JPH067758B2 - Stepping motor closed loop drive controller - Google Patents

Description

TECHNICAL FIELD The present invention relates to a closed loop drive control device for a stepping motor.

b. Prior Art FIG. 4 shows a conventionally known stepping motor drive control device, in which 1 is a stepping motor, 2 is a rotor of the stepping motor 1, and 3 is coaxial with one end of the rotor 2. An encoder (position detector) fixed to 4 is a light source, 5 is a photoelectric element, 6 is a control circuit, A ₁ , A ₂ ,
B ₁ and B ₂ are windings for each phase of the motor. Encoder 3 mentioned above
For example, 50 circular slits 7 are formed at an outer peripheral edge of the circular slit 7 at intervals of 7.2 °, and four pairs of light sources 4 and photoelectric elements 5 are arranged to face each other on both sides of the circular slit 7. Then, every time the rotor 2 rotates by 1.8 °, for example, high-level signals are sequentially output from the four photoelectric elements 5.

Further, the control circuit 6 described above logically determines the winding current and a logic circuit that creates a predetermined excitation state based on the rotor position pulse signal from the photoelectric element 5 and the stepping motor rotation command pulse signal from the command circuit (not shown). ON based on circuit output
It is composed of a power switching circuit which is turned off, and the control circuit 6 selectively excites the windings A ₁ , A ₂ , B ₁ and B ₂ in a phase excitation sequence as shown in the table below. It is like this. That is, the phase excitation sequence most suitable for the acceleration, deceleration or constant speed operation of the stepping motor 1 is selected by the rotor position pulse signal and the stepping motor rotation command pulse signal, whereby the stepping motor 1 is rotationally driven in a predetermined mode. It is supposed to be done.

Note that FIG. 5 shows the relationship between the excitation stable point and the rotor position in the conventional example, and FIG. 6 shows the connection state of the windings A ₁ , A ₂ , B ₁ , and B ₂ .

c. Problems to be Solved by the Invention However, in the conventional stepping motor drive control device as described above, when an unexpected external force is applied to the rotor 2, the excitation stable point of the final positioning of the rotor 2 shifts. was there. The circumstances will be described below.

Here, consider a state in which the stepping motor 1 has completed positioning and is waiting for the next stepping motor rotation command pulse signal. In this case, at the end of positioning,
It is assumed that the A ₁ B ₁ phase (see Fig. 5) is excited.

The rotor position at this time is P ₁ , and the rotor 2 of the stepping motor 1 tries to hold this position P ₁ . Under this condition, the rotor 2 is driven in the CW direction (clockwise) by the external force.
When the rotor is rotated to A, the A ₁ B ₁ phase is excited until just before the position P ₂ by the phase excitation sequence in the above table, so that the restoring force acts on the rotor 2 to return to the position P ₁ . However, when the rotor 1 passes the position P ₁ and is rotated to the position P ₂ , the phase excitation sequence is switched to excite the A ₂ B ₁ phase, and as a result, the position P ₂ becomes a new excitation stable point. Therefore, the excitation stable point of the final positioning of the rotor 2 is displaced by the external force applied to the rotor.

As described above, in the conventional device, when the rotor 2 of the stepping motor 1 is rotated by an external force, the phase excitation sequence is switched to the next state when the rotation angle becomes ± 0.5 steps or more. Therefore, if the rotor 2 at the final excitation stable point is rotated ± 0.5 steps or more by an external force, the rotor 2 shifts to another new excitation stable point, and even if the external force is removed, the rotor 2 returns to the original final excitation stable point. There was a problem that it did not return to the (predetermined position).

The present invention has been made to solve such a problem, and an object thereof is to obtain a positional deviation from the excitation stable point of less than ± 2 steps even when rotated by an external rotor force at the excitation stable point. In the region (1), it is an object of the present invention to provide a closed loop drive control device for a stepping motor that can automatically return to the original positioning stable point when the external force disappears.

d. Means for Solving the Problems In order to solve the above-mentioned problems, in the present invention, a position detector for detecting the rotational position of the rotor of the stepping motor,
A phase excitation sequencer that switches the phase excitation sequence based on the rotor position pulse signal output from the detection position detector, and the rotor position signal to the phase excitation sequencer based on the rotor position pulse signal and the stepping motor rotation command pulse signal And a shutoff circuit for shutting off the supply of each of the rotors, and by operating the shutoff circuit in a period from when the rotor is stopped at a predetermined position until a new stepping motor rotation command pulse signal is input, The phase excitation sequence cannot be switched when the rotor is rotated within ± 2 steps.

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a configuration diagram of a closed loop drive control device for a stepping motor according to the present invention. In FIG. 1, 10 is a stepping motor, 11 is a rotor, 12 is a position detector for detecting the rotational position of the rotor 11, and 13 is a stepping motor 10.
Is a phase excitation sequencer for rotationally driving by switching the phase excitation state. In this phase excitation sequencer 13, a rotor position pulse signal (feedback pulse) output from the position detector 12 is transmitted via a latch circuit 14. In addition to being supplied, a start / stop command signal is supplied from a command circuit (not shown).

Further, 15 is a pulse counter that counts the difference between the stepping motor rotation command pulse from the command circuit (not shown) and the feedback pulse from the position detector 12, and 16 is a residual pulse signal known from the pulse counter 15 and known. A zero hold circuit for stopping the rotor 11 at the excitation stable point of the final positioning based on the stepping motor rotation command pulse signal of
The final position hold signal output from 16 is supplied to the above-mentioned latch circuit 14. Therefore, the pulse counter 15, the zero hold circuit 16 and the latch circuit 14 constitute the cutoff circuit 17, and when the stepping motor 10 shifts to the final positioning, the zero hold circuit 16 transfers the final signal to the latch circuit 14. A position hold signal is supplied, whereby the rotor position pulse signal at that time is latched by the latch circuit 14. In addition, during the period from the stationary state of the rotor 11 to the input of a new stepping motor rotation command pulse signal, for example, even if the rotor 11 is displaced by an external force, the displacement amount is ± 2.
The zero position hold circuit 16 outputs the final position hold signal in order to maintain the original phase excitation sequence in the region less than the step. When the rotor 11 is rotated ± 2 steps or more, a cancel signal is output from the pulse counter 15 to cancel the final position hold signal from the zero hold circuit 16 to the latch circuit 14, and the latch circuit 14 is unlatched. It can be switched to the state.

FIG. 2 is a diagram showing the relationship between the excitation stable point and the rotor position pulse signal output from the position detector 12 when the rotor 11 of the stepping motor 10 is rotating in the CW direction (clockwise direction). is there. In FIG. 2, A, B ,,
Indicates the winding of the stepping motor, * indicates the stable excitation point of the rotor 11, S0 to S7 indicate the switching points of the phase excitation sequence (switching points), and channel A and channel B are position detectors. These are the 12 A channel and B channel output signals.

FIG. 3 shows the stiffness characteristics of the stepping motor 10. The horizontal axis indicates the phase excitation phase difference (angle) with the rotor 11 at a certain excitation stable point as a reference, and the vertical axis indicates the torque generated at that time. It is shown, and is usually approximated by a sine wave. As is clear from this stiffness characteristic, assuming that the reference stable point of the rotor 11 is the current phase, the rotor 11 is rotated in the CW direction by one step ahead, that is, when the phase is excited, with positive maximum torque. On the contrary, one step before, that is, when the B phase is excited, the rotor 11 is rotated in the CCW direction (counterclockwise direction) with the maximum negative torque.

Next, the operation of the closed loop drive controller for the stepping motor of this embodiment will be described.

First, when the stepping motor rotation command pulse signal is supplied to the pulse counter 15, the count number of the pulse counter 15 is set to a predetermined value. Along with this, a start command signal is supplied to the phase excitation sequencer 13, a predetermined phase excitation signal is supplied to the stepping motor 10, and the rotor 11 is rotationally driven. A rotor position pulse signal is output from the position detector 12 in accordance with the rotation of the rotor 11, and the count number of the pulse counter 15 is subtracted. At the same time, the rotor position pulse signal is fed back to the phase excitation sequencer 13 as rotor rotation position information without being latched by the latch circuit 14. Then, as the rotation of the rotor 11 progresses, the count number of the pulse counter 15 becomes zero. After that, a new stepping motor rotation command pulse signal is supplied to the pulse counter 15, and the count number is set to a predetermined value. Along with this, the phase excitation sequencer 13 is switched to the next phase excitation sequence, and the step rotation of the rotor 11 is continued.

Here, consider a case where the rotation command pulse is input to the pulse counter 15 to rotate the rotor 11, the stepping motor 10 is in the final positioning state, and the rotor 11 stops at the excitation stable point of the phase shown in FIG. At this time, since the count number of the pulse counter 15 becomes zero, the predetermined final position hold signal is supplied from the zero hold circuit 16 to the latch circuit 14. Along with this, the rotor position pulse signal output from the position detector 12 is latched by the latch circuit 14 until a new stepping rotation command pulse signal is input to the pulse counter 15 after the count number of the pulse counter 15 becomes zero.
Latched in. Then, until a new stepping motor rotation command pulse signal is input to the pulse counter 15, the cutoff circuit 17 functions to maintain the original excitation sequence within the range where the displacement of the rotor 11 is less than ± 2 steps, Therefore, the phase excitation sequence cannot be switched by rotation within ± 2 steps due to the external force of the rotor 11. As a result, the stepping motor 10 always exerts a restoring force to automatically return to the excitation stable point of the final positioning when the displacement of the rotor 11 is less than ± 2 steps.

If an external force is applied to the rotor 11 under such a condition and the rotor 11 is rotated in the CW direction, for example, a new rotor position pulse signal (feedback pulse) is first output from the position detector 12 in the pulse counter 15 and the latch. It is supplied to the circuit 14. At this time, if the latch circuit 14 is unlatched, as new rotor position information is input to the phase excitation sequencer 13, the next excitation sequence is switched and the next excitation stable point is excited. However, in the case of this example, since the latch circuit 14 is in the latch state at this time, the phase excitation sequence cannot be switched and the phase excitation sequencer 13 excites the original excitation stable point regardless of the rotor position pulse signal. Function to continue.
As a result, as is clear from the stiffness characteristic of FIG. 3, if the displacement of the rotor 11 due to the external force is less than ± 2 steps, the rotor 11 is not rotated until a new rotation command pulse is input.
Always generates a restoring force in the direction of returning to the original excitation stable point. Therefore, when the displacement of the rotor 11 due to the external force is less than ± 2 steps, if the external force disappears, the rotor 11 will automatically return to its original stable point and be positioned according to the stiffness characteristics described above. . In addition, zero
When a new stepping motor rotation command pulse signal is supplied to the hold circuit 16, the circuit 16 is reset, the latch circuit 14 is returned to the unlatched state, and the rotor 11 is step-driven again.

The above-mentioned phenomenon occurs even when the rotor 11 is rotated in the CCW direction by an external force, and the same action as in the CW direction occurs. As a result, if the displacement of the rotor 11 due to the external force is less than ± 2 steps, the external force disappears. It is possible to return to the original stable point.

The positional deviation of the rotor 11 and the restoring force thereof due to the external force have been described above. Next, the positional deviation of the rotor 11 due to the vibration of the stepping motor itself and its restoring action will be described.

Generally, during final positioning, the rotor 11 vibrates about its target position due to its inertial energy.

Here, assuming that the rotor 11 of the stepping motor 10 is rotating in the CW direction by the rotation command pulse signal and is moving toward the final positioning point (phase excitation) indicated by a mark in FIG. 2, the rotor 11 is stationary at the mark point. However, because of its inertial energy, the rotor 11 goes too far past the mark point. If the overshoot amount is within the range of less than 2 steps, the phase excitation sequencer 13 continues to excite the phase, so that the rotor 11 immediately decreases the speed in the CW direction when it receives the torque in the CCW direction, and finally the marking point from the CCW direction. Head to.

At this point, if the inertial energy of the rotor 11 is sufficiently small, it stops at the mark point as it is, but if the inertial energy is still large, it passes through the mark point and CC
Continue rotating in the W direction. Also in this case, if the displacement of the rotor 11 in the CCW direction is less than two steps, the phase excitation is continued, so that the rotor 11 receives the torque in the CW direction again and shifts to the mark point.

In this way, the rotor 11 moves in the CW direction and CC
While repeating the vibration with the W direction several times, the inertial energy is gradually released and finally stopped at the mark point.

Note that the positioning accuracy of the rotor 11 in this case is determined by the positioning accuracy of the stepping motor 10 itself, regardless of the stepping motor drive control circuit, because any phase excitation winding of the stepping motor 10 is DC-excited. Since the value is generally within ± 5 minutes, extremely accurate positioning can be performed.

e. Effects of the Invention As described above, according to the present invention, in the period from when the rotor is rotated and stopped at a predetermined position until a new stepping motor rotation command pulse signal is input, the rotor is ± 2.
Since the phase excitation sequence cannot be switched during rotation within a step, even if the rotor at the stable excitation point is rotated by an external force after the final positioning is completed, the positional deviation (displacement) from the stable excitation point will occur. In the region of less than ± 2 steps, the rotor can be automatically returned to the original positioning stable point by the stiffness characteristic of the stepping motor as the external force disappears.
Further, even if vibration occurs due to the inertial energy of the rotor during final positioning of the rotor, if the circumference of the vibration is less than ± 2 steps, the rotor can be automatically stopped at a predetermined final positioning position. In addition, while having such a practical effect, there is an advantage that the device configuration is simple and inexpensive.

Further, since the positioning accuracy at the time of final positioning is determined by the positioning accuracy of the stepping motor itself without depending on the stepping motor drive control circuit, the rotor can be positioned with extremely high accuracy of ± 5 minutes. .

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a closed loop drive control device for a stepping motor, and FIG. 2 is an excitation stable point and position detection of the stepping motor. 3 is a time chart showing the relationship with the output signal of the device, FIG. 3 is a stiffness characteristic diagram of the stepping motor, FIGS. 4 to 6 are for explaining a conventional example, and FIG. FIG. 5 is a schematic configuration diagram of a closed loop drive control device, FIG. 5 is a diagram showing a relationship between an excitation stable point of a stepping motor and a rotor position, and FIG. 6 is a wiring diagram of windings of the stepping motor. 10 ... Stepping motor, 11 ... Rotor, 12 ... Position detector, 13 ... Phase excitation sequencer, 14 ... Latch circuit, 15 ... Pulse counter, 16 ... Zero hold circuit, 17 ... Break circuit.

Claims (2)

[Claims] 1. A position detector for detecting a rotational position of a rotor of a stepping motor, a phase excitation sequencer for switching a phase excitation sequence based on a rotor position pulse signal output from the position detector, and the rotor position pulse signal. And a shutoff circuit for shutting off the supply of the rotor position signal to the phase excitation sequencer based on a stepping motor rotation command pulse signal, and a new stepping motor rotation command pulse signal after the rotor is stopped at a predetermined position. In the period until the input of the
A closed loop drive control device for a stepping motor, characterized in that the phase excitation sequence is not switched at a rotation of less than one step. 2. A pulse counter for inputting the stepping motor rotation command pulse signal and the rotor position pulse signal to output a residual signal, and a final circuit for the shutoff circuit when the count number of the pulse counter becomes zero. A zero hold circuit that outputs a position hold signal, and a latch circuit that latches the rotor position pulse signal based on the final position hold signal and shuts off the supply of the rotor position pulse signal to the phase excitation sequencer. A closed loop drive control device for a stepping motor according to claim (1).