JP2005328607A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller insusceptible to disturbance in which overshoot and vibration are suppressed. <P>SOLUTION: The motor controller comprises a speed control means 7 for driving a motor 1 depending on the difference signal between a speed command signal and a speed detection signal of the motor 1 and generating a motor drive command by performing proportional control operation and integration control operation on the difference signal, and a compensation control means 12 inserted into a speed loop in series with the speed control means 7. The compensation control means 12 sets the phase of a speed open loop to become -140° or more at the frequency between the first crossover frequency of the speed open loop when inertial moment is minimized and the second crossover frequency of the speed open loop when inertial moment is maximized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a motor control device, and more particularly to a control device suitable for driving and controlling a mechanical system such as a robot or a transfer device in which a moment of inertia of a mechanical load driven by a motor fluctuates during operation.

FIG. 10 conceptually shows the configuration of a speed control unit used in a conventional motor control device. In the figure, 1 is a motor, 2 is a mechanical load driven by the motor, and 3 is a shaft connecting the motor 1 and the mechanical load 2. The mechanical load 2 models a moving part of a machine driven by the motor 1 as one inertial load, and the shaft 3 models a mechanism for transmitting the torque generated by the motor 1 to the machine. Reference numeral 4 denotes a position detector that is attached to the motor 1 and detects the position of the motor 1, and 5 is a speed detector that generates a speed detection signal by differentiating the motor position detected by the position detector 4. is there. Reference numeral 7 denotes speed control means, which receives a speed command signal given from a host controller or position control unit (not shown) and a speed detection signal (motor speed) output from the speed detection means 5, and is a drive command for the motor 1. Output current command. Reference numeral 8 denotes current control means, which controls the motor current based on the current command output from the speed control means 7 to generate torque in the motor 1 and rotate the motor 1.

The speed control means 7 includes a comparator 6, a proportional controller 9, an integral controller 10, and an adder 11. The comparator 6 compares the speed command signal input to the speed control means 7 with the motor speed, and outputs a speed error that is the difference between them, that is, a deviation signal. The proportional controller 9 multiplies the speed error by the proportional gain KP and outputs it, and the integral controller 10 multiplies the integral value of the speed error by the integral gain KI and outputs it. The adder 11 adds the output of the proportional controller 9 and the output of the integral controller 10 and outputs the result as a current command. Reference numeral 15 denotes a mechanical system, which includes a motor 1, a mechanical load 2 and a shaft 3.

As described above, the conventional speed control system forms a speed loop from the speed detection means 5, speed control means 7, current control means 8 and the like, and controls the motor 1 so that the motor speed follows the speed command signal. Yes.

Here, the proportional gain KP of the proportional controller 9 and the integral gain KI of the integral controller 10 are generally determined based on the moment of inertia of the mechanical load so that the control system has an appropriate response characteristic. However, when the moment of inertia of the mechanical load varies during operation, the proportional gain KP and the integral gain KI cannot be set appropriately. As a result, the overshoot has increased, and the control performance has been lowered, such as being easily affected by disturbance.

The following patent document describes a technology that realizes high-performance control by estimating the moment of inertia during operation and correcting the control gain based on the estimated moment of inertia for a mechanical system in which the moment of inertia of the machine load varies. Is disclosed. However, since the acceleration or deceleration operation that satisfies the specified conditions is necessary to accurately estimate the moment of inertia, it cannot be used when the moment of inertia changes during constant speed operation in a robot, etc. Performance may not be obtained. Furthermore, since the moment of inertia cannot be estimated instantaneously and requires a certain amount of time, if the moment of inertia varies discontinuously depending on the presence or absence of workpieces in a transport device, etc., vibration will temporarily increase. Control performance will be degraded.

JP 2001-352773 A

As described above, when driving and controlling a mechanical system in which the inertia moment of the mechanical load fluctuates during operation, the conventional control device cannot appropriately set the proportional gain KP and the integral gain KI. There is a problem that overshoot and vibration become large, and it is easily affected by disturbances, resulting in a decrease in control performance.

The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a motor control device that is less susceptible to disturbance due to less overshoot and vibration.

In order to solve such a problem, the present invention is such that a motor is coupled to a mechanical load whose moment of inertia varies from a minimum value to a maximum value, and the motor is driven and controlled based on a speed command signal, and has a speed loop. In the control device, the motor is driven in accordance with a deviation signal between the speed command signal and the speed detection signal of the motor, and the deviation signal is subjected to proportional control calculation and integral control calculation to generate a motor drive command. Output speed control means and compensation control means inserted in series with the speed control means in the speed loop, the compensation control means open the speed loop when the minimum moment of inertia is reached. The first crossover frequency, which is the crossover frequency of the speed open loop, and the second crossover, which is the crossover frequency of the speed open loop when the maximum moment of inertia is reached. The speed open loop phase at the frequency between the frequency is set to be -140 degrees or more, and is characterized in.

Preferably, the compensation control means is a phase advance filter having a phase advance characteristic in which the phase advances in the intermediate frequency region and the phase becomes almost zero in the low frequency region and the high frequency region.

Preferably, a proportional gain used for the proportional control calculation and an integral gain used for the integral control calculation are set so that the moment of inertia is the minimum value and the control system has a desired response characteristic, and the phase advance filter has the second crossing frequency or The phase advance is set to be maximum at a frequency lower than the second crossing frequency.

  Preferably, the compensation control means is a phase delay filter having a phase delay characteristic in which the phase in the intermediate frequency region is delayed and the phase in the low frequency region and the high frequency region is substantially zero. is there.

Preferably, the speed control means has a proportional gain set so that the control system has a desired response characteristic when the moment of inertia is a minimum value, and the control system has a desired response characteristic when the moment of inertia is a maximum value. The integral gain is set, and the phase lag filter is set so that the phase lag of the phase lag filter is maximized at a frequency near the center between the first crossover frequency and the second crossover frequency. .

  According to the present invention, the compensation control means is inserted into the speed control loop of the motor control device, and the first cross frequency of the speed open loop and the moment of inertia of the machine load are maximized when the moment of inertia of the machine load is minimized. The characteristics of the compensation control means were set so that the phase of the speed open loop at a frequency between the second speed crossing frequency of the speed open loop is preferably −140 degrees or more. As a result, even if the moment of inertia of the mechanical load fluctuates, the phase margin is 40 degrees or more, and desirable control characteristics can be obtained.

  In addition, the motor control device according to the present invention has an effect that the phase margin is 40 degrees or more and desirable control characteristics can be obtained even if the moment of inertia of the mechanical load varies by using the phase advance filter.

  Furthermore, according to the present invention, the characteristics of the phase advance filter are set so that the phase margin can be secured in the specific frequency region as described above, so that the gain in the low frequency region does not become unnecessarily small, and the disturbance It is possible to realize a control system that is less susceptible to

  In addition, the motor control device according to the present invention has an effect that the phase margin becomes 40 degrees or more even when the moment of inertia of the mechanical load fluctuates by using the phase delay filter, and a desirable control characteristic is obtained.

  According to the present invention, even if the moment of inertia of the mechanical load varies, the phase is −140 degrees or more between the first crossing frequency and the second crossing frequency, so that the phase margin is preferably 40 degrees or more. There is an effect that control characteristics can be obtained.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of the motor control apparatus according to the first embodiment of the present invention. The same parts as those in FIG. 10 are denoted by the same reference numerals. In FIG. 1, 2 is a mechanical load having a varying moment of inertia, 12 is a phase advance filter as compensation means, and the phase advance filter 12 is inserted in the speed loop in series with the speed control means 7, and the speed command signal and speed A signal based on the deviation signal obtained by the comparator 6 with respect to the detection signal is input. However, it is sufficient that the phase advance filter 12 is simply inserted in the velocity loop.

FIG. 2 shows velocity open loop frequency characteristics when there is no phase advance filter in FIG. 1, with the upper diagram in FIG. 2 showing gain characteristics and the lower diagram showing phase characteristics. In the upper diagram of FIG. 2, the solid line is a gain diagram when the moment of inertia of the mechanical load is minimum, and the broken line is a gain diagram when the moment of inertia of the mechanical load is maximum. The phase characteristic is the same phase diagram when the moment of inertia is minimum and maximum, and is indicated by a solid line in the lower diagram of FIG. ωC1 is a first crossing frequency that is a crossing frequency when the moment of inertia of the mechanical load 2 is minimum, and ωC2 is a second crossing frequency that is a crossing frequency when the moment of inertia of the mechanical load 2 is maximum. Further, the proportional gain KP of the proportional controller 9 and the integral gain KI of the integral controller 10 in the speed control means 7 are set so as to have desired response characteristics when the moment of inertia of the mechanical load 2 is minimum. Here, the desired response characteristic means that the phase margin is 40 to 60 degrees as follows. The speed open loop frequency characteristic of FIG. 2 is obtained by measuring the speed detection signal which is the output of the speed detection means 5 by opening the speed loop in the comparator 6 and adding a random signal to the output of the comparator 6, for example. This is obtained by measuring other velocity open-loop frequency characteristics obtained by frequency analysis using an FFT analyzer. The same applies to other speed open loop frequency characteristics.

FIG. 2 shows that the phase margin when the moment of inertia of the mechanical load 2 is the minimum is 60 degrees. According to the literature (S53-3-5, “Control Engineering”, page 135, published by Kyoritsu Shuppan Co., Ltd.), it is desirable that the servo system has a phase margin of 40 degrees or more. In general, the phase margin is 40 considering the rapid response. It is set to -60 degrees.
This is a desirable characteristic when the moment of inertia of the mechanical load 2 is minimum. However, since the phase margin when the moment of inertia of the mechanical load 2 is maximum is only 20 degrees, the overshoot is large and a vibration response is obtained.

FIG. 3 shows velocity open loop frequency characteristics when the phase advance filter of FIG. 1 is inserted. As shown in FIG. 4, the frequency characteristic of the phase advance filter 12 has a phase advance characteristic in which the phase advances in the intermediate frequency region and the phases in the low frequency region and the high frequency region become almost zero. The frequency is zero and the phase is zero, the frequency is infinite and the phase is zero.
Further, the filter characteristics are set so that the phase advances most at a frequency slightly lower than the crossover frequency ωC2 when the moment of inertia of the mechanical load 2 is maximum.
Comparing FIG. 2 and FIG. 3, it can be seen that the phase lag near the crossing frequency ω C2 when the moment of inertia of the mechanical load 2 is maximum is reduced by inserting the phase advance filter 12. As a result, the phase margin when the moment of inertia of the mechanical load 2 is minimized is 60 degrees, and the phase margin when the moment of inertia of the mechanical load 2 is maximized is 45 degrees. In. Furthermore, the phase delay of the speed open loop is -140 degrees or more at all frequencies between the crossover frequency ωC1 when the inertial moment of the mechanical load 2 is minimum and the crossover frequency ωC2 when the inertial moment of the mechanical load is maximum. Therefore, no matter how the inertia moment of the mechanical load 2 fluctuates, the phase margin becomes 40 degrees or more, and a good response characteristic can be obtained.

Further, the phase advance filter has a characteristic that the gain decreases in the low frequency region as shown in FIG. 4, and the gain in the low frequency region decreases as the phase advance amount increases. For this reason, if the phase is unnecessarily advanced, the gain in the low frequency region of the speed loop is reduced and is vulnerable to disturbances. In the phase advance filter according to the present embodiment, the phase advance is performed in the vicinity of the crossing frequency ωC2 when the moment of inertia of the mechanical load 2 is maximum or slightly lower than the crossing frequency ωC2, for example, 1 to 0.5 times the crossing frequency ωC2. The amount is set to the maximum.
Thereby, a phase margin is ensured only in a necessary frequency region. As described above, since the phase lead amount is prevented from becoming unnecessarily large, a decrease in gain in the low frequency region can be suppressed to a necessary minimum, and the influence of disturbance can be reduced.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing the configuration of the motor control apparatus according to the second embodiment of the present invention. The same parts as those in FIG. 10 are denoted by the same reference numerals. In FIG. 5, 13 is a phase delay filter.

FIG. 6 shows velocity open loop frequency characteristics when there is no phase delay filter in FIG. The frequency response of the control system is the same as that of FIG. 2, but the difference from FIG. 2 is that the integral gain KI of the integral controller in the speed control means 7 is set so as to have a desired response characteristic when the moment of inertia of the mechanical load is maximum. It is that. That is, in FIG. 6, the integral gain KI is set to be smaller than that in FIG. 2 so as to have a desired response characteristic when the moment of inertia of the mechanical load 2 is maximum. Incidentally, the proportional gain KP of the proportional controller is set so as to have a desirable response characteristic when the moment of inertia of the mechanical load 2 is minimum, as in FIG. By setting the integral gain KI small, the phase margin when the moment of inertia of the mechanical load 2 is maximum was only 20 degrees in FIG. 2, but is 60 degrees in FIG. Inside.
However, when the integral gain KI is reduced, the gain in the low frequency region is reduced, and it is easily affected by disturbance.

FIG. 7 shows velocity open loop frequency characteristics when the phase delay filter of FIG. 5 is inserted. As shown in FIG. 8, the frequency characteristics of the phase delay filter have a phase advance characteristic in which the phase is delayed in the intermediate frequency region and the phase in the low frequency region and the high frequency region is almost zero. In this embodiment, the filter characteristics are set so that the phase is most delayed near the center of the crossover frequency ωC1 when the inertial moment of the mechanical load 2 is minimum and the crossover frequency ωC2 when the inertial moment of the mechanical load 2 is maximum. Yes.

FIG. 9 is a drawing in which the respective gain diagrams are superimposed to show the difference between FIG. 7 and FIG. Fig. (A) is a gain diagram when the moment of inertia of the mechanical load is minimum, and Fig. (B) is a gain diagram when the moment of inertia of the mechanical load is maximum. In each figure, a solid line indicates a case where the phase delay filter 13 is inserted, and a broken line indicates a case where the phase delay filter 13 is not provided. From FIG. 9, it can be seen that the gain in the low frequency region is increased by inserting the phase lag filter 13, which makes it less susceptible to disturbance.

Further, according to the present embodiment, the filter is arranged so that the phase is most delayed in the vicinity of the center between the crossover frequency ωC1 when the inertial moment of the mechanical load 2 is minimum and the crossover frequency ωC2 when the inertial moment of the mechanical load 2 is maximum. Although the characteristic is set, the phase lag of the phase lag filter 13 at ωC1 and the phase lag of the phase lag filter 13 at ωC2 are substantially the same by setting in this way, and the phase characteristics of the speed loop are well balanced. Can be shaped. As can be seen from FIG. 7, the phase delay of the speed open loop is at all frequencies between the crossover frequency ωC1 when the moment of inertia of the mechanical load 2 is minimum and the crossover frequency ωC2 when the moment of inertia of the mechanical load 2 is maximum. Since the phase margin is 40 degrees or more regardless of how the moment of inertia of the mechanical load 2 fluctuates, it can be seen that a favorable response characteristic can be obtained.

As described above, the present invention can be applied to a motor control device that controls a motor that drives a mechanical load whose inertia moment changes.

It is a block diagram which shows the structure of the motor control apparatus by embodiment of this invention. It is a speed open loop frequency characteristic figure before inserting the phase lead filter by an embodiment of the invention. It is a speed open loop frequency characteristic figure after inserting the phase advance filter by an embodiment of the invention. It is a frequency characteristic figure of the phase advance filter by an embodiment of the invention. It is a block diagram which shows the structure of the motor control apparatus by embodiment of this invention. It is a speed open loop frequency characteristic figure before inserting a phase delay filter by an embodiment of the invention. It is a speed open loop frequency characteristic figure before inserting a phase delay filter by an embodiment of the invention. It is a frequency characteristic figure of the phase lag filter by an embodiment of the invention. It is a gain diagram which shows the effect of the phase delay filter by embodiment of this invention. It is a block diagram which shows the structure of the speed control part in the conventional control apparatus.

Explanation of symbols

1 motor, 2 mechanical load, 7 speed control means, 12 compensation means (phase advance filter), 13 phase delay filter.

Claims (5)

In a motor control device in which a motor is coupled to a mechanical load whose moment of inertia varies from a minimum value to a maximum value, and the motor is driven and controlled based on a speed command signal,
A speed at which the motor is driven in accordance with a deviation signal between the speed command signal and the speed detection signal of the motor, and the deviation signal is subjected to proportional control calculation and integral control calculation to generate and output a motor drive command. Control means;
Compensation control means inserted in series with the speed control means in the speed loop,
The compensation control means includes a first crossing frequency that is a crossing frequency of a speed open loop that opens the speed loop when the minimum value of the moment of inertia and a speed open loop when the maximum value of the moment of inertia is reached. The phase of the velocity open loop at a frequency between the second crossing frequency which is the crossing frequency is set to be −140 degrees or more,
The motor control apparatus characterized by the above-mentioned. The compensation control means is a phase advance filter having a phase advance characteristic in which the phase advances in the intermediate frequency region and the phase becomes substantially zero in the low frequency region and the high frequency region.
The motor control device according to claim 1. A proportional gain used for the proportional control calculation and an integral gain used for the integral control calculation are set so that the moment of inertia is a minimum value and the control system has a desired response characteristic.
The phase advance filter is set such that the phase advance is maximum at the second crossing frequency or at a frequency lower than the second crossing frequency;
The motor control device according to claim 2. The compensation control means is a phase delay filter having a phase delay characteristic in which the phase in the intermediate frequency region is delayed and the phase in the low frequency region and the high frequency region is substantially zero.
The motor control device according to claim 1. The speed control means sets the proportional gain so that the control system has a desired response characteristic when the moment of inertia is a minimum value, and the control system has a desired response characteristic when the moment of inertia is a maximum value. The integral gain is set to
The phase lag filter is set so that the phase lag of the phase lag filter is maximized at a frequency near the center of the first cross frequency and the second cross frequency;
The motor control device according to claim 4.

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