JPS63206171A - Drive controlling circuit for ultrasonic wave motor - Google Patents

Abstract

PURPOSE:To stably drive a device, by a method wherein the rotational frequency of an ultrasonic wave motor is monitored, and wherein the rotational frequency is detected again when it is out of the tolerance of optimum frequency, and wherein the motor is driven with the newly detected optimum frequency. CONSTITUTION:Cyclic voltage (cyclic signal) is applied to an ultrasonic wave motor 10 at a driving circuit 19, and the motor 10 is rotated. Optical pulses synchronized with the ultrasonic wave motor 10 are formed by an encoder or the like, and from the collector of a phototransistor 11, pulse signal is obtained. The output of the phototransistor 11 is applied to the input terminal T of a T flipflop 13, and frequency-divided output is generated. The frequency- divided output B and the pulse signal C of a pulse generator 14 are supplied to a logical circuit 15, and its output signal D is counted by a counter 16 which supplies a processor 17 with a signal as the rotational frequency of the motor 10. Then, based on the rotational frequency the processor 17 computes optimum frequency and its tolerance, and the ultrasonic wave motor 10 is driven by an oscillating circuit 18 and the driving circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a drive control circuit that controls the rotational speed of an ultrasonic motor.

B. Prior Art An ultrasonic motor is known that supplies an alternating current signal to an electrostrictive element to cause it to vibrate, thereby forming a progressive vibration wave in an elastic body to drive a moving body.

There are two types of ultrasonic motors of this type: a rotary type and a linear type. As shown in FIGS. (not shown) is configured to press with a predetermined pressing force.

Further, an electrostrictive element 33 is attached to the back surface of the elastic body 31, and a segment electrode 34a is attached to the surface 33a of the electrostrictive element 33.
34d are formed, and the electrostrictive elements 33 under the segment electrodes 34b and 34d are alternately polarized.

Ultrasonic motors are generally driven by frequency signals of 30 KHz to 40 KHz (signals including alternating current and pulse signals), but the optimal frequency range is extremely narrow, several tens of I (z), and the optimal frequency is within the range of the power supply voltage. It changes depending on the drop, the magnitude of the load, the wear of various parts, etc.
Publication No. 981 states that prior to using the device, the motor drive frequency is increased from the lowest to highest by a predetermined operation, for example, by turning on the power switch of the camera, and the motor drive frequency is sequentially swept in one direction, and the motor rotation speed at that time is monitored to determine the optimum speed. A drive control circuit is disclosed that finds a frequency (eg, the frequency at which maximum rotational speed is obtained).

C0 Problems to be Solved by the Invention However, in the conventional ultrasonic motor drive control circuit described above, the optimal frequency is detected in response to the power switch-on operation, so after the power switch is turned on, the rotation speed is within the allowable range of the optimal frequency. There is a problem in that if the rotation speed of the motor deviates from the rotation speed or the number of revolutions of the motor suddenly changes, it is not possible to follow the fluctuation.

The object of the invention is to provide a method without performing any predetermined operations.

The ultrasonic motor drive control circuit constantly monitors whether the motor rotation speed is within the optimum frequency range, and if it deviates from the allowable range, resets the optimum frequency and drives the ultrasonic motor. is intended to provide.

Means for Solving the D0 Problem As shown in the claim correspondence diagram in FIG. 1, the ultrasonic motor drive control circuit according to the present invention includes a drive signal output means that supplies a frequency signal as a drive signal to the ultrasonic motor 51. 52, a rotation speed detection means 53 for detecting the rotation speed of the ultrasonic motor 51, a frequency change means 54 for sequentially changing the frequency of the frequency signal, and a frequency change means 54 for changing the frequency of the frequency signal to generate an ultrasonic wave. The ultrasonic motor 51 includes optimum frequency detection means 55 for detecting an optimum frequency at which the ultrasonic motor 51 efficiently rotates from the detected rotational speed when the ultrasonic motor 51 is rotated. The above-mentioned problem is solved by the determination means 56 that determines whether the detected motor rotation speed is within the permissible range of the optimum frequency, and when it is determined that the detected motor rotation speed is within the permissible range, the frequency of the drive signal is changed. First, if it is determined that the frequency is not within the allowable range, the frequency changing means 54 and the optimum frequency detecting means 55 are driven to detect the optimum frequency, and the drive signal outputting means is configured to supply a drive signal of the detected optimum frequency. 52
This problem can be solved by providing a frequency control means 57 for controlling the frequency.

The E0 action rotation speed detection means 53 constantly monitors the rotation speed of the ultrasonic motor 51. The determining means 56 determines whether the rotational speed of the ultrasonic motor 51 detected by the rotational speed detection means 53 is within the currently set allowable range of the optimum frequency, and if it is not within the allowable range, the frequency control means 57 drives the frequency changing means 54 and the optimum frequency detecting means 55 to detect the optimum frequency. Since the drive signal output means 52 applies a frequency signal of the detected optimal frequency to the ultrasonic motor 51 to drive it, the rotational speed of the ultrasonic motor 51 is always stable.

F. Example The present invention will be explained in detail with reference to FIGS. 2 to 4.

In FIG. 2, the ultrasonic motor 10 is rotated by application of a frequency voltage (frequency signal) by a drive circuit 19. A light pulse synchronized with the ultrasonic motor 1o is formed by an encoder (not shown) or the like, and a pulse signal as shown in FIG. 3(a) is obtained from the collector of the phototransistor 11.

The collector of the phototransistor 11 is held at a predetermined voltage via a resistor 12, while the emitter is grounded. Further, the aforementioned optical pulse signal corresponding to the rotational speed of the ultrasonic motor 10 is applied to the base of the phototransistor 11. The output of the phototransistor 11 becomes a pulse signal A as shown in FIG.
Flip-flop (hereinafter simply referred to as flip-flop) 13
, and is frequency-divided and output from the output terminal Q of the flip-flop 13. In the AND circuit 15,
The third frequency divided from the output terminal Q of the flip-flop 13
The output signal B as shown in FIG. 3(b) and the pulse signal C as shown in FIG. 3(c) from the pulse generator 14 are added, and the output signal B and the pulse signal C are logically The product signal is output as shown in FIG. 3(d).

The counter 16 receives the AND signal shown in FIG. 3(d), counts the number of pulses of the AND signal, and outputs this number of pulses to the processor 17 as an indication of the rotation speed of the ultrasonic motor 1o. .

The processor 17 calculates the optimal frequency and its allowable range based on the number of pulses counted by the counter 16, that is, the rotation speed of the ultrasonic motor 10, according to a processing procedure described later, and causes the ultrasonic motor 10 to constantly rotate within the allowable range. control to do so. The oscillation circuit 18 sends a frequency signal of the optimum frequency determined by the output from the processor 17 to the drive circuit 1.
9, a drive circuit 19 drives the ultrasonic motor 1o with a drive signal of an optimum frequency.

Note that the processor 17 normally resets the flip-flop 13 and the counter 16, and releases these reset states only for a predetermined period.

In the embodiment with the above configuration, the drive circuit 19 serves as the drive signal output means 52, the counter 16 serves as the rotation speed detection means 53, and the processor 17 serves as the frequency change means 54. Optimum frequency detection means 552, determination means 56, and frequency control means 57 are respectively constituted.

The operation of the drive control circuit for the ultrasonic motor having such a configuration will be explained using the flowcharts shown in FIGS. 4(a) to 4(c).

When driving the ultrasonic motor 10, as shown in FIG. 4(a), the processor 17 first detects the maximum value of the rotation speed of the ultrasonic motor 10, and detects the frequency that takes the maximum value as the optimum frequency (step 101). The detection of the maximum value is
As will be described later based on FIG. 4(b), this is basically carried out by sequentially sweeping the frequency of the frequency voltage applied to the ultrasonic motor 10 from the lower limit frequency to the upper limit frequency. Next, the processor 17 sets a permissible range of the optimum frequency that takes the maximum value of the rotation speed (step 102).
. After that, the rotation speed is monitored (step 103), and it is determined whether the rotation speed is within the allowable range (step 1).
04). If the rotational speed is within the allowable range, the process returns to step 103 and the rotational speed is constantly monitored. If it is determined in step 104 that the rotational speed is not within the allowable range, the process returns to step 101 and the optimum frequency and its allowable range are detected again.

FIG. 4(b) is a flowchart showing the flow of the process for detecting the optimum frequency performed in step 101 of FIG. 4(a). In FIG. 4(b), the processor 17 supplies the lower limit frequency value of the sweep to the drive circuit 19 via the oscillation circuit 18 (steps 201 and 20).
2) The drive circuit 19 applies a frequency voltage (drive signal) of the lower limit frequency to the ultrasonic motor 10 (step 203).

Next, it is determined whether a certain period of time has elapsed since the frequency voltage was applied (step 204). If the predetermined time has not elapsed, the rotational speed of the ultrasonic motor 10 is not yet stable, so the process returns to step 204 again to wait until the predetermined time has elapsed. When a certain period of time has elapsed in step 204, the T flip-flop 13 and the counter 1
6 is released from the reset state for a predetermined period of time (step 205
).

When the Q output rises during this predetermined time, a pulse as shown in FIG. 3(d) is input to the counter 16, and the counter 1
6 counts the number of pulses (steps 206, 207
). When a predetermined period of time has elapsed, the processor 17 stores the count result by the counter 16 in a count memory (not shown).
At the same time, the T flip-flop 13 and counter 16 are reset (step 208). As a result, the number of pulses counted for one frequency value is counted and stored in the count memory.

Next, it is determined whether the current frequency value is the upper limit frequency or not (step 209), and if it is not the upper limit frequency, the current frequency is increased by Δf and swept (step 210), and the process returns to step 202 again to perform the same processing. and store the number of pulses for the set frequency in memory. In step 209, when the planned upper limit frequency is determined, the count memory stores the number of pulses corresponding to the frequency value that is increased stepwise by Δf from the lower limit frequency to the upper limit frequency. Next, compare the number of pulses, that is, the number of rotations stored in this count memory (step 211), and select the largest one among them (step 211).
Step 212).

After that, a frequency value that gives the maximum rotation speed is set, and the oscillation circuit 18 is caused to oscillate at this frequency to supply a signal to the drive circuit 19 (step 213), and the drive circuit 19 converts the drive signal of that frequency into ultrasonic waves. Supplied to motor 1o.

FIG. 4(c) is a flowchart showing the flow of the process for monitoring the rotational speed carried out in step 103 of FIG. 4(a). In FIG. 4(c), the processor 17
First, set a predetermined time on a timer (not shown) (
Step 301). Next, the reset state of the T flip-flop 13 and the counter 16 is released (step 3).
02).

As a result, the counter 16 counts the number of pulses by the rise time of the Q output during the predetermined period set in the timer (
Steps 303, 304). This counted number of pulses represents the current rotational speed of the ultrasonic motor 10, and the result is stored in a count memory (not shown) (step 3o5).

After that, the T flip-flop 13 and the counter 16
is reset again (step 306).

In this way, according to this embodiment, the optimum frequency and allowable range at which the ultrasonic motor reaches its maximum rotation speed are set in advance, and it is constantly monitored whether the current rotation speed of the ultrasonic motor 10 deviates from the allowable range. However, if there is a deviation, the optimal frequency and tolerance range are found again, so even if the rotation speed of the ultrasonic motor suddenly fluctuates, it is possible to drive the ultrasonic motor stably. can.

Detailed explanation of the G0 invention According to the present invention, the rotational speed of the ultrasonic motor is constantly monitored, and if the rotational speed is not within the allowable range of the optimum frequency, the optimum frequency is detected again and a new Since the ultrasonic motor is driven using the optimal frequency detected, the ultrasonic motor can always be driven in a stable state.

[Brief explanation of the drawing]

FIG. 1 is a complaint correspondence diagram. FIG. 2 is a configuration diagram of an embodiment of the drive control circuit for an ultrasonic motor according to the present invention, FIGS. 3(a) to 3(d) are time charts of the drive control circuit shown in FIG. 2, and FIG. a) ~ (c)
is a flowchart showing the processing flow of the drive control circuit shown in FIG. 2, FIG. 5(a) is a schematic configuration diagram of the rotary ultrasonic motor, and FIG. FIG. 10.51: Ultrasonic motor 11: Phototransistor 13: T flip-flop 14: Pulse generator 15: AND circuit 16: Counter 17: Processor 18: Oscillation circuit 19: Drive circuit 52:
Drive signal output means 53: Rotation speed detection means 54: Frequency change means 55: Optimal frequency detection means 56: Judgment means 57: Frequency control means Patent applicant Nippon Kogaku Kogyo Co., Ltd. Representative patent attorney Nagai, Fuyu Ki Figure 1 dC Figure 5

Claims (1)

[Claims] Drive signal output means for supplying a frequency signal as a drive signal to an ultrasonic motor, rotation speed detection means for detecting the rotation speed of the ultrasonic motor, and sequentially changing the frequency of the frequency signal. a frequency changing means, and an optimum frequency for detecting an optimum frequency at which the ultrasonic motor efficiently rotates from the detected rotational speed when the ultrasonic motor is rotated by changing the frequency of the frequency signal by the frequency changing means. a drive control circuit for an ultrasonic motor, comprising a frequency detecting means, a determining means for determining whether or not the detected motor rotation speed is within an allowable range of an optimum frequency; Then, the frequency of the frequency signal is not changed, and if it is determined that it is not within the allowable range, the frequency changing means and the optimum frequency detecting means are driven to detect the optimum frequency, and the frequency of the detected optimum frequency is changed. A drive control circuit for an ultrasonic motor, comprising: frequency control means for controlling the drive signal output means to supply a signal.