JP2008131805A - Drive unit for motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the drive unit for a motor capable of obtaining the same speed resolution in the same speed area, even if using any of the encoders, without the maximum speed and the minimum speed being affected by the pulse resolution of the encoder used at which rotational speed data can be obtained. <P>SOLUTION: In a pulse counter circuit 7, a rotational speed pulse train from a rotary encoder 5 and a reference pulse train that has one sufficiently short period, as compared with the rotational speed pulse and is sent from a reference pulse generation circuit 6, are inputted. The number of reference pulses counted in a single period of the rotational speed pulse is sent to a rotational speed recognition means 1b as the rotational speed data. A reference pulse period dividing circuit 8 arbitrarily changes the dividing ratio by a command from the outside, divides the period of the reference pulse train sent from a reference pulse generation circuit 6, and inputs the divided reference pulse train into a pulse counter circuit 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor drive device.

  The vibration wave motor drive device performs feedback control in which the microcomputer recognizes the rotation speed information of the vibration wave motor output from the rotary encoder and outputs the next rotation speed command in comparison with the target rotation speed.

  FIG. 4 is a block diagram of a driving apparatus for a vibration wave motor according to a conventional example.

  In FIG. 4, the rotational speed command signal of the vibration wave motor is outputted from the rotational speed command means 18a inside the microcomputer (control means) 18, and a waveform forming circuit 19 forms a four-phase signal waveform having a frequency λ corresponding to the command speed. And output to the booster circuit 20.

  FIG. 5 is a block diagram of the booster circuit in FIG.

  In the booster circuit 20, the four FETs 11 are switched at the timing of the four-phase signal shown in FIG. 6, respectively, and the transformers 12a and 12b boost the two-phase AC waveforms with different phases, and the electro-mechanical conversion of the vibration wave motor is performed. Applied to each element.

  FIG. 7 is a configuration diagram of a vibration wave motor.

  In FIG. 7, a vibration wave motor 21 includes a vibrating body 13 in which a piezoelectric element 13a as an electro-mechanical energy conversion element is bonded to an annular elastic body 13b, and a moving body 15 in pressure contact with the elastic body 13. Prepare. A motor shaft 16 disposed at the center of the motor and connected to the moving body 15 and a pressure spring 14 that holds the vibrating body 13 are provided.

  By applying two-phase alternating waveforms with different phases from the booster circuit 20 to the piezoelectric element 13a, a driving wave as a traveling wave is formed on the elastic body 13 by, for example, synthesis of bending vibration. The moving body 15 that is in pressure contact with the drive surface of the elastic body 13 where the drive wave is formed is frictionally driven, and the rotational force is transmitted to the motor shaft 16.

  A rotary encoder 22 for detecting the rotational speed of the motor is provided at the rear end of the motor shaft 16.

  The rotary encoder 22 outputs a pulse train as the rotational speed information. When the rotational speed of the vibration wave motor 21 is fast, the frequency of the pulse train is high, and when the rotational speed is low, the frequency is low.

  The reference pulse generation circuit 23 outputs a reference pulse having a frequency sufficiently higher than that of the pulse train from the rotary encoder 22 and asynchronous with the encoder pulse train and having a temporally stable frequency. The reference pulse train and the pulse train from the rotary encoder 22 are input to the pulse counter circuit 24.

  FIG. 8 is a block diagram of the pulse counter circuit in FIG.

  In FIG. 8, five 4-bit counters 25a, 25b, 25c, 25d, and 25e are connected in series to form a 20-bit counter circuit. When the rotational speed pulse train from the rotary encoder 22 and the reference pulse train from the reference pulse generation circuit 23 are input to this counter circuit, the count number of the reference pulse train within one cycle of the rotational speed pulse train is output as 20-bit rotational speed data. .

  FIG. 9 is a diagram showing the timing of each signal in the pulse counter circuit of FIG.

  In FIG. 9, the rotational speed data is updated for each cycle of the encoder output pulse train. For example, when the reference pulse count number of the period t1 is D1, D1 is output from the pulse counter circuit as rotation speed data in the next encoder output pulse period.

The rotational speed recognition means 18b in the microcomputer 18 compares the current rotational speed with the target rotational speed, and transmits a rotational speed command that will be the target value to the rotational speed command means 18a. As a result, the encoder rotational speed data becomes a large value when the motor rotational speed is low, and becomes a small value when the motor rotational speed is high (see Patent Document 1).
JP 11-178373 A

  However, vibration wave motors are widely used depending on the purpose of use, from encoders with high pulse resolution to encoders with low pulse resolution in order to take advantage of the features of low speed, high torque, high response, and high positioning accuracy.

  When a rotary encoder with a high pulse resolution is used, the speed resolution at the same rotational speed is worse than that of a rotary encoder with a low pulse resolution.

  Also, rotary encoders with high pulse resolution will have poor speed resolution as their period approaches the period of the reference pulse train at high speeds, and rotation speed data cannot be obtained when the period becomes equal to the period of the reference pulse train. End up.

  As the rotation speed decreases, the number of reference pulse trains in the pulse counter circuit 24 increases, and the point at which the overflow of the 20-bit counter in FIG. 8 finally occurs is the minimum speed at which rotation speed data can be obtained. Become.

  As described above, the minimum speed and the minimum speed at which the rotation speed data can be obtained vary greatly depending on the pulse resolution of the encoder.

  The object of the present invention is that the maximum speed and the minimum speed at which rotational speed data can be obtained are not affected by the pulse resolution of the encoder used, and the same speed resolution can be obtained in the same speed range regardless of which encoder is used. The object is to provide a motor drive device.

  In order to achieve the above object, the motor drive device according to claim 1 is a rotary encoder that converts a rotational speed of the motor into a rotational speed pulse train, and the rotational speed pulse train from the rotary encoder is input, and the rotational speed A pulse counter circuit for converting a pulse train into rotational speed data, a rotational speed recognition means for comparing the rotational speed data from the pulse counter circuit with a target rotational speed and recognizing a difference from the target rotational speed, and the rotational speed A rotational speed command means for receiving a rotational speed recognition signal from the recognition means and outputting a rotational speed command signal so that the rotational speed of the motor becomes the target rotational speed, and between a reference pulse generating circuit and the pulse counter circuit A reference pulse period dividing circuit arranged, and the pulse counter circuit is connected to the front from the rotary encoder. The rotation speed pulse train and the rotation speed pulse train are sufficiently shorter than the rotation speed pulse train, the reference pulse train sent from the reference pulse generation circuit is input, and the number of reference pulses counted in one rotation speed pulse cycle is the rotation speed pulse. A counter that sends data to the rotational speed recognition means, and the reference pulse period divider circuit arbitrarily changes the division ratio in response to an external command, and the reference pulse train sent from the reference pulse generator circuit The period is divided, and the divided reference pulse train is input to the pulse counter circuit.

  In the motor drive device of the present invention, the pulse counter circuit has a rotational speed pulse train from the rotary encoder and a reference pulse train sent from the reference pulse generation circuit, which is sufficiently shorter in one cycle than the rotational speed pulse train. . Further, the number of reference pulses counted in one cycle of the rotational speed pulse is sent to the rotational speed recognition means as rotational speed data. The reference pulse cycle divider circuit arbitrarily changes the division ratio in response to an external command, divides the cycle of the reference pulse train sent from the reference pulse generator circuit, and uses the divided reference pulse train as a pulse counter circuit. To enter.

  With such a configuration, the maximum speed and the minimum speed at which rotational speed data can be obtained are not affected by the pulse resolution of the encoder used, and the same speed resolution can be obtained in the same speed range regardless of which encoder is used. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram of a vibration wave motor driving apparatus according to an embodiment of the present invention.

  In FIG. 1, the driving device for driving the vibration wave motor 4 includes a microcomputer 1, a waveform forming circuit 2, a booster circuit 3, a rotary encoder 5, a reference pulse generating circuit 6, a pulse counter circuit 7, and a reference pulse period dividing circuit 8. Is provided.

  The microcomputer 1 includes a rotation speed command means 1a, a rotation speed recognition means 1b, and a reference pulse train frequency division command means 1c.

  The rotational speed of the vibration wave motor 4 is transmitted to the rotary encoder 5 and sent to the pulse counter circuit 7 as a rotational speed pulse train. On the other hand, the reference pulse train from the reference pulse generating circuit 6 is sent to the reference pulse cycle dividing circuit 8, and the frequency division designated by the reference pulse train dividing command signal from the reference pulse train dividing command means 1c of the microcomputer 1 is performed. Divide by rate. The reference pulse train after frequency division is sent to the pulse counter circuit 7.

  FIG. 2 is a block diagram of the reference pulse period divider circuit in FIG.

  In FIG. 2, a reference pulse train is sent from the reference pulse generation circuit 6 in FIG. A reference pulse train frequency division command signal is sent from the reference pulse train frequency division command means 1c of the microcomputer 1.

  The reference pulse train and the reference pulse train dividing command signal are sent to the reference pulse dividing circuit 9, and the reference pulse train is divided by the n-th power of 2 instructed by the reference pulse train dividing command signal. The divided reference pulse train is input to the CLK terminal of a 20-bit counter composed of 4-bit counters 10a, 10b, 10c, 10D, and 10e.

  Then, when the rotational speed pulse train from the rotary encoder 5 is input to the CLEAR terminal, the frequency-divided reference pulse train is counted every rotational speed pulse train, and the rotational speed recognition in the microcomputer 1 is performed as the rotational speed data. It is sent to the means 1b.

  FIG. 3 is a signal timing chart at the time of pulse counting using the reference pulse period divider circuit of FIG.

  In FIG. 3, it is assumed that the rotary encoder A with a certain pulse resolution overflows when the reference pulse train is counted by the 20-bit counter in one cycle of the pulse train output at a certain rotation speed. In the encoder A, rotational speed data below the rotational speed cannot be obtained.

  Therefore, when the reference pulse train frequency dividing command means 1c detects that the pulse counter circuit 7 has overflowed, it transmits a reference pulse train frequency dividing command signal to the reference pulse cycle frequency dividing circuit 8 to change the cycle dividing rate. To increase the period of the reference pulse train.

  By this command, the cycle of the reference pulse train becomes longer, and the reference pulse number D1 in one cycle of the pulse train of the encoder A, t1, can be sent to the microcomputer 1 as rotation speed data in the next encoder pulse cycle.

  If the pulse counter circuit 7 still overflows even at this time, the reference pulse train frequency dividing command means 1c transmits the reference pulse train frequency dividing command signal to the reference pulse cycle frequency dividing circuit 8 again. Then, an instruction is issued to further increase the period of the reference pulse train by changing the period division ratio.

  On the other hand, if the count result of the pulse counter circuit 7 is sufficiently smaller than the overflow value, the reference pulse train frequency dividing command means 1c sends the reference pulse train frequency dividing command signal to the reference pulse cycle frequency dividing circuit 8. Send. Then, an instruction is issued to change the cycle division ratio to shorten the cycle of the reference pulse train.

  As described above, if information on how long the reference pulse train period is from the reference length and the count result obtained without causing an overflow from the pulse counter circuit 7 are used, the resolution of the encoder is wide. It becomes possible to respond.

It is a block block diagram of the drive device of the vibration wave motor which concerns on embodiment of this invention. FIG. 2 is a configuration diagram of a reference pulse period divider circuit in FIG. 1. It is a figure which shows each signal timing at the time of the pulse count using the reference | standard pulse period frequency divider circuit of FIG. It is a block block diagram of the drive device of the vibration wave motor which concerns on a prior art example. FIG. 5 is a configuration diagram of a booster circuit in FIG. 4. FIG. 5 is a four-phase output waveform diagram of the waveform forming circuit in FIG. 4. It is a block diagram of a vibration wave motor. It is a block diagram of the pulse counter circuit in FIG. It is a figure which shows the timing of each signal of the pulse counter circuit of FIG.

Explanation of symbols

1 Microcomputer (control means)
1a Rotational speed command means 1b Rotational speed recognition means 1c Reference pulse train frequency division command means 2 Waveform shaping circuit 3 Booster circuit 4 Vibration wave motor 5 Rotary encoder 6 Reference pulse generation circuit 7 Pulse counter circuit 8 Reference pulse cycle frequency division circuits 10a and 10b 10c, 10d 4-bit counter

Claims (2)

A rotary encoder that converts the rotational speed of the motor into a rotational speed pulse train;
A pulse counter circuit for inputting the rotational speed pulse train from the rotary encoder and converting the rotational speed pulse train into rotational speed data;
A rotational speed recognition means for comparing the rotational speed data from the pulse counter circuit with a target rotational speed and recognizing a difference from the target rotational speed;
A rotational speed command means for receiving a rotational speed recognition signal from the rotational speed recognition means and outputting a rotational speed command signal so that the rotational speed of the motor becomes the target rotational speed;
A reference pulse period dividing circuit disposed between a reference pulse generating circuit and the pulse counter circuit;
With
The pulse counter circuit is sufficiently shorter in one cycle than the rotation speed pulse train from the rotary encoder and the rotation speed pulse train, and the reference pulse train sent from the reference pulse generation circuit is input, and one cycle of the rotation speed pulse A counter that sends the number of reference pulses counted to the rotational speed recognition means as the rotational speed data;
The reference pulse period divider circuit arbitrarily changes a division ratio in response to an external command, divides the period of the reference pulse string sent from the reference pulse generation circuit, and the divided reference pulse string Is input to the pulse counter circuit.   The reference pulse train frequency dividing command means for sending a reference pulse train frequency dividing command signal to the reference pulse cycle frequency dividing circuit and arbitrarily changing a cycle frequency dividing ratio of the reference pulse train. Motor drive device.

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