JP7532207B2 - MOTOR CONTROL DEVICE AND MOTOR CONTROL METHOD - Google Patents

Description

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

In the manufacture of paper, film, etc., tension control devices are used to prevent wrinkles, sagging, etc. and improve quality. In controlling the unwinding motor with such tension control devices, the unwinding motor is driven with a constant torque according to the reel diameter to keep the tension constant.

In addition, torque control with a speed limiting function is implemented to prevent the speed of the unwinding motor from increasing if the workpiece is cut. In the case of a spot welding servo gun, the workpiece is clamped with the welding tip of the electrode part of the welding gun, and pressure is applied by controlling the torque of the motor, and electricity is passed between the electrode tips to weld the workpiece.

Even with this type of welding gun, position control and speed control are used to move the gun to the point just before it comes into contact with the object to be pressed, and torque control with a speed limiting function is implemented to prevent excessive speeds from occurring and causing it to collide with the object to be pressed when switching to torque control.

Patent Document 1 is an example of torque control with a speed limiting function.

Patent document 1 describes a motor control device that controls a motor based on an external input, and includes a motor that rotates based on an applied voltage, a magnetic pole position sensor that detects the magnetic pole position of the motor, a speed calculation unit that calculates the rotational speed of the motor based on a position signal output by the magnetic pole position sensor, a conversion unit that converts the external input into a torque current command, a torque current correction unit that corrects the torque current command based on the motor's limited rotational speed and the motor rotational speed calculated by the speed calculation unit, a vector calculation unit that calculates a voltage command using the corrected torque current command, and an applied voltage creation unit that creates a voltage to be applied to the motor based on the voltage command.

However, in a method of correcting such a torque command with the output of a torque current correction unit, it is necessary to output a torque current correction that cancels out the torque command when the speed is limited. When the torque command is large, the canceling signal also becomes large, resulting in problems such as slow response and large speed overshoot. When operating near the speed limit, the speed limit control is turned on and off, causing repeated large overshoots and making the behavior unstable. Also, since only one speed limit command can be input, the speed can only be limited in the direction of the torque command. When the torque command is 0, the direction is not determined and so the speed cannot be limited.

Patent Document 2 is an example of a solution to the problem of only being able to limit the speed in the direction of the torque command, as described above, and the problem of not being able to limit the speed when the torque command is 0 because the direction is not determined.

Patent document 2 describes a motor control device that controls a motor that drives a driven object to press the driven object against a pressurized object with a pressure corresponding to a target torque, and includes a speed controller that calculates a torque command for the motor and a regression torque for compensating for the torque command based on a speed detection value of the motor, and a regression torque controller that calculates a first speed command according to the deviation between the target torque and the regression torque calculated by the speed controller, the regression torque controller limits the calculated first speed command to a desired speed limit value determined based on the contact speed between the driven object and the pressurized object, and outputs the calculated first speed command, and the speed controller calculates a torque command so that the speed detection value follows the first speed command output by the regression torque controller.

In the method of Patent Document 2, the speed limit value can be set for both the forward and reverse rotation sides of the motor, and the speed can be limited regardless of the polarity of the torque command, eliminating problems such as only being able to limit the speed in the direction of the torque command, and not being able to limit the speed when the torque command is 0 because the direction is not determined. However, in a method in which such a torque command is compared with the regression torque to calculate a speed command using a regression torque controller to compensate for the torque command for the motor (motor torque command), the gain of the regression torque controller must be made quite high in order to generate a motor torque command that matches the torque command.

However, the regression torque control loop is composed of two controllers: a speed controller composed of a proportional-integral controller, and a regression torque controller also composed of a proportional-integral controller. Since there are two integral elements, the control system is prone to become unstable, and increasing the control gain causes the regression torque to oscillate. When oscillations occur in the regression torque, oscillations also occur in the motor torque command. For this reason, it is not possible to use a high gain, and there is the problem that only a motor torque slightly smaller than the torque command can be output.

In particular, increasing the proportional gain of the regression torque controller makes it prone to vibration, and since it is not possible to use it with the proportional gain increased, depending on the control parameters, recovery from the speed limit state may not work properly, making adjustments difficult and causing problems with the narrow range of parameters for stable operation.

In addition, because the integrator of the speed controller also functions as an integrator for the regression torque controller, if the torque command suddenly changes, the integrator of the speed controller also operates, resulting in problems such as large speed overshoots, and when operating near the speed limit, the speed limit control is turned on and off, causing repeated large overshoots and resulting in unstable behavior.

JP 2003-33068 A International Publication No. 2011/145366

The present invention has been made to solve the above problems, and its purpose is to provide a motor control device and a motor control method that can easily adjust control parameters, limit the speed during torque control regardless of the polarity of the torque command or the direction of motor rotation, reduce overshoot when the speed is limited, and output motor torque according to the torque command when the speed limit is not reached.

The present invention is a motor control device as follows:

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 includes:
a speed detection unit for detecting a speed of the motor;
a speed limiting unit that calculates a speed command based on the torque command based on the torque command, and outputs a motor speed command that is limited by 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 that adds a speed limit based on the speed limit command to the speed command based on the torque command and outputs the motor speed command,
The torque command-based speed command calculation unit includes a speed deviation calculator that calculates a speed deviation based on the torque command, and an adder that adds the speed deviation to the speed and outputs a speed command based on the torque command.
A motor control device comprising:

The present invention also relates to a motor control method as follows:

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, comprising:
Calculating a speed deviation based on the torque command;
outputting a speed command based on a torque command by adding the speed deviation to the speed of the motor;
a speed limit based on the speed limit command is added to a speed command based on the torque command to output a motor speed command;
A motor control method comprising:

The motor control device and motor control method of the present invention can be implemented in various ways as shown in the dependent claims of the patent, and these and other details and advantages are described in detail in the detailed description of the embodiment of the invention below.

With the above configuration, the present invention realizes speed limiting during torque control with a simple configuration in which a speed command based on a torque command is calculated based on the torque command using a method of performing reverse calculations to calculate a motor torque command from a motor speed command in a speed control loop, speed limiting is performed to obtain a motor speed command, and the motor speed is controlled based on the motor speed command. Therefore, it is possible to realize a motor control device that does not require special parameter adjustment, can limit the speed regardless of the polarity of the torque command or the rotation direction of the motor, has a small overshoot during speed limiting, and can output motor torque according to the torque command when the speed limit is not reached.

FIG. 1 is a block diagram illustrating one aspect of a motor control device and method. FIG. 2 is a block diagram illustrating another aspect of a motor controller and method. FIG. 3 is a graph showing the results of a speed change simulation for one embodiment (speed proportional control) of a motor control device and method. FIG. 4 is a graph showing simulation results of speed change for another embodiment of the motor control and method (speed proportional-integral control). FIG. 5 is a graph showing a simulation result of a speed change in an example of operation of a method for correcting a torque command.

Below, the embodiments of the motor control device and method according to the present invention will be described in detail with reference to the drawings. Note that the scope of the present invention is not limited by the description of the embodiments, and any embodiment is included in the scope of the present invention as long as it falls within the technical scope of the invention according to each claim of the claims.

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

The motor control device A of the present invention, which controls the motor torque T of the motor M, is roughly composed of an encoder EN for determining 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, and a motor torque controller 6.

Here, the encoder EN and the differentiator Dif for determining the motor speed S together constitute the speed detection unit B that detects the motor speed S. Note that the components of the speed detection unit B are not limited to the encoder EN and the differentiator Dif, and may be any components that can detect the speed.

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

The motor control device A configured in this manner is externally provided with 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, and the motor M is operated under the desired torque and a certain speed limit.

The desired torque command Tc given from outside is input to the speed deviation calculator 1, which calculates and outputs the speed deviation Sd1 based on the torque command Tc.

The motor speed S output from the speed detection unit B is added to the speed deviation Sd1 based on the torque command Tc in the adder 2, and a speed command Sc based on the torque command is output. This speed command Sc based on the torque command is input to the speed limiter 4, which performs speed limiting based on a desired speed limit command Suc given from the outside, and calculates the motor speed command Smc. The speed of the motor M is controlled based on this motor speed command Smc.

Specifically, the motor speed S is obtained by differentiating the position signal generated by the encoder EN attached to the motor M with a differentiator Dif. A speed deviation Sd2 signal obtained by subtracting the motor speed command Smc and the motor speed S in a subtractor 3 is input to a speed controller 5, which calculates a motor torque command Tmc. Based on the motor torque command Tmc, a motor torque T according to the motor torque command Tmc is output from the motor M by 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 loop is configured so that it matches the motor speed command Smc.

When the speed controller 5 is configured as a proportional controller with a gain of 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 × proportional controller gain G = motor torque command Tmc (2)

From these two equations, the motor speed command Smc can be calculated backwards from the motor torque command Tmc as follows:

Speed deviation Sd2=motor torque command Tmc/gain G of proportional controller (3)
Motor speed command Smc=speed deviation Sd2+motor speed S (4)

In the present invention, the speed command Sc is first calculated based on the torque command Tc given from the outside, using the relationship in equations (3) and (4) above.

Speed deviation based on torque command Sd1=torque command Tc/G (5)
Speed command based on torque command Sc=speed deviation based on torque command Sd1+motor speed S (6)

Then, the speed limiter 4 performs speed limiting on the speed command Sc based on the obtained torque command, based on the speed limit command Suc, to obtain the motor speed command Smc.

When the motor speed is controlled based on this motor speed command Smc,

Motor torque command Tmc = speed deviation Sd2 x G
= (Motor speed command Smc - Motor speed S) x G

Here, if there is no speed limit, i.e., if the speed command Sc based on the torque command is smaller than the speed limit command Suc, then the motor speed command Smc = the speed command Sc based on the torque command,

Motor torque command Tmc=(speed command Sc based on torque command−motor speed S)×G
= {(speed deviation Sd1 based on torque command + motor speed S)
-motor speed S}×G
= (Speed deviation Sd1 based on torque command) x G
= Torque command Tc/G×G
= Torque command Tc

The motor torque command Tmc coincides with the torque command Tc, and the motor M is torque-controlled based on this motor torque command Tmc, and the motor torque T according to the motor torque command Tmc, i.e., the torque command Tc, is output from the motor M.

When the speed limit is reached, that is, when the speed command Sc based on the torque command is equal to or greater than the speed limit command Suc, the motor speed command Smc becomes the speed limit command Suc, and the speed of the motor M is controlled based on the speed limit command Suc. Since the speed is limited only by adding the motor speed S to the speed deviation Sd1 based on the torque command, there is no torque control loop above the speed control loop to achieve the speed limit, and no special control parameters are required to configure the control loop.

The speed limit command Suc may be a single input that limits both the CW (clockwise) and CCW (counterclockwise) sides, or two speed limit commands may be provided to limit the CW and CCW sides independently.

The speed limit command Suc can also determine the upper limit of the motor speed S based on a predetermined threshold value, a predetermined table value, a predetermined function value, etc. In this case, "predetermined" obviously includes the possibility of being arbitrarily determined, and further includes the possibility of being arbitrarily set at any time, such as when the motor control device A is manufactured, tested, shipped, or used.

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

In addition, even if the gain G of the speed controller 5 is low, when there is no speed limit, the motor torque command Tmc is calculated according to the torque command Tc and is not affected by the gain G of the proportional controller of the speed controller 5. The gain G of the speed controller 5 can be adjusted in the usual way so that the speed loop is stable when controlling the speed of the motor M under normal operating conditions.

Figure 2 shows another aspect of the motor control device and method.

In this embodiment, in the motor control device and method shown in FIG. 1, in certain cases where resonance occurs in the mechanical system of the motor M or the shaft or winding device connected thereto, it is possible to provide a filter such as a notch filter NF or a low-pass filter LPF on the output side of the speed controller 5. In that case, the response to the torque command Tc will be reduced by the amount of the addition of a filter such as a low-pass filter LPF. The remaining configuration is the same as the first embodiment described above.

When the speed controller 5 is configured as a proportional controller, there is no overshoot. If the workpiece is cut while tension is being controlled by the motor M, the load torque is small due to only the rotational friction of the unwinding section, and even with proportional control, the error in the limited motor speed is small.

Two aspects have been described above, but depending on the application of the present invention, the load torque Tb of the load may be large, and a speed error may occur with respect to the speed limit command Suc, which is the load torque Tb divided by the speed control gain G.

In this case, the speed controller 5 is configured as a proportional-integral controller, which operates as a proportional controller when the speed limit is not reached, and activates the integral controller when the speed limit is reached. When the speed limit is reached, the integral controller suppresses the effects of the load torque Tb. However, since the value output from the integral controller is only a value that compensates for the load torque Tb, the compensation amount of the integral controller is small, and the overshoot of the motor speed is small.

In addition, if the load torque Tb is large and regeneration is also performed, the integral controller of the proportional-integral controller is turned off when the speed limit is reached during regeneration. Although a speed error occurs, this has the effect of preventing the integral controller from repeatedly turning on and off during regeneration, causing pulsation in the motor torque T.

Figures 3 and 4 show simulation results of speed change for multiple aspects of motor control and its method, while Figure 5 shows simulation results of speed change for an example of the operation of a method for correcting a torque command. In each case, the vertical axis shows the magnitude of speed, and the horizontal axis shows the passage of time. Both graphs are based on the same speed limit command Suc.

FIG. 3 shows the result when the load torque is absent when the time T is 0≦T≦0.25 in one embodiment of the motor control and method. In this time range, the speed is limited according to the setting of the speed limit command Suc. Also, in the range of 0.25≦T, the result when the load torque is present is shown. In this time range, as described later, a speed error occurs with respect to the speed limit command Suc, which is the load torque Tb divided by the speed control gain G. This example is merely an example, but shows an error of 29.4 min ⁻¹ . During powering, the speed is limited lower by the amount of this error, and during regeneration, the speed is limited higher by the amount of this error.

Jumping to Fig. 5, an example of the operation of the method for correcting the torque command in Patent Document 1 is shown for comparison with the motor control and method. The results are shown when the load torque is set to zero when the time T is 0≦T≦0.25. Also, the results are shown when the load torque is set to exist in the range of 0.25≦T. In both power running modes, large overshoots such as 290 min ^-1 and 265 min ^-1 occur when the speed rises, and when the torque command becomes 0 during regeneration, a situation occurs in which the speed is not limited. The reason for the large overshoot is that a time delay exists until a large counter torque command is issued, since the speed is limited by a torque command output from the speed loop that is large enough to counter the torque command.

FIG. 4 shows a simulation result of the speed change of another embodiment of the motor control and its method. In this embodiment, the speed controller is configured to perform proportional-integral control (PI control), and can be operated as proportional control (P control) when the speed limit value is not reached, and when the speed limit is reached, the integral controller is enabled to perform speed proportional-integral control (PI control). When the speed limit is reached, the integral controller is enabled to perform speed proportional-integral control (PI control). When the speed limit is reached in this time range, the integral controller is activated, but the overshoot is limited to 30 min ⁻¹ because the torque is not canceled. In addition, in the range of 0.25≦T, the load torque is activated. Even in this time range, the integral controller is activated when the speed limit is reached, so an overshoot occurs, but the amount of overshoot is considerably smaller than the operation example of the method of correcting the torque command shown in FIG. 5.

As described above, in all aspects of the present invention, it is possible to realize a motor control device that does not require special parameter adjustment, can limit the speed regardless of the polarity of the torque command or the direction of motor rotation, has a small overshoot when the speed is limited, and can output motor torque according to the torque command when the speed limit is not reached.

Each of the above-mentioned aspects represents one aspect of the present invention, and the present invention itself is not limited to the specific configurations represented by those aspects. The scope of the present invention includes everything that a person skilled in the art could imagine based on the matters described in the claims.

M...Motor S...Motor speed T...Motor torque A...Motor control device EN...Encoder Dif...Differentiator 1...Speed deviation calculator 2...Adder 3...Subtractor 4...Speed limiter 5...Speed controller 6...Motor torque controller B...Speed detection section C...Speed command calculation section D based on torque command...Speed limit section Tc...Torque command Suc...Speed limit commands Sd1, Sd2...Speed deviation Sc...Speed command Smc based on torque command...Motor speed command G...Speed controller gain Tmc...Motor torque command Tb...Load torque NF...Notch filter LPF...Low pass filter

Claims (6)

A motor control device that controls the torque of a motor while limiting a speed based on a torque command and a speed limit command given from an external source ,
The motor control device includes:
a speed detection unit for detecting a speed of the motor;
a speed limiting unit that calculates a speed command based on the torque command based on the torque command, and outputs a motor speed command that is limited by 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 that adds a speed limit based on the speed limit command to the speed command based on the torque command and outputs the motor speed command,
the torque command-based speed command calculation unit includes a speed deviation calculator that calculates a speed deviation based on the torque command, and an adder that adds the speed deviation to the speed and outputs a speed command based on the torque command ,
a speed controller that calculates a motor torque command based on a speed deviation between the motor speed command and the speed of the motor ;
a motor torque controller for controlling a motor torque based on the motor torque command;
A motor control device comprising: 2 . The motor control device according to claim 1 , wherein the speed limit command is set so that an upper limit of the speed of the motor is determined based on a predetermined threshold value, a predetermined table value, or a predetermined function value. The motor control device according to claim 1 , wherein the speed controller has at least one of a proportional controller and a proportional-integral controller. 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 given from an external source, comprising:
Calculating a speed deviation based on the torque command;
outputting a speed command based on a torque command by adding the speed deviation to the speed of the motor;
a speed limit based on the speed limit command is added to a speed command based on the torque command to output a motor speed command;
calculating a motor torque command by a speed controller based on a speed deviation between the motor speed command and the speed of the motor ;
controlling a motor torque based on the motor torque command;
A motor control method comprising: 5. The motor control method according to claim 4 , wherein the speed limit command is a command in which an upper limit of the speed of the motor is determined based on a predetermined threshold value, a predetermined table value, or a predetermined function value. 6. The motor control method according to claim 4, wherein the speed controller performs proportional control during torque control and proportional-integral control during speed limiting.

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