JP2005018670A - Motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device that is capable of positioning control more precisely than the resolution of a position detecting means, and capable of performing a smoother control. <P>SOLUTION: The motor control device 1 comprises a command device 11, a position compensation device 12, a velocity compensation device 13, a current compensation device 14, and a power amplifier 15. The command device 11 converts a target data Xd to a target displacement Xr, adds a half of the minimum step of an observation displacement Xy based on a resolution of a linear scale 7, to the converted target displacement Xr, and outputs the obtained value as a target displacement Xr'. The position compensation device 12 inputs a position deviation between the target displacement Xr' and the observation displacement Xy feedbacked from a position detecting device 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control device that detects a position by an encoder or scale that outputs a two-phase rectangular incremental pulse train, and performs positioning control based on a position deviation between a target displacement and an observed displacement obtained from the encoder or scale. In particular, the present invention relates to a motor control device that can perform positioning control independent of the resolution of an encoder by correcting a target displacement.
[0002]
[Prior art]
In general, a motor control device is configured to detect a position of a moving body by a position detection unit and compare a target displacement (movement command value) and an observed displacement (position detection value) to compensate for a position deviation. . The software servo system uses a rotary encoder, a linear scale, or the like as position detection means. In recent years, optical linear scales and laser length measuring devices capable of performing extremely precise position detection have been provided. For this reason, high-accuracy position displacement sensors have come to be used in devices that move a moving body with nano-level errors.
[0003]
Many encoders or scales are configured to digitize two sin curves whose phases are shifted by 90 ° and output a two-phase rectangular incremental pulse train of A phase and B phase. The position detector has a so-called quadruple circuit that counts rising and falling edges of each pulse of these pulse trains and outputs the count value as a detection value. The observed displacement from the position detector is input to the addition / subtraction circuit or the comparison circuit together with the target displacement output from the command device. The position deviation between the target displacement and the observed displacement is input to the position compensator. Although the configuration of such a motor control device is well known, for example, the one disclosed in Patent Document 1 is referred to.
[0004]
When the count value of the pulse train output from the encoder or scale is used as a detection value for feedback control, it depends on the resolution of the encoder or scale. As shown in FIG. 2, for example, when the resolution (1 count value) of the encoder is 1 μm, if the numerical value shown in the lower stage is used as the count value and the position 0 is the target position, there is a stop range α indicated by an arrow. . Within this stop range α, the moving body cannot be controlled. Accordingly, a motor control device has been invented that can output a predetermined control deviation even when the position deviation is zero. In Patent Document 2, when the deviation between the movement command value and the position detection value is 0, the operator selectively connects a plurality of deviation operation means for changing the operation deviation amount based on the output value of the multiplication circuit, For example, a motor control device is disclosed that outputs an operation deviation amount of 1 when the A phase of the encoder is 1, and outputs an operation deviation amount of -1 when the encoder is 0.
[0005]
For example, the control method disclosed in Patent Document 2 outputs the position deviation as it is when the deviation between the movement command value and the position detection value is larger than 0, and subtracts 1 from the position deviation when the position deviation is 0 or less. This can also be achieved by outputting the measured value as a positional deviation. For example, as shown in FIG. 2, the control method for correcting and outputting the positional deviation between the target displacement and the observed displacement when the positional deviation between the target displacement and the observed displacement is 0 is used. Then, even when the position deviation is 0, the moving body tries to move in the direction indicated by the arrow β, and the moving body does not stop. Therefore, more accurate positioning, which is smaller than the resolution of the encoder and scale, is performed. It is possible.
[0006]
[Patent Document 1]
JP-A-60-164818 (2nd page to 3rd page, FIG. 2)
[Patent Document 2]
JP-A-6-342307 (page 3, FIG. 3)
[0007]
[Problems to be solved by the invention]
Correcting the deviation between the target displacement and the observed displacement with a specific correction value enables more precise positioning, but tends to cause fluctuations in the output current output from the motor control device to the servo motor. . Such fluctuation hinders smooth movement of the moving body. Even in the case where high-precision positioning control is required, even slight fluctuations have an adverse effect. The present invention improves a motor control device that can be positioned more precisely than the resolution of an encoder or a scale, and makes use of the advantages of this type of motor control device, and a motor control device that can perform control more smoothly. The purpose is to provide.
[0008]
[Means for solving the problems]
In order to achieve the above object, the present invention provides a servo motor (4) that calculates a target displacement (Xr) based on target data (Xd) and reciprocates the moving body (3) according to the target displacement (Xr). In addition to outputting the control current, input the observed displacement (Xy) obtained by counting the rising and falling edges of each pulse of the two-phase rectangular incremental pulse train that is 90 degrees out of phase output from the encoder or scale. , A motor control device that outputs a control current by correcting the target displacement (Xr) based on the deviation between the target displacement (Xr) and the observed displacement (Xy), and an encoder or scale (7 And a command unit (3) for outputting a value obtained by adding or subtracting a value of 1/2 of the minimum unit of the observed displacement (Xy) based on the resolution of the target displacement (Xr ′). The motor control device (1) is used.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a configuration of an embodiment of a motor control device of the present invention. The motor control device 1 calculates a target displacement based on the target data from the command device 2, and outputs a control current to the servo motor 4 of the moving body 3 that is a control target. The servo motor 4 according to the embodiment is an AC synchronous linear motor having a coreless coil 5 having no iron core as a mover and two magnet plates 6 arranged opposite to each other as a stator. The position of the moving body 3 is detected by the linear scale 7.
[0010]
The command device 2 is a control device such as a computer control device. The computer control device includes a personal computer, a keyboard, a mouse, a monitor such as a liquid crystal display, and one or more substrates on which control devices suitable for a predetermined control target are mounted. For example, when the controlled object is a servo motor of a metal processing machine, the command device 2 is a computer numerical control device (CNC, Computerized Numerical Controller). The commanding device 2 generates position data and velocity data in accordance with a rule for a predetermined control target by operating an operation panel by an operator or inputting data obtained from a disk drive through a storage medium. The command device 2 outputs the generated position data and speed data to the motor control device as target data (movement command data) Xd.
[0011]
The linear scale 7 outputs the detection signal as an A-phase B-phase two-phase rectangular incremental pulse train whose phase is shifted by 90 °. The position detector 8 counts the rising and falling edges of the pulse train output from the linear scale 7, thereby measuring the amount of movement from the origin and outputting the observed displacement (position detection value) Xy. The speed detector 9 calculates the speed by obtaining the movement amount per unit time from the movement amount from the position detector 8 and the clock pulse, and outputs the observation speed (speed detection value) Vy. The current detector 10 measures the output current and outputs an observation current Iy that is given to the current control loop.
[0012]
The motor control device 1 includes a command unit 11, a position compensator 12, a speed compensator 13, a current compensator 14, and a power amplifier 15. The motor control device 1 is configured by arranging electrical components including electronic devices such as a central processing unit (CPU) and a memory on a substrate. The electrical components constituting the motor control device of the embodiment are basically the same as the electrical components constituting a known or known digital control circuit, and a detailed description of the main components constituting the motor control device is as follows. Omitted.
[0013]
The target data Xd output from the command device 2 is input to the command device 11. The command device 11 converts the target data Xd into a target displacement (movement command value) Xr. Further, the command unit 11 adds or subtracts ½ of the minimum unit of the observed displacement Xy based on the resolution of the linear scale 7 to the converted target displacement Xr, and outputs it as the target displacement (movement command value) Xr ′. To do. For example, if the resolution of the linear scale 7 is 1 μm, the distance to one count value in the position detector 8 is 1 μm, so the minimum of the observed displacement Xy based on the resolution of the linear scale 7 output from the position detector 8. The unit is 1 μm. Therefore, 0.5 (μm) is added to or subtracted from the target displacement Xr. If one count value is simply regarded as 1, even if the positional deviation between the target displacement Xr and the observed displacement Xy is 0, there will always be a positional deviation of 0.5 and the movement to the target position will continue.
[0014]
The target displacement Xr ′ output from the command device 11 and the observed displacement Xy output from the position detector 8 are input to an addition circuit or a comparison circuit, and a positional deviation (movement command) between the target displacement Xr ′ and the observed displacement Xy. Value-position detection value) is output. The position compensator 12 inputs the position deviation E and gives a predetermined position control gain. The speed deviation between the target speed Vr output from the position compensator 12 and the observed speed Vy from the speed detector 9 is input to the speed compensator 13 and given a predetermined speed control gain to output the target current Ir. . The current deviation between the target current Ir and the observed current Iy from the current detector 10 is input to the current compensator 14 and given a predetermined current control gain. The control current Iq is amplified by the power amplifier, and the output current is supplied to the servo motor 4.
[0015]
As explained above, the motor control device 1 gives the target displacement Xr from the commander 11 as a correction value by giving 1/2 of the minimum unit of the observed displacement Xr based on the resolution of the linear scale 7 as a correction value. Output as. Therefore, when the minimum unit of the target displacement is simply set to 1, the correction value 0.5 is added to the target displacement Xr, so that the correction is performed even when the positional deviation between the target displacement Xr and the observed displacement Xy is 0. Since the positional deviation 0.5 between the target displacement Xr ′ and the observed displacement Xy is output, the moving body is always controlled to move in the positive direction (when the correction value is subtracted, −0.5 is output). ). On the other hand, when the positional deviation between the target displacement Xr and the observed displacement Xy is other than 0, a positional deviation obtained by adding 0.5 to the positional deviation between the target displacement Xr and the observed displacement Xy is output. The moving body is always controlled to move in the direction of the positional deviation between the target displacement Xr and the observed displacement Xy. Therefore, as in the case shown in FIG. 2, the moving body does not stop and moves to the target position even in the stop range smaller than the resolution of the encoder and scale. At this time, since the position deviation between the target displacement Xr and the observed displacement Xy output from the command device 11 is not corrected with a specific value, no fluctuation occurs due to addition / subtraction of the correction value to / from the position deviation. The output control current (output current) is smoothly changed more linearly.
[0016]
The present invention is not limited to the embodiment described above. The apparatus shown in the embodiment can be replaced or changed. Also, a number of known devices can be employed as a device that is not directly related to the important features of the present invention, such as a speed detector. Although the embodiment has been described in terms of the PID control method, it can be changed to another known control method, or several control methods can be combined.
[0017]
【The invention's effect】
Since the motor control device of the present invention includes a controller that outputs a value obtained by adding or subtracting a half value of the minimum unit of the observed displacement based on the resolution of the encoder or the scale to the target displacement as the target displacement. Even when the positional deviation between the displacement and the observed displacement is zero, the movement control of the moving body is performed. Therefore, positioning control can be performed more precisely than the resolution of the encoder or scale. And, it is configured to correct the target displacement before obtaining the position deviation between the target displacement and the observed displacement, and the position deviation is not corrected with a specific value, so the output current output to the motor is changed more smoothly. The Therefore, the motor control device of the present invention can perform positioning control more precisely than the resolution of the encoder and scale, and can reciprocate the moving body more smoothly. In particular, in positioning control of a moving body of the order of micromillimeters or less, there is an excellent effect that a more precise and smooth operation of the moving body can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a motor control device of the present invention.
FIG. 2 is a timing chart showing a control method in the present invention and a conventional motor control device.
[Explanation of symbols]
1, motor control device 2, command device 3, moving body 4, servo motor 7, linear scale 8, position detector 9, speed detector 11, command device 12, position compensator 13, speed compensator 14, current compensator 15. Power amplifier

Claims (1)

The target displacement is calculated based on the target data, and the control current is output to the servo motor that reciprocates the moving body according to the target displacement, and the phase pulse output from the encoder or scale is shifted by 90 degrees. A motor control device that inputs an observed displacement obtained by counting rising and falling edges of each pulse, corrects the target displacement based on a deviation between the target displacement and the observed displacement, and outputs the control current A motor control apparatus comprising: a command device that outputs a value obtained by adding or subtracting a value of 1/2 of the minimum unit of the observed displacement based on the resolution of the encoder or scale to the target displacement as the target displacement.

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