JPS6111080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positioning method using a stepping motor.

When a stepping motor is connected to an object to be controlled with a friction system, and one pulse is applied to it to see where it stops, in many cases it rarely stops at the same stopping position as the previous one within one step angle. In an apparatus that uses a stepping motor to move a controlled object, this error appears as a variation in the initial position, so it is prevented as follows.

Figure 1 shows a schematic configuration of a conventional drive mechanism using a stepping motor, where 1 indicates an object to be controlled;
2 is a power transmission mechanism that moves the controlled object 1 in the target direction; 3a and 3b are pulleys that drive the power transmission mechanism 2; 4 is a stepping motor that rotationally drives the pulley 3b; C ₁ , C ₂ . . . ...Cn are the first, second, ... nth positions to stop, respectively,
C- ₁ is the stop position immediately to the left of the first one.

The controlled object 1 is moved to the right by the forward rotation of the stepping motor 4, and moves from the first position _C1 toward the n-th position Cn. When the high-speed drive signal is generated, the stepping motor 4 rotates in reverse, and returns the controlled object 1 to the initial position, ie, the first adjacent stop position C- ₁ , in a short time at high speed.
At this time, it takes a certain period of time for the controlled object 1 to stabilize, and then it moves to the right by l pitches corresponding to one position, and then stops at the first position _C1 .
This movement is a dummy stepping operation to prevent the stepping motor from shifting its stop position.

In this way, conventional methods have prevented variations in the stopping position of the stepping motor from affecting variations in the processing start position of a plotter, etc., but this method reduces processing speed and increases the complexity of the control circuit. There is no escape.

The present invention eliminates these drawbacks by detecting the end of the stepping operation and changing the magnitude or application time of the current applied to the windings to ensure stable positioning of the stepping motor. be.

The present invention will be explained in detail below with reference to Examples.

FIG. 2 is a diagram showing a schematic configuration of an embodiment according to the present invention, and 1 to 4 are the same as the configuration in FIG. 1. 5 is the initial position of the controlled object 1, that is, the first position
A sensor ₆ detects that the controlled object 1 is located near the initial position; DSV is a distributor that distributes drive pulses to each phase of the stepping motor 4;
DV is a driver that drives the stepping motor 4, _D1 is a detector that detects the excitation phase of the winding, _D2 is a detector that determines the initial position of the controlled object 1,
G is a gate that receives signals from the two detectors D ₁ and D ₂ as input, and CC is a control circuit that changes the current value and drive pulse width of the driver DV.

Figure 3 is a signal waveform diagram for explaining the operation of the circuit in Figure 2. The waveform of the signal line is shown, a is a step pulse, b-1
~b-4 is the output of the distributor DSV, c
is the signal of the detector _D2 , d is the output of the gate G, e is the overdrive command from the control circuit CC, f-1
~f-4 is the excitation current of each phase.

FIG. 4 shows the torque-angle characteristics of two-phase excitation of the stepping motor, where 7 is the torque curve during overdrive, 8 is the torque curve during normal drive, and 9 is the stable point. Next, the operation of the above configuration will be explained based on FIGS. 2, 3, and 4. Step pulses P ₁ , P ₂ , . . . are input to the distributor DSV by commands from other control circuits not shown in this figure. At this time, it is assumed that the controlled object 1 completes the movement operation in the direction of the target R and moves toward the initial position H. When the output of the distributor DSV is changed from b-1 to b-4 in response to the input step pulse a, the controlled object 1 approaches the initial position following the step pulse a. By inserting the step pulse of P _o-1 , the signal from sensor 5 to c
A signal like this is sent out. This signal indicates that the controlled object 1 is at the initial position, that is, the first stop position C ₁
This indicates that the object is within range. Furthermore, in many of these types of mechanisms, the stepping motor 4 rarely moves one position in one step, and most of them move one position in multiple steps. 1
Even if it falls within the first stop position range, an error of about one step angle of the stepping motor 4 often occurs due to variations in the detection level of the sensor 5 or the step speed, so the variation of about this one step angle In order to eliminate this problem, the output of the excitation command signal of the distributor DSV is also detected by the detector _D1 , and the initial position is determined at the same time. In this way, the controlled object 1 finally takes a number of steps equal to the number of step pulses and then stops, but another problem at this time is the error in the stopping position of the stepping motor 4 within one step angle. Power from the stepping motor 4 is transmitted to the controlled object 1 by the power transmission mechanism 2. Most of these transmission mechanisms are belts, wire ropes, gears, etc., and the degree of friction varies greatly depending on the tension strength of belts and wire ropes, and the meshing of gears. If this friction is kept constant and the number of positions in which the controlled object 1 steps is varied randomly, the position where the high-speed drive command signal is input will no longer be constant, and therefore the step speed will also vary considerably. Therefore, even if the final step pulse Pn at the stop position is inserted, it is unlikely that it will stop correctly at the stop point (stable point) created by Pn. This is the same even if the pulse rate is changed in a trapezoidal waveform. Therefore, variations in the stop position within one step angle directly result in variations in the start of operation, that is, in the initial position, which is unsightly. Now detector D ₁ ,
When the signal from the detector D ₂ is determined by the gate circuit G and the output signal d is obtained, a control circuit including a timer circuit that measures the time t from the rising edge of the signal e, as shown in the signal e.
When CC is operated and the overdrive currents f-1 and f-2 are passed through the overdrive currents f-1 and f-2 (shaded areas), there is almost no variation in the stop position within one step angle. This is clear from the difference between the torque curve 7 when overdrive is applied (see FIG. 4) and the torque curve 8 when normal drive is applied. That is, the stable point when the motor is stopped and two-phase excited is at position 9, but the smaller the torque at this time, the more uncertain the stable position becomes as the load becomes larger. Therefore, when the controlled object 1 enters a stop cycle, an overdrive current is applied to the excitation winding at that time to reliably create a stable point. After stabilization, the current is returned to its original size after a certain period of time to prevent heat generation and reduce power consumption. Furthermore, when the step pulses P _o+1 , P _o+2 . Of course, the magnitude of the overdrive current may be gradually changed from before the stop position.

As explained above, according to the present invention, the movement position of the controlled object is determined and the position is determined by changing the current flowing through the winding. Since the amount of movement of the object to be controlled can be kept constant regardless of the amount of movement of the object to be controlled, and there is no need to make the object to be controlled perform a dummy step operation, there are effects such as speeding up the movement operation.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of a controlled object driving mechanism using a conventional positioning method, FIG. 2 is a diagram showing a schematic configuration of a controlled object driving mechanism using a positioning method according to the present invention, and FIG. FIG. 2 is a waveform diagram showing signal waveforms at various parts, and FIG. 4 is a diagram showing torque-angle characteristics of a stepping motor with two-phase excitation. 1... Controlled object, 2... Power transmission mechanism, 4...
...Stepping motor, 5, 6...sensor.

Claims (1)

[Claims] 1. In a method of positioning a controlled object at a stop position using a stepping motor, a detection means for detecting a predetermined stop position of the controlled object, a detector for detecting an excitation phase of a winding, this detection means and A determining means receives a signal from the detector and determines the stop position; and a control circuit receives the signal from the determining means and controls the overdrive current to flow through the winding that is currently being excited for a predetermined period of time. 1. A positioning method using a stepping motor, characterized in that the object to be controlled is determined to have reached the stop position, and the current in a winding that is excited at that time is increased for a certain period of time.