the torque control signal are output to the machine 2 as a motor torque command signal.
The machine 2 includes a motor 17 that drives a load 18 in accordance with a motor torque command signal.

Next, the operation will be described.
In FIG. 1, the position command signal is smoothed by the FIR filter 6 and output to the mechanical characteristic compensator 4. Here, the FIR filter 6 is configured by connecting two or more moving average filters having a time constant _Tf in series. Here, the time constant of the moving average filter refers to a value obtained by multiplying the number of taps of the moving average filter by the sampling period. Further, the time constant _Tf is calculated by a predetermined calculation from the required trajectory accuracy parameter so that the response trajectory satisfies the required trajectory accuracy. The required trajectory accuracy parameters include the amount of droop when passing through the corner (distance to the corner apex when the response trajectory is closest to the corner apex), the amount of inward rotation of the arc (the amount of decrease in the radius of the response trajectory relative to the command radius) .

In mechanical characteristic compensation unit 4, first, the input signal x _r1 mechanical characteristic compensation unit 4 is input to the position command calculator 7, a feed-forward signal x _a position is calculated. Position command calculator 7 is a calculator for outputting the attenuated components of the anti-resonance frequency omega _z of the machine 2 in the input signal x _r1, the relation between the input signal x _r1 and the output signal x _a next It is represented by the formula (1). Note that s is a Laplace operator.

The input signal x _r1 mechanical characteristic compensation unit 4, after being differentiated by differentiator 8, is input to the speed command calculator 9, the speed of the feed-forward signal v _a is calculated. Speed command calculator 9 is to attenuate the components of the anti-resonance frequency omega _z of the machine 2 in the input signal v _r1 is a calculator for output, the relationship between the input signal v _r1 and the output signal v _a following (2)

Further, the output signal of the differentiator 8 after being multiplied by the total inertia J of the machine 2 is differentiated by computing unit 10, is input to the torque command calculator 11, a feed-forward signal tau _a torque is calculated. The total inertia referred to here is the total inertia of the motor inertia and the load inertia. Torque command calculator 11 is an arithmetic unit for outputting the attenuated components of the resonance frequency omega _p of the machine 2 in the input signal tau _r1, the relationship between the input signal tau _r1 and the output signal tau _a is the following It is represented by Formula (3).

Next, the position feedforward signal x _a , the speed feedforward signal v _a , and the torque feedforward signal τ _a are input to the feedback compensator 5. The feedback compensation unit 5, the subtractor 12 subtracts the motor position signal x _m output from the machine 2 from the feed-forward signal x _a position output to the position controller 13, the speed in the position controller 13 control signal v _c is obtained. The position controller 13 may have any configuration as long as the feedback control system becomes stable, but a proportional controller or the like is usually used. The outputs in the adder-subtracter 14, from the value obtained by adding the feed-forward signal v _a a speed control signal v _c of the speed, the speed controller 15 subtracts the motor speed signal v _m outputted from the machine 2 speed The controller 15 obtains the torque control signal τ _c . The speed controller 15 may have any configuration as long as the feedback control system becomes stable, but a proportional, integral controller or the like is usually used. Further, the adder 16 outputs a value obtained by adding the torque feedforward signal τ _a and the torque control signal τ _c to the machine 2 as the motor torque command signal τ _m to drive the motor 17. Machine 2 the motor 17 and the load 18 which is installed on the motor installation base is coupled by a torque transmission mechanism, the motor position signal x _m and the motor speed signal v _m is output by the rotation detector attached to the motor 17 Is done. Here, the torque generated by the motor 17 follows the motor torque command signal τ _m sufficiently quickly.

また、モータ位置ｘ_ｍと負荷位置ｘ_ｌの間の関係は次の式（５）のようになる。

また、モータ速度ｖ_ｍとモータ位置ｘ_ｍの間の関係は、次の式（６）のようになる。
ｖ_ｍ（ｓ）＝ｓ・ｘ_ｍ（ｓ） （６） According to such a configuration, the position, speed, and torque appropriately calculated so that the load position of the machine 2 completely follows the input signal x _r1 of the mechanical characteristic compensation unit 4 according to the vibration characteristics of the machine 2. Therefore, the load position x ₁ completely follows the input signal x _r1 of the mechanical characteristic compensator 4. This can be expressed as follows: When the machine 2 can be approximated by a two-inertia resonance system, the relationship between the motor torque command signal τ _m and the motor position x _m is expressed by the following equation (4).

The relationship between the motor position x _m and the load position x _l is as follows in equation (5).

Further, the relationship between the motor speed v _m and the motor position x _m is expressed by the following equation (6).
v _m (s) = s · x _m (s) (6)

Further, assuming that the transfer functions of the position controller 13 and the speed controller 15 are C _p (s) and C _v (s), respectively, the input / output relationship of the feedback compensator 5 is expressed by the following equation (7). .
τ _m (s) = C _v (s) (C _p (s) (x _a (s) −x _m (s))
+ V _a (s) −v _m (s)) + τ _a (s) (7)
Considering that the relational expressions of Expression (1) to Expression (5), Expression (6), and Expression (7) hold, the input signal x _r1 of the mechanical characteristic compensator 4 and the machine 2 in Embodiment 1 are as follows. When determining the relationship between the load position _{x l,} the _x l ₌ x _r1. That is, the load position x ₁ completely follows the input signal x _r1 of the mechanical characteristic compensator 4. Therefore, the response characteristic from the command position to the load position is equal to the response characteristic of the FIR filter 6.

FIG. 2 is a characteristic diagram showing a symmetric impulse response. If the impulse response of the FIR filter 6 is close to a symmetric shape as shown in FIG. 2, the output is also symmetric if the input is symmetric as is well known. Therefore, the response trajectory with respect to the symmetrical command trajectory is symmetric, and the reciprocal response trajectory when the trajectory having the same shape is reciprocated has substantially the same shape. Furthermore, if the impulse response of the FIR filter 6 is completely symmetrical, that is, if it is a linear phase FIR filter, the response trajectory with respect to the symmetric command trajectory is completely symmetrical, and when the trajectory having the same shape is reciprocated. The reciprocal response trajectories coincide. Further, the feedforward signal tau _r1 torque includes fourth order ingredients input signal x _r1 mechanical characteristic compensation unit 4 at the maximum, if the input signal x _r1 mechanical characteristic compensation unit 4 is not sufficiently smooth It is considered that the torque feedforward signal τ _r1 becomes an impulse-like very large value and adversely affects the machine 2, but the configuration of the FIR filter 6 is composed of two series couplings of moving average filters. As a result, if the position command signal _xr1 is an acceleration step command often used in position control, even if the input signal _xr1 of the mechanical characteristic compensator 4 is fourth-order differentiated, it does not become an impulse signal, and torque It is avoided that the feedforward signal τ _r1 of FIG. Further, since the impulse response of the FIR filter 6 has a symmetric shape, the response trajectory with respect to the symmetric command trajectory is completely symmetric, and the reciprocal response trajectories when the trajectories having the same shape are reciprocated coincide.

  The FIR filter 6 preferably has a linear phase characteristic like a linear phase FIR filter. However, even if a general FIR filter having no linear phase characteristic is used, the output is determined from a history of a finite time in the past. There is an advantage that it is easier to obtain a symmetric response locus than when using a filter other than the FIR filter, that is, an IIR (Infinite Impulse Response) filter. As for the FIR filter, for example, F.R. R. There are detailed explanations in Conner's Introduction to Filter Circuits (Morikita Publishing).

Next, the effect of the first embodiment will be shown by numerical simulation.
FIG. 3 is an overall configuration diagram showing the servo control device according to the first embodiment of the present invention. In FIG. 3, a machine 2 having two-axis freedom is provided by the x-axis and y-axis servo control devices 1a and 1b. It is driven using x-axis and y-axis motors 17a and 17b.
FIG. 4 is a characteristic diagram showing a command locus and a response locus of the servo control device according to the first embodiment of the present invention. The command trajectory has a corner shape with an angle of 90 degrees, and the response trajectory shows the case where the traveling direction of the command trajectory is set to the traveling direction A and the traveling direction B, that is, the trajectory having the same shape is reciprocated. The resonance frequency ω _p of the machine 2 is 300 rad / s, and the anti-resonance frequency ω _z is 200 rad / s.
In the example shown in FIG. 4, it can be seen that the response trajectory suppresses vibration compared to the conventional patent document 1, and the reciprocal response trajectory difference is reduced compared to the patent document 2. As described above, even when a die or the like is reciprocated, a machined surface without scratches can be obtained.

As described above, according to the first embodiment, when the mechanical characteristic compensator 4 can regard the machine 2 as a two-inertia resonance system and the damping characteristic due to viscous friction of the machine 2 can be ignored, the characteristic of the machine 2 By determining the position, speed, and torque feedforward signals using the values (resonance frequency, antiresonance frequency, total inertia), vibration due to the characteristics of the machine 2 can be reduced.
Further, the feedforward signal obtained by the mechanical characteristic compensator 4 is output to the feedback compensator 5 so that the position of the machine 2 completely follows the input of the mechanical characteristic compensator 4, that is, the output of the FIR filter unit 3. Can do.
Further, since the trajectory can be easily made symmetrical by the FIR filter unit 3 and the trajectories at the time of reciprocation can be matched, a processed surface having no step can be obtained even when reciprocating.
Further, the FIR filter unit 3 is a moving average filter having two or more stages, and the time constant of the moving average filter is set according to the required trajectory accuracy, so that the symmetry of the trajectory is maintained and the signal input to the feedback compensation unit 5 It is possible to avoid giving a large shock to the machine 2 as a large impulse signal, and to make the error of the response trajectory from the command trajectory within the required trajectory accuracy.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing a servo control apparatus according to Embodiment 2 of the present invention. In the figure, a first-order lag filter 21 is provided in the mechanical characteristic compensator 4, and the influence of the damping characteristic due to viscous friction of the machine 2 is shown. The time constant is set according to the damping constant, anti-resonance frequency, and load inertia of the machine 2 so as to reduce the position command signal.
Further, the position command calculator 22 attenuates the anti-resonance frequency component of the machine 2 in consideration of the damping characteristic due to the viscous friction of the machine 2 from the position command signal corrected by the first-order lag filter 21, and feeds forward the position. The speed command calculator 23 attenuates the anti-resonance frequency component of the machine 2 in consideration of the damping characteristic due to the viscous friction of the machine 2 from the value calculated by the differentiator 8 to calculate the feed forward of the speed. The torque command calculator 24 attenuates the resonance frequency component of the machine 2 in consideration of the damping characteristic due to the viscous friction of the machine 2 from the value calculated by the calculator 10, and outputs a torque feedforward signal. It is to calculate.
Other configurations are the same as those in FIG.

Next, the operation will be described.
In FIG. 5, the difference from the first embodiment is that the input signal _xr1 of the mechanical characteristic compensator 4 is corrected by the first-order lag filter 21 and then output to the position command calculator 22 and the differentiator 8. The position command calculator 22, the speed command calculator 23, and the torque command calculator 24 are configured in consideration of the damping characteristics of the machine 2.
When the damping characteristic due to viscous friction of the machine 2 cannot be ignored, in the configuration shown in the first embodiment, due to this characteristic, between the input signal x _r1 of the mechanical characteristic compensation unit 4 and the load position x _l. resulting phase shift is, it may become impossible to accurately follow the load position x _l to the input signal x _r1 mechanical characteristic compensation unit 4.

ここで、ζ_ｚは機械の減衰定数ｃ、反共振周波数ω_ｚ、負荷イナーシャＪ_ｌを用いて次の式（９）のように表せる。

Therefore, the time constant as the first-order lag filter 21, the phase shift between the input signal x _r1 mechanical characteristic compensation unit 4 due to the damping characteristics due to viscous friction of the machine 2 and the load position x _l is eliminated To correct the input signal _xr1 of the mechanical characteristic compensator 4. Relationship between the input signal _{x r1} of the first-order lag filter 21 and the output signal _{x r2} is expressed by the following equation (8).

Here, ζ _z can be expressed by the following equation (9) using the mechanical damping constant c, the anti-resonance frequency ω _z , and the load inertia J _l .

The position command calculator 22, first-order lag calculator for attenuating and outputting the anti-resonance frequency omega _z components of the machine 2 in consideration of the attenuation characteristic of the machine 2 of the corrected in the input signal x _r2 by the filter 21 , and the relationship between the input signal x _r2 and the output signal x _a is expressed by the following equation (10).

The speed command calculator 23, an input signal v calculator for outputting the attenuated components of the anti-resonance frequency omega _z of the machine 2 in consideration of the attenuation characteristic of the machine 2 in _r1, the input signal v _r1 and output relationship between the signal v _a is expressed by the following equation (11).

ここで、減衰比ζ_ｐは機械の減衰定数ｃ、共振周波数ω_ｐ、負荷イナーシャＪ_ｌ、モータイナーシャＪ_ｍを用いて次の式（１３）のように表せる。

Further, the torque command calculator 24 is an arithmetic unit for attenuating and outputting the components of the resonance frequency omega _p of the consideration to machine 2 a damping characteristic of the machine 2 in the input signal tau _r1, the input signal tau _r1 and the output signal The relationship between τ _a is expressed by the following equation (12).

Here, the damping ratio ζ _p can be expressed by the following equation (13) using the mechanical damping constant c, the resonance frequency ω _p , the load inertia J _l , and the motor inertia J _m .

According to such a configuration, the machine 2 is completely follow the load position x _l, even if the input signal x _r1 mechanical characteristic compensation unit 4 having an attenuation characteristic due to viscous friction. This can be expressed as follows: When the machine 2 can be approximated by a two-inertia resonance system and has a damping characteristic, the relationship between the motor torque command signal τ _m and the motor position x _m is expressed by the following equation (14).

Further, the relationship between the motor position x _m and the load position x _l is expressed by the following equation (15).

Further, the relationship between the motor speed v _m and the motor position x _m and the input / output relationship of the feedback compensation unit 5 are the same as those in the first embodiment, and are expressed by the equations (6) and (7), respectively. . Considering that the relational expressions (6), (7), and (8) to (15) hold, the input signal x _r1 of the mechanical characteristic compensator 4 and the machine 2 in the second embodiment When determining the relationship between the load position _{x l,} the _x l ₌ x _r1. That is, the load position x ₁ completely follows the input signal x _r1 of the mechanical characteristic compensator 4. Therefore, the response characteristic from the command position to the load position of the machine 2 matches the response characteristic of the FIR filter 6, and a response locus that is symmetrical and does not excite vibration can be obtained.

Next, the effect of the second embodiment will be shown by numerical simulation.
FIG. 6 is a characteristic diagram showing a command trajectory and a response trajectory of the servo control device according to Embodiment 2 of the present invention. FIG. 6 (a) shows a machine having two degrees of freedom of the x-axis and the y-axis. FIG. 6B shows the command trajectory and the response trajectory according to the first embodiment, and FIG. 6B shows the command trajectory and the response trajectory when driven by the servo control device according to the second embodiment. The command locus has a corner shape of 90 degrees, and the resonance frequency ω _p of the machine 2 is 300 rad / s, and the anti-resonance frequency ω _z is 200 rad / s. Further, the damping ratio ζ _{p is set} to 0.2.
In the example shown in FIG. 6, when the machine 2 has a damping characteristic, the servo control device according to the second embodiment is used, compared with the case where the servo control device according to the first embodiment is used. It can be seen that the vibration of the response locus can be suppressed.

As described above, according to the second embodiment, in the position command calculator 22, the speed command calculator 23, and the torque command calculator 24, the anti-resonance frequency of the machine 2 considering the viscous friction damping characteristics of the machine 2. attenuating components or resonance frequency component, the first-order lag filter 21, the time constant is set so that the phase shift between the input signal x _r1 mechanical characteristic compensation unit and the load position x _l is resolved, the input By correcting the position command signal generated, even if the machine 2 can be regarded as a two-inertia resonance system and there is a damping characteristic due to the viscous friction of the machine 2, the machine position, that is, the load position does not excite machine vibration. It is possible to completely follow the input of the compensation unit 4, that is, the output of the FIR filter unit 3.

Embodiment 3 FIG.
FIG. 7 is a block diagram showing a servo control apparatus according to Embodiment 3 of the present invention. In FIG. 7, a fifth-order IIR filter (n-order filter) 31 is provided in the mechanical characteristic compensator 4 and has a desired frequency cutoff characteristic. The position command signal is corrected.
Other configurations are the same as those in FIG.

ここで、Ｋ_１からＫ_５は５次ＩＩＲフィルタ３１の周波数遮断特性を決定する極を表すパラメータである。
図８は５次ＩＩＲフィルタのゲイン曲線の一例を示す特性図である。一例として、Ｋ_１＝Ｋ_２＝Ｋ_３＝Ｋ_４＝Ｋ_５＝１０００のときの５次ＩＩＲフィルタ３１のゲイン曲線を示すとこの図８のようになり、４００ｒａｄ／ｓ付近よりも高い周波数領域が遮断されていることがわかる。 Next, the operation will be described.
In FIG. 7, the difference from the first embodiment is that the input signal _xr1 of the mechanical characteristic compensator 4 is corrected by the fifth-order IIR filter 31 and then output to the position command calculator 7 and the differentiator 8. is there. The fifth-order IIR filter 31 has a configuration represented by the following formula (16), for example.

Here, K ₁ to K ₅ are parameters representing poles that determine the frequency cutoff characteristics of the fifth-order IIR filter 31.
FIG. 8 is a characteristic diagram illustrating an example of a gain curve of a fifth-order IIR filter. As an example, the gain curve of the fifth-order IIR filter 31 when K ₁ = K ₂ = K ₃ = K ₄ = K ₅ = 1000 is shown in FIG. 8 and is a frequency region higher than around 400 rad / s. It can be seen that is blocked.

According to such a configuration, can not be approximated by the machine 2 is two-inertia resonance system, even if another resonance point frequency region higher than the resonance frequency omega _p is present, the fifth-order frequency components near the resonance point Since it is blocked by the IIR filter 31, the vibration of the response trajectory can be reduced. Even when vibration occurs in the response trajectory due to high-frequency noise included in the position command signal, the component in the high frequency region included in the position command signal is blocked by the fifth-order IIR filter 31, so that the vibration of the response trajectory Can be reduced.

Next, the effect of the third embodiment is shown by numerical simulation.
FIG. 9 is a characteristic diagram showing a command trajectory and a response trajectory of the servo control device according to Embodiment 3 of the present invention. FIG. 9A shows a machine having two degrees of freedom of the x-axis and the y-axis. FIG. 9B shows a command locus and a response locus when driven by the servo control device according to the third embodiment, and FIG. 9B shows a command locus and a response locus according to the first embodiment. The command locus has a corner shape of 90 degrees, and the resonance frequency ω _p of the machine 2 is 300 rad / s, and the anti-resonance frequency ω _z is 200 rad / s. Further, the machine has a second resonance frequency at 1000 rad / s and a second anti-resonance frequency at 700 rad / s.
In the example shown in FIG. 9, when the machine 2 cannot be approximated by a two-inertia resonance system and has the second resonance frequency and the second anti-resonance frequency, the servo control device according to the third embodiment is used. Thus, it can be understood that the vibration of the response locus can be suppressed as compared with the case where the servo control device according to the first embodiment is used.

As described above, according to the third embodiment, the mechanical characteristic compensator 4 includes the fifth order IIR filter 31 having a desired frequency cutoff characteristic, and the input position command signal is received by the fifth order IIR filter 31. When there is another resonance point and antiresonance point in a frequency region higher than the noise included in the position command signal, the resonance frequency of the machine 2 that is a parameter of the mechanical characteristic compensation unit 4, and the antiresonance frequency by correcting Adverse effects appearing in the response trajectory can be reduced.
In the third embodiment, the fifth-order IIR filter 31 having five desired poles is provided, but any first-order or higher-order IIR filter may be provided.

Embodiment 4 FIG.
FIG. 10 is a block diagram showing a servo control apparatus according to Embodiment 4 of the present invention. In the figure, Embodiment 4 uses a position command signal directly input to mechanical characteristic compensator 4 as a position feedforward. The signal is output to the subtractor 12, the differentiator 8 differentiates the position command signal to calculate the speed feedforward signal, and outputs it to the adder / subtractor 14. The calculator 10 differentiates the value calculated by the differentiator 8. The vibration suppression filter 41 calculates the torque feedforward signal by attenuating the resonance frequency component of the machine 2 and amplifying the anti-resonance frequency component from the value calculated by the calculator 10. And output to the adder 16.
Other configurations are the same as those in FIG.

このように演算器１０による演算値から機械２の共振周波数成分を減衰し、反共振周波数成分を増幅するものである。 Next, the operation will be described.
10, the position command signal is input directly into the machine characteristic compensation unit 4 x _r is output to the feedback compensation unit 5 as a feed forward signal x _a position. The position command signal is differentiated by the differentiator 8 and output to the feedback compensator 5 as _a velocity feedforward signal va. Further, the operation value obtained by the differentiator 8 is differentiated by the operator 10 and multiplied by the total inertia of the machine 2 and then output to the vibration suppression filter 41. The output signal of the vibration suppression filter 41 is a torque feedforward signal τ _a. Is output to the feedback control unit 5. The configurations and operations of the feedback compensation unit 5 and the machine 2 are the same as those in the first embodiment.
Next, the vibration suppression filter 41 will be described. The relationship between the input signal τ _r1 and the output signal τ _a in the vibration suppression filter 41 is expressed by the following equation (17) using the resonance frequency ω _p of the machine 2 and the anti-resonance frequency ω _z of the machine 2. To do.

In this way, the resonance frequency component of the machine 2 is attenuated from the value calculated by the calculator 10 and the anti-resonance frequency component is amplified.

According to such a configuration, it is possible to reduce mechanical vibration with a simpler configuration. In addition, the machine 2 has high rigidity between the motor 17 and the load 18 but low rigidity between the motor 17 and the motor installation base, and mechanical vibration causes resonance and anti-resonance between the motor 17 and the motor installation base. There when it occurs due to vibration components due to the resonance and anti-resonance is removed by vibration reduction filter 41, the load position x _l is completely follows the position command signal x _r.
This can be expressed as follows: When the machine 2 can be approximated by a model in which the rigidity between the motor 17 and the load 18 is sufficiently high and the rigidity between the motor 17 and the motor mounting base is low, the motor torque command signal τ _m and the motor position x _m The relationship between is as shown in the following equation (18).

The relationship between the motor position x _m and the load position x _l is as follows in equation (19).
x _l (s) = x _m (s) (19)
Further, the relationship between the motor speed v _m and the motor position x _m and the input / output relationship of the feedback compensation unit 5 are the same as those in the first embodiment, and are expressed by the equations (6) and (7), respectively. Equation (6) and (7), taking into account that each relation of formula (19) from equation (17) holds, the load position x _l of the position command signal x _r and the machine 2 in the fourth embodiment When the relationship between is obtained, x _l = x _r . That is, the load position x _l is completely follows the position command signal x _r. Therefore, mechanical vibration can be effectively suppressed.

Next, the effect of the fourth embodiment will be shown by numerical simulation.
FIG. 11 is a characteristic diagram showing a command trajectory and a response trajectory of the servo control device according to the fourth embodiment of the present invention. The command trajectory when the machine 2 having the two degrees of freedom of the x and y axes is driven. And the response trajectory. The command trajectory has a 90-degree corner shape, and the response trajectory shows the case where the travel direction of the command trajectory is the travel direction A and travel direction B according to FIG. 14, that is, the trajectory having the same shape is reciprocated. Yes. The machine 2 has a sufficiently high rigidity between the motor 17 and the load 18 but has a low rigidity between the motor 17 and the motor installation base. The resonance frequency ω _p of the machine 2 is 300 rad / s, and the anti-resonance frequency ω _z is 200 rad / s.
In the example shown in FIG. 11, even when the rigidity between the motor 17 and the motor installation base is low in the machine 2, the response locus is compared with the conventional example by using the servo control device according to the fourth embodiment. It can be seen that the vibration of the response trajectory and the difference between the reciprocal response trajectories are suppressed.

  As described above, according to the fourth embodiment, in the vibration suppression filter 41, the resonance frequency component of the machine 2 is attenuated from the value calculated by the calculator 10, the anti-resonance frequency component is amplified, and torque feedforward is performed. By calculating the signal, it is possible to obtain a vibration suppression effect with a simpler configuration than that of the first embodiment. In particular, when vibration occurs due to low rigidity between the motor 17 of the machine 2 and the motor installation base, the vibration of the machine 2 can be suppressed.

Embodiment 5. FIG.
FIG. 12 is a block diagram showing a servo control apparatus according to Embodiment 5 of the present invention. In the figure, a position command correction unit 51 is provided between the FIR filter unit 3 and the mechanical characteristic compensation unit 4, and is an FIR filter. It has a characteristic to reduce the influence of the gain reduction in the low frequency region below the cut-off frequency of these filters caused by the 6th and 5th order IIR filters 31, and corrects the position command signal.
The simulated position control loop unit 52 calculates a simulated speed signal by performing a simulation simulating the feedback compensation unit 5 from the position feedforward signal and the speed feedforward signal. The torque correction signal is calculated according to the change in the sign of the simulated speed signal and output to the adder 16.
Further, in the simulated position control loop unit 52, the subtractor 54 subtracts the simulated position signal from the position feedforward signal and outputs the result to the second position controller 55. The second position controller 55 The same calculation is performed and output to the adder 56. The adder 56 adds the output of the second position controller 55 and the speed feedforward signal to obtain a simulated speed signal, and the integrator 57 calculates the simulated speed signal. To obtain a simulated position signal.
Other configurations are the same as those in FIG.

Next, the operation will be described.
In FIG. 12, the difference from the third embodiment is that the output signal of the FIR filter unit 3 is corrected by the position command correction unit 51 and then output to the mechanical characteristic compensation unit 4, and the position feedforward signal. A speed feedforward signal is output to the simulated position control loop unit 52 to obtain a simulated speed signal, and the simulated speed signal is input to the torque correction signal calculation unit 53 to calculate the torque correction signal and add it to the motor torque command signal. Is a point.
The FIR filter 6 and the fifth order IIR filter 31 smooth the command to prevent the input signal to the feedback compensation unit 5 from becoming a large impulse and adversely affecting the machine 2, and the high frequency region included in the position command signal. However, all of these are low-pass filters, and the gain decreases as the frequency becomes higher. These filters have a slight gain reduction even in a low frequency region below the cut-off frequency, and this may cause the radius of the response trajectory to be smaller than the radius of the command trajectory during an arc command.
Therefore, the position command correction unit 51 corrects the position command signal so that the influence of the gain reduction caused by the FIR filter 6 and the fifth order IIR filter 31 is reduced. The relationship between the input signal _xr1 and the output signal _xr11 of the position command correction unit 51 is expressed by the following equation (20).
x _r11 (s) = (1 + α · s) x _r1 (20)
Here, α is a parameter for adjusting the correction amount, and is set so that the gain reduction in the low frequency region from the position command signal x _r to the output x _r2 of the fifth-order IIR filter 31 is not more than a desired value. .

In addition, when a frictional force is applied to the motor 17, a follow-up delay occurs when the rotation direction of the motor 17 is reversed, which may cause an error between the command locus and the response locus. In such a case, the follow-up delay can be eliminated by giving a correction command to the torque command when the sign of the motor speed changes. However, in the method in which a correction command is given when the sign of the motor speed signal changes, the direction of rotation of the motor 17 also changes when the sign of the motor speed signal changes due to a slight disturbance applied to the motor 17 or the load 18 when the motor 17 is stopped. A correction command is given assuming that it is reversed, which is not preferable.
Therefore, the simulated position control loop unit 52 performs a simulation of the feedback compensation unit 5 from the position feedforward signal and the speed feedforward signal, calculates a simulated speed signal, and outputs the simulated speed signal to the torque correction signal calculation unit 53. In the simulated position control loop unit 52, the subtractor 54 subtracts the simulated position signal from the position feedforward signal and outputs it to the second position controller 55. The second position controller 55 is the same as the position controller 13. The calculation is performed and output to the adder 56. The adder 56 adds the output of the second position controller 55 and the speed feedforward signal to obtain a simulated speed signal, and the integrator 57 integrates the simulated speed signal. A simulated position signal is obtained. The torque correction signal calculation unit 53 calculates a torque correction signal according to a change in the sign of the simulated speed signal and outputs it to the adder 16. As the torque correction signal, a signal obtained by measuring in advance the change in torque when the direction of the motor 17 is reversed is used.

As described above, according to the fifth embodiment, the position command correction unit 51 corrects the gain decrease in the low frequency region caused by the FIR filter 6 and the fifth order IIR filter 31. The radius does not become smaller than the radius of the command trajectory, and the error between the command trajectory and the response trajectory can be reduced.
The simulated position control loop unit 52 calculates a simulated speed signal from the position feedforward signal and the speed feedforward signal, and the torque correction signal calculation unit 53 responds to the change in the sign of the simulated speed signal. Is calculated and added to the motor torque command signal, the follow-up delay when the rotation direction of the motor 17 is reversed is eliminated, and the error between the command locus and the response locus can be reduced.
In the fifth embodiment, the configuration including the position command correction unit 51, the simulated position control loop unit 52, and the torque correction signal calculation unit 53 has been described. However, only the position command correction unit 51 is included. A configuration or a configuration including only the simulated position control loop unit 52 and the torque correction signal calculation unit 53 may be used.
Further, in the fifth embodiment, the position command correction unit 51 has been described as being provided between the FIR filter unit 3 and the mechanical characteristic compensation unit 4, but the previous stage of the FIR filter unit 3 and the subsequent stage of the mechanical characteristic compensation unit 4 are described. May be provided.
Furthermore, although the torque correction signal is added to the motor torque command signal in the fifth embodiment, it may be added to the torque feedforward signal. When the speed controller 15 is a controller that performs proportional / integral control, a torque correction signal may be added to an integral term in the speed controller 15.

In the above description, the case where the input of the feedback compensation unit 5 is the position, speed, and torque has been described. However, acceleration may be input instead of torque. In this case, the same effect can be obtained by replacing the arithmetic unit 10 in each of the above embodiments with one that performs only differentiation. Alternatively, a current may be input instead of torque. In this case, the same effect can be obtained by replacing the value multiplied by the arithmetic unit 10 in each of the above embodiments with a value obtained by dividing the total inertia of the machine 2 by the torque constant of the motor 17.
In the above description, the motor 17 is described as being a rotary type and generating torque, but it may be one that obtains thrust like a linear motor. In this case, the same effect can be obtained by replacing the inertia in each of the above embodiments with mass and torque with thrust.

  Furthermore, although the case where position control is performed has been described in the above description, it may be a case where speed control is performed. In the case of speed control, similar effects can be obtained by removing the position feedback loop and the position feedforward signal in the above embodiments.

  Further, in each of the above embodiments, the position command calculation unit, the speed command calculation unit, and the torque command calculation unit multiply the adjustment factor for adjusting the dead time caused by the discretization and the slight model error of the controlled object. It may be. Alternatively, the differentiator 8 and the arithmetic unit 10 may be multiplied by the same adjustment coefficient.

Further, in each of the above-described embodiments, the mechanical characteristic compensator 4 may have a different order of components or the like unless the transfer functions from input to output are different. For example, feed-forward signal v _a velocity may be determined by differentiating the feedforward signal x _a position.
Further, in each of the above embodiments, the differentiation may be replaced by pseudo-differentiation (calculating an approximate differential value by multiplying the difference between the current value and the previous value by the reciprocal of the sample period).

  Furthermore, in the first to third embodiments, the order of the FIR filter unit 3 and the mechanical property compensation unit 4 may be switched. That is, a position command signal may be input to the mechanical characteristic compensation unit 4 and each output thereof may be input to the FIR filter unit 3 to obtain position, speed, and torque feedforward signals.

It is a block diagram which shows the servo control apparatus by Embodiment 1 of this invention. It is a characteristic view which shows a symmetrical impulse response. BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows the servo control apparatus by Embodiment 1 of this invention. It is a characteristic view which shows the command locus | trajectory and response locus | trajectory of the servo control apparatus by Embodiment 1 of this invention. It is a block diagram which shows the servo control apparatus by Embodiment 2 of this invention. It is a characteristic view which shows the command locus | trajectory and response locus | trajectory of the servo control apparatus by Embodiment 2 of this invention. It is a block diagram which shows the servo control apparatus by Embodiment 3 of this invention. It is a characteristic view which shows an example of the gain curve of a 5th-order IIR filter. It is a characteristic view which shows the command locus | trajectory and response locus | trajectory of the servo control apparatus by Embodiment 3 of this invention. It is a block diagram which shows the servo control apparatus by Embodiment 4 of this invention. It is a characteristic view which shows the command locus | trajectory and response locus | trajectory of the servo control apparatus by Embodiment 4 of this invention. It is a block diagram which shows the servo control apparatus by Embodiment 5 of this invention. It is a characteristic view which shows the command locus | trajectory and response locus | trajectory of the conventional servo control apparatus. It is a characteristic view which shows the command locus | trajectory and response locus | trajectory of the conventional servo control apparatus.

Explanation of symbols

  1 servo control device, 1a x-axis servo control device, 1b y-axis servo control device, 2 machine (machine to be driven), 3 FIR filter unit, 4 mechanical characteristic compensation unit, 5 feedback compensation unit, 6 FIR filter, 7 , 22 Position command calculator, 8 Differentiator, 9, 23 Speed command calculator, 10 Calculator, 11, 24 Torque command calculator, 12, 54 Subtractor, 13 Position controller, 14 Adder / subtractor, 15 Speed controller , 16, 56 Adder, 17 motor, 17a x-axis motor, 17b y-axis motor, 18 load, 21 1st order lag filter, 31 5th order IIR filter (nth order filter), 41 vibration suppression filter, 51 position command Correction unit, 52 Simulated position control loop unit, 53 Torque correction signal calculation unit, 55 Second position controller, 57 Integrator.

Claims (2)

A position controller that performs position control on a signal obtained by subtracting a motor position signal from the position feedforward signal among a position feedforward signal, a speed feedforward signal, and a torque feedforward signal calculated from a position command signal; A speed controller that adds the speed feedforward signal to the output of the controller and performs speed control on the signal obtained by subtracting the motor speed signal, and adds the torque feedforward signal to the output of the speed controller By outputting a signal as a motor torque command signal, the object to be driven has two or more shafts, and the rigidity between the motor and the motor installation base is lower than the rigidity between the motor and the load. In the servo control device that controls the trajectory by driving the machine,
A differentiator that calculates a feedforward signal of speed by differentiating the position command signal;
An arithmetic unit for differentiating an operation value by the differentiator and multiplying a total inertia of the driven machine;
The value calculated by the calculator is used as an input signal and the torque feedforward signal is calculated as an output signal, and the gain of the output signal relative to the input signal is set to be lower than the resonance frequency component of the driven machine. A servo control device comprising: a vibration suppression filter set to increase the anti-resonance frequency component of the machine to be driven . A second position controller that performs the same operation as the position controller on a signal obtained by subtracting a simulated position signal from the position feedforward signal, and adds the velocity feedforward signal to the output of the second position controller A simulated position control loop unit that calculates the simulated position signal by integrating the simulated speed signal, and a torque correction signal calculation that calculates a torque correction signal according to a change in the sign of the simulated speed signal And when the sign of the simulated speed signal changes , the torque correction signal calculation unit outputs a torque change at the time of reversing the rotation direction of the motor measured in advance as a torque correction signal, The servo control device according to claim 1, wherein the servo control device adds the motor torque command signal.

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