JP2002078385A - Motor driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent strong motion step out at acceleration control performed at rotation start of a motor or the occurrence of discomforting sound. SOLUTION: In a motor driver which employs a constant current chopper control system for controlling a drive current to be constant for a motor which rotates, switching its exciting phases in the order, such as a stepping motor, etc., a constant-current chopper control circuit compares the reference voltage set by a potential-dividing resistance for reference with the voltage value of the resistance for current detection detected by the current flowing to the motor, by means of a comparator, and performs the on/off control of the current flowing into the motor, based on the comparison result. Further, a filter is connected between the resistance for current detection and the comparator. The time constant of the filter can be switched, and the time constant is switched, depending on the condition of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor driving device for supplying a current to a motor, such as a stepping motor, which sequentially rotates an exciting phase and rotates by a constant current chopper method.

[0002]

2. Description of the Related Art A constant current circuit for controlling a motor driving current in a motor driving device to a constant value includes a reference voltage set by a reference voltage dividing resistor, a voltage value of a current detecting resistor for detecting a current flowing through the motor, and Are compared by a comparator, and based on the comparison result, ON / OFF control (chopping control) of a current flowing into the motor is performed. However, during the actual chopping operation, the S
Due to the influence of the W element, ringing noise appears on the current detection signal, causing a comparator to perform erroneous detection.

Generally, as shown in FIG. 1, a filter is connected between a current detecting resistor and a comparator to prevent this malfunction. When the excitation pulse is input to the motor, the filter constants are set so that the current flows into the reference current value determined by rl / r2 immediately after the input of the phase switching signal as shown in the lower diagram of FIG. I do. Thus, the motor can output a specified torque.

[0004]

However, in order to output a high torque in a high-speed rotation region (pull-out characteristic), an unnecessarily high torque is output even when the motor starts rotating (pull-in characteristic). In general, during acceleration control used at the start of motor rotation, strong earthquake out-of-step or unpleasant vibration noise may be generated. As a solution to the above problem, there is a method of interposing a rubber damper between a motor and a motor mounting device to absorb vibrations caused by the motor. However, this method has problems that the damper is expensive and that a space for mounting the dambar is required between the motor and the mounting device.

[0005]

In order to solve the above-mentioned problems, a motor driving apparatus according to the present invention comprises a constant current chopper for controlling a driving current of a rotating motor such as a stepping motor by sequentially switching excitation phases. In a motor drive device using a control method, the constant current chopper control circuit compares a reference voltage set by a reference voltage dividing resistor with a voltage value of a current detecting resistor for detecting a current flowing through the motor by a comparator. Based on the comparison result, ON / OFF control (chopping control) of the current flowing into the motor is performed, and a filter is connected between the current detecting resistor and the comparator. The time constant of the filter is switchable, and the time constant is switched and controlled depending on the state of the motor.

As a result, a pseudo soft-start control is performed as shown in the upper diagram of FIG. 3 by increasing the filter constant when the motor drive current rises without installing an expensive damper, thereby smoothly generating torque. To reduce noise and vibration. When the motor starts to rotate, the motor drive current is detected, and control is performed to reduce the filter constant so that the current becomes the current at the time of steady rotation of the motor. As a result, the high torque inherent in the motor can be used even during high-speed rotation.

[0007]

(Embodiment 1) An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 4 shows a configuration diagram of an embodiment to which the motor drive device of the present invention is applied. 101 is a stepping motor to be controlled, 102 is a central processing unit (hereinafter referred to as CPU) for outputting a drive signal of the stepping motor, 103 is a driving circuit for supplying a current necessary for rotating the stepping motor, and 106 is a motor A timer for generating the control CLX, a ROM 107 storing a motor control program, and a RAM 108 used by the CPU as a temporary storage area.

First, a stepping motor to be controlled by the motor driving device of the present invention will be described. The most characteristic of the stepping motor is that the rotation angle is displaced in proportion to the input pulse, and the rotation speed is displaced in proportion to the input pulse frequency. For this reason, it is possible to control the motor without feeding back the rotation angle or the rotation speed.

In the motor driving device of the present embodiment, the CPU
Calls the stepping motor control program stored in the ROM device, and in accordance with the instructions of the program,
It has a role of outputting a phase excitation signal which is a drive signal of the stepping motor to the drive circuit. That is, a phase excitation signal having a frequency corresponding to the target motor speed is output.

[0010] The ROM device is a nonvolatile storage device. On the other hand, instead of the conventional CPU called a microcomputer, RISC-type CPUs that achieve high speed and low power consumption by reducing the number of instructions and equalizing the instruction length, and DSPs, which are processors specialized in real-time digital signal processing, are also becoming popular. Therefore, the present invention can be realized also in the motor driving device of the present invention. The ROM device stores a motor control program, and the program is loaded into the CPU as needed.

The RAM device is a rewritable storage device for storing a calculation result and temporarily saving a calculation result when the CPU performs a calculation.

In recent years, some CPUs have a ROM and a RAM integrated in the same package as the CPU. When such a CPU is used, the ROM device and the RAM device can be omitted.

With the above-mentioned motor driving device, the CPU generates a phase excitation switching signal and an excitation signal necessary for acceleration / deceleration control of the motor as shown in FIG. 5, and a filter time constant switching signal which is a main part of the present invention. Control. Here, generally, the excitation signal 501 is a signal for permitting a current to flow into the motor, and is a control signal for executing excitation when the motor is rotating or stopped. The phase excitation switching signal 502 is a control signal for switching the current flowing into the motor, which is generated by arithmetic processing by DMA or DSP inside the CPU. The motor drive IC outputs a phase excitation switching signal from 1 CLX to several CLX. By controlling the phase excitation switching signal to increase its cycle, the motor smoothly performs an acceleration operation (504).
The same applies to deceleration / constant speed driving.

In the drive circuit, constant current chopping control is implemented by hardware, and the current supplied to the stepping motor is adjusted in accordance with the phase excitation switching signal from the CPU.
Turns on / off, performs chopping control so that the current flowing to the motor becomes constant, and supplies the current to the stepping motor.

In the characteristic drive control of the present invention, FIG.
This will be described in detail with reference to 1, 2, and 3. FIG. 1 is a block diagram showing a part of the chopping control. The voltage dividing resistor rl · r2 is a resistor for setting a predetermined chopping current value, and the voltage dividing value is determined by the ratio between the reference voltage and rl · r2. A current flows into the driving motor 1008 by a driver circuit, and the current value is measured by a current detection resistor Rl. The partial pressure value and the detection value are compared and calculated by a comparator, and when the detection value exceeds a predetermined partial pressure value, the chopper ON / OFF control means 1005
As a result, the chopper control is executed on the driver circuit 1007 so that a certain amount of current does not flow into the motor.

Here, the driver circuit is, for example, a MOS FET
When the chopper operates, the driver
A noise filter 1003 mainly composed of CR is configured so that ringing noise is added to the detected value and the divided voltage value due to noise generated during ON / OFF control, and erroneous comparison calculation processing does not occur. Often done. If the time constant is too small, the noise cannot be eliminated, and if it is too large, the timing for comparing the change in the current that actually flows into the motor will be shifted, and the chopping operation will start from a current value lower than the reference current value shown in Fig. 3. And then
It becomes a state gradually approaching the reference current value.

In this state, the effective value of the current that actually flows into the motor is smaller than the effective value of the set current that should flow, and the torque during high-speed rotation cannot be sufficiently extracted. Therefore, usually, when determining this time constant, it is adjusted so as to stably perform the chopping operation with the reference current value as shown in the lower diagram of FIG. 3 while observing the chopping waveform.

However, at the same time as outputting a high torque in the high-speed rotation region, an unnecessarily high torque is output even at the time of starting when the motor starts rotating, and the torque is reduced with respect to the load and inertia connected to the motor. Oversupply is often seen. Excessive torque output may cause harshness or start-up noise exceeding the noise standard, and in the worst case, may lead to strong earthquake step-out.

Therefore, this problem can be solved by applying the characteristics shown in the upper diagram of FIG. 3 at the time of starting the motor. Figure 3
In the upper diagram, it seems as if the slow start control is applied to the lower diagram, which is an appropriate chobber control, and the current actually flowing into the motor gradually increases. Therefore, at the stage when the motor starts rotating by the step angle, the torque is relatively low because the current value is small,
Rotation starts smoothly by that amount, and thereafter, a prescribed current value flows over time. As a result, the motor rises smoothly at the time of start-up, so that a smooth acceleration drive can be executed without generating an unpleasant start-up sound.

Thereafter, when the rotation speed becomes high, the filter constant is changed so that the chopping control as shown in the lower diagram of FIG. 3 can be performed. Here, even at the time of high-speed rotation, with the control as shown in the upper diagram of FIG. 3, the pull-out torque characteristic is lower by about 10% to 20% than the original (the state of the lower diagram), and the motor performance cannot be sufficiently brought out. I know.

FIG. 2 is a block diagram showing a control circuit capable of switching the time constant of the above-mentioned filter. The noise filter 2001 is composed of at least two or more switching circuits. In this embodiment, the resistance R is switched among the CR circuits.
Alternatively, a means for switching the time constant by another circuit may be used. As an example of the switching circuit 2002, it is possible to switch the filter time constant by using an analog switch and a digitizer, and turning on / off the analog switch via a digital time using a filter time constant switching signal from the CPU.

The above operation will be described with reference to FIG. At the start of motor rotation, first, in step S601, the motor is set in an excited state by excitation signal control. Thereafter, control is performed such that an appropriate time constant 1 is selected when the motor is started (S602). At this time, the operation order of steps S601 and S602 may be reversed. At this stage, the phase excitation switching signal 502 for acceleration control is transmitted to the motor drive circuit 104, and the motor performs a smooth acceleration operation under the filter time constant 1 (step S604). Thereafter, when the motor rotates at high speed and constant speed (state 3) (step S605), the filter time constant is switched to constant 3 (step S606). The motor continues to rotate while having sufficient pull-out characteristics under the filter time constant 3 (step S607).

[0023]

According to the present invention, when the motor drive current rises, the constant of the filter is increased to perform pseudo soft start control as shown in the upper diagram of FIG. 3, and noise and vibration are generated by generating a gentle torque. suppress. At the time of high-speed rotation, the constant of the filter is reduced to a necessary and sufficient value for noise, so that the high torque inherent in the motor can be used even at high-speed rotation.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a conventional chopping control.

FIG. 2 is a block diagram illustrating a typical drive circuit of the present invention.

FIG. 3 is a waveform diagram of a current flowing into a motor during a chopping operation.

FIG. 4 is a block diagram of a control unit according to the present invention.

FIG. 5 is a diagram illustrating a correlation between control signals.

FIG. 6 is a flowchart illustrating control according to the present invention.

[Explanation of symbols]

 101 Stepping motor 102 CPU 103 Drive circuit 106 Timer 107 ROM device 108 RAM device 1001,2 Voltage dividing resistance value 1003,2001 Noise filter 1004 Comparison means 1005 Chopper control means 1006 Driver circuit 1007 Current detection resistance

Claims (7)

[Claims] 1. A motor drive device using a constant current chopper control method for controlling a drive current of a motor that rotates by sequentially switching an excitation phase of a stepping motor or the like, wherein the constant current chopper control circuit includes a constant current chopper control circuit. A comparison means for comparing, by a comparator, a reference voltage determined by a reference voltage dividing resistor to set a value and a voltage value of a current detection resistor for detecting a current flowing through the motor, provided at a comparator input unit; A noise removing unit in which at least a plurality of time constants are switchably selectable between a reference voltage and the detected voltage value, based on a result of the comparing unit,
A motor drive device comprising: control means for performing ON / OFF control (chopping control) of a current flowing into a motor, and selectively controlling a noise removal time constant according to a rotation state of the motor. 2. A motor drive device using a constant current chopper control method according to claim 1, wherein when the rotation state of the motor is a high-speed rotation or a constant-speed rotation, a time constant sufficient to remove noise is selected. A motor driving device for selecting a time constant larger than the time constant at the time of starting or stopping. 3. A motor drive device using a constant current chopper control method according to claim 2, wherein the speed is accelerated to increase at the time of start-up, and the speed is decreased to decrease at the time of stop. A motor driving device characterized by the following. 4. A motor driving device using a constant current chopper control system according to claim 1, wherein the noise removing means is a noise filter constituted by a resistor R and a capacitor C. . 5. A motor drive device using a constant current chopper control method according to claim 1, wherein the time constant switching selection function is to switch one of a resistor and a capacitor of a noise filter composed of CR by an analog switch. A motor driving device characterized by the above-mentioned. 6. A motor driving device using a constant current chopper control method according to claim 1, wherein the driving frequency for rotating the motor is less than a predetermined frequency.
A motor driving device characterized in that at the time of high-speed rotation or constant-speed rotation, a time constant larger than the time constant is selected while selecting a time constant necessary and sufficient for noise removal. 7. A motor driving apparatus using a constant current chopper control system according to claim 1, wherein said first filter of said noise removing means is provided when the rotation operation of said motor is started.
First filter-time constant selecting means for selecting a time constant;
Motor rotation speed determining means for determining the rotation speed of the motor; and when the motor rotation speed determination means determines that the motor rotation speed has reached a predetermined rotation speed, at least a second filter-time constant of the noise removing means. The second to choose
And a filter-time constant selecting means.