JP3053964B2 - Step motor control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a step motor.

[0002]

2. Description of the Related Art A technique of controlling the position of an object by moving the object with a step motor is often used at present. In this case, the moving range of the object is often limited. For example, when the object is a throttle valve, a structure is provided that prohibits the object from moving further to the closing side than the maximum closing position. When the moving range of the object is limited as described above, a technique of adding an urging means such as a spring and maintaining the object at the movable limit position while the energization of the step motor is cut off is known. Often used. For example, in the case of a sub-throttle valve for traction control of an engine, a stopper for regulating a fully open position of the sub-throttle valve, a spring for biasing the sub-throttle valve toward the stopper, and a A step motor is provided that rotates against the force of the motor, and when traction control is not required, the step motor is cut off and the throttle valve is brought into contact with the full-opening stopper by the spring. Can be

In order to control the stepping motor, it is necessary to detect the number of steps of the stepping motor and to switch the energized phase accordingly. For this purpose, an absolute step number detecting means for directly detecting the absolute value of the step number of the step motor may be used. However, in many cases,
A method is employed in which it is detected that the number of steps has increased or decreased by 1, and the number of steps is calculated from this. In this case, unless the reference position becomes clear, the absolute step number at that time is not calculated. Therefore, usually, the step motor is once rotated to the reference position, and the number of steps from that time is calculated.

[0004] As described above, once moved to the reference position,
In the case of using the technique of calculating the number of steps thereafter, energization to the step motor may be cut off for some reason. In this case, the technique disclosed in Japanese Patent Application Laid-Open No. 58-6097 employs a technique in which the number of steps at the time of energization cutoff is stored, and when the energization is resumed, the energized phase is determined based on the stored number of steps.

[0005]

SUMMARY OF THE INVENTION The above-mentioned JP-A-58-60
According to the technique described in Japanese Patent Publication No. 97-97, no inconvenience occurs unless the stepping motor rotates between the time when the power supply is cut off and the time when the power supply is restarted.

However, as described above, when the power supply to the stepping motor is cut off, the object is maintained at the movable limit position by a biasing means such as a spring. The numbers do not always match. This also occurs when the energization is interrupted after the object returns to the movable limit position. One of the reasons is that the number of steps at the time of energization cutoff and the number of steps abutting on the stopper that regulates the movable limit position may not exactly match. In such a case, since the actuator further moves and comes into contact with the stopper after the energization is cut off, the number of steps when the energization is cut off and when the energization is restarted differs. When the step motor and the object are linked by a speed reduction mechanism, the object position and the number of steps do not match within the range of the backlash of the speed reduction mechanism. In particular, when an object comes into contact with the stopper and the movement range is restricted, the influence of the backlash is strong, and the number of steps when power is cut off and when power is restarted may be largely different.

Each time the step motor moves to the movable limit position, if the step motor can be moved to the reference position again to compensate for the number of steps, even if the step motor rotates between the time of shut-off and the time of re-energization, it is not affected. The displacement can be compensated again. However, for example, in the case of the above-described traction control device, it is possible to temporarily move the engine to the reference position at the time of starting the engine to compensate for the number of steps. The road is closed inconveniently. That is, after the engine starts rotating, it cannot be moved to the reference position.

In such a case, the above-mentioned Japanese Patent Application Laid-Open No. 58-6 / 1983
In the case of the technique described in Japanese Patent Application Laid-Open No. 097, the energization phase at the time of resumption of energization is determined on the assumption that the number of steps at the time of energization cutoff is equal to the number of steps at the time of resumption of energization. When the four-phase stepping motor illustrated in FIG. 2D is clockwise, A → B → A ′ →
B '(where the dash symbol is a substitute for the upper horizontal line and is indicated by the upper horizontal line in the figure), and when it is counterclockwise, it is excited as A → B' → A '→ B Will be described as an example. Here, it is assumed that when the rotor R reaches the maximum number of steps in the A-phase excitation, the rotor R is located at the movable limit position and the energization is interrupted. Further, it is assumed that the number of steps is deviated at the time of resumption of energization due to the deviation from the stopper contact position and the backlash described above. Assuming that there is a deviation within ± 1 step when power is restarted, the same phase excitation and
That is, by applying the A-phase excitation, the rotor R is attracted to the A-phase, and the deviation is eliminated. However, if the number of shift steps is +3 to +4 or -3 to -4, the rotor R is completely inverted by the A-phase excitation, and the number of steps is shifted by ± 4 steps. If the number of shift steps is ± 2 steps, it will match the MAX step number or will shift to MAX ± 4 step numbers.

This situation is well shown in FIG.
When the number of shift steps is 3 or more or -3 or less, there is a shift of ± 4 steps when the energization is restarted, and when the number of shift steps is ± 2, it returns to the step number (MAX) at the time of energization interruption or ± 4 steps. It becomes unstable whether the number of steps is shifted. Therefore, as shown in FIG. 2 (a), if there is a deviation of ± 2 steps or more between when the power is cut off and when the power is restarted, the control is shifted by ± 4 steps after the power is restarted, and the target number of steps (TARGET) is given. Even if it is opened, there is a possibility that it is controlled to a position where it is opened four extra steps or less than the four steps. A deviation of ± 2 steps or more while the object is located at the movable limit position and the energization is interrupted is a common occurrence every day, and this problem cannot be ignored.

[0010]

In order to solve this problem, the present invention provides a method whose concept is schematically shown in FIG. 1, that is, it is movable within a predetermined range and is provided with mechanical biasing means. This is a control method of a step motor E for moving an object C which is urged to return to the movable limit position D, and the energization of the step motor E is cut off to move the object C to the movable limit position D. A step F of rotating the step motor E until the object C moves from the position to the reference position J, and a step of counting the number of steps that the step motor E rotates during the rotating step F G, a deviation step number calculation step H for calculating a difference between the number of steps counted in the step G and the predetermined step number,
In the case where the number of shift steps calculated in the number of shift step calculation step H substantially corresponds to the number of steps corresponding to the number of phases of the step motor E, the number of steps at the time of restarting the energization is set to the predetermined number of steps. One-half of the number of shift steps calculated in the number-of-shift-steps calculation step H or 1 / of the number of phases.
And a step I of increasing or decreasing the number of steps corresponding to step 2.

[0011]

FIG. 2 (b) shows a state when the number of steps is compensated by moving to the reference position, that is, an initial check state. If the difference between the number of steps when the power is stopped and when the step motor is first started next is within ± 1 step, the number of steps matches the number of steps when the power is stopped by energizing in the same phase as when the power is stopped. On the other hand, if it is shifted by +3 or more, it rotates in a state shifted by +4 steps, and if it is shifted by -3 steps or more, it rotates in a state shifted by -4 steps. Then, from the number of steps and the number of steps when the object is moved to the reference position, the number of steps required to move the object from the movable limit position to the reference position is known (process G). If there is no deviation, the number of steps is a fixed number of steps, which is set as a predetermined number of steps . Therefore, from the difference between the number of steps required to move the object from the movable limit position to the reference position and the predetermined number of steps, it is determined whether there has been a shift of +4 steps, no shift, or a shift of -4 steps. You.

According to the present invention, when the shift is automatically canceled, that is, when the number of shift steps is zero,
Since the gap should be eliminated even when the power supply is cut off and the power supply is restarted because it has reached the movable limit position, the number of steps when the power supply is restarted is not corrected (step I).

On the other hand, as a result of the initial check at the time of starting, when it is found that the number of steps is shifted by 4 steps, the power supply is temporarily stopped because the vehicle has reached the movable limit position during operation, and then the power supply is restarted. There is a possibility that the control is shifted by four steps. Therefore, in this case, according to the present invention, the number of steps at the time of restart is corrected by １ ／ of the deviation (four steps in this case) (process I). That is, FIG.
(c) As shown in S1, the number of steps at the time of restart of energization is increased by two steps in this case. After the two-step increase correction, in the case of the motor shown in FIG. Therefore, +1 is added to the number of steps at the time of interruption.
Even if there is a deviation of up to +3 steps, the phase is attracted to the A 'phase after the resumption of the energization, and is counted from the position corrected and increased by 2 steps. As a result, the deviation is compensated, and the target number of steps (TARGET) can be controlled as shown in FIG.

As a result of the initial check shown in FIG.
If it is found that the steps are shifted by 4 steps, then the energization is restarted with the number of steps reduced by 2 steps from the number of steps at the time of interruption (step I). In this case, as shown in FIG. 2 (b), there is a tendency to shift by -2 to -6 steps.
Of these, those which tend to shift by -2 to -4 steps are eliminated by starting the energization from the number of steps reduced by 2 steps (see FIG. 2C).

In the above, for convenience of explanation, FIG.
Although the motor of (d) has been described by way of example, the operation of the present invention is not limited to this, as is clear from the embodiments described later. According to the present invention, if the deviation is very large, the deviation cannot be eliminated at once. However, in practice, by correcting half the number of steps of the deviation, the deviation can often be resolved at one time, and the present invention can sufficiently and effectively prevent the deviation. Further, even when the deviation is very large and cannot be corrected at once, the deviation is eliminated by repeating the correction according to the present invention. The moving range of the object according to the present invention may be restricted in both directions of the moving direction, or may be restricted only at one end. The reference position may be at the movable limit position or at an intermediate position. When setting the reference position as the movable limit position
Regulates the range of movement of an object in both directions of its movement,
Movable where the object is located when the step motor is de-energized
The movable limit position opposite to the limit position is set as the reference position.
You. The movement of the object includes various movements such as a linear movement and a rotational movement.

[0016]

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a system diagram of the traction control device.
Main throttle valve 6 and sub throttle valve 8
Is provided. The main throttle valve 6 is opened and closed in conjunction with an accelerator pedal (not shown), and opens and closes the intake pipe 4 in a manner according to the driver's driving intention. The sub-throttle valve 8 is controlled so as to close the intake pipe 4 when a slip occurs on the wheel and reduce the output of the engine 2 to suppress the slip. The sub-throttle valve 8 is opened and closed by a step motor 12, and the number of steps of the step motor 12 is controlled by a motor controller 18. Sub throttle valve 8
A reference position detection switch 10 that is turned on when the sub-throttle valve 8 is located at the reference position is installed near the sub-throttle valve 8, and this signal is input to the control device 18. The reference position is set at an idling opening position where the sub-throttle valve 8 is substantially closed.

In the figure, reference numeral 14 denotes an accelerator opening sensor;
Reference numeral 6 denotes a wheel speed sensor.
Is input to The control device 18 is constituted by a microcomputer system mainly including an I / O interface 20, a CPU 22, a ROM 24, a RAM 26, and a drive circuit 28 for a step motor. The control device 18 executes a process of calculating the target number of steps TARGET for rotating the sub-throttle valve 8 in order to eliminate the slip when a slip is detected, in addition to a process of correcting the number of steps described later. .

FIG. 4A schematically shows the step motor 12, which is a four-phase step motor having eight poles. As shown in FIG.
Since it is driven by -two-phase excitation, it has 16 steps per rotation.

FIG. 5 shows a processing procedure executed by the program stored in the ROM 24, which is executed when the engine 2 is started and when the set interrupt condition is satisfied after the start. . This interrupt is repeatedly executed at short time intervals. The control device 18
Executes, in addition to this process, the process of calculating the target step number TARGET of the sub-throttle valve 8 every moment as described above.

Now, when the engine is started, the flag F
LG1 and FLG2 are both zero. Then, when the engine is started and the process of FIG. 5 is first executed, step S4 is NO, step S6 is YES, and step S8 is executed. Here, MAXSTEP is substituted for the current step number STEP. Here MAX
In STEP, the number of steps measured from the reference position when the sub-throttle valve 8 is at the fully open position is predetermined. This corresponds to the number of steps indicated by MAX in FIG. 2 (b). If the number of steps at the time of energization cutoff matches the fully open position and the backlash is zero, M
When the energization is cut off when the number of steps matches AXSTEP, the sub-slot valve 8 is located at the fully open position (this corresponds to the movable limit position at this time), and a value at which no deviation occurs even when the energization is resumed. It has become. Next, 1 is set to the flag FLG2 (step S1).
0), prohibiting from being YES in the next step S6.

After the processing in step S10, step S12
Is executed. Here, XSTEP is a variable for determining the energized phase, and SOFFSET is the excitation pattern number at the previous reference position. Here, the excitation pattern number is one of 0 to 7 as shown in FIG. If the zero excitation pattern corresponds to the reference position (that is, the number of steps is zero), the excitation pattern should be one when the number of steps becomes one, and two when the number of steps becomes two. That is, if the energizing phase is switched in accordance with the lower three bits of the number obtained by adding the excitation pattern number to the number of steps, the excitation shown in FIG. 4B is executed. Here, it is not always clear whether the 0 excitation pattern corresponds to the 7 excitation pattern at the reference position, and this is adjusted by SOFFSET. SOFFSET is stored in the nonvolatile RAM together with MAXSTEP, and is not deleted even when the engine key is turned off.

After XSTEP is calculated in this way, step S14 is executed, and excitation is performed according to the determined excitation pattern. This excitation pattern is an excitation pattern when the sub-throttle valve 8 returns to the fully open position and the excitation stops at the end of the previous operation.

When the processing of FIG. 5 is executed at the next interrupt,
This time, step S6 becomes no. If it is found in step S18 that the shutter has not been closed to the reference position, one step is subtracted from the current step number STEP in step S20. Next, steps S12 and S14 are executed. As a result, the excitation pattern shifts in the one-step closing direction, and the stepping motor 12 rotates one step in the closing direction. As described above, when the step motor 12 is closed and reaches the reference position, the step S18 becomes YES.

Then, at this time, in step S22, the STE
It is compared whether P is zero. Here, STEP becomes zero when the step motor 12 actually rotates to the number of MAX STEPs as a result of the execution of the first step S14, as indicated by the line L in FIG. 2B. At this time, the MAXSTE at the time of the next startup determined in step S30
Step S30 is skipped because there is no need to modify P. Then, in step S36, the flag FLG1 indicating the completion of the initial check is set to 1 to prepare for the next execution.

If NO in step S22, it is then compared in step S24 whether or not STEP is 8. Here, FIG.
As shown in the K line of (b), if the step motor 12 corresponds to the number of steps smaller than MAXSTEP by eight steps when step S14 is first executed, the result of step S24 is YES (however, FIG. 2). In this embodiment, there are four steps in FIG. 2 because the excitation method is different.) That is, the stepping motor 12 rotates counterclockwise by 4 to 1 until the engine is temporarily stopped and restarted.
When there is a two-step shift, step S24 is YES. Therefore, in this case, MAXSTEP is reduced by four steps. In this way, during the start of the engine, the sub-throttle valve 8 returns to the fully open position, and when the power is cut off and the power is turned on again, the number of steps indicated by -4 in FIG. A measure is taken to start energization from the energizing phase (the phase energizing the A ′ phase). As a result, even if the control is performed in a state of being shifted by -4 steps to -8 steps during the energization cutoff, and if the present invention is not used, a shift of -8 steps is eliminated.

The same processing is performed in steps S26 and S3 in FIG.
Also achieved by 0. In this case, the stepping motor is shifted by +4 to +12 steps from the stop of the engine 2 to the restart, and as a result of the execution of the first step S14, FIG.
As shown by the line M in (b), this corresponds to the case where the rotation is performed by 8 steps larger than MAXSTEP. In this case, during the operation of the engine, when the power supply is resumed, a process for eliminating the deviation is performed by supplying power from a position shifted by +4 steps (that is, A ′ phase conduction). Step S28 executes a process of correcting a small error that does not reach half of the number of steps per rotation of the motor. After the end of this process, the excitation pattern number at the reference position is updated in step S32,
Store again as OFFSET. And step S3
In step 4, the number of steps at the reference position is set to zero. The flag FLG1 is set to 1 in step S36 because the initial check is completed as described above.

Since the engine running flag FLG1 is kept set to 1, normal traction control is performed in step S40. Here, when the target number of steps reaches the fully open position, the power supply to the step motor is cut off, but the processing of FIG.
Remains at 1. Therefore, when the traction control is required and the energization is restarted, the energization is restarted from MAXSTEP corrected in step S28 or S30. As described above, the number of steps does not shift as described above.

In this embodiment, steps S24 and S24
Compare with ± 8 at 26. This is because this motor has 16 steps per revolution. However, in practice, the error may overlap with the number of steps obtained by dividing the number of 16 steps by 2. Therefore, the determination values in steps S24 and S26 may be corrected in the range of ± 8 to ± 4. The term "substantially" used in the step I of the present invention means that this overlap of errors is taken into account. This makes it possible to make a determination in consideration of an error. Further, in this embodiment, it is assumed that a deviation of ± 12 steps or more does not occur, but if a deviation of ± 12 steps or more can occur, step S24 is performed.
In S26, it may be compared with +8 or more or -8 or less. +8 or more or -8 in steps S24 and S26
When comparing with the following, for example, +16 step shift
In the event of failure, step S of the first initial check
By the processing of 30, the +8 step, which is 1/2 of the +16 step,
Gap is corrected, and the second initial check
Due to the processing in step S30, +4 of 1/2 of the +8 step
Step deviations are corrected. And the third Initi
Correction of misalignment by processing of step S28
Is completed. In this way, the deviation is very large and
Even if it cannot be corrected by the initial check,
The gap is eliminated by repeating the check
You.

In the above embodiment, an example in which the present invention is applied to the control of the step motor 12 for opening and closing the sub-throttle valve 8 has been described. However, the present invention is naturally applicable to a system in which the power supply to the step motor is cut off while the main throttle valve is in the idle position, and the main throttle valve is opened and closed by the step motor. In addition, there is no particular restriction on the object moved by the step motor.

[0030]

According to the present invention, a system is provided in which the power supply to the step motor is cut off while the object is at the movable limit position, and the step motor is again energized when it becomes necessary to move the object from the movable limit position. It is most suitable for the control method of the step motor in the above. According to this method, the number of steps at the time of re-energization and hence the excitation phase are controlled in accordance with the tendency of the deviation occurring during the interruption of the energization, so that the deviation occurring during the interruption of the energization is eliminated. As a result, the probability of occurrence of a deviation before the initial check is significantly reduced, and the number of steps is adjusted to an accurate number immediately after re-energization.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the concept of the present invention.

FIG. 2 is a diagram schematically showing the operation of the present invention in comparison with the conventional operation.

FIG. 3 is a system diagram of an embodiment.

FIG. 4 is a diagram showing a step motor and an excitation pattern;

FIG. 5 is a processing procedure diagram of the embodiment.

[Explanation of symbols]

 E Step motor D Movable limit position F Rotation process G Counting process H Step number calculation step I Step number correction step when power is restarted

Continuation of the front page (56) References JP-A-58-6097 (JP, A) JP-A-3-57846 (JP, A) JP-A-61-244852 (JP, A) JP-A-63-157697 (JP) , A) JP-A-4-71396 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 8/00-8/38 G05D 3/10-3/12 F02D 41/00 -41/40

Claims (1)

(57) [Claims] 1. A stepping motor control method for moving an object which is movable within a predetermined range and is urged by a mechanical urging means so as to return to a movable limit position. Turning off the step motor until the object moves from the state where the object is located at the movable limit position to the reference position, and the step motor rotates during the turning step. Counting the number of steps performed in the step; calculating the difference between the number of steps counted in the step and the predetermined number of steps; calculating the number of steps; and calculating the number of steps in the number of steps calculated in the number of steps. If the number of steps substantially corresponds to the number of phases of the motor,
Step of increasing or decreasing the number of steps corresponding to 1/2 of the number of shift steps or の of the number of phases calculated in the shift step number calculation step to the predetermined number of steps. Method.