TWI499197B - Method of controlling motor and motor controlling system - Google Patents

Description

Motor control method and device

The present invention relates to a motor control method and apparatus for performing high-precision positioning of a motor used in a work machine or the like.

In a positioning device for a motor such as a work machine using a motor, a digital encoder is used to detect the current position of the movable element of the motor, and the movable element of the motor is positioned at a position corresponding to the position command. In such a conventional device, for example, when the position command is made to zero, and the motor is stopped at the command position, since the position detection is detection based on the digital value, the output of the encoder is often generated in the movable element. 1 fluctuation of the pulse component. If the mechanical system connecting the motor and the load is a rigid body, the change will not increase, and no major problem will occur. However, if there is a portion where the mechanical system connecting the motor and the load has a low rigidity, the fluctuation is increased depending on the condition, and a micro-vibration that resonates with the mechanical system occurs.

For example, when the ball screw coupling mechanism is connected to the shaft of the motor to constitute the mechanical system, the balls of the ball screw coupling mechanism are elastically deformed as shown in Figs. 6(A) to 6(C). Fig. 6(B) is a view showing a ball in a ball screw coupling mechanism that is not elastically deformed, and Figs. 6(A) and 6(C) are views exaggeratingly depicting a ball that is elastically deformed by vibration. Arrows in the sixth (A) and sixth (C) diagrams indicate the moving direction at the time of vibration.

Position detection of the moving elements of the motor by the digital encoder, It is implemented in the sampling cycle. Therefore, the position detected by the last sampling is used as the position of the moving element until sampling is performed. As a result, as shown in Fig. 5, the position is detected with a delay with respect to the "actual position". Further, when the speed is calculated, the delay due to the difference calculation is also caused, and the speed is also detected along with the detection roughness and the time lag determined by the sampling period. The speed control system is such that the speed at which the motion is detected is suppressed. Further, the operation of the ball connected to the ball screw of the motor re-delays the elastic deformation component in accordance with the operation of the motor. Therefore, even if the movable element of the motor is stopped at the stop position, it is viewed magnificently, and when the motor is rotated by ±1 pulse, the direction of movement of the ball is reversed [from the state of Fig. 6(A) to the sixth (B) In the state of the figure, or when returning from the 6th (C) diagram to the state of the 6th (B) diagram], the speed at which the ball is recovered from the elastic deformation, the conventional positioning position is a moving motor The situation of the axis. At this time, the balls of the ball screw are repeatedly elastically deformed and slightly vibrated, and mechanical sound is generated from the periphery of the ball screw. Such microvibration is related to deterioration of the ball screw or the like, and thus it is preferable to suppress it as much as possible.

As a method of suppressing the microvibration, there is a method of reducing the gain of the speed loop or the position loop of the motor control device until the mechanical system does not resonate. However, in such a method, there is a problem that the response characteristics are lowered and the servo rigidity is also lowered. As another method, there is a method in which a torque command is passed through a notch filter, and a frequency component of the microvibration is excluded from the torque command. However, when the notch filter is inserted, the phase is delayed at a frequency lower than the notch frequency, and thus there is a problem that the speed control response characteristic is peaked and the control characteristic is deteriorated.

Further, as another technique for suppressing microvibration, there is a technique of the motor control device shown in Patent Document 1. In the device disclosed in Japanese Laid-Open Patent Publication No. 2007-252093, a motor stop determination circuit and a dead zone forming circuit are provided. The motor stop determination circuit is zero in the position command data, and if the position deviation data is within the positioning completion range, it is determined that the motor is in the stop state. The dead zone forming circuit sets a dead zone for the torque command in order to ignore the torque command component that changes due to the fluctuation of the ±1 pulse component from the positioning point when the motor stop determination circuit determines that the motor is stopped.

In the prior art described in Japanese Laid-Open Patent Publication No. 2007-252093, a dead zone is set in the torque command when the position command is zero. Since there is a dead zone, if the position of the movable element of the motor in the stopped state is not subjected to +2 pulse or -2 pulse change by an external force or the like, the torque is not output. If such a dead zone is set, positioning control cannot be performed in the dead zone. Because of this, in the conventional device, the positioning accuracy cannot be improved. In particular, when an external force is applied when the motor is stopped, positioning control cannot be performed even if a deviation of a pulse component occurs. Therefore, in the case where the working machine requires high positioning accuracy, if the conventional motor is used to control the motor, there is a problem that the machining accuracy is lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control device capable of suppressing microvibration of a mechanical system even in a motor control device using a digital encoder, even in a portion where a mechanical system has a low rigidity, without lowering the positioning accuracy. Law and equipment.

In the motor control method according to the present invention, the position command data of the moving position of the movable element of the command motor and the current position data of the movable element detected by the digital encoder are used to calculate the deviation to generate the positional deviation. data. Further, the difference between the current position data of the sample and the current position data of the previous sample is calculated to generate the difference current position data. Further, the current velocity data of the active component is generated based on the difference current location data. Further, the calculation generates a speed deviation data based on the deviation between the speed command data created by the position deviation data and the current speed data, and generates torque command data based on the speed deviation data. Further, the torque of the motor is controlled in accordance with the torque command data. In particular, in the present invention, when the movable element passes through the target position, the polarity of the current position data changes. Therefore, it is first determined whether the polarity of the difference current position data has changed. Further, after it is determined that there is a change in polarity, the current speed data is generated by taking the difference current position data as zero, that is, an integer of 1 or more, that is, a period of n sampling periods.

In theory, when the polarity of the difference current position data changes, it is when the moving element passes the target position. If the position command data is the command target position (positioning point), then in theory, the active component is the target position. However, when the dead zone is not set as in the prior art (when it is continuously controlled), the movable element is in a state of being finely shaken within ±1 pulse of the output of the encoder with the target position as the center. That is, it is determined that there is a polarity change Then, if the current velocity data is immediately generated based on the difference current position data, the torque of moving the movable element in a direction opposite to the moving direction before the change in polarity occurs. For example, when the mechanical rigidity is low to the extent that the connection mechanism connecting the motor and the load is elastically deformed, a large repulsive force to restore the elastic deformation to the original is generated. This repulsive force acts to increase the torque that moves the movable element in the opposite direction. As a result, the amount of movement of the movable element becomes large, and in the worst case, resonance occurs, and a vibration sound to a degree that can be confirmed by the human ear occurs. According to the present invention, if it is determined that there is a change in polarity, if the period of the differential current position data is 1 or more, that is, the period of the n sampling period, the speed data is zero and the activity is active during the period. The component acts only on the repulsive force of the elastic deformation. During the period of the n sampling period, the displacement of the movable element due to the repulsive force according to the elastic deformation ends. Also, after the n sampling period, the differential current position data is returned from zero to the actual data. In this case, regardless of the cause, if the uncontrollable force acts on the movable element after the polarity of the difference current position data is inverted, the integer value of 1 or more, that is, the period of the n sampling period, When it is zero, it is possible to prevent the vibration of the movable element from increasing due to the uncontrollable force and causing noise. Further, since the dead zone is not provided as in the prior art, the positioning accuracy can be improved as compared with the prior art.

The numerical value of n is not constant, and may be appropriately set in accordance with the mechanical rigidity of the connection mechanism that is elastically deformed between the movable element and the load. The setting criterion of n is a value set so that the microvibration of the movable element that is generated is not affected by the rigidity of the connection mechanism. Made this way, The effects of the present invention are effectively exerted.

When the connection mechanism is a general rigid ball screw coupling mechanism, n may be set to 1. When using a connection mechanism of other construction, it is sufficient to select an appropriate value of n.

A motor control device embodying the method of the present invention includes: an encoder that outputs a current position of a movable element of a motor with a digital value; a position deviation data generating unit; a difference current position data generating unit; a current speed data generating unit; and a position controller; Speed deviation data generating unit; speed controller; and torque control unit. The positional deviation data generating unit generates positional deviation data by calculating a deviation from the position command data indicating the movement position of the movable element and the current position data indicating the current position of the movable element detected by the encoder. The difference current position data generating unit calculates the difference between the current position data of the current sampling and the current position data of the previous sampling to generate the difference current position data. The velocity data generation unit now generates the current velocity data of the active component based on the difference current location data. The position controller generates speed command data based on the position deviation data. The speed deviation data generation unit calculates the deviation of the current speed data from the speed command data to generate the speed deviation data. The speed controller generates torque command data based on the speed deviation data. The torque control unit controls the torque of the motor based on the torque command data. The current speed data generating unit is a polarity determining unit that includes a determination as to whether or not the polarity of the difference current position data has changed. In addition, the current speed data generating unit generates the current speed data as zero immediately after the polarity determination unit determines that the polarity has changed, and immediately sets the difference current position data to an integer of 1 or more, that is, the n sampling period. According to the invention, it can be implemented simply and surely The method of the invention.

In the device of the present invention, when a coupling mechanism that elastically deforms is disposed between the movable element and the load, the value of n is determined to be a numerical value that the microvibration of the movable element that is generated is not affected by the rigidity of the coupling mechanism. Further, if the connection mechanism is a general rigid ball screw coupling mechanism, n may be set to 1.

The invention is of course also applicable when the operation is stopped, that is, when the position command data is zero. At this time, after determining that the polarity has changed, the current velocity data is generated by taking the difference current position data as an integer of 1 or more, that is, a period of the n sampling period as zero.

Fig. 1 is a block diagram showing a configuration of an example of an embodiment of a motor control device for carrying out the motor control method of the present invention. The motor control device 1 of the present embodiment is provided with a digital encoder E that outputs the current position of the movable element M (including both the rotary motor and the linear motor) of the movable motor M (including both the rotary motor and the linear motor) at a digital value; Deviation data generating unit 3; position controller 5; difference current position data generating unit 7, current speed data generating unit 9, speed deviation data generating unit 15, speed controller 17, and torque control unit 19. As the digital encoder E, a known encoder such as an optical encoder or a magnetic encoder can be used.

The positional deviation data generating unit 3 formed by the subtractor is a position command data indicating the moving position of the movable element of the motor M, and The position deviation data is generated by calculating the deviation using the current position data of the current position of the moving element detected by the digital encoder E.

The difference current position data generating unit 7 calculates the difference between the current position data of the current sampling and the current position data of the previous sampling by the digital encoder E to generate the difference current position data. Therefore, the difference current position data generating unit 7 includes a memory unit that memorizes at least the output from the digital encoder E and the current sample component, and the difference between the difference between the previous data stored in the memory unit and the current data. The calculation unit and the result memory unit of the calculation result of the memory difference calculation unit.

The current speed data generating unit 9 generates the current speed data of the moving element of the motor M based on the difference current position data generated by the difference current position data generating unit 7. The current speed data generating unit 9 includes a polarity determining unit 11 and a gain multiplying unit 13 that determine whether or not the polarity of the difference current position data generated by the difference current position data generating unit 7 has changed. As shown in the second figure (A), the polarity determination unit 11 determines whether or not the polarity is determined by using the difference current position data generated by the difference current position data generation unit 7 as a reference based on the "0" level. Variety. The state shown in the second (A) diagram is a state in which the positional command data input to the positional deviation data generating unit 3 is zero, indicating that the movable element is slightly vibrated. In the present embodiment, as shown in the second figure (B), the current speed data generating unit 9 immediately sets the difference current position outputted by the difference current position data generating unit 7 after the polarity determining unit 11 determines that the polarity has changed. The data is generated as zero at the time of an integer of 1 or more, that is, a period of n sampling periods. In Figure 2(B), this state is called "insertion hysteresis" After the difference position." Here, "hysteresis" means that "the pre-state is inserted as a post-state (predetermined period)". In the example of the second (B) diagram, the "0" state before the polarity inversion determination is maintained by one sampling period component after the polarity inversion determination. The gain multiplying unit 13 multiplies the predetermined gain by the difference current position data output from the difference current position data generating unit 7 and outputs it as speed feedback. The gain multiplying unit 13 calculates the speed feedback by applying a gain in accordance with the decomposition energy of the digital encoder E.

The position controller 5 generates speed command data based on the positional deviation data generated by the positional deviation data generating unit 3. The speed deviation data generating unit 15 formed by the subtractor calculates the deviation between the current speed data (speed feedback) output from the gain multiplying unit 13 of the current speed data generating unit 9 and the speed command data outputted by the position controller 5, and The output is used as the speed deviation data. The speed controller 17 generates torque command data based on the speed deviation data output from the speed deviation data generating unit 15. The torque control unit 19 controls the torque of the movable element based on the input torque command data.

Theoretically, when the polarity of the difference current position data changes, the movable element of the motor M passes as the target stop position. In response to the position command input to the position deviation data generating unit 3 (input by the upper controller), the active element is theoretically stopped at the target position. However, actually, the movable element is in a state of being finely shaken within ±1 pulse of the output of the digital encoder E with the target position as the center. Therefore, when the polarity determination unit 11 determines the change in the polarity, the current speed data generation unit 9 generates the current speed data based on the difference difference current position data thereafter, and then the direction occurs. The torque of the movable element is moved in a direction opposite to the direction of movement before the polarity change. As described above with reference to Fig. 6, when the connection mechanism that connects the motor M and the mechanical system MS of the load is a ball screw coupling mechanism that elastically deforms, as shown in Fig. 6(A) or Fig. 6(C) Since the mechanical rigidity of the mechanical system is low, the elastic deformation of the ball is restored to the original large repulsive force. This repulsive force acts to increase the torque that moves the movable element in the opposite direction. As a result, the amount of movement of the movable element becomes large, and at the worst, resonance occurs, and a vibration sound to the extent that the human ear can confirm is generated.

In the present embodiment, the polarity determination unit 11 immediately sets the period of the n-sample period, which is an integer of one or more, which is the difference current position data output from the difference current position data generation unit 7, to zero. Therefore, during the sampling period, the current velocity data is zero. During this period, the movable element acts on the repulsive force according to the elastic deformation, but during the period of the n sampling period, the displacement of the movable element due to the repulsive force according to the elastic deformation is ended. Further, the current speed data generating unit 9 returns the difference current position data from zero to the actual data after the n sampling period. In this way, it is possible to prevent the vibration of the movable element from being increased due to the uncontrollable force (repulsive force due to elastic deformation, etc.), and noise is generated.

Referring to Fig. 2, more specifically, when the polarity of the difference current position data in the second (A) figure is changed, the difference in the insertion magnetic lag of the second (B) figure is the position data. There is a change after a sampling period. That is, the speed of the moving parts of the motor When there is a change in polarity, there is a sample component (a sampling period component), and the speed feedback is not output. After that, the value is presented in the speed feedback when the samples of the same polarity are sampled twice in succession. Therefore, in the case where the hysteresis of a sampling component (a sampling period component) is inserted in time. Thereby, the operation of the control system that is controlled by the fluctuation of the ±1 pulse of the encoder when the motor is stopped becomes a delayed sampling component (a sampling period component). Therefore, according to the present embodiment, in the control system in which the movable element of the motor is moved so that the ball expansion of the ball screw coupling mechanism is restored by the elastic deformation, the detection speed is delayed by one sampling component. As a result, according to the present embodiment, the ball of the ball screw coupling mechanism does not accelerate the operation of recovering from the elastic deformation, and the microvibration of the ball screw coupling mechanism is suppressed. Further, when the rigidity of the mechanical system is lower, the number of pulses of hysteresis (the number of n of the n sampling period) is increased.

In the present embodiment, for the difference calculation result of the position at which the speed feedback is calculated, when the polarity of the speed changes, a hysteresis of a short time for controlling the sampling (sampling period) is inserted. Thereby, the positioning accuracy is not lowered, and the microvibration which is elastically deformed when the rigidity of the mechanical system is low can be suppressed. Further, it is possible to prevent deterioration of the machine, and it is possible to realize high-precision machining due to high servo response.

The third (A) and third (B) diagrams show the relationship between the torque command in the vicinity of the positioning point and the encoder output when moving in one direction. Fig. 3(A) is a diagram showing a torque command when the torque command is changed for a longer period of time (period) than the sampling period. If the torque command changes in a long time (cycle), the change in the torque command becomes a sampling week. The period of the period is the same as the change of the torque command when the differential current position data is zero and the hysteresis is not inserted. Fig. 3(B) is a view showing a torque command when the torque command is changed in a time corresponding to the sampling period. The case of the third (B) diagram is that a hysteresis with a difference current position data as zero is inserted during a sampling period. The fourth (A) and fourth (B) drawings show the positions of the movable elements when the motor is stopped by the actual machine. Fig. 4(A) shows the case of no hysteresis, in which case a microvibration of ±2 pulses is generated. Fig. 4(B) shows the case where the hysteresis with the difference current position data as zero is inserted during one sampling period, and the microvibration is suppressed.

(industrial availability)

According to the present invention, regardless of the cause, when the force that cannot be controlled after the polarity inversion of the difference current position data is applied to the movable element, the integer of 1 or more, that is, the period of the n sampling period, is made zero by the difference current position data. It can prevent the vibration of the movable element from increasing due to the uncontrollable force and causing noise. The dead zone of the prior art is not provided, so that the positioning accuracy can be improved more than the conventional one.

1‧‧‧Motor control unit

3‧‧‧Location Deviation Data Generation Department

5‧‧‧Location Controller

7‧‧‧Differential Current Position Data Generation Department

9‧‧‧Speed data generation department now

11‧‧‧Polarity Determination Department

13‧‧‧Gain Multiplication Department

15‧‧‧Speed Deviation Data Generation Department

17‧‧‧Speed controller

19‧‧‧Torque Control Department

Fig. 1 is a block diagram showing a configuration of an example of an embodiment of a motor control device for carrying out the motor control method of the present invention.

Figs. 2(A) to 2(C) are timing charts for explaining the operation of the embodiment of Fig. 1.

The third (A) and third (B) drawings are diagrams showing the relationship between the torque command in the vicinity of the positioning point and the encoder output when moving in one direction.

4(A) and 4(B) are diagrams showing the positions of the movable elements when the motor is stopped measured by the actual machine.

Fig. 5 is a timing chart for explaining the position detecting operation of the movable element of the motor of the embodiment.

6(A) to 6(C) are diagrams for explaining elastic deformation of a ball using a ball screw coupling mechanism as a mechanical system.

1‧‧‧Motor control unit

3‧‧‧Location Deviation Data Generation Department

5‧‧‧Location Controller

7‧‧‧Differential Current Position Data Generation Department

9‧‧‧Speed data generation department now

11‧‧‧Polarity Determination Department

13‧‧‧Gain Multiplication Department

15‧‧‧Speed Deviation Data Generation Department

17‧‧‧Speed controller

19‧‧‧Torque Control Department

M‧‧‧Motor

MS‧‧‧Mechanical system

E‧‧‧Encoder

Claims (7)

A motor control method characterized in that a position command data indicating a moving position of a movable element of a command motor and a current position data indicating a current position of the movable element detected by a digital encoder are used to calculate a deviation to generate a position Deviation data, calculating a difference between the current position data of the sample and the current position data of the last sample to generate a difference current position data, determining whether the polarity of the difference current position data is changed, and generating the movable element according to the difference current position data. The current velocity data, but after determining that the polarity is changed, the current velocity data of the movable element is generated by using the difference current position data as an integer of 1 or more, that is, the period of the n sampling period, and the calculation is based on the positional deviation data. The speed command data is generated from the current speed data to generate speed deviation data, the torque command data is generated based on the speed deviation data, and the torque of the motor is controlled based on the torque command data. The motor control method according to claim 1, wherein a coupling mechanism that elastically deforms is disposed between the movable element and the load, and n is set to be a micro-vibration of the movable element that is generated. A value that is affected by the rigidity of the above-described linkage mechanism. The motor control method as described in claim 2, The connection mechanism is a ball screw coupling mechanism, and the above n is 1. A motor control device comprising: an encoder that outputs a current position of a movable element of a motor with a digital value; and position command data for instructing a movement position of the movable element, and a detected by the encoder a positional deviation data generating unit that generates a positional deviation data by calculating a deviation of the current position data of the current position of the movable element; and calculating a difference between the current position data of the current sampling and the current position data of the last sampling to generate a difference current position a difference current position data generating unit of the data; and a polarity determining unit that determines whether or not the polarity of the difference current position data has changed, and generates the current speed data of the movable element based on the difference current position data, but determines that the polarity changes Then, the current speed data generating unit that generates the current speed data by using the difference current position data as an integer of 1 or more, that is, the period of the n sampling period, and a position controller for generating the speed command data based on the position deviation data ;and Operator information with said current speed deviation and the velocity command data to generate a velocity deviation data speed deviation data generating unit; generates a torque command and data in accordance with the speed deviation of the speed control information And a torque control unit that digitally controls the torque of the motor based on the torque command data. The motor control device according to claim 4, wherein a coupling mechanism that elastically deforms is disposed between the movable element and the load, and n is set to be a micro-vibration of the movable element that is generated. A value that is affected by the rigidity of the above-described linkage mechanism. The motor control device according to claim 5, wherein the connection mechanism is a ball screw coupling mechanism, and the n is 1. The motor control device according to claim 4, wherein the current speed data generating unit determines that the difference current polarity has changed after the position command data is zero, and samples the difference current position data at n. The current speed data is generated as zero during the period of the cycle.