JPH089686A - Driving method of stepping motor - Google Patents

Abstract

(57) [Summary] [Object] To provide a driving method of a stepping motor capable of preventing a malfunction of the stepping motor due to a decrease in power supply voltage during PWM control. [Configuration] Stepping motor 3 by PWM control means
In the stepping motor drive method, the stepping motor drive circuit 12e is supplied with the on-duty ratio of the drive signal for step driving
The power supply voltage of the stepping motor drive circuit 12e is detected, and the on-duty ratio is changed according to the value of the power supply voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor driving method, and more particularly to a vibration suppressing technique during driving.

[0002]

2. Description of the Related Art Conventionally, as a method of driving a stepping motor, for example, there is a "stepping motor driving device" as described in Japanese Patent Application Laid-Open No. 4-58790.

In this "stepping motor driving device", when switching the step drive signal waveform for stepwise driving the stepping motor, the on duty ratio of the drive signal is gradually increased by PWM (pulse width modulation) control. The stepping motor driving method is adopted in which the settling due to the abrupt step rotation movement is suppressed by changing to, and thereby the vibration noise during the step driving can be reduced.

[0004]

However, the above-described conventional stepping motor driving method has the following problems.

That is, the PWM used in the conventional method
The control controls the time during which the drive signal supply is turned on so that the drive current output to the stepping motor rises gently, so the average value of the drive current at each step decreases. Therefore, the drive torque of the stepping motor is reduced during the PWM control.

When the power supply voltage of the stepping motor drive circuit drops during the PWM control, the drive torque is further reduced. Therefore, the stepping is performed depending on the relationship between the load and the drive torque. The motor may malfunction.

For example, when the stepping motor is an actuator for driving the damping force characteristic varying means in the damping force varying type shock absorber of the vehicle, the damping force characteristic varying means receives a load due to the fluid force, while the Depending on the usage of other electrical components, the power supply voltage may fluctuate greatly or the battery may deteriorate, causing the voltage to drop.Therefore, the power supply voltage of the stepping motor drive circuit during PWM control that reduces the drive torque. Decrease and / or suddenly when a large load acts, the stepping motor goes out of step,
This leads to incorrect control. However, it is possible to solve the fluctuation of the power supply voltage by providing a constant current circuit by current feedback control, but another problem that the cost is high because the circuit configuration is complicated and the number of parts increases. Occurs.

Further, in the conventional driving method, only the rising portion of each step is smoothly performed, and it is the same as the conventional one in that the step driving is greatly performed along the step driving signal. Therefore, it occurs during the step driving. The vibration that occurs cannot be completely eliminated.

Incidentally, FIG. 9A shows a damping force waveform when the driving stepping motor for driving the damping force characteristic varying means in the variable damping force characteristic type shock absorber is driven based on the conventional driving method. As shown in this figure, the damping force waveform is disturbed. This is because the switching of the damping force characteristics is performed intermittently. Therefore, as the width of each step in the stepping motor increases, the disturbance of the damping force waveform also increases.

The present invention has been made by paying attention to the conventional problems as described above, and a method of driving a stepping motor capable of preventing malfunction of the stepping motor due to a decrease in power supply voltage during PWM control. It is a second object to provide a stepping motor driving method capable of suppressing the occurrence of vibration during driving by further subdividing the steps of the stepping motor.

[0011]

In order to achieve the above object, a method of driving a stepping motor according to a first aspect of the present invention is a state in which an on-duty ratio of a drive signal for step-driving the stepping motor is controlled by a PWM control means. In the stepping motor driving method of supplying the stepping motor driving circuit to the stepping motor driving circuit, the power source voltage of the stepping motor driving circuit is detected and the on-duty ratio is changed according to the value of the power source voltage.

According to a second aspect of the present invention, there is provided a method of driving a stepping motor according to the first aspect, in which a drive signal for each step of driving the stepping motor is divided into a plurality of signals in the time axis direction. Then, by performing PWM control of the drive signal for each division step by the PWM control means, the on-duty ratio of the drive signal in each division step is supplied to the stepping motor drive circuit in a stepwise increased or decreased state. did.

According to a third aspect of the present invention, there is provided a stepping motor driving method according to the first or second aspect, wherein the stepping motor for driving the damping force characteristic varying means of the damping force characteristic varying shock absorber is a driving stepping motor. Is applied.

[0014]

In the stepping motor driving method according to the first aspect of the present invention, as described above, the on-duty ratio of the driving signal by the PWM control means is changed according to the value of the power supply voltage of the stepping motor driving circuit. With this, it is possible to compensate for the decrease in the drive torque due to the decrease in the power supply voltage by the change (increase) in the on-duty ratio.

In the stepping motor driving method according to the second aspect of the invention, the driving signal for each step for driving the stepping motor in steps is divided into a plurality in the time axis direction, and the driving signal for each divided step is PWM-controlled. By supplying the stepping motor drive circuit with the on-duty ratio of the drive signal in each divided step increased or decreased stepwise, each step is further divided into a plurality of steps. As a result, the generation of vibration when driving the stepping motor is suppressed.

According to a third aspect of the present invention, there is provided a stepping motor driving method according to the first aspect, wherein the stepping motor for driving the damping force characteristic varying means in the variable damping force characteristic type shock absorber has the driving method of the stepping motor according to the first aspect. By applying it, it is possible to reduce the level of abnormal noise transmitted to the inside of the vehicle by the vibration of each stepping motor, and the damping force characteristics are switched in more detailed steps, so that the damping force waveform is disturbed. Can be eliminated.

[0017]

【Example】

(First Embodiment) FIG. 1 is a first embodiment in which a stepping motor driving method of the present invention is applied to a driving stepping motor 3 for driving a damping force characteristic changing means in a variable damping force characteristic type shock absorber SA of a vehicle. It is a system block diagram which shows an example.

Variable damping force type shock absorber SA
As shown in FIG. 2, a cylinder 1, a piston 2 defining the inside of the cylinder 1 into an upper chamber A and a lower chamber B, an outer cylinder 4 having a reservoir chamber C formed on the outer periphery of the cylinder 1, and a lower chamber B
And a reservoir chamber C, a guide member 7 for guiding sliding of a piston rod 6 connected to the piston 2, a suspension spring 8 interposed between the outer cylinder 4 and the vehicle body, It includes a bumper bar 9 and
The piston rod 6 is provided with a rotary valve 10 which constitutes the damping force characteristic varying means of the claims, and a stepping motor for driving the rotary valve 10 to rotate stepwise via a control rod 11 at the upper end of the shock absorber SA. It has a structure in which 3 is attached. As the stepping motor 3, a 2-2 phase excitation system using a unipolar 4-phase drive as shown in FIG. 3 is used.

In the system block diagram of FIG. 1, reference numeral 12 is a control unit. The control unit 12 includes an interface circuit 12a, an arithmetic circuit 12b, a drive signal generating circuit 12c, a PWM control circuit 12d, and a stepping motor drive circuit. 12e.

Further, each of the stepping motors 3 has
The vehicle power supply (DC12V) is supplied, and the DC5V power supply obtained from the vehicle power supply via the transformer circuit 12f is supplied to the arithmetic circuit 12b. The voltage (power supply voltage) supplied to the stepping motor 3 is detected by the voltage detection circuit 12g and fed back to the arithmetic circuit 12d.

The interface circuit 12a includes an acceleration sensor (G sensor) 13, a steering angle sensor 14,
Each signal from the vehicle speed sensor 15 and the brake sensor 16 is input, and in the subsequent arithmetic circuit 12b, a control signal for optimally controlling the damping force characteristic of each shock absorber SA in the vehicle based on each signal from the interface circuit 12a. Is required.

Further, in the drive signal generating circuit 12c,
A step drive signal for step-driving the stepping motor 3 in each shock absorber SA to a target step position is output based on each control signal input from the arithmetic circuit 12b.

In the PWM control circuit 12d, the drive signal for each step of the step drive signal output from the drive signal generation circuit 12c is divided into four in the time axis direction, and the drive signal for each divided step is PWM. By performing the control, correction control is performed so that the on-duty ratio of the drive signal in each division step is gradually increased or decreased and is supplied to each stepping motor drive circuit 12e.

In the arithmetic circuit 12b, the PWM control circuit 12d drives the drive signal generation circuit 1 based on the fluctuation of the power supply voltage fed back from the voltage detection circuit 12g.
Selection control of the drive pattern of the drive signal output to 2c is performed. That is, when the supply voltage (power supply voltage) to the stepping motor 3 is DC 12 V or higher, selective switching control to the basic drive pattern is performed, and DC 12
When the voltage is less than V and is equal to or higher than DC 9V, selection switching control to the first correction drive pattern is performed, and further, DC 9V
When it is less than DC8V and is less than 8V, the selection switching control to the second correction drive pattern is performed.

First, the basic drive pattern when the power supply voltage is normal will be described. FIG. 4 is a time chart showing the applied voltage and the on-duty ratio of the drive signal in each division step for each phase (A phase, A ′ phase, B phase, B ′ phase) of the stepping motor. , 0%, 38%, 71%, 92%, 100%, and 0% and 1% for the on-duty ratio (%) of each divided step.
It is possible to switch in 4 steps between 00% and
By increasing the on-duty ratio (%) stepwise from 0% in the phase and decreasing stepwise from 100% in the phase B, each step can be further subdivided into four steps. That is, in this embodiment, the sampling cycle is 6.66 ms and the chopping frequency is 4 KHz.

In addition, FIG. 5A shows the on-duty ratio (0%, 38%, 71%, 92%, 100% of each divided step.
%) In the form of a bar graph. As shown in this figure, each step is equally divided so that the on-duty ratio approximates to a sine wave, and the phase of A phase and B phase is 90%.
By shifting the angle, as shown by the solid line in FIG. 5B, the rotor of the stepping motor 3 can be held in quarter steps by the balance of the applied current (magnetic force). That is, the width of each step can be reduced to 1/4 of that of the conventional one, and thus, the vibration generated when the stepping motor 3 is driven can be significantly suppressed.

Next, (b) of FIG. 9 is a time chart showing a damping force waveform when the stepping motor 3 is step-driven based on the driving method of the above embodiment. The disturbance of the damping force waveform that has occurred in the conventional example ((a) in FIG. 9) is eliminated.

Next, the correction drive pattern when the power supply voltage drops will be described. First, in the first correction drive pattern, the on-duty ratio (%) of each division step
Are 0%, 52%, 80%, 95%, and 100%, respectively. That is, FIG. 6 is a bar graph showing the on-duty ratios (0%, 52%, 80%, 95%, 100%) of the divided steps, and as shown in FIG. Compared with the normal drive pattern, the initial on-duty ratio is increased to make the overall shape closer to a rectangle, thereby increasing the average value of the drive current in each step.

Next, in the second correction drive pattern,
In order to further increase the average value of the drive current in each step, as shown in FIG. 7, the on-duty ratio (%) of each divided step is 100%, that is, PWM.
The PWM control of the drive signal by the control circuit 12d is stopped.

FIG. 8 is a graph showing the on-duty ratio of each division step in the drive pattern. (A) is the basic drive pattern, (b) is the first corrected drive pattern, and (c) is the second. The correction drive patterns are shown respectively.

Therefore, when the power supply voltage drops, by controlling the switching to the first correction drive pattern or the second correction drive pattern according to the extent of the decrease, the decrease in the generated torque due to the decrease in the power supply voltage is compensated by the increase in the average current value. Will be able to.

As described above, in the method of driving the stepping motor 3 of the embodiment, the effects listed below can be obtained. It becomes possible to prevent the malfunction of the stepping motor 3 due to the decrease of the power supply voltage during the PWM control.

Vibration generated when the stepping motor 3 is driven can be significantly suppressed, and as a result,
It is possible to reduce the level of abnormal noise transmitted in the vehicle. Since the switching of the damping force characteristic is performed in more detailed steps, it is possible to eliminate the disturbance of the damping force waveform.

Next, another embodiment of the present invention will be described. In addition, in the other embodiments, only the differences from the first embodiment will be described.

(Second Embodiment) In the second embodiment, FIG.
As shown in the map of 0, the switching of each divided drive pattern with respect to the fluctuation of the power supply voltage V is mapped so that the switching can be performed in seven stages more finely than in the first embodiment.

(Third Embodiment) In the third embodiment, the on-duty ratio of each divided drive pattern ,, is calculated based on the following formulas (1), (2), (3), (4). It's something I asked for.

D ₁ = −K ₁ · V + α (1) D ₂ = −K ₂ · V + β (2) D ₃ = −K ₃ · V + γ (3) D ₄ = 100 (4) where α, β, γ are basic coefficients, K ₁ , K ₂ , K ₃ is a correction coefficient according to the power supply voltage V, and these respective coefficients are divided drive patterns for the power supply voltage V shown in FIG.
, Is set to a value that provides a variable characteristic of the on-duty ratio.

(Fourth Embodiment) In this fourth embodiment, the first
~ The third embodiment has four divided drive patterns,
In contrast to the 7 divisions by, the 11 divisions by 6 division drive patterns ,.

That is, as shown in FIG. 12, the sampling period is divided into 6 with a sampling period of 5 ms, and the chopping frequency is 8 KHz. In this way, by increasing the number of divisions, the driving of the stepping motor 3 can be made smoother.

The embodiment has been described above with reference to the drawings. However, the specific structure is not limited to this embodiment, and the present invention is applicable even if there are design changes and the like within the scope not departing from the gist of the present invention. include.

For example, in the embodiment, the whole step is P
Although the case where the WM control is performed is shown, the present invention can be applied to the case where only the rising portion of each step is PWM controlled.

Further, in the embodiment, the stepping motor 3
As an example, the case of using the 2-2 phase excitation system by unipolar 4-phase drive has been taken as an example, but the type, drive system, etc. are arbitrary.

In the embodiment, the arithmetic circuit 12b outputs a signal in parallel to the drive signal generating circuit 12c and the PWM control circuit 12d, and at the same time, the drive signal generating circuit 12c.
The signal is output from the PWM control circuit 12d to the drive signal generation circuit 12c in a form of correcting the drive signal of the interface circuit 12a, the arithmetic circuit 12
b, drive signal generation circuit 12c, PWM control circuit 12d,
All the circuits may be arranged in series in the order of the stepping motor drive circuit 12e.

[0044]

As described above, in the method of driving the stepping motor according to claim 1 of the present invention, P
In a stepping motor driving method, the WM control means supplies the stepping motor driving circuit with the on-duty ratio of the driving signal for stepwise driving the stepping motor detected, by detecting the power supply voltage of the stepping motor driving circuit, By changing the on-duty ratio according to the value of the power supply voltage, it is possible to prevent the stepping motor from malfunctioning due to a decrease in the power supply voltage during PWM control. .

In the stepping motor driving method according to the second aspect, the driving signal for each step for driving the stepping motor stepwise is divided into a plurality in the time axis direction, and the driving signal for each divided step is PWM-controlled. As a result, the on-duty ratio of the drive signal in each division step is supplied to the stepping motor drive circuit while being increased or decreased stepwise,
Since each step can be subdivided into multiple stages,
It is possible to obtain an effect that it is possible to suppress the occurrence of vibration when driving the stepping motor.

In the stepping motor driving method according to the third aspect, the stepping motor driving method according to the first aspect is applied to the driving stepping motor that drives the damping force characteristic varying means in the damping force characteristic varying type shock absorber. By doing so, the level of abnormal noise transmitted to the inside of the vehicle by the vibration of each stepping motor can be reduced, and the damping force characteristics are switched in smaller steps, so that the disturbance of the damping force waveform can be eliminated. become able to.

[Brief description of drawings]

FIG. 1 is a system block diagram showing a first embodiment in which the stepping motor driving method of the present invention is applied to a driving stepping motor that drives damping force characteristic varying means in a vehicle damping force characteristic varying shock absorber. .

FIG. 2 is a sectional view showing a damping force characteristic variable type shock absorber of a vehicle applied to the first embodiment of the present invention.

FIG. 3 is a diagram showing details of a stepping motor and its drive circuit portion in the first embodiment of the present invention.

FIG. 4 is a time chart showing an applied voltage and an on-duty ratio of a drive signal in each division step for each phase of the stepping motor in the first embodiment of the present invention.

FIG. 5 is a time chart showing a drive signal and a step drive state of a stepping motor in a basic drive pattern in the first embodiment.

FIG. 6 is a time chart showing drive signals in a first corrected drive pattern in the first embodiment.

FIG. 7 is a time chart showing drive signals in a second corrected drive pattern in the first embodiment.

FIG. 8 is a graph showing the on-duty ratio of each division step in each drive pattern in the first embodiment,
(A) shows a basic drive pattern, (B) shows a first correction drive pattern, and (C) shows a second correction drive pattern.

FIG. 9 is a diagram showing a damping force waveform when a driving stepping motor that drives damping force characteristic varying means in a variable damping force characteristic type shock absorber is driven;
Shows the case based on the driving method of the conventional example, and (b) shows the case based on the driving method of the embodiment.

FIG. 10 is a map showing switching characteristics of divided drive patterns with respect to variations in power supply voltage in the second embodiment.

FIG. 11 is a diagram showing a variable characteristic of the on-duty ratio in each divided drive pattern with respect to the power supply voltage in the third embodiment.

FIG. 12 is a diagram showing a division state of drive signals in the fourth embodiment.

[Explanation of Codes] 3 stepping motor 12e stepping motor drive circuit

Claims (3)

[Claims] 1. A method of driving a stepping motor, wherein a PWM control means supplies the stepping motor driving circuit with a stepping motor driving circuit for stepwise driving the stepping motor in a controlled state, the power source of the stepping motor driving circuit. Detect the voltage,
A method for driving a stepping motor, wherein the on-duty ratio is changed according to the value of the power supply voltage. 2. Driving in each divided step by dividing the drive signal for each step for driving the stepping motor into a plurality of steps in the time axis direction and PWM-controlling the drive signal for each divided step by the PWM control means. The stepping motor drive method according to claim 1, wherein the signal is supplied to the stepping motor drive circuit in a state where the on-duty ratio of the signal is increased or decreased stepwise. 3. The method for driving a stepping motor according to claim 1, wherein the stepping motor is a driving stepping motor for driving a damping force characteristic changing means in a variable damping force type shock absorber.