JP3219111B2 - Motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device using a stepping motor as a drive source, and more particularly to a motor control device having several kinds of operation modes, that is, a case of driving by means such as ramp up and down, and a plurality of speed modes. The present invention relates to a motor control device for performing constant-speed driving and holding in a motor.

[0002]

2. Description of the Related Art In recent years, stepping motors have been widely used as driving sources for industrial equipment because of their excellent rotational positioning accuracy. In particular, it is widely used as a drive motor for office office equipment, so-called OA equipment.

A typical driving method of such a stepping motor is a constant voltage driving. This method is widely used because it has the simplest circuit configuration and the lowest cost. However, when the driving frequency is increased, there is a problem that the rise of the current of the motor winding is delayed due to the influence of the inductance of the motor winding, the torque is reduced at high rotation, and high-speed rotation cannot be performed.

[0004] A constant current drive is known as a drive method for coping with high-speed rotation. In this method, the time constant of the motor winding is reduced, the inductance of the motor winding is detected, and the current is turned on and off by a switching element of a transistor so as to have a set current value. Although it can be realized, there is a disadvantage that the circuit becomes complicated and the cost increases. Furthermore, in the case of a stepping motor, since motor vibration occurs at the time of drive switching, noise is generated when the current value is kept constant and the number of revolutions is changed. Therefore, it is necessary to change the current value to a value suitable for the number of revolutions. There were further disadvantages that were required.

As a more advanced drive system, an encoder having a higher accuracy than the resolution of the motor is attached to the shaft of the motor, and the phase is switched in synchronization with the movement of the motor based on the information, and the voltage or current is chopped to obtain a higher voltage. A control method for changing a rotation speed by a duty is known. According to this control method, appropriate phase switching can be performed even when the number of revolutions of the motor changes, so that a so-called step-out state does not occur. Further, since the rotation frequency is determined according to the power to the winding, noise is generated. It is possible to hold down.
However, there is a drawback that the circuit components are maximized including the encoder of the motor and the configuration becomes expensive.

[0006] Further, since there is a drawback that the circuit configuration becomes complicated in the above-described constant current method by detecting the current of the winding and in the closed loop control, a firmware for controlling the power supplied to the winding of the motor is required. The amount of power supplied to the windings of the motor, that is, the pulse duty, is set in advance by a firmware program by the pulse generation means capable of setting the duty by the wearer for each excitation of the motor or by dividing the excitation into a plurality of parts. Accordingly, there has been proposed a stepping motor driving method for performing motor control in an open loop, supplying electric power necessary for driving the motor, and performing efficient driving. As an improvement of this method, the power supply amount to the windings, that is, the pulse duty, that is, the pulse duty is set close to a sine wave by a plurality of drive methods in one excitation, or the stop, hold, ramp up and down, and constant speed running are performed. A stepping motor drive system that changes the pulse duty for each mode has also been proposed.

[0007]

However, in the above-mentioned conventional example, there is a drawback that the circuit configuration becomes complicated as described above in the constant current method by detecting the current of the winding and in the closed loop control. The amount of power supplied to the winding of the motor, that is, the number of pulses supplied to the windings of the motor, is divided by a single excitation of the motor or by multiple divisions within one excitation by means of pulse generation means capable of setting the duty by firmware for controlling the power supplied to the motor. Low-noise according to multiple constant-speed rotations in open-loop motor control by setting the duty in advance by a firmware program and stepping motor drive in which the pulse duty is changed for each constant-speed running mode However, it has been difficult to achieve high precision.

[0008]

In order to solve the above-mentioned problems, the present invention provides an MPU for controlling a motor drive, a setting means for setting a duty to obtain a current waveform input to a motor, and Current control means for controlling the current input to the motor according to the duty set by the setting means, a low-speed ramp-up mode, a low-speed constant speed mode, a low-speed ramp-down mode,
A high-speed ramp-up mode, a high-speed constant-speed mode, and a high-speed ramp-down mode are provided. In the low-speed ramp-up mode, the current waveform in one excitation input to the motor is changed from a sine wave to a first half current value with respect to a first half current value. In the low speed constant speed mode, the current waveform is changed to a waveform in which the latter half current value is lower than the former half current value, and in the low speed ramp down mode, the current waveform is changed to the first half current value. The duty of the setting means is set so as to change from the waveform in which the latter half of the current value becomes lower than the current value to the sine wave.

[0009]

Embodiment (Reference Example 1) FIG. 1 is a block diagram showing components of Embodiment 1 (Reference Examples 1 and 2) of the present invention. In FIG. 1, reference numeral 1 denotes an MPU for performing motor drive control, and 2 denotes a PULs connected to an MPU bus, the frequency and duty of which can be set.
e indicates a width modulator (hereinafter referred to as a PWM unit), 3 indicates an output port connected to the MPU bus, indicates an I / O port for generating a signal coded for driving a stepping motor, and 4 indicates a two-phase signal. 5 shows a unipolar-connected stepping motor, 5 is an I / O port output 3
Denotes a current control transistor for controlling the winding current of the stepping motor 4. Reference numeral 7 denotes a flywheel diode that forms a path for flowing a current when the current control transistor 5 is turned off, 8 denotes a diode that prevents reverse current due to an induced voltage of the coil, and 9 denotes an MPU of the MPU 1.
2 shows a programmable timer unit connected to the bus.

In the above arrangement, the MPU 1 generates signals from the output port 3 as shown in FIGS. 2A, 2B, 2C, and 2D for two-phase excitation required for driving the stepping motor 4. The timing at which the output changes is controlled by the timer 9 by software of the MPU 1 and output. The control of each mode such as acceleration, constant high speed, constant low speed, and deceleration is performed according to the changing time.

The MPU 1 outputs a predetermined duty pulse for each excitation to the PWM unit 2 at a constant frequency, for example, at a frequency of 20 KHz or more higher than the audible range of the human ear, similarly to the stepping motor table for driving the motor. Set to. Examples of the output are shown in FIGS.
With this output, the current control transistor 6 is turned on to supply a current to the stepping motor 4. In addition, the power stored in the inductance of the winding of the stepping motor 4 is released through the flywheel diode 8 at the time of off and the power stored in the inductance of the winding of the stepping motor 4 is repeated. It is possible to flow a current having a proportional value.
FIG. 3 shows an example of the speed of the stepping motor at this time. In FIG. 3, a is a holding mode, b is a low speed ramp-up mode, c is a low speed constant speed mode, d is a low speed ramp down mode, e is a high speed ramp up mode, f is a high speed constant speed mode, g is a high speed ramp down mode, h is the hold mode,
i indicates the slow mode, and j indicates the holding mode.

The value of PWM required when the stepping motor rotates at a certain frequency depends on the power supply voltage, the inductance of the winding of the stepping motor, and the resistance value.
Within the range of the variation of the elements, it is possible to set the minimum required power value for each mode with a PWM value that takes the variation into consideration. In each of the modes, the required torque is different from each other. Therefore, by inputting a pulse having a duty corresponding to the required torque in each mode to the transistor 6, it is possible to supply electric power required for operating the stepping motor.

In general, in the low speed constant speed mode as compared with the high speed constant speed mode, the torque of the stepping motor becomes excessive. Therefore, the duty of the PWM must be reduced.
If the PWM duty is set too low, the current curve supplied to the stepping motor becomes unstable as shown in FIG. 5, and the influence of the power supply voltage, the inductance of the winding of the stepping motor and the resistance value greatly increases. I will. When such a current waveform is input to a stepping motor, the rotation becomes unstable and rotation unevenness occurs.

Therefore, by setting the PWM duty so as to have a current waveform as shown in FIG. 4, a region where the PWM duty is low is eliminated, and the output torque of the stepping motor is reduced to a level necessary and sufficient for low-speed constant-speed rotation. descend.

REFERENCE EXAMPLE 2 In reference example 1, the input current waveform (curve) in the excitation is lower in the latter half than in the first half in the excitation, but as shown in FIG. The same effect can be obtained with a lower input current waveform (curve).

Embodiment 1 FIG. 7 shows Embodiment 1 of the present invention. As described in Reference Example 1, it is desirable to set the PWM duty so that the current waveform becomes as shown in FIG. 4 during low-speed constant-speed rotation. Further, in order to reduce the operation noise of the stepping motor, it is desirable to set the current by the PWM duty so as to form a sine wave. Therefore, to satisfy these two conditions, the holding mode a, the low-speed ramp-up mode b, the low-speed constant-speed mode c, the low-speed ramp-down mode d, the high-speed ramp-up mode e,
Control is performed to change the shape of the current curve in each of the high-speed constant speed mode f and the high-speed ramp-down mode g. In particular, in the low-speed ramp-up mode b, in order to obtain the driving current waveform c at the low-speed constant-speed rotation, the sine-wave driving is gradually changed from the sine-wave driving to the c-wave driving as in b1, b2, and b3. Similarly, in the low-speed ramp-down mode d, the drive is gradually changed from the c-waveform drive to the sine-wave drive as in d1, d2, and d3.

Since the current value in the above invention is determined by the winding resistance of the stepping motor, its reactance, and the PWM duty, the winding specification of the stepping motor preferably has a resistance value of 25 ohms to 40 ohms and an inductance of 15 mh. It is desirable that: However, since this value does not affect the effect of the control itself of the present invention, a sufficient effect can be obtained for a stepping motor having a value other than the above value.

[0018]

As described above, according to the present invention, the MPU for controlling the motor drive, the setting means for setting the duty to obtain the current waveform input to the motor, and the setting means for setting the duty. A current control means for controlling a current input to the motor in accordance with the duty; a low speed ramp up mode, a low speed constant speed mode, a low speed ramp down mode, a high speed ramp up mode, a high speed constant speed mode, a high speed Equipped with ramp down mode,
In the low-speed ramp-up mode, the signal is input to the motor.
1 The current waveform in the excitation is changed from a sine wave to a waveform in which the latter half current value is lower than the former half current value, and in the low speed constant speed mode, the current waveform is changed to the latter half with respect to the former half current value. In the low-speed ramp-down mode, the duty of the setting means is set such that the current waveform is changed from a waveform in which the latter half current value is lower than the former half current value to a sine wave. As a result, a motor control device with less rotation unevenness and noise can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of Embodiment 1 (Reference Examples 1 and 2) of the present invention.

FIG. 2 is a time chart of Example 1 (Reference Examples 1 and 2) of the present invention.

FIG. 3 is an explanatory diagram of a traveling speed according to the first embodiment (Reference Examples 1 and 2) of the present invention.

FIG. 4 is a waveform chart for explaining a current curve of Reference Example 1.

FIG. 5 is a waveform chart for explaining a disadvantage of the conventional example.

FIG. 6 is a waveform diagram for explaining a current curve of Reference Example 2.

FIG. 7 is a waveform diagram for explaining a current curve according to the first embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 MPU 2 PWM unit 3 I / O port 4 Stepping motor 5 Current control transistor 6 Current control transistor 7 Flywheel diode 8 Diode 9 Timer unit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuo Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Satoshi Toshikawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Hiroyuki Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masahiro Taniguro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Kinoshita 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hideaki Kawakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-2-231999 (JP, A) JP-A-57-13998 (JP, A) JP-A-1-315298 (JP, A) JP-A-61-147799 (JP, A) 58-15497 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) H02P 8/00

Claims (1)

(57) [Claims] An MPU for controlling a motor drive; setting means for setting a duty to obtain a current waveform input to the motor; and controlling a current input to the motor in accordance with the duty set by the setting means. A low-speed ramp-up mode, a low-speed constant-speed mode, a low-speed ramp-down mode, a high-speed ramp-up mode, a high-speed constant-speed mode, and a high-speed ramp-down mode. Now, input to the motor
(1) The current waveform in the excitation is changed from a sine wave to a waveform in which the second half current value is lower than the first half current value, and in the low speed constant speed mode, the current waveform is changed to the second half with respect to the first half current value. In the low-speed ramp-down mode, the duty of the setting means is set such that the current waveform is changed from a waveform in which the latter half current value is lower than the former half current value to a sine wave. A motor control device.