JP6291309B2 - Control device and control method for vibration actuator - Google Patents

Description

  The present invention relates to a control device and a control for a vibration actuator (for example, an ultrasonic motor) that drives a moving body such as a rotor (rotor) or a slider (linear advance) using a traveling wave generated by ultrasonic vibration, for example. Regarding the method.

  Conventionally, a rotary ultrasonic motor using traveling waves is known as an example of a vibration actuator.

The ultrasonic motor includes a vibrating body (stator) including a piezoelectric element and an annular elastic body to which the piezoelectric element is bonded, an annular moving body (rotor), and the moving body as the vibrating body. A pressurizing means for pressurizing contact and an electrode for applying a drive signal (high frequency voltage) to the piezoelectric element are provided.
The ultrasonic motor generates a traveling wave in the vibrating body by the expansion and contraction motion of the piezoelectric element generated by applying a driving signal to the piezoelectric element, and frictionally drives the moving body by the traveling wave.
In addition, the traveling wave is generated by synthesizing waves generated by applying two-phase driving signals having a temporal phase difference of 90 ° to the piezoelectric element.

JP 7-123752 A

  By the way, depending on the use of the above-described ultrasonic motor, for example, intermittent driving (starting / stopping) of the moving body may be continuously repeated like a wobbling operation at the time of moving image shooting in a digital camera or the like.

  In such intermittent driving of the ultrasonic motor, when the ultrasonic motor shifts from the driving state to the stopped state, the above-described two-phase driving signal is instantaneously interrupted, and the vibration of the vibrating body is settled. There is a problem that noise and vibration are generated when the ultrasonic motor is stopped because the moving body is struck against the vibrating body by the pressure applied by the pressurizing means.

  Further, when the ultrasonic motor shifts from the stopped state to the driving state, that is, at the moment when the above-described two-phase driving signal is applied at the time of starting the ultrasonic motor, it is pressed against the vibrating body by the pressing force of the pressurizing means. There was a problem that noise was generated because the moving body was floating by the traveling wave instantly.

  The present invention provides a control device and a control method for a vibration actuator that can suppress generation of noise and vibration at the time of stopping and generation of noise at the time of start-up in intermittent driving of a vibration actuator such as an ultrasonic motor. is there.

In order to achieve such an object, the present invention provides a vibration actuator control device including a vibrating body that generates a traveling wave by applying a two-phase driving signal, and a moving body that is driven by the traveling wave. A frequency control unit that controls a frequency of at least one of the two-phase drive signals; and the frequency control unit varies the frequency of the two-phase drive signal to thereby change the frequency of the two-phase drive signal. The phase difference is changed, and when the phase difference between the two-phase drive signals is near 0 ° or near 180 °, the movable body is stopped to continuously perform the intermittent drive of the vibration actuator. To do.
According to another aspect of the present invention, there is provided a vibration actuator control method comprising: a vibrating body that generates traveling waves by applying a two-phase driving signal; and a moving body that is driven by the traveling waves. The phase difference between the two-phase drive signals is changed by changing the frequency, and when the phase difference between the two-phase drive signals is near 0 ° or near 180 °, the moving body stops to cause the vibration. The intermittent drive of the actuator is continuously performed.
Here, the vicinity of 0 ° (or the vicinity of 180 °) does not mean that the moving body stops only when the phase difference between the two-phase drive signals is 0 ° (or 180 °). This means that the moving body stops within a certain frequency range (for example, about ± 5 ° to 10 °) around ° (or 180 °).
This frequency width differs depending on the magnitude of the pressure contact force between the vibrating body and the moving body, the size of the load driven by the vibration actuator, the voltage value or current value of the drive signal, and the like.
For example, when the phase difference between two-phase drive signals is 355 ° to 10 °, or when the phase is 175 ° to 190 °, the moving body stops within a certain frequency range including 0 ° or 180 °. Are also within the scope of the present invention.
In the present invention described above, the rotation direction of the moving body may be different before and after stopping (forward rotation-reverse rotation, reverse rotation-forward rotation), and the rotation direction is the same (forward rotation-forward rotation, reverse rotation). -Reverse rotation).
Further, in the present invention described above, not only a rotary vibration actuator in which both the vibrating body and the moving body are ring-shaped but also a linear vibration actuator in which both the vibrating body and the moving body are linear is included.
Furthermore, the above-described vibration actuator according to the present invention is not limited to the ultrasonic actuator using the vibration in the ultrasonic band, and includes one using the vibration outside the ultrasonic band.

  According to the present invention, for example, in the intermittent drive of a vibration actuator such as an ultrasonic motor, it is possible to suppress the generation of noise and vibration at the time of stopping and the generation of noise at the time of activation.

It is a figure which shows the waveform etc. of the drive signal applied to a vibrating body in the control method of the ultrasonic motor which concerns on one Embodiment of this invention. FIG. 2 is a partially enlarged view showing a part of FIG. (A) is a perspective view partially showing a configuration of an ultrasonic motor according to an embodiment of the present invention, (b) is a two-phase electrode provided on a piezoelectric body joined to a vibrating body. FIG. It is a block diagram which shows the structure of the drive signal output circuit of the ultrasonic motor which concerns on one Embodiment of this invention.

Hereinafter, a control device of a vibration actuator (for example, an ultrasonic motor) according to an embodiment of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 3A, the ultrasonic motor 100 according to the present embodiment rotates together with an output shaft 2 that is rotatably supported, and an annular movement configured concentrically around the output shaft 2. The movable body 4 includes a body (rotor) 4 and an annular vibrating body (stator) 8 arranged on the base 6 and concentrically formed around the output shaft 2. It is maintained in a state where it is always pressed against the vibrating body 8 by the applied pressure.

  The moving body 4 includes an annular rotor ring 4a and a friction material 4b provided in an annular shape along a surface of the rotor ring 4a that faces the vibrating body 8. The rotor ring 4a is made of, for example, an aluminum alloy. On the other hand, the friction material 4b is for obtaining a stable frictional force when the moving body 4 and the vibrating body 8 are pressed against each other. For example, a synthetic resin or the like is used.

  The vibrating body 8 includes an annular stator ring 8a and an annular piezoelectric body 8b disposed on a surface of the stator ring 8a facing the base 6. In the stator ring 8a, a plurality of slits (grooves) 8g are formed at equal intervals along the circumferential direction in a portion opposite to the surface on which the piezoelectric body 8b is provided. A plurality of comb teeth 8c projecting toward the moving body 4 (specifically, the friction material 4b) are formed along the circumferential direction.

The stator ring 8a is made of, for example, a copper alloy. On the other hand, the piezoelectric body 8b (also referred to as piezoelectric ceramic) is formed of an element having a property (electrostriction) that expands and contracts when a high frequency voltage is applied thereto, and is a surface of the stator ring 8a that faces the base 6. It is joined to.
In the piezoelectric body 8b, adjacent sections are alternately polarized in the thickness direction, and electrodes 8b1 to 8b8 are provided for each section in one area of the piezoelectric body 8b, and electrodes 8b9 to 8b15 are provided in the other area. Is provided for each category.

  The spring 10 is sandwiched between the pressing member 12 fixed to the output shaft 2 and the moving body 4. In this state, the elastic force of the spring 10 is transmitted to the moving body 4, and the moving body By pressing the 4 toward the vibrating body 8, the moving body 4 (specifically, the friction material 4b) and the vibrating body 8 (specifically, each comb tooth 8c of the stator ring 8a) are always pressed. Is maintained in the state.

  Further, as shown in FIG. 3B, the electrodes 8b1 to 8b8 provided in one region of the piezoelectric body 8b include the electrode 14A of the two-phase electrodes 14A and 14B (1 in FIG. 3B). The electrode 8b9 to 8b15 provided in the other region of the piezoelectric body 8b is joined to the electrode 14B (FIG. 3B) of the two-phase electrodes 14A and 14B. Are joined).

In such a configuration, when drive signals (high-frequency voltages) S1 and S2 having different temporal phases (except when the phase difference is 180 °) are applied to the two-phase electrodes 14A and 14B, each comb of the stator ring 8a A traveling wave is generated on the top surface of the tooth 8c. Then, the moving body 4 pressurized toward the vibrating body 8 by the spring 10 rotates around the output shaft 2 by this traveling wave.
When the phase difference between the drive signals S1 and S2 changes from 0 ° to 90 °, the rotational speed of the moving body 4 increases. When the phase difference changes from 90 ° to 180 °, the rotational speed of the moving body 4 increases. Decrease.
Further, when the phase difference between the drive signals S1 and S2 changes from 180 ° to 270 °, the rotational speed of the moving body 4 increases, but when the phase difference changes from 0 ° to 90 °, the moving body When the rotation direction of 4 is reversed and the phase difference changes from 270 ° to 360 °, the rotational speed of the moving body 4 decreases, but when the phase difference changes from 90 ° to 180 °, it moves. The direction of rotation of the body 4 is opposite.
When the phase difference between the drive signals S1 and S2 is 0 ° (or 360 °) and 180 °, no traveling wave is generated on the top surfaces of the comb teeth 8c of the stator ring 8a, so the moving body 4 does not rotate. Stop.
Note that the rotation of the moving body 4 is not limited to the case where the phase difference between the drive signals S1 and S2 is 0 ° (or 360 °) and 180 °, but is 0 ° (or 360 °), Naturally, the moving body 4 stops within a certain frequency range before and after that including 180 ° (for example, about ± 5 ° to 10 °).
When the phase difference between the drive signals S1 and S2 is other than 0 ° (or 360 °) or 180 °, a traveling wave is theoretically generated on the top surface of each comb tooth 8c of the stator ring 8a. If the traveling wave required to rotate the moving body 4 is not generated, the moving body 4 may stop before the phase difference reaches 0 ° (or 360 °) or 180 °, and the 0 ° ( This is because the mobile body 4 may not restart even if it exceeds 360 ° or 180 °.
The frequency width described above depends on the pressure contact force between the vibrating body 8 and the moving body 4, the size of a load (not shown) driven by the ultrasonic motor 100, and the voltage values and current values of the drive signals S1 and S2. Different.

  Next, the drive signal output circuit for the drive signals S1 and S2 applied to the electrodes 8b1 to 8b8 and the electrodes 8b9 to 8b15 via the two-phase electrodes 14A and 14B will be described.

  As shown in FIG. 4, the drive signal output circuit 200 of the present embodiment is based on the drive command signal (ON command pulse) output from the drive trigger generation circuit 15, and a drive signal (for example, a SIN wave having a frequency f1). The oscillation circuit 16 that outputs S1 is provided, and the oscillation circuit 16 is configured to stop the output of the drive signal based on the stop command signal (OFF command pulse) output from the drive trigger generation circuit 15. Yes.

The oscillation circuit 16 is connected to the first output circuit 17, and the drive signal S1 is amplified by the first output circuit 17 and supplied to the electrode 14A.
The oscillation circuit 16 is connected to the second output circuit 20 via the phase control circuit 18 and the frequency control circuit 19, and the drive signal S1 output from the oscillation circuit 16 is supplied to the phase control circuit 18 and the frequency control circuit. After the phase adjustment and the frequency adjustment are performed by 19, the drive signal S2 is amplified by the second output circuit 20 and supplied to the electrode 14B.

The phase control circuit 18 adjusts the phase difference between the drive signal S1 and the drive signal S2.
By arbitrarily setting the phase difference between the drive signals S1 and S2 at the time of startup from 0 ° to 90 °, the rotational speed at the time of startup can be arbitrarily adjusted. For example, if the phase difference between the drive signals S1 and S2 at the time of activation is 90 °, the moving body 4 of the ultrasonic motor 100 is activated at the maximum speed, and if the phase difference is 0 °, the movement of the ultrasonic motor 100 is performed. Body 4 starts up at zero speed.
The frequency control circuit 19 adjusts the frequency difference between the drive signal S1 and the drive signal S2, and outputs the drive signal S1 having the frequency f1 output from the oscillation circuit 16 as the drive signal S2 having the frequency f2.
An alternating rotational motion is performed based on the frequency difference between the frequency f1 of the drive signal S1 and the frequency f2 of the drive signal S2, and the frequency difference between the frequency f1 and the frequency f2 becomes an alternating rotational frequency. The alternating rotation frequency can be adjusted by arbitrarily setting the frequency difference of f2.
Further, the rotational direction when the moving body 4 of the ultrasonic motor 100 is activated can be determined depending on which of the frequency f1 of the drive signal S1 and the frequency f2 of the drive signal S2 is set higher, and the drive signal S1. When the frequency f1 of the driving signal S2 is higher than the frequency f2 of the driving signal S2, the moving body 4 of the ultrasonic motor 100 starts in the forward rotation direction, and when the frequency f1 of the driving signal S1 is lower than the frequency f2 of the driving signal S2. The moving body 4 of the ultrasonic motor 100 is activated in the reverse direction.
In the present embodiment, the adjustment of the phase difference and the frequency difference between the drive signal S1 and the drive signal S2 are performed by a command signal from the drive control unit 21 or an operation switch (not shown).

  Thus, in this embodiment, by providing the frequency control circuit 19, the drive signal S1 having the frequency f1 is applied to the electrode 14A of the ultrasonic motor 100, and the drive signal S2 having the frequency f2 is applied to the electrode 14B. Will be applied.

  The rotation detector 22 detects the rotation speed and rotation angle or the rotation direction of the moving body 4 and the output shaft 2 of the ultrasonic motor 100, and the rotation speed and rotation of the driven body driven by the ultrasonic motor 100. The angle or rotation direction is detected, and the detection signal from the rotation detector 22 is configured to be input to the drive control unit 21.

  The position detector 23 detects the position of the driven body driven by the ultrasonic motor 100, and the detection signal from the position detector 23 is configured to be input to the drive control unit 21.

Next, a control method during intermittent drive of the ultrasonic motor 100 using the drive signal output circuit 200 will be described with reference to FIGS.
First, when a drive command signal (ON command pulse) is output from the drive trigger generation circuit 15 to the oscillation circuit 16 at time t0, the oscillation circuit 16 sends the drive signal having the frequency f1 to the first output circuit 17 and the phase control circuit 18. The output of S1 is started.

The drive signal S1 output to the first output circuit 17 is amplified by the first output circuit 17 and applied to the electrode 14A of the ultrasonic motor 100.
On the other hand, if the phase difference in the phase control circuit 18 is set to 0 °, the drive signal S1 output to the phase control circuit 18 is output to the frequency control circuit 19 with the phase unchanged without being phase-shifted. The frequency control circuit 19 generates a drive signal S2 having a frequency f2. The drive signal S2 is amplified by the second output circuit 20 and applied to the electrode 14B of the ultrasonic motor 100.

Thus, in the present embodiment, the drive signal S1 having the frequency f1 is applied to the electrode 14A of the ultrasonic motor 100, and the drive signal S2 having the frequency f2 is applied to the electrode 14B.
Since the frequencies of the drive signal S1 and the drive signal S2 are different, the phase difference between the drive signal S1 and the drive signal S2 is 0 ° at time t0, but the phase difference thereafter increases, and the phase difference at time t1. The phase difference is 90 °, the phase difference is 180 ° at time t2, the phase difference is 270 ° at time t3, and the phase difference is 360 ° (= 0 °) at time t4.

Then, the moving body 4 of the ultrasonic motor 100 starts at the time t0 at the speed 0, forward rotation (CW) at the time t0 to t2, stops at the time t2, reverse rotation (CCW) at the time t2 to t4, and the time t4. Thereafter, until the stop command signal (OFF command pulse) from the drive trigger generation circuit 15 is output to the oscillation circuit 16 and the output of the drive signal from the oscillation circuit 16 is stopped, the rotation is stopped (CW) and stopped. , Reverse rotation (CCW), stop, forward rotation (CW), stop, reverse rotation (CCW), stop, forward rotation (CW),...

As described above, the moving body 4 of the ultrasonic motor 100 continuously repeats intermittent driving (start / stop), but in the present embodiment, the drive signal S1 is also applied at the time of stopping at times t2 and t4. , S2 are continuously applied to the electrodes 14A, 14B, and the rotation of the moving body 4 stops, but the moving body 4 maintains a floating state by the drive signals S1, S2.
For this reason, the moving body 4 is not knocked against the stator ring 8 a by the pressure of the spring 10, and the generation of noise and vibration when the ultrasonic motor 100 is stopped can be suppressed.
In addition, since the moving body 4 maintains a floating state even when it is stopped, it is possible to suppress generation of noise at the time of start-up in the intermittent drive of the ultrasonic motor 100.
As described above, according to the control apparatus for an ultrasonic motor according to the present embodiment, it is possible to suppress the generation of noise and vibration during stopping and the generation of noise during startup in intermittent driving of the ultrasonic motor.

  In the above-described embodiment, an example in which the rotation direction of the moving body 4 is reversed before and after the time t2 is illustrated. For example, at the time t2, the phase of the drive signal output from the phase control circuit 18 is changed. By reversing (shifting the phase by 180 °), the rotational direction of the moving body 4 can be set to the positive rotation (CW) at times t2 to t4, and thereafter the phase difference between the drive signals S1 and S2 is 180 °. By inverting the phase of the drive signal output from the phase control circuit 18 at the time (shifting the phase by 180 °), forward rotation (CW), stop, forward rotation (CW), stop, forward rotation (CW), ... can be repeated.

  Further, in the above-described embodiment, the example in which the rotational speed of the moving body 4 changes from the acceleration to the deceleration before and after the times t1 and t3 is exemplified. However, for example, at the times t1 and t3, a certain time thereafter. The frequency of the drive signal output from the frequency conversion circuit 19 over the width is set to f1, and the phase difference between the drive signals S1 and S2 is maintained at 90 ° or 270 °, so that the rotational speed of the moving body 4 can be increased over the certain time width. The frequency of the drive signal output from the frequency conversion circuit 19 can be set to f1 over a certain time width starting from the time when the phase difference between the drive signals S1 and S2 becomes 90 ° and 270 °. By doing so, it is also possible to maintain the rotation speed of the moving body 4 at a constant speed over a certain time width.

  In the embodiment described above, the drive signals S1 and S2 are all illustrated using the full-wave SIN wave. However, in the drive signal output circuit 200, for example, the first output 17 and the second output are used. A half-wave rectifier circuit may be provided on the input side of the circuit 18. Thus, if a half-wave drive signal is used, an energy saving effect can be achieved by reducing the amount of power used, compared to the case where a full-wave drive signal is used.

  In the embodiment described above, the frequency conversion circuit 19 is provided only on the second output circuit 20 side, but the frequency conversion circuit is also provided on the first output circuit 17 side and applied to the electrodes 14A and 14B. It is also possible to cause a frequency difference in the drive signal to be generated.

  In the embodiment described above, the control device and the control method of the rotary ultrasonic motor 100 are exemplified, but the control device and the control method of the present invention can be applied to a direct acting ultrasonic motor, and The present invention is not limited to an ultrasonic actuator that uses vibrations in the ultrasonic band, and can be applied to those that use vibrations other than the ultrasonic band.

2 Output shaft 4 Moving body 4a Rotor ring 4b Friction material 6 Base 8 Vibrating body 8a Stator ring 8b Piezoelectric body (piezoelectric ceramics)
DESCRIPTION OF SYMBOLS 10 Spring 14A, 14B Electrode 19 Frequency conversion circuit 100 Ultrasonic motor 200 Drive signal output circuit S1 Drive signal S2 Drive signal

Claims (2)

In a vibration actuator control device comprising a vibrating body in which a traveling wave is generated by applying a two-phase driving signal, and a moving body driven by the traveling wave,
A frequency control unit for controlling the frequency of at least one of the two-phase drive signals;
By changing the frequency of the two-phase drive signal by the frequency control unit to change the phase difference of the two-phase drive signal,
When the phase difference between the two-phase drive signals is near 0 ° or near 180 °, the vibration actuator is continuously driven by stopping the moving body, and the vibration actuator control device is characterized in that . In a control method of a vibration actuator comprising a vibrating body in which a traveling wave is generated by applying a two-phase driving signal, and a moving body driven by the traveling wave,
By changing the frequency of the two-phase drive signal to change the phase difference of the two-phase drive signal,
When the phase difference between the two-phase drive signals is near 0 ° or near 180 °, the vibration actuator is intermittently driven by stopping the moving body, so that the vibration actuator is controlled. .

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