JP3949134B2 - Stepping motor control device - Google Patents

Description

  The present invention relates to a stepping motor control device that performs positioning control in accordance with a pulse train position command, and more particularly to a microstep control device for a stepping motor.

JP, 6-343294, A There is the thing indicated in JP, 6-343294, A as a drive device of a stepping motor conventionally. FIG. 5 shows a configuration of a conventional stepping motor driving apparatus.

In FIG. 5, 59 is a stepping motor, 51 is an up / down counter for counting up or down a pulse train command P * applied from the outside in accordance with a rotation direction signal U / D, and 52a and 52b. Is a ROM storing excitation signal data corresponding to the count value of the up / down counter 2, 53a and 53b are D / A converters for converting ROM data into voltage signals, and 54a and 54b are for amplifying the voltage of the D / A converter. This is a drive amplifier for driving the stepping motor.

  In the above configuration, the count value of the up / down counter is converted to the address of the ROMs 52a and 52b, and the data of the ROMs 52a and 52b searched by the address value are converted into voltage and applied to the stepping motor. Here, the data of the ROMs 52a and 52b is changed to a pseudo sine wave, and the stepping motor can be smoothly rotated by increasing the number of divisions in one period of the pseudo sine wave.

However, in the conventional configuration, in order to smoothly rotate the stepping motor, the processing from the generation of the pseudo sine wave in the ROM to the voltage output for driving the stepping motor is promptly performed every time the pulse train command P * is generated. Need to run. Conventionally, devices configured with hardware such as logic ICs and OP amplifiers were capable of relatively high-speed processing, but nowadays there are an increasing number of devices equipped with microcomputers for the purpose of realizing complex operations and improving maintainability. ing. In a device equipped with a microcomputer or the like, it is necessary to increase the processing speed of the microcomputer or the like in order to execute a predetermined calculation every time the pulse train command P * is generated and to output an appropriate voltage to the stepping motor. There was a problem of becoming. In addition, there is a problem that it is difficult to control the motor with high accuracy because there is a limit to speeding up the processing speed of the microcomputer.
As a countermeasure against this, there is a sampling process (hereinafter referred to as a sampling process) in which the processing speed of the microcomputer or the like is executed at a constant cycle by counting the number of steps of the pulse train command at a constant cycle with an internal reference signal with respect to the pulse train command of the stepping motor. Although there is an irregular time difference between the sampling cycle and the external pulse train command generation time, the position command fluctuates during rotation, causing vibration. It was.

  The present invention solves the above-described conventional problems, and generates microstep data with high precision at a constant sampling period that is asynchronous with a pulse train command applied from the outside to a microcomputer, etc. An object of the present invention is to provide a control device for a rotating stepping motor.

  In order to solve the above problems, the present invention provides a counter for counting the number of steps of a pulse train command applied from the outside and converting it into a position command, a latch circuit for holding the count value of the counter, and a latch signal for the latch circuit A reference signal generator for generating a reference clock signal, a counting circuit for measuring a time interval from generation of a pulse train command to generation of a latch signal with the reference clock signal, and a counting circuit for measuring a pulse interval of the pulse train command with the reference clock signal Measured by the counting circuit that measures the number of steps of the pulse train command, the command pulse interval information measured by the counting circuit that measures the pulse interval of the pulse train command, and the time interval from the generation of the pulse train command to the generation of the latch signal The position command is corrected using the time difference information, and microstep drive is performed using the corrected position command.

  As a result, the microcomputer can correct the position command error caused by the difference between the position command generation timing and the sampling timing, and obtain an accurate position command. A stable sampling process can be performed.

  FIG. 4 is an explanatory diagram showing the relationship between the pulse train command and the position command. (A) indicates that the position command has the meaning of θ (n) when the pulse train command P (n) is applied. On the other hand, (A) shows the case where the position command is sampled by the sampling pulse t (n), and the time is shifted by T2 (n) from (A). However, if the stepping motor rotates at an average rotational speed ω = θd / T1 (n), the position command is not θ (n) but a position further advanced by Δθ (n) at time t (n). Because it can be considered, position (c) is desirable. That is, an error of Δθ (n) occurs when the position command θ (n) given by the pulse train command P (n) is sampled by the sampling pulse t (n). This sampling error changes every sampling because the pulse train command and the sampling pulse are asynchronous, and a vibration component is generated in the command.

Therefore, the sampling error is estimated by, for example, Equation 1, and the position command is corrected by Equation 2 with respect to the original position command.
Where Δθ (n) is a position command correction value, T1 (n) is a count value indicating a pulse train command interval, T2 (n) is a count value indicating a time interval from the generation of the pulse train command to the generation of a latch signal, θd Is a step angle per pulse of a pulse train command applied from the outside, θ * (n) is a value obtained by counting the pulse train command and converting it to a position command, and θc (n) is a position command after correction. However, n in the parenthesis indicates that the value corresponds to the nth pulse train command P * (n), and (n) will be omitted in the future description unless it is particularly necessary to indicate the pulse order. To do.
For example, when the sampling pulse t (n) ′ is generated before the pulse train command θ * (n + 1) is input, T2 (n) ′ is used for T2 (n) in Equation 1, 4 is corrected to the state indicated by (c) ′.

  Since the control apparatus of the present invention can reduce the sampling error of the position command, it can realize stable sampling processing by suppressing fluctuation of the pulse train command over a wide rotation range. Therefore, the stepping motor can be smoothly rotated without increasing the processing speed of the microcomputer or the like.

  The best mode for carrying out the present invention is an apparatus related to a stepping motor control device that performs positioning control in accordance with a pulse train position command, and more particularly to a microstep control device for a stepping motor.

FIG. 1 shows an embodiment of the present invention, in which 10a is a direction command input terminal, 10b is a pulse train command input terminal, 20a and 20b are first and second phase current command input terminals, and 1 is a position from the pulse train command. Counter unit for converting to command, 2 is a position command corrector, 3 is a current command generator, 4 is a current controller, 7 is an inverter, 8a and 8b are current detectors for the first and second phases, and 9 is a stepping. It is a motor.
A position command corrector is added to the conventional stepping motor control device shown in FIG.
The operation of FIG. 1 will be outlined. A position command is applied to 10a and 10b in the form of a rotation direction and a pulse train from the outside, and the pulse train is converted into a position command θ * by the counter unit 1. The terminal 10c is an input terminal for a signal for determining the number of divisions of microsteps, and a coefficient Ms proportional to the rotation amount per pulse is set. The position command correction unit 2 receives the position command θ * and the coefficient Ms and outputs a corrected position command θ **. Details of a specific example of the method of generating the correction position command θ ** will be described later. The current command generator 3 receives the current amplitude commands Iαp * and Iβp * set in the terminals 20a and 20b and the correction position command θ ** and outputs current commands iα * and iβ *.
The current controller 4, the inverter 7, and the current detectors 8 a and 8 b constitute a current control unit, and the motor applied voltage is controlled so that the energized currents iαf and iβf of the stepping motor 9 coincide with the current commands iα * and iβ *. Therefore, microstep drive is realized.

FIG. 2 is a detailed explanatory diagram of the counter unit 1 and the position command correction unit 2.
The counter unit 1 includes an up / down counter 11 and a latch circuit 12. The pulse circuit command is counted by the up / down counter 11 and is latched by a latch signal (a signal synchronized with the sampling signal) Ts generated by the reference signal generating unit 25. Is converted into a position command θ *, which is a binary value, at regular intervals.
The position command correction unit 2 includes a timing pulse generation unit 21, a counter 22, an adder 23, a latch circuit 24a, a latch circuit 24b, a reference signal generation unit 25, a divider 26, a multiplier 27, and a sign switching unit 28. The
The operation of the position command correction unit 2 will be described in comparison with FIG. The reference signal generator 25 generates a reference clock signal CKs and a latch signal Ts as control signals for the timing pulse generator 21, and the timing pulse generator 21 generates internal control timing signals pt1, pt2, and pt3.
pt1 is a signal obtained by sampling the pulse train command P * with CKs, and pt2 is a signal delayed in time by one pulse of CKs. Further, pt3 is a signal that becomes “L” at the rising edge of pt1 and returns to “H” at the rising edge of the latch signal Ts. Immediately after the pulse train command P * is input, the counter 22 is cleared at the rising edge of pt2, and thereafter the period until the next pt2 is generated is counted with CKs. The value of the counter 22 is held by the latch circuit 24a at the timing of the rising edge of pt1 immediately before the counter 22 is cleared. Therefore, the output T1 of the latch circuit 24a holds a value corresponding to the time interval P *.

The latch circuit 24b holds the value of the counter 22 at the timing of the rising edge of pt3. The rising edge of pt3 substantially coincides with the rising edge of Ts, and the output T2 of the latch circuit 24b holds a value corresponding to the time from when P * is input until Ts is generated.
The divider 26 divides the output T2 of the latch circuit 24b by the output T1 of the latch circuit 24a, and the sign switching unit 28 converts the output of the divider 26 into signed information corresponding to the rotation direction, thereby obtaining a correction amount Δθ. . Note that θd in Equation 1 is the step angle per pulse of the pulse train command, and therefore corresponds to the minimum change amount of the latch circuit 12. Therefore, since θd in Equation 1 when adding to the output θ * of the latch circuit 12 is 1, the output of the sign switching unit 28 corresponds to the result of executing the operation of Equation 1.
A value obtained by adding the position command θ *, which is the output of the latch circuit 12, and the correction amount Δθ, which is the output of the sign switching unit 28, by the adder 23 corresponds to θc which is the calculation result of Equation 2, and Δθ is θ *. [Theta] c is a value obtained by linearly interpolating the lower bits of [theta] * and extending.

The multiplier 27 is provided for multiplying the output of the adder 23 by a factor Ms and converting it into a corrected position command θ ** corresponding to the number of microstep divisions. That is, since the output of the position command correction unit 2 is an input of the current command generation unit 3 and is used as address information for searching the amplitude data of the sinusoidal current command, for example, when Ms = 1 and Ms = 2, the latter is Since the change in address per pulse is doubled, the rotation is performed at a step angle twice that of the former.
Although not clearly shown in FIGS. 1 and 2, the latch signal Ts of the reference signal generator 25 is obtained by dividing the reference clock signal CKs, and can be sampled by synchronizing with a motor control cycle of a microcomputer or the like. It is possible to configure a motor control device that reduces vibration components associated with processing.

The present invention can be used not only for a stepping motor control device for position control but also for a stepping motor speed control device that uses a pulse train as a command, an AC servo motor position control device that uses a pulse train as a command, and a speed control device. is there.
Further, although the pulse train command form is shown by way of example as a direction signal and a pulse train, it can also be applied to other command forms such as a direction-specific pulse train command and a two-phase rectangular wave pulse train command.
The present invention is intended for a motor control device that performs control using a microcomputer or the like, but is applicable to all control devices that perform sampling processing on signals input asynchronously from the outside.
In addition, the present invention is often applied to a hardware configuration device as well as a software hardware processing device, although a control device that performs sampling processing is often equipped with a microcomputer to perform software processing. .

It is explanatory drawing which showed the Example. It is detailed explanatory drawing of an Example. It is operation | movement timing explanatory drawing of the detailed explanatory drawing of an Example. It is a principle explanatory view of the present invention. It is explanatory drawing of the conventional stepping motor drive circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Counter part 2 Position command correction | amendment part 3 Current command generation part 4 Current controller 7 Inverter 8a, 8b Current detector of 1st phase and 2nd phase 9 Stepping motor 10a Direction command input terminal 10b Pulse train command input terminal 11 Up / down counter 20a, 20b First and second phase current command input terminals 21 Timing pulse generator
21a, 21b, 21c Flip-flop 22 Counter 23 Adder 24a, 24b Latch circuit 25 Reference signal generator 26 Divider 27 Multiplier 28 Sign switching unit 51 Up / down counter 52a, 52b ROM
53a, 53b D / A converter 54a, 54b Drive amplifier 59 Stepping motor

Claims (2)

In a stepping motor driving apparatus for energizing a sinusoidal staircase current according to an externally applied pulse train command, a counter that counts the number of steps of the pulse train command and converts it into a position command, and a latch circuit that holds the count value of the counter A reference signal generator for generating a latch signal and a reference clock signal of the latch circuit, a counting circuit for measuring a time interval from generation of the pulse train command to generation of the latch signal by the reference clock signal, and a pulse interval of the pulse train command A counting circuit for measuring with the reference clock signal, the number of steps of the pulse train command, the command pulse interval information measured by the counting circuit for measuring the pulse interval of the pulse train command, and from the generation of the pulse train command to the generation of the latch signal The position command is compensated using the time difference information measured by the counting circuit that measures the time interval. Control device for a stepping motor, characterized by. In a stepping motor driving apparatus for energizing a sinusoidal staircase current in accordance with a pulse train command applied from outside, a counter for counting the number of steps of the pulse train command and converting it into a position command, and a latch circuit for holding the count value of the counter A reference signal generator for generating a latch signal and a reference clock signal of the latch circuit, a counting circuit for measuring a time interval from generation of a pulse train command to generation of a latch signal by the reference clock signal, and a pulse interval of the pulse train command And a counting circuit for measuring with the reference clock signal, wherein the microstep control of the stepping motor is periodically performed in synchronization with the latch signal of the reference timing generator for generating the latch timing of the latch circuit. A control device for a stepping motor according to claim 1.