JPH0614799B2 - Stepping motor stop control system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a stepping motor stop control system, and more particularly to a stepping motor which can be stopped at a predetermined position accurately at high speed.

Conventional technology and problems Stepping motors are widely used, for example, as a drive for a print wheel of a serial printer or a driving force source for a print head carrier, but it is necessary to stop the motor accurately at a predetermined position. As a method of stopping the stepping motor at the target position accurately and quickly, reverse-phase excitation of the stepping motor is used to apply a rapid brake near the stop position, to give a friction load to the stepping motor, Three methods are mainly used: one that has a protrusion and one that has a groove on the hammer pin to forcefully hold the type in the proper position.

In this method, as shown in FIG. 1, for example, a 4-phase stepping motor is excited by 2-phase excitation (or 1-2-phase excitation).
When the drive is controlled by ... DA-AB-BC-CD-DA
When excited with, for example, D near the stop position
When A should normally be excited after A, the CD phase excitation is performed in reverse to generate a braking force to suppress hunting because the inertia of the print wheel is small and to stop it. In this case, if the stepping motor is manufactured so as to have the characteristics shown by the solid line in FIG. 1, it can be stopped at a predetermined position as ideal. However, the speed and position of the reverse-phase excitation change due to variations in inertia and temperature fluctuations during manufacturing of this motor, and fluctuations in the power supply voltage. Therefore, the characteristics are shown in the dotted and dotted lines in Fig. 1. There is a problem that the hunting cannot be pressed down as shown. Therefore, there is a drawback that an overshoot is likely to occur when driving a load having a small friction such as a stepping motor for driving a print wheel in a printer.

Further, the above-mentioned method is constructed, for example, as shown in FIG. 2, in which a detent 1-B is provided on the rotary shaft of the stepping motor 1 for driving the print wheel 1-A and a frictional force is constantly applied to the detent 1-B. Therefore, not only is a motor with a large force sufficient to drive both the detent inseparable force, which is the frictional force, and the load of the print wheel 1-A during operation, but the frictional force also decreases if this detent member wears, Further, if oil adheres to the Danant member, the frictional force changes significantly and normal stop operation cannot be performed. And the above has the drawback that the type is only for the manufacturer and general type cannot be used.

OBJECT OF THE INVENTION The object of the present invention is to solve such a problem by using two-phase excitation up to the vicinity of the stop position in order to accurately stop at a predetermined position without using a special friction member. And 1-2 phase excitation to move efficiently, and control the exciting current near the stop position to make finer stepped phases than the phase unique to the stepping motor, and stop at a fine step angle. The present invention provides a stepping motor stop control system that is designed to do so.

To achieve this object, in a stepping motor stop control system of the present invention, a main control unit for controlling driving and stopping operations of a stepping motor, time information for controlling the stepping motor, control information, etc. Is provided with a control information storage unit that stores the phase, a phase switching control unit that switches the excitation phase of the stepping motor, a current value control unit that controls the magnitude of the excitation current of the stepping motor, and a timer that operates according to the phase switching time. Then, in the stop control of the stepping motor, the main control unit first obtains the exciting current of the exciting phase based on the phase exciting method that produces a large step angle, and the phase switching control unit and the current value control unit And the timer is operated according to the time information, and each time the timer times out, the next excitation phase and its excitation Flow, control the phase switching control unit and the current value control unit by these, each time the time required to decelerate to the state of the overshoot of the movement amount less than the step angle until then, By sequentially switching to the excitation phase and excitation current control based on the phase excitation method that produces a smaller step angle, the stop control is initially performed at a large step angle, and the step angle is gradually reduced to a stop control. And

Main Points of the Invention Before describing the present invention in detail based on an embodiment, the main points of the present invention will be outlined with reference to FIGS. 3 to 6 in the case of using a 4-phase stepping motor.

In the present invention, two-phase excitation and 1-2-phase excitation are used to efficiently move to the vicinity of the stop position, and the stop is controlled by a fine step angle from the vicinity of the stop position to the stop.

This will be described with an example in which the fine phase switching control is performed before the four characters before the stop position.

As shown in FIG. 3, the stepping motor is started at time T ₀ and the phase is advanced by two-phase excitation until time T ₁ . Then, at time T _{1, the} braking force is applied. The step angle 2 to time T ₃ characters levels reaches 1-2 phase excitation when reaching the example 4 characters before the stop position at time T _2, is controlled so that half of the time of two-phase excitation , The step angle is controlled with a resolution of 1/4 from time T ₃ to time T ₄ when the character reaches a position before one character, and the step angle is controlled with a resolution of 1/2 from time T ₄ to the stop phase. is there.

That is, by two-phase excitation, for example, AB phase-BC phase-CD
When the two-phase excitation is performed in sequence, the step angle of the stepping motor is vector AB → vector B as shown in FIG.
One step of 90 degrees with C → vector CD. However, after two-phase excitation with AB phase, one-phase excitation with B phase is performed,
Next, in the case of 1-2 phase excitation in which two-phase excitation of BC phase is performed, the step angle becomes 45 °, which is 1/2 the step angle in the case of two-phase excitation. Further, if the A-phase current A'following the AB-phase excitation is A '= A _COS 67.5 ° = 0.38A, the step angle becomes 22.5 ° as shown by the vector A'B and the two-phase excitation is performed. It can be set to 1/4 step angle. By further controlling the current in this way, 1/8 step angle, 1/16 step angle, and so on, can be approached to steps where overshoot does not occur.

In this way, if the step angles are successively added, as shown in FIG. 5, the braking force can be gradually reduced and the vehicle can accurately stop at the stop position.

By doing so, the stepping device can be smoothly brought to the stop position smoothly as shown in FIG. If it is stopped at phase S ₁ in FIG. 6, the overshoot will be 1 step or more, but if stopped at phase S ₂ of the next step, the overshoot will be 1 step or less → 1/2 step step braking. To be able to The While connexion switched to 1/2 step controlled by 1-2 phase control in this period T _2. When the stop control is performed in the phase S ₃ in FIG. 6, the overshoot becomes a state where 1/2 step → 1/4 step step braking can be performed, so the control is switched to the 1/4 step control at time T ₃ . After that, when the stop control is performed at the phase S ₄ , the overshoot becomes a state where 1/4 step or less → 1/8 step step braking can be performed, so the control is switched to the 1/8 step control at time T ₄ . Then, when the stop control is performed in the phase S ₅ , the overshoot is controlled so as to be within 1/8 step. Therefore, the control is switched to the stop phase in the next phase S ₆ , that is, at the SP point.
At this time, if the amount of overshoot is switched to the expected stop phase, it is possible to stop at the target position with almost no error.

Embodiment of the Invention One embodiment of the present invention will be described based on FIG. 7 and with reference to other drawings as necessary.

In the figure, 1 is a stepping motor, 2 is a CPU, 3 is a phase switching time measuring unit, 4 is a control program and time table storage unit, 5 is a current value control unit, 6 is a phase switching control unit, and 7 and 8 are digital. -Analog converter (hereinafter referred to as DA converter), 9 and 10 are comparators, 11 is a common current limiting driver for A phase and C phase, 12 is a common current limiting driver for B phase and D phase, 13 , 14 are protection diodes, 15 is an I / O port for inputting / outputting signals, DA to DD are drivers, for example, phase switching sections of A phase to D phase constituted by switching transistors, I ₁ , I ₂ is a current detector.

The phase switching time measuring unit (hereinafter referred to as PTM) 3 is a programmable timer module, and the CPU 2 is read from a control program and time table storage unit (hereinafter referred to as ROM) 4 configured by a read-only memory. Time is set, and when this set time has elapsed, this time-up information is sent to the CPU.
2 is sent as an interrupt signal IRQ.

The ROM 4 stores a control program for controlling the CPU 2 and also stores a time table in which time information for controlling the stepping motor 1 is entered. This time table has a stepping motor 1
It contains the phase switching time information when starting and the phase switching time information when stopping.

The current value control unit 5 controls the current value flowing in the A-phase to the D-phase during the operation of starting and stopping the stepping motor 1, and the current value and the current value adjustment time are CP.
It is sent from U2.

The phase switching control unit 6 energizes and controls the A-phase to D-phase exciting windings of the stepping motor 1. When the driver DA is turned on, a current flows through the A-phase exciting windings, and similarly the driver is driven. When DB to DD are turned on, a current flows through the B-phase to D-phase excitation windings. The magnitude of this exciting current is checked by the current detectors I ₁ and I ₂ .

The current limiting driver 11 commonly controls the magnitudes of the currents flowing in the A-phase and C-phase exciting windings, and the control signal is output from the comparator 9. The current limiting driver 12 commonly controls the current values flowing in the B-phase and D-phase excitation windings, and the control signal is output from the comparator 10.

Next, the operation of the present invention will be described with reference to FIG.

(1) When the CPU 2 receives the type selection information via the I / O port 15, the CPU 2 reads the first start control time for starting the stepping motor 1 from the time table in the ROM 4 and writes it to the PTM 3. At the same time, the phase to be excited is selected based on the stopped state of the stepping motor 1 at that time, and the phase excitation signal is set to the phase switching control unit 6 to selectively turn on the drivers DA to DD, and the step The ping motor 1 is excited in two phases to advance the phase advance by one step. In this case, for example, when one equilibrium point is reached when the AB phase is excited, the A phase is switched to the C phase and then to the BC phase excitation.

(2) The PTM 3 transmits the time-up information as an interrupt signal IRQ to the CPU 2 when the time written in it has elapsed.

(3) The CPU 2 receives the interrupt signal IRQ,
The time required for the next step is read from the time table in the ROM 4 and written in the PTM 3, and the next phase excitation signal is set in the phase switching control unit 6 to advance the phase excitation of the stepping motor 1 one step.

(4) The above (2) and (3) are sequentially repeated to perform two-layer excitation such as AB-BC-CD-DA-AB ...
As a result, the stepping motor 11 is advanced step by step and added, and the stepping motor 1 is fed stepwise at high speed. Then, the back to the stop step calculated from the type selection information is added up to the position where braking is applied.

(5) Next, when deceleration braking should be started, when the time T in Fig. 3 is reached, the braking is started, but the braking at this time is decelerated by two-phase excitation, and this control is stopped at that step. This deceleration is continued until there is no one-step overshoot. The control method at this time is (2) and (3) above.
Similarly, the control time is read from the ROM 4 and monitored by the PTM 3, and the phase switching control unit 6 selectively controls the drivers DA to DD according to the instruction of the CPU 2 for the phase excitation.

(6) Then, when the CPU moves to the step (S _{2 in} FIG. 6) where the overshoot for one step is eliminated, the CPU 2
Controls the phase switching control unit 6 so that the phase switching step becomes 1/2 step. Thereby, for example, AB-B-BC-
1-2 phase excitation such as C-CD ... is performed and 1/2 step operation is performed. Then, the deceleration by this is performed up to step S _{3 at} which the overshoot for 1/2 step does not occur.

(7) When the CPU moves to the step S ₃ where the overshoot for 1/2 step has been eliminated, the CPU 2 controls the phase switching control unit 6 to the 1/4 step mode this time. In the 1/4 step mode, the current value control unit 5 is controlled to selectively control the current limiting driver 11-12, and the excitation current of the A phase is A'as shown by the vector A'B in FIG. That is, it can be performed by performing control such that the normal level is suppressed to about 0.38. Then, the deceleration control in the 1/4 step mode is performed until step S ₄ at which the overshoot for the 1/4 step does not occur.

(8) In this way, control is then performed in the 1/2 step mode. Then, the phase step switching time is adjusted so that the 1/3 step overshoot is at the predetermined position of the stop phase, and the stop phase is set when the peak position of the overshoot is just at the stable position of the stop phase. Switch and stop braking.

In the above embodiment, the example of stopping in the 1/8 step mode has been described, but it is of course possible to drive up to 1/16 step or 1/32 step, and the accuracy is further improved by doing so. . Then, the four-phase stepping motor has been described, but of course the present invention is not limited to this, and a six-phase or another type can be similarly applied.

EFFECTS OF THE INVENTION According to the present invention, the operation control of the stepping motor is performed by switching the excitation phase and the excitation time based on the phase switching time information set in the time table storage unit, so that the stepping motor is stopped. It is possible to stop and reach the target position quickly, accurately, with less hunting.

Therefore, as in the case of the motor drive circuit disclosed in Japanese Patent Laid-Open No. 57-119695, for example, when the exciting current is switched when the stepping motor is temporarily stopped, the stepping motor is temporarily operated. Since the present invention does not need to be restarted in a stopped state, the present invention eliminates the need for restarting the motor, has a small range of speed fluctuations, and, because the method of change is performed continuously, the generation of sounds due to discontinuous speed fluctuations is also possible. Absent. Moreover, when the motor is moved to the next step, its inertia can be utilized, and the load can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a conventional anti-phase excitation control system for a stepping motor, FIG. 2 is an explanatory diagram of a stepping motor having a detent, and FIGS. 3 to 6 are explanations of the operating principle of the present invention.
FIG. 7 is a block diagram of an embodiment of the present invention. In the figure, 1 is a stepping motor, 2 is a CPU, 3 is a phase switching time measuring unit, 4 is a control program and time table storage unit, 5 is a current value control unit, 6 is a phase switching control unit, and 7 and 8 are digital.・ Analog converter, 9 and 10 are comparators, 11
Is a common current limiting driver for A phase and C phase, 12 is a common current limiting driver for B phase and D phase, 13 and 14 are protection diodes, 15 is an I / O port for inputting / outputting signals, DA Denoted by DD is a driver, for example, a phase switching unit of A phase through D phase which is composed of switching transistors, I
₁ and I ₂ are current detectors.

Claims (1)

[Claims] 1. A main control unit (2) for controlling driving and stopping operations of a stepping motor, a control information storage unit (4) for storing time information, control information and the like for controlling the stepping motor, It is provided with a phase switching control unit (6) for switching the excitation phase of the motor, a current value control unit (5) for controlling the magnitude of the excitation current of the stepping motor, and a timer (3) that operates according to the phase switching time. In the stop control of the stepping motor, the main control unit (2) first obtains an excitation phase and its excitation current based on a phase excitation method that produces a large step angle, and the phase switching control unit (6) And controlling the current value control unit (5) and operating the timer (3) according to the time information, and each time the timer (3) times out, the next excitation phase and its excitation current. The phase switching control unit (6) and the current value control unit (5) are controlled by these values, and the time required to decelerate to the state where the movement amount overshoots the step angle up to that point Each time, by sequentially switching to the excitation phase and excitation current control based on the phase excitation method that produces a smaller step angle, initially,
A stepping motor stop control method characterized by performing stop control with a large step angle and gradually reducing the step angle.