JPS63314184A - Positioning device for dc motor - Google Patents

Abstract

PURPOSE:To reduce the number of components in use and to simplify a constitution of circuit so as to attain the cost down by making an output signal from an encoder necessary for a speed control, that of one system. CONSTITUTION:A positioning device for a DC electric motor is constituted of a speed instruction means 1, speed detecting means 2, switching means 3 comprising switches SW1-SW2, comparator means 4, counting means 5, error amplifying means 6 and a driving means 7, while an output signal Aen is input from an encoder of only one phase. Further a delay circuit 8 is connected to an output side of the counting means 5. Here the output signal Aen from the encoder is connected to each input part of the speed instruction means 1, speed detecting means 2 and the comparator means 4 while to the switch SW1 of the switching means 3 for a speed control mode and stop control mode. As the result, connecting only one output system, the positioning device simplifies also its circuit constitution.

Description

Detailed Description of the Invention Technical Field The present invention relates to a speed control circuit for a DC motor suitable for use in a DC servo motor of a printer and various other high-speed positioning devices, and particularly relates to a speed control circuit for an encoder necessary for speed control. The present invention relates to a speed control circuit that can sufficiently handle high speeds with a simple and inexpensive circuit configuration that uses only one phase of output.

Paper feed, carriage feed,
DC servo motors are used as control means for positioning control such as character selection in serial impact printers, pen feeding for plotters, and other various positioning control devices.

For speed control, a conventional DC servo motor uses an encoder that outputs two-phase pseudo sine waves whose phases are shifted by 90 degrees from each other depending on the rotation of the motor.

Then, the output of this two-phase encoder generates an actual speed signal with a voltage value proportional to the rotation speed and a speed command signal with a voltage value corresponding to a preset rotation speed, and by comparing both signals. .

Obtain the speed error signal.

Based on the speed error signal obtained in this way, speed control is performed to drive and rotate the DC motor, and the output signal of one of the encoders of the pair is adjusted to the center value of the output voltage range, such as the ground level. Based on the error signal obtained by comparing the two, stop control is performed to drive and stop the DC motor.

In this conventional control method, in order to stop the DC motor after rotating it for n steps (n cycles in encoder period), the output signal of the other encoder of the pair is compared in addition to the signal used for stop control. Rise of digital signal (
(or falling) regardless of the direction of rotation, and when the count value reaches n, it is necessary to switch from speed control to stop control.

FIG. 6 is a functional block diagram showing an example of the configuration of main parts of a conventionally used positioning device for a DC motor. In the drawings, 1 is a speed command means, 2 is a speed detection means, 3 is a switching means consisting of a switch SW and SW2, 4 is a comparison means, 5 is a counting means, 6 is an error amplification means, and 7 is a driving means. , A e n indicates the output signal of the first encoder, Ben indicates the output signal of the second encoder, and 0c11 indicates the comparison output signal of the comparison means 4.

FIG. 7 is a time chart for explaining the operation when the conventional DC motor positioning device shown in FIG. 6 stops after four steps of rotation in the forward direction. The symbols in the drawings correspond to the symbol positions in FIG. 6, and ■ indicates the time.

In the conventional DC motor positioning device shown in FIG. 6, one encoder output, that is, the output signal Aen of the first encoder, is connected to the input sides of the speed command means 1 and the speed detection means 2, and the switching means It is connected to switch SW of No. 3.

On the other hand, the output of the other encoder, that is, the output signal Ben of the second encoder, is connected to the input sides of the speed command means 1 and the speed detection means 2, similarly to the output signal Aen of the first encoder. , and is also connected to the input side of the comparison means 4.

The comparison means 4 compares the inputted output signal Ben of the second encoder with, for example, a ground level (earth potential), and generates a digital binary comparison output signal ○ of the ``H'' level or the ``L'' level. Generate cIIl.

In the case of FIG. 7, this comparison output signal Ocm is input to the next counting means 5.

By counting the rising edge using the counting means 5, the number of steps in one rotation can be determined.

In most cases, a microprocessor is used as the counting means 5, and the switch SW1. Activate sw2. Note that the states of the switches SW, SW2 in FIG. 6 are the speed control mode.

In the time chart of FIG. 7, at time (X), the control system is in the stop control mode, and in this state, the output signal Aen of the first encoder is at the ground level.

In this state, when switching to the speed control mode, a speed command signal is generated from the speed command means 1 shown in FIG. 6, and the motor starts rotating.

Then, when the count value of the rising edge of the rectangular wave of the comparison output signal Ocm of the comparison means 4 reaches #4'1, the mode is switched to the stop control mode, and the motor is then operated for only 1/4 cycle of the encoder cycle. Rotate and stop.

In this stopped state, the output signal Aen of the first encoder
becomes the ground level, and the motor has rotated in the positive direction by 4 steps from the position at time 1.

Next, FIG. 8 is a time chart for explaining the operation of the conventional DC motor positioning device shown in FIG. 6 when the motor stops after rotating four steps in the opposite direction. Reference numerals in the drawings are the same as in FIG. 6.

This FIG. 8 shows the case of rotating in the opposite direction to that shown in FIG. 7, but the control operation is the same as that shown in FIG. 7 for basic line fishing.

FIG. 9 is an exploded perspective view showing an example of the structure of an encoder used in a conventional DC motor positioning device. In the drawing, 11 is the main body, 11a is the mounting step, and 12 is the mounting is a lower block, 13a and 13b are light receiving elements such as photodiodes and phototransistors, 14
Reference numeral 15 indicates a mask member, 15 indicates a rotating disk, 16 indicates a light emitting element such as an LED, and 17 indicates an upper block for mounting.

As is clear from FIG. 9, the encoder requires a pair of light receiving elements 13a and 1.3b in order to output a two-phase pseudo sine wave whose phase is shifted by 90 degrees from each other. High precision is also required for the relative mounting position with respect to the light emitting element 16.

Furthermore, since the encoder outputs signals in two systems, the configuration of one circuit becomes correspondingly more complicated.

Therefore, there is an inconvenience in that the cost inevitably increases and it cannot be used in a relatively inexpensive positioning device.

Purpose Therefore, the positioning device for a DC motor of the present invention solves the inconveniences that occur in conventional positioning devices for a DC motor, and achieves high-performance and high-speed positioning with a simple configuration that uses only one encoder output. It is an object of the present invention to realize a positioning device in which a DC servo motor can also be used to control relatively inexpensive printers and the like.

4 Next, regarding the positioning device for a DC motor of this invention,
Examples thereof will be described in detail with reference to the drawings.

FIG. 1 is a functional block diagram showing an embodiment of the main structure of a positioning device for a DC motor according to the present invention. Reference numerals in the drawings are the same as in Fig. 6, and 8
indicates a delay circuit.

As is clear from a comparison between the positioning device shown in FIG. 1 and the positioning device shown in FIG. 6 which shows a conventional example, in FIG. 1 showing the positioning device of the present invention, the encoder output is only one phase. be.

However, in FIG. 1, a delay circuit 8 is connected to the output side of the counting means 5.

FIG. 2 is a time chart for explaining the operation when the DC motor positioning device of the present invention shown in FIG. 1 stops after four steps of rotation in the forward direction.
The symbols attached to each signal waveform in the drawings correspond to the symbol positions in FIG.

The output signal Aen of this encoder is connected to each input section of the speed command means 1, the speed detection means 2, and the comparison means 4, and is also connected to the input parts of the speed command means 1, the speed detection means 2, and the comparison means 4, and also to the switching means 3 for switching between the speed control mode and the stop control mode. It is connected to switch SW.

The comparison means 4 receives the input encoder output signal Ae.
Comparing n with, for example, the ground level, 11H''
Generates a digital binary comparison output signal OC- of level L or "Ln."

This comparison output signal 0C11 is input to the next counting means 5.

Then, in the case of FIG. 2, that is, in the case of rotation in the positive direction, this counting means 5 counts the falling edges, thereby making it possible to know the number of steps rotated.

In many cases, a microprocessor is used as the counting means 5, and based on the counting result, the switch SWI t SW2 of the switching means 3 for switching between the speed control mode and the stop control mode is activated.

Furthermore, the delay time of the delay circuit 8 required in this case can be easily managed by a microprocessor.

Note that the state of the switches sw, , sw2 in FIG. 2 is the speed control mode.

In the time chart of FIG. 2, at time {circle around (2)} the control system is in the stop control mode, and in this state, the encoder output signal Aen is at ground level.

At this time, the comparison output signal Ocm of the comparison means 4 is "H"
Level or 11 L It is in an undetermined state at the 11th level,
The counting means 5 ignores this output signal.

In this state, when switching to the speed control mode, a speed command signal is generated from the speed command means 1 shown in FIG. 1, and the motor starts rotating.

Then, after a certain period of time has elapsed since the count value of the falling edge of the rectangular wave of the comparison output signal Ocm of the comparison means 4 reaches 114 II, when switching to the stop control mode,
The motor stops when the encoder output signal Aen reaches ground level.

At this time, the motor has rotated in the forward direction by 4 steps from the position at time ■.

In the positioning device of the present invention, the switching from the speed control mode to the stop control mode is not performed when the count value reaches II 417, but after a certain period of time has elapsed from that point, for the following reason. be.

FIG. 3 is a characteristic diagram showing an example of the relationship between the output of the encoder and the generated torque for the positioning device for a DC motor of the present invention shown in FIG. The vertical axis T in the drawing indicates torque.

The horizontal direction in FIG. 3 is the displacement from the stop position, that is, the phase shift, and the vertical direction is the generated torque.

When the displacement of the target position gradually increases from 810 g,
A corresponding torque is generated and acts to return the displacement to "0".

However, such an effect is valid only within the range of ±π/2 in FIG. 3, and when the displacement becomes larger than that, the torque tends to decrease as the displacement increases.

Therefore, in order to perform stable stop control, it is necessary to keep the displacement amount within the range of ±π/2 shown in FIG. 3.

On the other hand, the comparison output signal Ocm of the comparison means 4 is separated by π from the stop position at the fourth falling edge, that is, at time ■ in the time chart of FIG. 2, and the above-mentioned condition is not satisfied. Not yet.

Then, the motor rotates and waits for the time required to move further π/2 minutes from the state separated by π.

This time period is from time ■ to time ■ in Figure 2,
After this time has elapsed, switching to stop control is performed.

The next FIG. 4 is a time chart for explaining the operation of the DC motor positioning apparatus of the present invention shown in FIG. 1 when the motor stops after rotating four steps in the opposite direction. Reference numerals in the drawings are the same as in FIG. 1.

This FIG. 4 shows the case of rotating in the opposite direction to that of FIG. 2 above.

The difference from the previous FIG. 2 is that the polarity of the waveform of the comparison output signal indicated by Ocm is reversed.

Therefore, when rotating in the opposite direction as shown in Figure 4,
Contrary to the case of the second @, in the counting means 5.

Rising edges will be counted.

Such switching between detection of falling edges and rising edges may be performed by a microprocessor serving as the counting means 5, or may be performed by gate circuit means such as exclusive OR.

Other operations are similar to those in FIG. 2.

As described above, in the positioning device for a DC motor of the present invention, the output of the encoder is one phase and there is one output system, so the circuit configuration of the one positioning device is also simplified. In addition,
Edge detection performed by the counting means 5 requires switching between rising and falling edges depending on the direction of rotation, but this point can be easily solved with a microprocessor program, and is not particularly difficult. isn't it.

FIG. 5 is a perspective view showing an example of the structure of an encoder section used in the positioning device of the present invention.

Reference numerals in the drawings are the same as those in FIG. 9, and 18 indicates a photointerrupter.

As is clear from comparing FIG. 5 with FIG. 9 showing the conventional example, in the positioning device of the present invention, the encoder section only needs to output an l-phase pseudo sine wave, so it is not used. The number of parts is significantly reduced.

In addition, since the number of light-receiving elements is reduced to 11/2 compared to that shown in Fig. 9, there is no need for positioning between two elements as in the conventional example. Positioning is also not necessary.

Furthermore, there is no need for a mask, and since the positioning accuracy between the block and motor can be mounted with normal precision, no groove machining is required, and inexpensive commercial products such as the light receiving and emitting elements and photointerrupter 18 can be used. becomes.

Therefore, according to the positioning device for a DC motor of the present invention, the number of parts used and the circuit configuration can be significantly simplified by using only one system of encoder output signals necessary for speed control. , a low-cost positioning device is realized.

In other words, the number of components of the encoder section in Fig. 5 has been reduced to approximately 1/2 compared to Fig. 9 which shows the conventional example, and the accuracy of the encoder installation has also been reduced by two. 1
Compared to when paired.

The required accuracy is relaxed to the extent that there are no constraints on mutual position,
Cost reduction is achieved.

As a result, DC servo motors, which have higher performance but are more expensive than stepping motors, can now be widely used in various relatively inexpensive positioning devices, such as type selection type serial printers, etc. Excellent effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of the main configuration of a positioning device for a DC motor according to the present invention, and FIG. 2 is a functional block diagram showing an embodiment of the positioning device for a DC motor according to the present invention shown in FIG. FIG. 3 is a time chart for explaining the operation when stopping after four steps of rotation in the forward direction. FIG. A characteristic diagram showing an example. FIG. 4 is a time chart for explaining the operation when the positioning device for a DC motor of the present invention shown in FIG. 1 stops after four steps of rotation in the opposite direction. FIG. 6 is a perspective view showing an example of the structure of an encoder section used in a positioning device, and FIG. 6 is a functional block diagram showing an example of the main part configuration of a conventionally used positioning device for a DC motor. FIG. 7 is a time chart for explaining the operation when the conventional DC motor positioning device shown in FIG. 6 stops after four steps of rotation in the forward direction. FIG. 8 is a time chart for explaining the operation when the conventional DC motor positioning device shown in FIG. 6 stops after four steps of rotation in the opposite direction. FIG. 2 is an exploded perspective view showing an example of the structure of an encoder used in the positioning device. In the drawings, 1 is speed command means, 2 is speed detection means,
3 is a switching means consisting of switches SWI and SW2; 4
5 is a comparing means, 5 is a counting means, 6 is an error amplifying means, 7 is a driving means, and 8 is a delay circuit. O 3 Figures 4 Figures 5 Figures 7 Figures Shin 8 Figures

Claims (1)

[Claims] 1. A DC motor, an encoder that outputs a pseudo sine wave according to the rotation of the DC motor, and an encoder connected to the output side of the encoder means to output a DC voltage value proportional to the rotation speed. a speed detecting means, a speed command means connected to the output side of the encoder and outputting a DC current value proportional to a desired rotational speed, and between the speed detecting means and the output side of the speed command means and an error amplifier described below. an error amplifier connected to the output side of the switching means to amplify the difference between the two DC voltage values output from the speed detection means and the speed command means; and the output side of the encoder. a comparing means connected to the reference potential for comparison with a reference potential and outputting the comparison result as a binary signal; a counting means connected to the output side of the error amplifier for counting the comparison output of the comparing means; and a driving means connected to the output side of the error amplifier. and a drive means for supplying a drive current to the DC motor that is proportional to the difference in voltage values, firstly, the encoder outputs a single-phase pseudo sine wave. and is connected so as to be commonly inputted to the speed detection means, the speed command means, and the comparison means, and secondly, the switching means switches the outputs of the speed detection means and the speed command means in the speed control mode. and thirdly, in the stop control mode, the output of the encoder and a DC voltage value that is approximately equal to the center value of the output voltage range are input to the error amplifier. delay time detection means connected to the output side of the counting means to operate the switching means after a predetermined period of time has elapsed from the output of the counting means; When rotating and stopping the rotation to a second stop position separated by n cycles, the switching means changes the speed control mode to the stop control after a predetermined period of time has elapsed from the moment the count value of the counting means reaches n. A positioning device for a DC motor, characterized by switching between modes. 2. In the positioning device for a DC motor according to claim 1, the predetermined period of time is such that the DC motor is at least 1/4 period in the period of the pseudo sine wave of the output of the encoder.
A positioning device for a DC motor, characterized in that the time for rotating is an angle corresponding to two cycles or less.