CN113054888A - Motor control device and motor control method - Google Patents

Abstract

The present invention provides a motor control device and a control method, which controls the torque of a motor while limiting the speed based on a torque command and a speed limiting command, and the device comprises: a speed detection unit that detects a speed of the motor; and a speed limiting unit that calculates a speed command based on the torque command and outputs a motor speed command obtained by limiting the speed command based on the torque command, the speed limiting unit including: a speed command calculation unit that calculates a speed command based on the torque command from the torque command; and a speed limiter for limiting a speed based on the speed limit command to a speed based on the torque command and outputting the motor speed command, wherein the speed command calculation unit based on the torque command includes: a speed deviation calculator that calculates a speed deviation based on the torque command; and an adder that adds the speed to the speed deviation and outputs a speed command based on the torque command.

Description

Motor control device and motor control method

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from japanese patent application No. 2019-238211, filed from 35.12.2019 to the present patent office, the entire contents of which are hereby incorporated by reference.

Technical Field

The present invention relates to a motor control device and a control method for controlling a torque of a motor while limiting a motor speed based on a torque command and a speed limit command.

Background

In the production of paper, sheets, and the like, the quality is improved in order to avoid wrinkles, sagging, and the like, and the production is performed using a tension control device. In the control of the wire releasing motor in such a tension control device, the wire releasing motor is driven at a constant torque corresponding to the coil diameter to keep the tension constant.

Then, torque control having a speed limiting function is performed in order to suppress a speed increase of the pay-off motor when the workpiece is cut. In the case of a servo torch for spot welding, a workpiece is clamped by a welding piece of an electrode portion of a welding gun, and the welding gun is pressurized by controlling the torque of a motor, and the workpiece is welded by energizing between electrode pieces.

In such a welding gun, torque control having a speed limiting function is also performed to avoid an excessive speed occurring when switching to torque control and causing a collision with the pressurized object immediately before the welding gun is moved to contact the pressurized object by position control and speed control.

An example of implementing torque control having such a speed limiting function is japanese patent application laid-open No. 2003-33068.

Japanese patent application laid-open No. 2003-33068 discloses a motor control device for controlling a motor based on an input from the outside, the motor control device including: a motor that rotates based on an applied voltage; a magnetic pole position sensor for detecting a magnetic pole position of the motor; a speed calculation unit for calculating the rotational speed of the motor based on the position signal output from the magnetic pole position sensor; a conversion unit for converting an input from the outside into a torque current command; a torque current correction unit for correcting the torque current command based on the limited rotation speed of the motor and the rotation speed of the motor calculated by the speed calculation unit; a vector operation unit for calculating a voltage command using the corrected torque current command; and an applied voltage generation unit that generates an applied voltage to be applied to the motor based on the voltage command.

However, in the above-described method of correcting the torque command by the output of the torque current correction unit, there are the following problems: torque current correction is required to be output to cancel a torque command during speed limitation, and when the torque command is large, a cancellation signal becomes large, so that response is slow, and speed overshoot is large; when the operation is performed near the speed limit, the speed limit control is turned ON/OFF, so that large overshoot occurs repeatedly, and the operation becomes unstable; only one speed limit command can be input, so that the speed can be limited only in the direction of the torque command; when the torque command is 0, the direction is not determined, and therefore the speed cannot be limited.

As an example of overcoming the above-described problem that the speed can only be limited in the direction of the torque command and the problem that the speed cannot be limited because the direction is not determined when the torque command is 0, there is international publication No. 2011/145366.

International publication No. 2011/145366 describes a motor control device that controls a motor that drives a driving target and presses the driving target against a pressurized target with a pressure corresponding to a target torque, the motor control device including: a speed controller that calculates a torque command for the motor and a regression torque for compensating the torque command based on a speed detection value of the motor; and a regression torque controller for calculating a 1 st speed command corresponding to a deviation between the target torque and the regression torque calculated by the speed controller, wherein the regression torque controller limits the calculated 1 st speed command by a desired speed limit value determined based on a contact speed between the driving object and the pressurizing object and outputs the limited value, and the speed controller calculates the torque command so that the speed detection value follows the 1 st speed command output by the regression torque controller.

In the method of international publication No. 2011/145366, speed limit values are set for both the forward rotation side and the reverse rotation side of the motor, and the speed can be limited regardless of the polarity of the torque command, so that the problem that the speed can only be limited in the direction of the torque command and the problem that the speed cannot be limited because the direction is not determined when the torque command is 0 are overcome. However, in such a method of compensating a torque command (motor torque command) to a motor by comparing a torque command with a regression torque and calculating a speed command by a regression torque controller, a motor torque command such as a torque command cannot be generated unless the gain of the regression torque controller is sufficiently high.

However, the regression torque control circuit is configured by 2 controllers, that is, a speed controller configured by a proportional-integral controller and a regression torque controller configured by a proportional-integral controller, and the control system is liable to be unstable since the integral element is doubly involved, and the regression torque vibrates if the control gain is increased. When the return torque vibrates, the motor torque command also vibrates. Therefore, the motor torque slightly smaller than the torque command cannot be output and used with an increased gain.

The following problems arise in particular: since the proportional gain cannot be increased for use because it is likely to vibrate if the proportional gain of the regression torque controller is increased, recovery from the speed limit state may not be performed appropriately depending on the control parameter, and therefore, adjustment may be difficult, and the parameter range in which stable operation is possible is narrow.

Further, since the integrator of the speed controller also operates as an integrator of the regression torque controller, the integrator of the speed controller also operates when the torque command abruptly changes, and as a result, the following problems arise: the overshoot of the speed is large; when the operation is performed near the speed limit, the speed limit control is turned ON/OFF, and therefore, a large overshoot is repeated, and the operation becomes unstable.

Disclosure of Invention

The present invention has been made to overcome the above-described problems, and an object of the present invention is to provide a motor control device and a motor control method that facilitate adjustment of control parameters, can limit the speed during torque control regardless of the polarity of a torque command or the rotation direction of a motor, reduce overshoot during speed limitation, and can output a motor torque in accordance with the torque command without involving the speed limitation.

The present invention is a motor control device as described below.

A motor control device that controls a torque of a motor while limiting a speed based on a torque command and a speed limit command, the motor control device comprising: a speed detection unit that detects a speed of the motor; and a speed limiting unit that calculates a speed command based on the torque command and outputs a motor speed command obtained by limiting the speed command based on the torque command, the speed limiting unit including: a speed command calculation unit that calculates a speed command based on the torque command from the torque command; and a speed limiter for limiting a speed based on the speed limit command to a speed based on the torque command and outputting the motor speed command, wherein the speed command calculation unit based on the torque command includes: a speed deviation calculator that calculates a speed deviation based on the torque command; and an adder that adds the speed to the speed deviation and outputs a speed command based on the torque command.

In addition, the present invention also includes the following motor control method.

A motor control method for controlling a torque of a motor while limiting a speed based on a torque command and a speed limit command, wherein a speed deviation is calculated based on the torque command, the speed of the motor is added to the speed deviation to output a speed command based on the torque command, and the speed limit based on the speed limit command is applied to the speed command based on the torque command to output a motor speed command.

The embodiments of the motor control apparatus and the motor control method according to the present invention can be variously embodied as set forth in the dependent claims of the claims, and the respective embodiments and other detailed matters and advantages thereof will be described in detail in the following detailed description.

According to the above configuration, in the present invention, the speed limitation in the torque control can be realized by the following simple configuration: in a method of calculating the inverse of the calculation of a motor torque command from a motor speed command in a speed control loop, a speed command based on the torque command is calculated based on the torque command, a motor speed command is obtained by limiting the speed, and the motor is speed-controlled based on the motor speed command. Therefore, it is possible to realize a motor control device that can limit the speed regardless of the polarity of the torque command or the rotation direction of the motor without requiring any special parameter adjustment, that can reduce overshoot at the time of speed limitation, and that can output the motor torque as the torque command without involving the speed limitation.

Drawings

Fig. 1 is a block diagram showing one embodiment of a motor control device and method.

Fig. 2 is a block diagram showing another mode of the motor control device and method.

Fig. 3 is a graph showing a speed change simulation result of one mode (speed proportional control) of the motor control device and method.

Fig. 4 is a graph showing a simulation result of a speed change in another mode (speed proportional-integral control) of the motor control and the method thereof.

Fig. 5 is a graph showing a simulation result of a speed change in an operation example of the mode of correcting the torque command.

Detailed Description

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

Embodiments of a motor control device and a method according to the present invention will be described below in detail with reference to the accompanying drawings. The scope of the present invention is not limited by the description of the embodiment, but is intended to be encompassed by the scope of the present invention in any manner as long as the technical scope of the invention is defined by the claims of the claims.

Fig. 1 shows one embodiment of a motor control device and method.

A motor control device a for controlling a motor torque T of a motor M according to the present invention includes: an encoder EN for obtaining the motor speed S, a differentiator Dif, a speed deviation calculator 1, an adder 2, a subtractor 3, a speed limiter 4, a speed controller 5, a motor torque controller 6, and the like.

Here, both the encoder EN and the differentiator Dif for obtaining the motor speed S constitute a speed detection unit B for detecting the motor speed S. The constituent elements of the speed detection unit B are not limited to the encoder EN and the differentiator Dif, and any constituent elements may be used as long as they can detect the speed.

The speed deviation calculator 1 and the adder 2 constitute a speed command calculation unit C based on the torque command, and the speed command calculation unit C and the speed limiter 4 based on the torque command constitute a speed limitation unit D.

In the motor control device a configured as described above, a torque command Tc for controlling the motor torque T of the motor M and a speed limit command Suc for limiting the motor speed S of the motor M are externally supplied, and the motor M is operated under a desired torque and a certain speed limit.

A desired torque command Tc supplied from the outside is input to the speed deviation calculator 1, and a speed deviation Sd1 based on the torque command Tc is calculated and output.

The adder 2 adds the motor speed S output from the speed detection unit B to the speed deviation Sd1 based on the torque command Tc, and outputs a speed command Sc based on the torque command. The speed command Sc based on the torque command is input to the speed limiter 4, and here, the motor speed command Smc is calculated by performing speed limitation based on a desired speed limit command Suc supplied from the outside. The motor M is speed-controlled based on the motor speed command Smc.

Specifically, a differentiator Dif differentiates a position signal from an encoder EN attached to the motor M to obtain a motor speed S. A speed deviation Sd2 signal, which is output by subtracting the motor speed command Smc from the motor speed S in the subtractor 3, is input to the speed controller 5, and the speed controller 5 calculates the motor torque command Tmc. Based on the motor torque command Tmc, a motor torque T in accordance with the motor torque command Tmc is output from the motor M through the motor torque controller 6. The position rotated by the motor torque T output from the motor M is detected by the encoder EN, and a speed control circuit is configured so as to match the motor speed command Smc.

The speed controller 5 is constituted by a proportional controller, and when the gain is G, the calculation of the speed control loop is performed based on the following equations (1) and (2).

Motor speed command Smc-motor speed S-speed deviation Sd2 … (1)

Speed deviation Sd2 × gain G of proportional controller ═ motor torque command Tmc … (2)

The motor speed command Smc can be obtained from the motor torque command Tmc by performing an inverse operation using the two equations as follows.

Speed deviation Sd2 ═ motor torque command Tmc/gain of proportional controller G … (3)

Motor speed command Smc ═ speed deviation Sd2+ motor speed S … (4)

In the present invention, a speed command Sc based on a torque command is first calculated for a torque command Tc supplied from the outside using the relationships of the following equations (5) and (6).

Speed deviation Sd1 ═ torque command Tc/G … (5) based on torque command

Torque command-based speed command Sc-torque command-based speed deviation Sd1+ motor speed S … (6)

Then, the speed limiter 4 limits the speed of the speed command Sc based on the torque command, and determines the motor speed command Smc.

If the speed control of the motor is performed based on the motor speed command Smc, then:

motor torque command Tmc is speed deviation Sd2 × G

(motor speed command Smc-motor speed S) × G

Here, when the speed limit is not involved, that is, when the speed command Sc based on the torque command is smaller than the speed limit command Suc, the motor speed command Smc is the speed command Sc based on the torque command, and therefore,

motor torque command Tmc ═ (speed command Sc based on torque command — motor speed S) × G

{ (speed deviation Sd1+ motor speed S based on torque command)

-motor speed S } × G

Where the speed deviation Sd1 is equal to (based on the torque command) × G

Torque command Tc/GXG

Torque command Tc

Motor torque command Tmc is matched with torque command Tc, motor M is torque-controlled based on motor torque command Tmc, and motor torque T in accordance with motor torque command Tmc, that is, torque command Tc, is output from motor M.

When speed limitation is involved, that is, when the speed command Sc based on the torque command is equal to or greater than the speed limit command su, the motor speed command Smc becomes the speed limit command su, and speed control of the motor M based on the speed limit command su is performed. Since the speed is limited only by adding the motor speed S to the speed deviation Sd1 based on the torque command, a torque control circuit for realizing the speed limitation is not provided at an upper stage of the speed control circuit, and a special control parameter constituting the control circuit is not required.

The speed limit command Suc may be limited to both the CW (clockwise rotation direction) side and the CCW (counterclockwise rotation direction) side by one input, or 2 speed limit commands may be provided to limit the CW side and the CCW side independently.

The speed limit command Suc can determine the upper limit of the motor speed S based on a predetermined threshold value, a predetermined table value, a predetermined function value, and the like. In this case, the term "predetermined" naturally includes that the motor control device a can be arbitrarily determined, and that the motor control device a can be arbitrarily set at any time such as at the time of manufacture, at the time of test, at the time of shipment, and at the time of use.

As described above, in the present invention, the motor speed command Smc is obtained by calculating the speed command Sc based on the torque command Tc by the inverse calculation of the motor torque command Tmc from the motor speed command Smc in the speed control system, performing the speed limitation, and the motor torque command Tmc is calculated based on the motor speed command Smc.

When the gain G of the speed controller 5 is low, if no speed limitation is involved, the motor torque command Tmc in accordance with the torque command Tc is calculated without being affected by the gain G of the proportional controller of the speed controller 5. When the speed of the motor M is controlled in a normal operation state, the gain G of the speed controller 5 may be adjusted in a normal manner so that the speed loop is stable.

Fig. 2 shows a further embodiment of the motor control device and method.

In this embodiment, in the motor control device and method shown in fig. 1, when a predetermined condition such as resonance occurs in the motor M, a shaft connected thereto, a winding device, or other mechanical system, a filter such as a notch filter NF or a low pass filter LPF may be provided on the output side of the speed controller 5. In this case, the response to the torque command Tc is reduced by an amount corresponding to the addition of a filter such as the low pass filter LPF. The other constitution is the same as the first embodiment.

In the case where the speed controller 5 is constituted by a proportional controller, there is no overshoot. In the case where the workpiece is cut during tension control by the motor M, for example, since only rotational friction of the pay-off part exists, the load torque is small, and even in proportional control, an error occurring in the limited motor speed is slight.

Although the 2 systems have been described above, depending on the application of the present invention, the load torque Tb of the load is large, and a speed error may occur in which the load torque Tb is divided by the gain G of the speed control in response to the speed limit command Suc.

In this case, the speed controller 5 is configured by a proportional-integral controller, and operates as a proportional controller when the speed limitation is not involved, and activates the integral controller when the speed limitation is involved. The influence of the load torque Tb is suppressed by the integral controller in the case where the speed limitation is involved. However, the value output from the integral controller is only a value that outputs the amount of the compensation load torque Tb, the compensation amount of the integral controller is minute, and the overshoot of the motor speed is also minute.

When the load torque Tb is large and the regeneration operation is also performed, the integral controller of the proportional-integral controller is turned OFF when the speed limitation is involved in the regeneration. Although a speed error occurs, the integral controller repeats ON/OFF during regeneration, and plays a role of avoiding generation of pulsation of the motor torque T.

Fig. 3 and 4 show simulation results of speed changes in a plurality of modes of motor control and methods thereof, and fig. 5 shows simulation results of speed changes in an operation example of a mode of correcting a torque command. In each of the above figures, the vertical axis represents the magnitude of the velocity, and the horizontal axis represents the passage of time. All are graphs under the same speed limit command Suc.

In FIG. 3, the result of making the load torque zero is shown when the time T satisfies 0 ≦ T ≦ 0.25 in one embodiment of the motor control and method thereof. In this time range, the speed is limited in accordance with the setting of the speed limit command Suc. In addition, in the range of 0.25. ltoreq.T, the result of the case where the load torque is made to be some is shown. In this time range, as described later, a speed error occurs in which the load torque Tb is divided by the gain G of the speed control with respect to the speed limit command Suc. The example here is just one example, showing an error of 29.4 min-1. During power running, the error is limited to be low, and during regeneration, the error is limited to be high.

Fig. 5, which skips one figure, shows an example of the operation of the method of correcting the torque command disclosed in japanese patent application laid-open No. 2003-33068, as a comparison with the motor control and method. When time T satisfies 0. ltoreq. T.ltoreq.0.25, the result in the case where the load torque is made zero is shown. In addition, in the range of 0.25. ltoreq.T, the result of the case where the load torque is made to be some is shown. During the arbitrary power running, when the speed is increased, large overshoot such as 290 min-1 and 265 min-1 occurs, and when the torque command is 0 during regeneration, the speed is not limited. Since the speed is limited by outputting the torque command from the speed circuit only for canceling the magnitude of the torque command, there is a time delay until the large cancel torque command appears, and overshoot is large.

Fig. 4 shows simulation results of speed variations of other modes of motor control and methods thereof. This embodiment shows the following operation example: the speed controller is configured to perform proportional-integral control (PI control), and when the speed limit value is not reached, the speed controller can operate as proportional control (P control), and when the speed limit value is reached, the speed controller is configured to activate the integral controller to perform speed proportional-integral control (PI control). When time T satisfies 0. ltoreq. T.ltoreq.0.25, the result in the case where the load torque is made zero is shown. In this time frame, when the speed limit is concerned, the integral controller is operated, but the torque cancellation is not performed, and therefore the overshoot of 30 min-1 remains. In addition, in the range of 0.25. ltoreq.T, the result of the case where the load torque is made to be some is shown. Even in this time range, the integral controller operates when the speed limit is concerned, and therefore overshoot occurs, but the amount of overshoot is considerably smaller than in the operation example of the method of correcting the torque command shown in fig. 5.

As described above, according to the aspect of the present invention, it is possible to realize a motor control device capable of limiting the speed regardless of the polarity of the torque command or the rotation direction of the motor without requiring any special parameter adjustment, reducing overshoot at the time of speed limitation, and outputting the motor torque in accordance with the torque command without involving the speed limitation.

The above-described embodiments are only illustrative of one embodiment of the present invention, and the present invention is not limited to the specific configurations illustrated in these embodiments. The scope of the present invention includes modifications that can be conceived by those skilled in the art based on the items recited in the claims.

The detailed description has been presented for purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. The detailed description is not intended to be exhaustive or to limit the subject matter described herein. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts described are disclosed as example forms of implementing the claims.

Claims (8)

1. A motor control device for controlling a torque of a motor while limiting a speed based on a torque command and a speed limit command,

the motor control device includes: a speed detection unit that detects a speed of the motor; and a speed limiting unit that calculates a speed command based on the torque command, and outputs a motor speed command obtained by limiting the speed command based on the torque command,

the speed limiting unit includes: a speed command calculation unit that calculates a speed command based on the torque command from the torque command; and a speed limiter for applying a speed limit based on the speed limit command to a speed command based on the torque command and outputting the motor speed command,

the speed command calculation unit based on the torque command includes: a speed deviation calculator that calculates a speed deviation based on the torque command; and an adder that adds the speed to the speed deviation and outputs a speed command based on the torque command.

2. The motor control apparatus according to claim 1,

further comprises a speed controller for calculating a motor torque command based on the motor speed command,

the speed deviation calculator outputs the speed deviation based on the torque command according to the following formula,

the speed deviation (Sd1) based on the torque command

The torque command (Tc)/gain (G) of the speed controller.

3. The motor control device according to claim 1 or 2,

the speed limit command determines an upper limit of the motor speed based on a prescribed threshold value, a prescribed table value, or a prescribed function value.

4. The motor control device according to claim 2 or 3,

the speed controller includes at least one of a proportional controller and a proportional-integral controller.

5. A motor control method for controlling a torque of a motor while limiting a speed based on a torque command and a speed limit command,

a speed deviation is calculated based on the torque command,

outputting a speed command based on a torque command by adding the speed of the motor to the speed deviation,

a speed limit based on the speed limit command is applied to a speed command based on the torque command to output a motor speed command.

6. The motor control method according to claim 5,

a motor torque command is also calculated by the speed controller based on the motor speed command,

the speed deviation based on the torque command is calculated based on the following formula,

the speed deviation (Sd1) based on the torque command

The torque command (Tc)/gain (G) of the speed controller.

7. The motor control method according to claim 5 or 6,

the speed limit command determines an upper limit of the motor speed based on a prescribed threshold value, a prescribed table value, or a prescribed function value.

8. The motor control method according to claim 6 or 7,

the speed controller performs proportional control in torque control and proportional-integral control in speed limitation.

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