JPH0775385A - Steeping motor controller - Google Patents

Abstract

PURPOSE:To increase the accuracy of a setting current by securing the turn-on/ turn-off time at an output stage and reducing the load of the output stage in the controller of a current drive stepping motor. CONSTITUTION:In a controller 5 of a stepping motor 1, a means 9 for varying the frequency of a current control signal and a means for increasing the frequency of the frequency varying means when a high current accuracy is required are provided or a means for changing the frequency varying means according to a duty ratio is provided. When a high current accuracy is required, a period T of the current control signal is reduced and a position accuracy increases. When the duty ratio approaches an upper limit or a lower limit, the period T increases, thus securing turn-on/turn-off time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for a current drive stepping motor.

[0002]

2. Description of the Related Art FIG. 2 shows a drive circuit of a current drive stepping motor. The output stage 2 including a bridge circuit of FET1 to FET4 is assembled between the power source 3 (+ B) and the ground GND, and the winding 11 of the stepping motor 1 is connected to the output side of the bridge circuit. In the figure, the winding 11 shows only one phase, and the circuits of other phases are omitted. Each FET1 to FET4 forming the output stage 2
The gate of FIG.
The current control signal and the phase switching signal shown in are input.

A target position 7 and an operation pattern 8 are input to the CPU 5 from the outside. The CPU 5 determines the rotation direction, the rotation speed, etc. of the stepping motor 1 from these instruction inputs and the current step of the stepping motor 1, and outputs a current control signal and a phase switching signal to each FET 1 to FET 4. FIG. 3 shows an example of the current control signal and the phase switching signal.

In the period t1, the phase switching signal which is turned on during the period is input to the FET4, and the period T is applied to the FET1.
A current control signal that is repeatedly turned on and off during (reciprocal of frequency) is input. Further, in the subsequent period t2, the phase switching signal that is on during the period is input to the FET3, and the current control signal that is repeatedly turned on and off during the period T is input to the FET2. The stepping motor 1 is rotated by sequentially repeating the above steps.

The relationship between the current control signal and the current flowing through the winding 11 of the stepping motor 1 is shown in FIG. The current value I flowing through the winding wire 11 is determined by the ratio of the ON time and the period T, that is, the duty ratio, and is independent of the period T. Also,
FIG. 4a shows a case where the period T of the current control signal is small, and FIG. 4b shows a case where the period T is large. In addition, winding 1 in FIG.
An example of the excitation pattern of No. 1 will be shown. In FIG. 5b, the constant current I is sequentially supplied to the windings A and B, and the steps of the motor are
It is a large step for each magnetic pole. FIG. 5a shows winding A,
The current of B is multi-divided and the current value is changed in multiple steps of I1, I2, I3, and a large number of steps of the motor can be set between the magnetic poles to enable more precise position adjustment.

[0006]

In the control device for the stepping motor 1 described above, as shown in FIG. 4, the smaller the cycle T of the current control signal is set, the higher the accuracy of the set current becomes. it can. However, if the cycle T is made too small, it becomes difficult to secure the turn-on time or turn-off time of the FET of the output stage 2, and the on / off frequency increases, so that the load of the output stage 2 increases. .

Therefore, the conventional stepping motor 1
In the above drive circuit, the cycle T is set to an appropriate value within a range in which the turn-on / turn-off time of the output stage 2 can be secured and an excessive load is not applied to the output stage 2.
However, if the cycle T is set in this way, the accuracy of the set current cannot be sufficiently obtained, and the position control of the stepping motor 1 cannot be performed accurately.

SUMMARY OF THE INVENTION It is an object of the present invention to increase the accuracy of a set current in a controller for a current-driven stepping motor while ensuring turn-on / turn-off time of the output stage and reducing the load of the output stage. It is a thing.

[0009]

In order to achieve the above object, the present invention makes the frequency or period T of the current control signal variable. Then, when it is necessary to increase the current accuracy, the period T is made smaller than that during normal control. When the duty ratio is close to the upper limit or the lower limit, the cycle T is increased.

In order to realize this control, the present invention provides a means for varying the frequency of a current control signal in a controller for a current drive stepping motor, and a means for varying the frequency when the high current accuracy is required. A means for increasing the frequency is provided. Alternatively, a means for changing the frequency varying means according to the duty ratio is provided.

[0011]

According to the above means, when high current accuracy is required, such as when performing accurate position control, the cycle varying means makes the cycle T smaller than the cycle T in the normal state. At this time, the load of the output stage is increased by reducing the cycle T, but since such an operation is performed during a part of the control period of the stepping motor, the load on the output stage becomes excessive. It never happens.

When the duty ratio is close to the upper limit value or the lower limit value, for example, 10% or less or 90% or more, the cycle T is increased. Accordingly, even when the duty ratio is 10% or less and the turn-on time is extremely short, the turn-on time can be sufficiently taken. Further, even when the duty ratio is 90% or more and the turn-off time is extremely short, the turn-off time can be sufficiently taken.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the present invention is applied to a stepping motor control device for adjusting the opening of a throttle valve of a vehicle will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of the present invention. First, the block configuration will be described.

The output stage 2 is inserted between the power source 3 and the stepping motor 1. A control signal is input to the output stage 2 from the CPU 5 via the buffer 4. The contents of the output stage 2, the current control signal, and the phase switching signal have already been described with reference to FIGS. 2 to 5, so please refer to them. An instruction input 7 for a target position of the stepping motor 1 and an instruction input 8 for an operation pattern are input to the control unit 6 of the CPU 5 from the outside. The driving pattern is, for example,
As in "slow-up, slow-down", the instruction is how to advance the step to the target position.

The control unit 6 determines the rotation direction, the number of steps of the difference, and the excitation pattern of the winding 11 from the input target position and operation pattern and the present position stored inside.
As the excitation pattern of the winding 11, several patterns as shown in FIG. 5 are prepared. When position accuracy is not required as in the middle of rotation of the stepping motor, FIG.
A simple pattern as shown in b is used, and a multi-divided pattern as shown in FIG. 5a is used near the target position.

The control unit 6 outputs the current value I or I ₁ , I ₂ , I ₃ determined by the determined excitation pattern to the excitation sequencer 9. At the same time, the control unit 6 outputs the step number of the difference and the duty ratio in the current control command to the frequency determining unit 10. Frequency determining means 10
Detects that the stepping motor 1 has approached the target position from the step number of the difference, the excitation sequencer 9
The command is to increase the frequency of the current control signal, that is, to reduce the cycle T. When the duty ratio is 10% or less or 90% or more, the frequency of the current control signal is instructed to be low, that is, the period T is increased.

The excitation sequencer 9 operates each FET of the output stage 2 in a predetermined order according to a command from the control unit 6.
Further, the excitation sequencer 9 has a frequency changing means for changing the frequency of the reciprocal of the period T of the turn-on / turn-off time of the FET. In this example, the frequency is
It can be switched to three levels: large, medium and small. Next, the operation of the control device described above will be described.

Now, when the accelerator is depressed while the vehicle is idling, the target position corresponding to the depression amount is input from the target position instruction input 7 to the control unit 6. Further, slow-up / slow-down is input from the operation pattern instruction input 8 as the operation pattern of the throttle valve. The control unit 6 calculates the number of steps of the difference from the target position and the current position, and the speed, the rotation direction of the stepping motor 1 and the excitation pattern of the winding 11 are determined from the operation pattern and the number of steps of the difference. This excitation pattern determines the current value flowing in each winding 11 at that time.

This current value is input to the excitation sequencer 9. The excitation sequencer 9 outputs a current control signal and a phase switching signal to each FET of the output stage 2 with a duty ratio according to this current value. Normally, the cycle T of the current control signal is set to an intermediate value among the three levels. When the current value is selected such that the duty ratio of the current control signal is 10% or less, or 90% or more, the duty ratio is 10%.
Turn-on time and duty ratio 90% when
In the above case, the turn-off time becomes extremely short, and the time required for turn-on / turn-off cannot be secured.
Therefore, when such a duty ratio is detected,
The frequency determination means 10 issues an instruction to the excitation sequencer 9 to lower the frequency of the current control signal. As a result, the cycle T of the current control signal is increased and a sufficient turn-on / turn-off time is secured.

When the step advances and approaches the target position, the frequency determining means 10 detects from the number of steps of the difference that the target position has approached, and the excitation sequencer 9 receives the frequency of the current control signal. Give instructions to raise.
As a result, the cycle T of the current control signal is reduced from the state shown in FIG. 4b as shown in FIG. 4a, and the accuracy of the set current and the accuracy of the position of the stepping motor 1 are increased.
Therefore, the accuracy of position control at the target position can be improved.

In the above embodiments, the accuracy of the current is improved when the stepping motor is at or near the target position, but the accuracy of the current is not limited to such a case. Not something.
In the process of controlling the stepping motor, the current accuracy can be arbitrarily increased where it is desired to improve the position accuracy.

[0022]

According to the present invention, in a control device for a current-driven stepping motor, it is possible to secure the turn-on / turn-off time of the output stage and to reduce the load of the output stage while improving the accuracy of the set current. You can

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a drive circuit diagram of a stepping motor.

FIG. 3 is a waveform diagram showing a current control signal and a phase switching signal supplied to the output stage of FIG.

FIG. 4 is a waveform diagram showing the relationship between the current control signal of FIG. 2 and the motor current.

5 is a waveform diagram showing an excitation pattern of the winding of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Stepping motor 2 ... Output stage 3 ... Power supply 5 ... CPU 6 ... Control part 7 ... Target position instruction input 8 ... Operation pattern instruction input 9 ... Excitation sequencer 10 ... Frequency determination means

Claims (2)

[Claims] 1. A current drive stepping motor control device comprising means for varying the frequency of a current control signal, and means for increasing the frequency of the frequency varying means when high current accuracy is required. A stepping motor control device characterized by: 2. A stepping motor control device for controlling a current driven stepping motor, comprising: a means for varying a frequency of a current control signal; and a means for varying the frequency varying means according to a duty ratio. apparatus.