JP2012104047A - Servo controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a servo controller which is capable of performing high-accuracy control with a high followup property by surely reducing a ripple generated in a manipulated variable given from a feedforward controller to a feedback controller, even when a resolution of a position detector to be used is low in a servo controller in a double-degree-of-freedom control configuration.SOLUTION: A command generator 10 converts an inputted position command A into an internal position command 150 of which the resolution is higher than that of a position detector 5, from a resolution of a controller 2. On the basis of the internal position command 150, a feedforward controller 11a generates a speed feedforward component 152 using a differentiator 110 and a filter 111 and, on the basis of the speed feedforward component 152, generates a torque feedforward component 154 using a differentiator 112 and a filter 113. The resolution of the internal position command 150 is higher than that of the position detector 5, so that a ripple generated in the feedforward components 152 and 154 is reduced rather than the case where an internal position command having the resolution of the position detector 5 is used.

Description

  The present invention relates to a servo controller that drives a motor.

  A servo controller targeted by the present invention includes a command generator that converts a position command input from a host controller into an internal position command, a feedback controller that receives an internal position command generated by the command generator in parallel, and And a feedforward controller. The feedforward controller uses the internal position command to perform follow-up control that reduces a response delay to the input position command. The feedback controller suppresses the disturbance by controlling to reduce the difference between the internal position command and the motor position information detected by the position detector attached to the motor. As described above, the servo controller generally has a configuration in which followability to a command and suppression of disturbance are performed by two-degree-of-freedom control.

  In addition, as a structure of a servo controller, as shown, for example in patent document 1, it may be comprised only with a feedback controller. In the servo controller composed of only the feedback controller, the feedback controller is configured to follow the command and suppress disturbance.

  Here, in the servo controller targeted by the present invention, the feedforward controller differentiates the internal position command to generate the speed feedforward component, differentiates it to generate the torque feedforward component, It is given to the feedback controller as the operation amount. Then, the feedback controller controls the motor that drives the target position indicated by the input position command so as to follow each feedforward component of speed and torque.

  By the way, in the conventional servo controller, the internal position command is generated by the following method. That is, based on a detector resolution command input from the host controller or another resolution command, the position command input from the host controller is converted from the resolution of the host controller into a position command based on the position detector resolution. The internal position command is generated by dividing each control cycle. This internal position command has a characteristic that changes in a stepped manner so as to be the target position indicated by the position command input from the host controller in a resolution unit corresponding to the resolution of the position detector. The internal position command that changes in a staircase pattern is input to the feedback controller and the feedforward controller, and the above-described control operation is performed.

  In other words, the internal position command generated in the conventional servo controller has a characteristic that shows a small step and small step change with a small step width if the position detector is high resolution, but the position detector is low. The resolution is a characteristic that shows a rough step change with a large step and a large step width.

  For this reason, the operation amount (speed and torque feedforward components) generated by using the differential value of the internal position command in the feedforward controller is small and smooth when using a high-resolution position detector. In the case of using a low-resolution position detector, there is a large change and a ripple occurs.

Japanese Patent Laid-Open No. 4-24808

  Here, in the conventional servo controller that performs the two-degree-of-freedom control, when the low-resolution position detector is used, the operation amounts (speed and torque feeds) given from the feedforward controller to the feedback controller are used. A large change in the forward component) causes ripples, which is a bottleneck in improving the followability to the position command.

  That is, it is necessary to increase the feedforward gain in order to improve the followability to the position command. However, when a low-resolution position detector is used, if the feedforward gain is increased, the amount of operation given to the feedback controller will change further, resulting in a phenomenon in which the ripple becomes larger, so the feedforward gain cannot be increased. For this reason, when a low-resolution position detector is used, it is difficult to improve the followability to the position command.

  Such a problem also occurs in a servo controller having only a feedback controller. In a servo controller having only a feedback controller, the feedback controller performs tracking of the position command and suppression of disturbance, but it is necessary to increase the feedback gain in order to improve tracking of the position command. However, since the amount of change in position becomes speed and the amount of change in speed becomes torque, when using a low-resolution position detector, increasing the feedback gain causes a phenomenon that the ripple of the operation amount given to the motor increases. Therefore, the feedback gain cannot be increased.

  As a technique for solving this problem, in Patent Document 1, the resolution of the internal position command is made higher than the detector resolution, and the position estimation process is performed based on the detection information of the position detector, so that the actual detector resolution is obtained. A technique for performing feedback control based on estimated position information with higher resolution has been proposed.

  However, in the technique proposed in Patent Document 1, various estimations are performed in order to obtain position information having a resolution higher than the position detector resolution. Happens.

  The present invention has been made in view of the above. In a servo controller having a two-degree-of-freedom control configuration, even if the position detector to be used has a low resolution, it occurs in the amount of operation given from the feedforward controller to the feedback controller. It is an object of the present invention to obtain a servo controller that can reliably reduce ripples and enables high-precision control with high followability.

  In order to solve the above-described problems and achieve the object, the present invention includes a feedforward controller that generates feedforward components of speed and torque based on an internal position command generated from an input position command, and a position A feedback controller for controlling the motor driving the target position indicated by the input position command to follow the respective feedforward components of the speed and torque, using the motor position information detected by the detector as a feedback signal; In the servo controller, the internal position command is generated so as to have a resolution higher than that of the position detector.

  According to the present invention, feedforward compensation is performed using an internal position command obtained by converting the position command input to the servo controller to a resolution higher than the resolution of the position detector. Ripple generated in each feedforward component of speed and torque, which is an operation amount given from the feedforward controller to the feedback controller, can be reduced as compared with the case where feedforward compensation is performed using a command. Therefore, even if the position detector to be used has a low resolution, it is possible to increase the gain of each of the feedforward components of speed and torque, and it is possible to control the motor with high accuracy.

FIG. 1 is a block diagram showing the configuration of the servo controller according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a configuration example of the command generator shown in FIG. FIG. 3 is a waveform diagram showing the operation of the command generator and feedforward controller shown in FIG. 1 in comparison with the conventional configuration. FIG. 4 is a waveform diagram showing the effect of the embodiment in comparison with the conventional configuration. FIG. 5 is a block diagram showing the configuration of the servo controller according to the second embodiment of the present invention.

  Embodiments of a servo controller according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of the servo controller according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a configuration example of the command generator shown in FIG.

  In FIG. 1, the servo controller 1 a drives the motor 4 incorporated in the load device 3 in accordance with the position command A input from the controller 2. A low-resolution position detector (ENC) 5 is attached to the motor 4 directly or in the vicinity thereof. The servo controller 1a uses the motor position information 251 detected by the position detector 5 as a feedback signal when driving the motor 4.

  The servo controller 1a includes a command generator 10, a feedforward controller 11a, and a feedback controller 12.

  The command generator 10 converts the position command A input from the controller 2 into an internal position command 150 having a higher resolution than the resolution of the low-resolution position detector 5, for example, with the configuration shown in FIG. Then, the converted internal position command 150 is output to the feedforward controller 11a and the feedback controller 12 in parallel.

  The feedforward controller 11a includes a series circuit of a differentiator 110 and a filter 111 to which an internal position command 150 is input, and a series circuit of a differentiator 112 and a filter 113 that receive the output of the series circuit. This configuration is a conventional general configuration.

  In the feedforward controller 11a, the series circuit of the differentiator 110 and the filter 111 generates the velocity feedforward component 152 from the internal position command 150 having a resolution higher than that of the low resolution position detector 5. The series circuit of the differentiator 112 and the filter 113 generates a torque feedforward component 154 from the speed feedforward component 152. Each is output to the feedback controller 12 as an operation amount.

  The feedback controller 12 includes multipliers 201, 202, and 203, a position controller 204, a speed controller 205, a torque controller 206, a differentiator 207, and adders 208, 209, and 210. . The feedback controller 12 has a multiplier 201 added to the conventional general configuration.

  The multiplier 201 multiplies the internal position command 150 converted to a higher resolution than the resolution of the position detector 5 by a unit conversion gain and converts the internal position command 150 into the internal position command 250 having the same resolution as the resolution of the position detector 5. Multiplier 202 multiplies velocity feedforward component 152 by a unit conversion / compensation gain and outputs velocity feedforward command 252. Multiplier 203 multiplies torque feedforward component 154 by a unit conversion / compensation gain and outputs torque feedforward command 254. The differentiator 207 obtains the motor speed 253 from the motor position information 251.

  The adder 208 obtains a difference (position deviation) 290 between the internal position command 250 and the motor position information 251. The position controller 204 obtains an operation amount (speed command) 291 that makes the position deviation 290 small. The adder 209 adds the speed feedforward command 252 to the speed command 291 and obtains a difference (speed deviation) 292 between the added value (speed command) and the motor speed 253. The speed controller 205 obtains an operation amount (torque command) 293 that makes the speed deviation 292 small. Adder 210 adds torque feed forward command 254 to torque command 293 and outputs torque command 294. The torque controller 206 obtains an operation amount 295 for driving the motor 4 from the torque command 294 output from the adder 210.

  The command generator 10 includes an input stage detection unit converter 101, an intermediate stage high resolution unit converter 102, and an output stage control period divider 103, for example, as shown in FIG. Yes. That is, the command generator 10 has a configuration in which a high-resolution unit converter 102 is added to a command generator generally used in the past.

  The detector unit converter 101 detects the position command A input from the controller 2 from the resolution of the controller 2 based on the detector resolution command or another resolution command input from the controller 2. The position is converted into a position command having the resolution of the device 5.

  The high resolution unit converter 102 converts the position command having the resolution of the low resolution position detector 5 converted by the detector unit converter 101 into the position command having a resolution higher than the resolution of the low resolution position detector 5. Convert.

  The control period divider 103 divides a position command having a resolution higher than the resolution of the low resolution position detector 5 converted by the high resolution unit converter 102 for each control period of the servo controller 1a, and internally divides it. The position command 150 is output.

  FIG. 3 is a waveform diagram showing the operation of the command generator and feedforward controller shown in FIG. 1 in comparison with the conventional configuration. FIG. 3A is a waveform diagram for explaining the operation of the command generator and the feedforward controller according to this embodiment. FIG. 3B is a waveform diagram for explaining operations of a command generator and a feedforward controller that are generally used conventionally.

  As shown in FIG. 3 (2), the command generator generally used conventionally has a low resolution position command (c) having the resolution of the low resolution position detector output from the detector unit converter, Since the control period divider divides the servo controller for each control period as the internal position command, the internal position command has a step that increases with the low resolution (d) of the low resolution position command. It becomes the characteristic which shows the rough step-like change with the big step width over a some control period.

  As a result, in the feedforward controller in the conventional servo controller to which the internal position command indicating the rough step change characteristic is input, each feedforward of the speed and torque generated using the differential value of the internal position command. The component is a fluctuation waveform having a ripple.

  On the other hand, in this embodiment, as shown in FIG. 3 (1), the command generator 10 has a low resolution position command having the resolution of the low resolution position detector 5 output from the detector unit converter 101. (B) is converted into a high-resolution position command (b) having a resolution higher than that of the low-resolution position detector 5 by the high-resolution unit converter 102, and the control period divider 103 converts it into the servo controller 1a. The internal position command 150 is divided into each control cycle, so that the internal position command 150 has a step that becomes smaller according to the high resolution (b) of the high resolution position command and is as small as one control cycle. It becomes the characteristic which shows the fine step-like change with the step width.

  As a result, in the feedforward controller 11a to which the internal position command 150 indicating this fine step change characteristic is input, the speed feedforward component 152 and the torque feedforward component 154 generated using the differential value of the internal position command 150. Minutes have a smooth waveform with reduced ripple.

  Next, FIG. 4 is a waveform diagram showing the effect of this embodiment in comparison with the conventional configuration. In FIG. 4, the characteristic indicated by the solid line is the characteristic according to this embodiment, and the characteristic indicated by the broken line is the characteristic according to the conventional configuration.

  In FIG. 4, waveform examples of (1) position command, (2) speed command, and (3) torque command are shown. (1) The position command is an internal position command input to the feedforward controller. (2) The speed command is a speed command that is input to the speed controller by reflecting the speed feedforward command in the feedback controller. (3) The torque command is a torque command that is reflected in the torque feedforward command and input to the torque controller.

  As indicated by a broken line in FIG. 4, in the conventional configuration, (1) the position command changes in units of resolution of the low resolution detector, so that (2) the speed command generated in the conventional feedback controller and (3) Ripple increases in each feedforward component of the torque command. Therefore, in the conventional feedback controller, fluctuations have occurred in the speed and torque when the motor is operated at a constant speed.

  On the other hand, in the configuration according to this embodiment, as indicated by the solid line in FIG. 4, (1) the position command changes in a unit of resolution higher than the unit of resolution of the low resolution detector 5. Ripple generated in each feedforward component of (2) speed command and (3) torque command generated in 12 is reduced. Therefore, in the feedback controller 12, the accuracy of the input internal position command 250 remains the same as the resolution of the low-resolution position detector 5, but the ripple of the speed feedforward component 152 and the torque feedforward component 154 does not change. Since the influence can be reduced, fluctuations in speed and torque when the motor is operated at a constant speed are reduced.

  As described above, according to the first embodiment. The position detector used has a low resolution, but feedforward compensation is performed using a position command input to the servo controller converted from the controller resolution to a resolution higher than the resolution of the low resolution position detector. In addition, ripples generated in the speed feedforward component and the torque feedforward component can be reduced. Therefore, it is possible to increase the gains of the speed feedforward component and the torque feedforward component, and the motor can be controlled with high accuracy.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing the configuration of the servo controller according to the second embodiment of the present invention. In FIG. 5, the same reference numerals are given to components that are the same as or equivalent to the components shown in FIG. 1 (Embodiment 1). Here, the description will be focused on the portion related to the second embodiment.

  As shown in FIG. 5, the servo controller 1b according to the second embodiment is different from the servo controller 1a shown in FIG. 1 (Embodiment 1) in that a feedforward controller 11b is used instead of the feedforward controller 11a. Is provided.

  The feedforward controller 11b is a so-called model following type that simulates an ideal operation of a motor or a machine including a motor and controls to follow the ideal operation. The adder 120, the model position controller 121, An adder 122, a model speed controller 123, a motor model 125, and an integrator 128 are provided.

  The internal position command 150 output from the command generator 10 is input to the addition input terminal of the adder 120. The output of the adder 120 is input to the model position controller 121, and the output of the model position controller 121 is input to the addition input terminal of the adder 122. The output of the adder 122 is input to the model speed controller 123, the output of the model speed controller 123 is input to the motor model 125, and the output of the motor model 125 is input to the subtraction input terminal of the adder 120 via the integrator 128. , And the position feedforward component 301 is input to the multiplier 201 of the feedback controller 12. The output of the model speed controller 123 is input to the multiplier 203 of the feedback controller 12 as a torque feedforward component 303. The output of the motor model 125 is input to the subtraction input terminal of the adder 122, and is input to the multiplier 202 of the feedback controller 12 as the speed feedforward component 302.

  In the feedforward controller 11b, a model including a transfer characteristic from torque applied to the motor 4 to speed is calculated in the motor model 125, and in the model position controller 121 and the model speed control unit 123, a reference model including control parameters is calculated. , And a position feedforward component 301 that is a model position calculated therefrom, a speed feedforward component 302 that is a model speed, and a torque feedforward component 303 that is a model torque are respectively supplied to the feedback controller 12. Since the internal position command 150 having a resolution higher than the resolution of the position detector 5 is used, the speed feedforward component 302 and the torque feedforward component 303 are in a state where there is little ripple, as in the first embodiment. Is input.

  In the feedback controller 12, the position feedforward component 301 having a resolution higher than that of the low-resolution position detector 5 is converted into an internal position command 250 having the resolution of the position detector 5 in the multiplier 201, The feed forward component 302 is converted into a speed feed forward command 252 in the multiplier 202, and the torque feed forward component 303 is converted into a torque feed forward command 254 in the multiplier 203.

  As a result, the feedback controller 12 performs control for causing the motor 4 driven to the target position to follow the ideal operation of the motor by the feed-forward compensated internal position command 250, speed feed-forward command 252 and torque feed-forward command 254. .

  According to the second embodiment, feedforward compensation can be performed for the position, speed, and torque, so that the motor can be controlled with high accuracy as in the first embodiment. Even in response to a sudden acceleration / deceleration command from, control can be performed stably in order to follow the ideal operation of the motor.

  As described above, the servo controller according to the present invention is generated in the operation amount given from the feedforward controller to the feedback controller in the servo controller of the two-degree-of-freedom control configuration even if the position detector used is low. Ripple can be reliably reduced, and it is useful as a servo controller that enables high-precision control with high followability.

1a, 1b Servo controller 2 Host controller 3 Load device 4 Motor 5 Position detector (low resolution)
DESCRIPTION OF SYMBOLS 10 Command generator 11a, 11b Feedforward controller 12 Feedback controller 101 Detector unit converter 102 High resolution unit converter 103 Control period divider 110,112,207 Differentiator 111,113 Filter 120,122,208-210 Adder 121 Model position controller 123 Model speed controller 125 Motor model 128 Integrator 201, 202, 203 Multiplier 204 Position controller 205 Speed controller 206 Torque controller

Claims (5)

A feedforward controller that generates feedforward components of speed and torque based on an internal position command generated from an input position command;
A feedback controller for controlling the motor that drives the target position indicated by the input position command to follow the respective feedforward components of the speed and torque, using the motor position information detected by the position detector as a feedback signal; Servo controller with
The servo controller according to claim 1, wherein the internal position command is generated to have a resolution higher than that of the position detector. The input position command is:
The servo controller according to claim 1, wherein the servo controller is a resolution of the position detector, and the internal position command is generated so as to have a resolution higher than the position detector resolution. The feedback controller is
An internal position command having a resolution higher than the resolution of the position detector is converted into a low resolution internal position command having a resolution of the position detector, and the control operation is performed according to the low resolution internal position command. The servo controller according to claim 1 or 2. A feedforward controller having a reference model control unit for calculating a model position, model speed, and model torque that simulates an ideal operation of a motor and a machine including the motor based on an internal position command generated from an input position command;
The motor position information detected by the position detector is used as a feedback signal, and the motor driven to the target position indicated by the input position command is controlled to follow each feedforward component of the model position, model speed and model torque. In a servo controller comprising a feedback controller,
The servo controller according to claim 1, wherein the internal position command is generated to have a resolution higher than that of the position detector. The feedback controller is
The model position generated based on an internal position command having a resolution higher than the resolution of the position detector is converted into a low resolution internal position command having a resolution of the position detector, and the control is performed according to the low resolution internal position command. The servo controller according to claim 4, wherein the servo controller is operated.

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