JPH06296377A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To output moving information of a high resolution by counting an oscillation frequency of a drive circuit with reference to a signal of an encoder, etc., which is added to an ultrasonic motor. CONSTITUTION:A moving information output circuit 111 is added to an ultrasonic motor 107 and a counting circuit 109 which counts signals from an oscillator of the ultrasonic motor 107 with reference to an output signal from the moving information output circuit 111 is also provided. Moreover, an interporation arithmetic circuit 110 for executing interporation arithmetic operation of an output signal of the moving information arithmetic circuit 110 on the basis of the counting result of the counting circuit 109 is also comprised and an output circuit for outputting the result of interporation arithmetic operation as a high resolution moving information is provided. As exaplained, an output of a low resolution moving information detector is converted to moving information of a high resolution with a simplified method in view of facilitating the control for the number of rotations and positional control of the ultrasonic motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detection and control of position information of an ultrasonic motor by electromechanical conversion such as piezoelectric and magnetostriction.

[0002]

2. Description of the Related Art Conventionally, in order to detect movement information such as the number of revolutions and the position of a moving body such as a rotor of an ultrasonic motor, is a device such as a magnetic or optical encoder added to the ultrasonic motor? As an example in which a detector is incorporated in an ultrasonic motor by utilizing a part of the ultrasonic motor, for example, in JP-A-62-221885, a rotor is provided with a discontinuous portion such as a groove, which is generated in a stator. There is one that obtains rotation information by detecting intermittent waveform distortion. In addition, JP-A-3-82
There is also one disclosed in Japanese Patent No. 380 that obtains rotation information by detecting a change in acoustic mechanical impedance.

[0003]

However, even if the encoder is added to the ultrasonic motor as described above, the resolution is low for downsizing, and the encoder becomes large when the resolution is increased. The volume of the whole motor increases, a large installation space is required, the range of use is limited, and the cost of the ultrasonic motor itself increases. Therefore, JP-A-62-221885 and JP-A-3-221885
The method according to Japanese Patent Laid-Open No. 82380 is an effective remedy for miniaturization, but has a problem that the resolution is extremely low.

Therefore, an object of the present invention is to reduce the resolution by a simple method by downsizing the above-mentioned conventional encoder in order to solve the above-mentioned conventional problems.
We have made it possible to provide an ultrasonic motor capable of extremely highly accurate position control.

[0005]

In order to solve the above-mentioned problems, the ultrasonic motor of the present invention is provided with an additional movement information detector, and the drive frequency is set by using the signal from the movement information detector as a gate signal. By counting and calculating, interpolation calculation between signals of the movement information detector can be performed.

[0006]

In the ultrasonic motor configured as described above, the resolution is improved by performing interpolation calculation on the part which is not detected in the operating state of the moving body based on the output signal of the moving information detector. It can be significantly improved and the movement information of the moving body can be taken out as a digital signal, and highly accurate movement information of the ultrasonic motor and equipment using the ultrasonic motor can be obtained, and the rotation speed, movement amount, speed, position, etc. can be obtained. Enables highly accurate control.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings. In each of the drawings of the embodiments, the same parts are designated by the same reference numerals, and the duplicated description will be omitted. (First Embodiment) FIG. 1 is an explanatory diagram showing a block diagram of a circuit for driving an ultrasonic motor and obtaining rotation information of a rotor as a moving body when the moving body of the present invention is a rotating body. is there. FIG. 2 is a diagram showing the relationship between the output signal of the oscillator and the drive signal of the ultrasonic motor.

In FIG. 1, the signal of the oscillator 101 includes an inverter 102, a flip-flop (FF) 103, and an FF.
It is divided into two signals having a phase difference of 90 ° by 104. The state of the two divided signals is shown in FIG. Figure 2
2A is an output signal from the oscillator 101, FIG.
2C shows an output signal from the FF 103, and FIG. 2C shows an output signal from the FF 104 when the signal whose phase is inverted by the inverter 102 is applied to the FF 104.

The output signal from the oscillator 101 of FIG. 2 (a) has a frequency twice that of the output signal of FIGS. 2 (b) and 2 (c). Further, the signals divided into two signals having a phase difference of 90 ° are respectively the amplifier 105 and the amplifier 106.
And is applied to the ultrasonic motor 107. The ultrasonic motor 107 rotates, and the rotation detector 108 outputs a rotation information signal.

The signal from the rotation detector 108 is pulse-shaped and applied to the gate of the counting circuit 109. Oscillator 1
The signal from 01 is applied to the clock terminal of the counting circuit 109. The counting circuit 109 counts the number of signal pulses from the oscillator 101 between the pulses of the rotation detector 108.

FIG. 3 is a diagram showing the relationship between the output signal of the rotation detector 108 of the ultrasonic motor of the present invention and the signal of the oscillator 101. 3A shows the pulse signal from the rotation detector 108, FIG. 3B shows the signal from the oscillator 101, and the counting circuit 109 shows the rotation detector 108 of FIG. 3A.
The pulse signal from is used as a gate, and the oscillator 1 of FIG.
Count the number of signals since 01. The pulse signal per rotation from the rotation detector 108 is N, and the number of counted signals from the oscillator is M. Encoder resolution is N *
Therefore, the resolution is M times higher than that when only the rotation detector 108 is used.

The interpolation calculation circuit 110 counts and stores the output pulses of the rotation detector 108, which is a movement information detector, and further calculates and interpolates movement information between the output pulses of the rotation detector 108. The interpolation calculation circuit 110 includes the counting circuit 1
09 counted between pulses of the rotation detector 108,
The average value of the number of output signals of the oscillator 101 or the immediately preceding count value is stored as M.

It is assumed that the number of output pulses of the rotation detector 108 currently counted is n, and the number of output signals of the oscillator 101 counted by the counting circuit 109 is m. The interpolation value of the current rotational speed is calculated by the interpolation calculation circuit 110 as (n + m /
M) / N is calculated.

The movement information output circuit 111 calculates by the interpolation calculation circuit 110, stores the result, and outputs the data at that moment as digital data or a pulse signal. A method of controlling the rotation speed of the ultrasonic motor is performed by controlling the drive voltage, the phase, and the drive frequency. The method of controlling the drive frequency is the easiest method for controlling the rotation speed of the ultrasonic motor, and is generally performed. In the method of controlling the frequency, the frequency of the oscillator 101 changes. However, since the ultrasonic motor is a kind of mechanical resonator, the rate of change of the frequency is extremely small, and therefore the rotational accuracy becomes sufficiently practical even if the frequency of the oscillator is counted.

FIG. 4 shows an embodiment in which higher precision interpolation is required. As shown in FIG. 4, the counting circuit 109
It is also possible to use another high-precision oscillator 112 such as a crystal oscillation circuit instead of the oscillator 101 for the clock terminal of 1. However, there is a problem that the circuit becomes complicated and the number of elements increases, so that the ultrasonic motor can be made compact. It becomes unsuitable for the purpose of becoming.

FIG. 5 is an example of a sectional view showing the structure of the ultrasonic motor of the embodiment of the present invention. As shown in FIG. 5, a vibrator 2 in which a driving piezoelectric element 201 is joined by adhesion or the like
02 is driven by the drive circuit 100 in the vicinity of the resonance frequency to generate a traveling wave, and the friction material 21 is generated by the generated traveling wave.
The rotor body 212 is rotated by frictional force through 1.
The pressure mechanism 213 generates and adjusts a pressing force by a spring or the like to adjust the frictional force. The central shaft 215 constitutes the center of the ultrasonic motor, and is driven and fixed to a support plate 214 for fixing and supporting the vibrator 202 and for mounting the motor to the outside. The rotation detector 108 has a rotor body 212 in the rotating portion.
The rotor is rotated and the rotating portion is rotated by the rotation of the rotor body 212 to output rotation information.

(Second Embodiment) Next, a second embodiment of the present invention will be described. If the present invention is applied, rotational speed control and position control become very easy. Regarding the rotation speed control, means for controlling the oscillation frequency of the oscillator 101 is provided, and the number of output pulses of the oscillator 101 during one pulse of the rotation detector 108 is counted, compared with the control value, and the oscillator is controlled so as to reach the control value. The rotation speed can be controlled only by controlling the frequency of 101.

FIG. 6 is a block diagram of the rotation speed control circuit. From FIG. 6, the rotation speed is the rotation input circuit 1
When specified to 22, the specified value of the rotation speed, the oscillator 10
When the output frequency of 1 and the number of pulses per rotation of the rotation detector 108 are set as follows, the specified value of the rotation number Rn The output frequency of the oscillator 101 Fosc The number of pulses per rotation of the rotor of the rotation detector 108 N rotation The set value Mc of the control value of the output pulse number of the oscillator 101 for one pulse of the detector 108 is given by the following equation, and is calculated and stored in the setting calculation circuit 123.

Mc = Fosc / (Rn / 60 * N) Next, the motor rotates, the counting circuit 109 counts the number m of output pulses of the oscillator 101 during one pulse of the rotation detector 108, and the interpolation calculation circuit 110. Memorized in
Comparing with the set value Mc stored in the set value calculation circuit 123, the movement information output circuit 111 generates a signal for controlling the oscillation frequency control circuit 121 according to the comparison result, and controls the oscillation frequency of the oscillator 101. Controls the rotation speed of the motor. In addition, the movement information output circuit 111
Simultaneously outputs the rotation signal of the motor at this time to the external device 124 such as a display.

(Third Embodiment) Since the ultrasonic motor is minutely driven by friction, the resolution of the stop position is high, and the resolution is greatly different from that of the electromagnetic core motor and the electromagnetic step motor which cannot accurately stop at an arbitrary position due to coking. . Therefore, in order to bring out the characteristics of the ultrasonic motor, highly accurate and high resolution stop position control is desired.

FIG. 7 shows a flowchart of the stop position control. From FIG. 7, when the stop position is designated, the number of control target pulses from the rotation detector 108 corresponding to the stop position is calculated and set as Nstop + ΔN. Nstop is an integer, ΔN is a surplus of the quotient of the stop position designation value and the number N of output pulses per rotation of the rotation detector 108, and is a real number of 1 or less including 0.

The ultrasonic motor rotates several times before reaching the set value Nstop, or at a speed lower than before the proper number of pulses,
Control to constant speed. As the means for controlling the rotation speed at this time, the designated value of the rotation speed is automatically set to a preset value and controlled by the control method according to the present invention described above.

By controlling the rotation speed to a low speed, not only the inertia when the motor is stopped is suppressed as much as possible, but also the rotation detector 1
The count value m of the number of oscillator output pulses during one pulse of 08 is
Since it is large, the resolution is remarkably improved. When the ultrasonic motor is controlled to a constant rotation speed and the count value m of the oscillator output pulse number stabilizes at a constant value, the stable value of m is used as a reference for the interpolation value for one pulse of the rotation detector 108. Store as value M. At the stop position, when the number of output pulses of the rotation detector 108 reaches Nstop and the count value m of the counting circuit 109 becomes M * ΔN, the output of the oscillation circuit 101 is stopped, and the ultrasonic wave is stopped. Stop the motor rotation. Therefore, according to the present invention, a high resolution rotation detector,
The stop position of the ultrasonic motor can be controlled with high resolution without requiring a high-performance control circuit.

(Fourth Embodiment) Although the case where the moving body is the rotary moving body has been described above, the same applies to the case where the moving body is a linear moving body, and the embodiment will be briefly described. FIG. 8 shows an embodiment in which the moving body is a linear moving body. FIG. 8A is a sectional view when the moving body is a linear moving body, and FIG. 8B is a diagram showing a part of the linear scale.

The piezoelectric element 201 bonded by adhesion or the like causes the vibrator 202 to generate a traveling wave and drive the linear moving body 203. The linear moving body 203 includes a linear scale 20.
4 is provided, and the optical sensor 205 outputs a movement signal. Therefore, since it is equivalent to the rotation detector 108 shown in FIG. 1, the present invention can be implemented even in the case of a linear moving body.

[0026]

As described above, according to the present invention, the ultrasonic motor is provided with the movement information detector for detecting the movement information of the moving body, and the movement information signal from the movement information detector of the moving body is used as a reference. A means for counting the output signal from the oscillator of the ultrasonic motor and a means for interpolating the movement information signal from the movement information detector of the moving body are provided, and the movement information signal is interpolated to obtain high resolution movement information. It is possible to provide an ultrasonic motor capable of controlling the rotation speed and the position by a simple method by using the interpolated signal.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a block diagram of a circuit for driving an ultrasonic motor and obtaining rotation information of a rotor of the present invention.

FIG. 2 is a diagram showing the relationship between the output signal of the oscillator 101 of the ultrasonic motor of the present invention and the drive signal of the ultrasonic motor.

FIG. 3 is a diagram showing the relationship between the output signal of the rotation detector of the ultrasonic motor of the present invention and the signal of the oscillator.

FIG. 4 is a block diagram showing a circuit for obtaining movement information by the high precision oscillator of the ultrasonic motor of the present invention.

FIG. 5 is a sectional view showing an embodiment of the structure of the ultrasonic motor of the present invention.

FIG. 6 is a block diagram of a rotation speed control circuit for an ultrasonic motor according to the present invention.

FIG. 7 is a flowchart showing a procedure for controlling a stop position by using a circuit for obtaining movement information of an ultrasonic motor according to the present invention.

FIG. 8 is a diagram showing an embodiment in which the moving body of the ultrasonic motor of the present invention is a linear moving body.

[Explanation of symbols]

 100 Driving Circuit 101 Oscillation Circuit 102 Inverter 103 Flip-Flop 104 Flip-Flop 105 Amplifier 106 Amplifier 107 Ultrasonic Motor 108 Rotation Detector 109 Counting Circuit 110 Interpolation Calculation Circuit 111 Movement Information Output Circuit 112 High Precision Oscillation Circuit 121 Oscillation Frequency Control Circuit 122 Rotation Number input circuit 123 Set value calculation circuit 124 External device 201 Piezoelectric element 202 Transducer 203 Linear moving body 204 Linear scale 205 Linear optical sensor 211 Sliding plate 212 Rotor body 213 Pressing mechanism 214 Support plate 215 Central axis

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Kasuga 6-31-1, Kameido, Koto-ku, Tokyo Seiko Denshi Kogyo Co., Ltd.

Claims (5)

[Claims] 1. An oscillator for generating a high-frequency AC signal,
An amplifier that amplifies and outputs an AC signal from the oscillator, and a vibrating body excited by the output from the amplifier,
In an ultrasonic motor composed of a moving body frictionally driven by the vibrating body, a moving information detector for detecting an operation state of the moving body is provided, and a moving information signal from the moving information detector of the moving body is transmitted. As a reference, a means for counting the output signal from the oscillator of the ultrasonic motor is provided, and the movement information signal output from the movement information detector of the moving body is input,
It is provided with a calculation means for interpolating the operation state of a part which is not detected in the operation state of the moving body, and has a function of interpolating the movement information signal and outputting the result of the calculation as movement information. And ultrasonic motor. 2. The ultrasonic motor according to claim 1, further comprising a movement information detector that detects a rotating state of the moving body in the ultrasonic motor. 3. The ultrasonic motor according to claim 1, wherein the ultrasonic motor has a moving body detector that detects a linear movement of the moving body and the moving body moves linearly. 4. The ultrasonic motor is provided with a control means for controlling an oscillation frequency of an oscillator, and the number of oscillator output pulses counted during one pulse of the movement information detector is set in advance for the operation of the moving body. 2. The ultrasonic motor according to claim 1, wherein the number of revolutions of the ultrasonic motor is controlled by controlling the oscillation frequency by controlling the oscillation frequency of the oscillator compared with a set value corresponding to the state. . 5. In the ultrasonic motor, the rotational speed control means for controlling the rotational state of the moving body controls the rotational speed to a predetermined rotational speed from several pulses before several pulses to reach the stop position set value, and the main motor is controlled by the rotational speed control means. The ultrasonic motor according to claim 1, wherein the movement information detecting means of the invention controls the stop position based on the detected position information.