JP2017034758A - Control device of vibration type actuator, control method of the same, vibration device, interchangeable lenses, imaging apparatus, and automatic stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a resonant frequency change caused by an environmental change of a vibration type actuator and correct a startup frequency without using a temperature sensor.SOLUTION: By performing frequency sweep with a drive voltage generating a push-up vibration or a standing wave vibration without generating a vibration in a drive direction, a current for a frequency in a stop state is detected without activating a vibration type actuator. On the basis of detected current properties, a startup frequency is corrected.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for a vibration type actuator and a control method thereof, a vibration device, a replacement lens, an imaging device, and an automatic stage, for example.

  A vibration type motor is an example of a vibration type actuator, and includes a vibration body having an elastic body and an electro-mechanical energy conversion element such as a piezoelectric element coupled to the elastic body, and a driven body that is in pressure contact with the vibration body. The vibration type motor is configured to generate high-frequency vibrations in the electro-mechanical energy conversion element by applying an AC voltage, and to extract the vibration energy as a continuous mechanical motion. Motor.

  The control device for the vibration type actuator includes a pulse signal generation unit that generates a pulse signal and a booster circuit that applies an amplified AC voltage to a piezoelectric element included in the vibration body. The vibration type actuator can control the speed by the frequency, amplitude, phase difference and the like of the AC voltage applied to the piezoelectric element, and is used for, for example, autofocus driving of a camera. The autofocus drive requires highly accurate positioning control. For example, position feedback control using a position sensor is performed.

  During control, the vibration amplitude increases as the drive frequency approaches the resonance frequency of the drive vibration mode of the piezoelectric element, and the vibration amplitude decreases as the drive frequency moves away from the resonance frequency to the high frequency side. Drive the lens at high speed or low speed. Here, since the resonance frequency of the vibration type actuator changes depending on the environmental temperature, the characteristic of the driving speed (relative speed between the vibrating body and the driven body) with respect to the driving frequency changes. Therefore, when the control is performed without correcting the drive parameter, the control performance may be impaired by the environmental temperature.

  The following methods have been proposed for the above problem.

  Japanese Patent Application Laid-Open No. 2004-228561 uses a means for detecting an environmental temperature such as a temperature sensor to control the reference frequency of the drive voltage based on frequency correction amount data corresponding to the environmental temperature stored in advance.

Japanese Patent No. 5391595

  However, the control method that corrects the drive frequency using the temperature sensor increases the cost of the control device. Accordingly, an object of the present invention is to provide a control method for correcting a starting frequency by detecting a resonance frequency change due to an environmental change of a vibration actuator without using a temperature sensor.

One embodiment of the present invention is:
Current detection means for detecting current in the characteristic detection period;
A frequency acquisition unit for acquiring a frequency at which the current reaches a predetermined current based on the output of the current detection means;
A first parameter acquisition unit that acquires an AC voltage parameter using a correction amount based on an output of the frequency acquisition unit;
AC voltage generating means for generating the AC voltage input to the vibration type actuator based on the output of the first parameter acquisition unit;
Have
During the characteristic detection period, vibration in a direction perpendicular to the contact surface is excited in a contact portion of the vibration body of the vibration actuator with the driven body, and the vibration actuator is in a stopped state. The present invention relates to a control device for a vibration type actuator.

Moreover, one embodiment of the present invention is as follows.
In the characteristic detection period,
A vibration is detected in a state in which an alternating voltage is applied so that vibration in a direction perpendicular to the contact surface is excited and stopped in a contact portion of the vibration body of the vibration type actuator with the driven body,
Based on the detected current, correct the parameter of the AC voltage applied to the vibration type actuator,
During this driving period,
The present invention relates to a method for controlling a vibration type actuator, wherein an AC voltage having the corrected parameter is applied to the vibration type actuator.

  According to the present invention, the drive frequency can be corrected by detecting a change in the resonance frequency due to an environmental change of the vibration type actuator without using a temperature sensor. It is also possible to cope with variations in individual differences.

It is a figure explaining the vibration type actuator in the 1st Embodiment of this invention, the vibration apparatus which has its control apparatus, the drive part of a control apparatus, and a pulse signal. It is a figure explaining the drive principle of a vibration type actuator of a linear drive type. It is a figure explaining the drive mechanism part of the lens of a lens barrel. It is a figure explaining the characteristic of the frequency and actuator speed by the difference in environmental temperature. It is a figure which shows the measurement result of the speed and electric power when sweeping a frequency in this drive period and a characteristic detection period. It shows a method of detecting a change in resonance frequency due to environmental temperature with electric power. It is a flowchart which shows the control sequence of a characteristic detection period and this drive period. It is the measurement result of electric power when changing the pulse width of a pulse signal. This shows the peak frequency and frequency difference when the pulse width is changed. The change in driving speed due to the difference in environmental temperature and the measurement result of the power characteristic during the characteristic detection period are shown. 4 shows a vibration type actuator using traveling waves in a second embodiment of the present invention. It shows a pulse signal during a characteristic detection period and a standing wave vibration in a vibration type actuator using a traveling wave. It is the top view which shows the external appearance of the imaging device which is an application example of the control apparatus of this invention, and the schematic of an internal structure. It is a figure which shows the external appearance of the microscope which is an example of application of the control apparatus of this invention.

  The control method of the present invention is applied to, for example, the following vibration type actuator. That is, the vibration type actuator to which the present invention is applied includes a vibrating body including an electro-mechanical energy conversion element such as a piezoelectric element and an elastic body to which the electro-mechanical energy conversion element is joined, and pressurizing and contacting the elastic body. A driven body whose relative position to the vibrating body changes. A plurality of alternating voltages (drive voltages) having different phases are respectively applied to the electro-mechanical energy conversion element, and a vibration wave is generated in the elastic body. The elastic body generates an elliptical motion in the driving portion (contact portion with the driven body) of the elastic body due to the generated vibration wave, and the relative position of the elastic body (vibrating body) and the driven body changes due to the elliptical motion.

  The control method of the vibration type actuator of the present invention can be widely applied to various vibration type actuators. For example, a ring-shaped vibration actuator used for rotational driving of a photosensitive drum of a copying machine or a transfer belt of an image forming apparatus, and a traveling wave is formed on the vibrating body to change the relative position of the vibrating body and the driven body. The present invention can be applied to an annular vibration actuator. Further, the present invention can be applied to a vibration type actuator used for camera lens zoom driving and autofocus driving. In the vibration type actuator, for example, a first-order bending vibration in two directions orthogonal to the friction surface of the elastic body (contact surface between the vibration body and the driven body) is excited and overlapped at a time phase of π / 2. This is a rod-shaped vibration type actuator that generates a spheroid motion on the friction surface.

  In the present invention, the driving direction refers to the direction of relative movement between the vibrating body and the driven body that is parallel to the contact surface between the vibrating body and the driven body. The contact surface between the vibrating body and the driven body is a surface containing a plurality of contact points between the vibrating body and the driven body when viewed microscopically. Or a friction surface of a driven body.

  Driving a vibration type actuator means that a drive voltage is input to the vibration type actuator and vibration is excited in the electromechanical energy conversion element. The drive period includes the characteristic detection period and the main drive. Including period.

  The characteristic detection period is a period in which information is acquired about whether or not there is a change in the speed characteristic of the vibration type actuator due to a change in the resonance frequency of the vibration type actuator and how it has changed. In addition, the main drive period is a period in which an AC voltage for driving for moving the driven object is input to the electromechanical energy conversion element. During the characteristic detection period, vibration in the push-up direction (direction perpendicular to the contact surface) is excited at the contact portion of the vibration type actuator with the driven body, and the vibration type actuator is in a stopped state. Further, during the main driving period, elliptical motion is excited in the contact portion.

  The activation frequency refers to the frequency of the alternating voltage input to the vibration type actuator when driving of the vibration type actuator is started.

(First embodiment)
<Principle explanation of vibrating body>
FIG. 2 is a diagram for explaining the drive principle of a linear drive type vibration actuator. The vibration type actuator shown in FIG. 2A includes a vibrating body 205 in which a piezoelectric element 204 is bonded to an elastic body 203 and a driven body 201 driven by the vibrating body 205. By applying an alternating voltage to the piezoelectric element 204, two vibration modes as shown in FIGS. 2C and 2D are generated, and the driven body 201 that is in pressure contact with the protrusion 202 is moved in the direction of the arrow. Let

  FIG. 2B is a diagram showing an electrode pattern of the piezoelectric element 204. For example, the piezoelectric element 204 of the vibrating body 205 is formed with an electrode region that is divided into two equal parts in the longitudinal direction. In addition, the polarization direction in each electrode region is the same direction (+). Of the two electrode regions of the piezoelectric element 204, an AC voltage (VB) is applied to the electrode region located on the right side in FIG. 2B, and an AC voltage (VA) is applied to the electrode region located on the left side. . Assuming that VB and VA are AC voltages in the vicinity of the resonance frequency of the first vibration mode and in the same phase, the entire piezoelectric element 204 (two electrode regions) extends at a certain moment, and at another moment. It will shrink.

  As a result, vibration in the first vibration mode shown in FIG. 2C (hereinafter referred to as “push-up vibration”) is generated in the vibrating body 205. Also, assuming that VB and VA are alternating voltages having a frequency in the vicinity of the resonance frequency of the second vibration mode and having a phase shifted by 180 °, at a certain moment, the electrode region on the right side of the piezoelectric element 204 shrinks and the left side The electrode area extends. At the other moment, the relationship is reversed. As a result, vibration in the second vibration mode (hereinafter referred to as feed vibration) shown in FIG.

  In this way, by combining the two vibration modes, the driven body 201 is driven in the direction of the arrow in FIG. In addition, the generation ratio of the first vibration mode and the second vibration mode can be changed by changing the phase difference of the AC voltage input to the bisected electrode. In this vibration type actuator, the speed of the driven body can be changed by changing the generation ratio.

  Hereinafter, as the present embodiment, a configuration example in which the control device and the control method of the present invention are applied to a lens driving mechanism of a camera which is an optical apparatus will be described. In the present embodiment, a configuration example mounted on a camera will be described, but the present invention is not limited to this.

  FIG. 3 is a diagram illustrating a lens driving mechanism of the lens barrel. A driving mechanism for a lens, which is an object to be driven using the vibration type actuator of this embodiment, includes a vibrating body, a driven body, and a first guide arranged in parallel to hold the driven body slidably. A bar and a second guide bar. Relative moving force is generated between the vibrating body and the second guide bar in contact with the protruding portion of the elastic body by the elliptical motion generated in the protruding portion of the vibrating body by applying a driving voltage to the electromechanical energy conversion element. Let Thus, the driven body is configured to be movable along the first and second guide bars in the driving direction (here, the direction parallel to the direction in which the second guide bar extends).

  Specifically, the drive mechanism 300 of the object to be driven by the vibration type actuator of the present embodiment mainly includes a lens holder 302 that is a lens holding member, a lens 306, and a vibrating body 205 to which a flexible printed board (not shown) is coupled. Have. Moreover, it has the pressurization magnet 305, the two guide bars 303 and 304, and the base | substrate not shown. Here, the vibrating body 205 will be described as an example of the vibrating body.

  Both ends of the first guide bar 303 and the second guide bar 304 are held and fixed by a base (not shown) so as to be arranged in parallel to each other. The lens holder 302 includes a cylindrical holder portion 302 a, a holding portion 302 b that holds and fixes the vibrating body 205 and the pressing magnet 305, and a first guide portion 302 c that fits with the first guide bar 303 and serves as a guide. Have.

  The pressing magnet 305 included in the pressing means is a permanent magnet. A magnetic circuit is formed between the pressure magnet 305 and the guide bar 304, and an attractive force is generated between these members. The pressurizing magnet 305 is disposed at a distance from the guide bar 304, and the guide bar 304 is disposed in contact with the vibrating body 205. A pressing force is applied between the guide bar 304 and the vibrating body 205 by the suction force.

  The protruding portion of the elastic body comes into pressure contact with the second guide bar 304 and functions as a second guide portion. Since the second guide portion forms a guide mechanism using the magnetic attraction force, the vibrating body 205 and the guide bar 304 may be pulled apart by receiving an external force or the like. It is dealt with like this. That is, the lens holder 302 is returned to a desired position when the drop prevention portion 302d provided in the lens holder 302 hits the guide bar.

  By applying a desired AC voltage to the vibrating body 205, a driving force is generated between the vibrating body 205 and the guide bar 304, and the lens holder is driven by this driving force.

<Changes in actuator characteristics due to environmental temperature>
FIG. 4 is a diagram for explaining the characteristics of the frequency and the driving speed due to the difference in environmental temperature.

  Due to the influence of the temperature characteristics of the piezoelectric element included in the vibrating body, the resonance frequency of the vibrating body changes with the environmental temperature. As shown in the figure, the resonance frequency changes from fm0 to fm1 by changing from the normal temperature environment to the low temperature environment. Along with this, the driving speed characteristic with respect to the frequency shifts to the high frequency side by about the amount of the resonance frequency change.

  Here, the normal temperature environment and the low temperature environment have a temperature range relationship such as 15 ° C. to 30 ° C. and −15 ° C. to 0 ° C., for example. When the frequency at which the predetermined starting speed is reached is compared with the ambient temperature, a difference between f0 and f1 occurs. In contrast to the case where the speed is controlled in the range of the starting frequency f0 to fm0 in the normal temperature environment, it is desirable to control in the range of the starting frequency f1 to fm1 in the low temperature environment. If the start-up frequency can be adjusted with changes in the environmental temperature, the same control performance can be obtained with the same control parameters.

<Control Device and Vibration Device of the Present Invention>
A vibration type actuator control device of the present invention and a vibration device having the control device will be described with reference to the drawings.

  FIG. 1A is a diagram illustrating a vibration type actuator control device according to the present invention, and a vibration device including the vibration type actuator and the control device. The vibration device 10 includes a piezoelectric element 101, a driving object 121, a control device 20, and a relative speed detection unit 115. The driven object may be a driven body that is directly driven by the vibrating body, or may be an object that is driven via the driven body. For example, the driven body 201 shown in FIG. 2A may be used, or the lens 306 and the lens holder 302 shown in FIG. 3 may be used.

  Accordingly, the relative speed obtained by the relative speed detecting means 115 may be the relative speed between the vibrating body and the driven body, or may be the relative speed between the vibrating body and the driven object. Further, the relative speed between the vibrating body and the driving object is obtained from the relative position between the vibrating body and the driving object. Therefore, the relative speed detecting means 115 may be a relative position detecting means.

  The control device 20 includes a control unit 21, a drive unit 22, and a power source 105. The control unit 21 includes a command value generation unit 109, a PID calculation unit 110, a frequency acquisition unit 117, a correction amount acquisition unit 118, and a parameter acquisition unit 111.

  The command value generation unit 109 is configured to output a command value related to position and speed, and the PID calculation unit 110 is configured to obtain a control amount based on the difference between the command value and the output of the relative speed detection unit. ing.

  The frequency acquisition unit 117 acquires the frequency at which the power consumption reaches a predetermined power (or a predetermined current that becomes the predetermined power) from the output of the current detection circuit 102 for detecting the power consumed by the vibration actuator. It is configured as follows. Since the power is proportional to the current, the frequency may be acquired based on the detected current, or the detected current may be used to obtain the power. The correction amount acquisition unit 118 is configured to acquire a correction amount in the AC voltage parameter based on the output of the frequency acquisition unit 117.

  The parameter acquisition unit 111 is configured to acquire an AC voltage parameter based on at least an output from one of the PID calculation unit 110 and the correction amount acquisition unit 118. The parameter is, for example, at least one of the frequency, amplitude, and phase of the AC voltage. The parameter acquisition unit 111 calculates an AC voltage parameter using the correction amount based on the output of the frequency acquisition unit (based on the output of the correction amount acquisition unit 118) during the characteristic detection period. An AC voltage parameter is obtained based on the output of the calculation unit 110.

  The parameter acquisition unit 111 includes two parameters, a first parameter acquisition unit 111-1 to which the output of the correction amount acquisition unit 118 is input and a second parameter acquisition unit 111-2 to which the output of the PID calculation unit 110 is input. You may have a parameter calculating part. In this case, the two parameter acquisition units are switched and used depending on whether the process is the characteristic detection period or the main drive period. The parameter acquisition unit 111 may be a single parameter acquisition unit having the functions of the two parameter acquisition units.

  Next, a specific configuration of the parameter acquisition unit 111 will be described. The parameter acquisition unit 111 includes, for example, a phase difference conversion unit 112 that acquires parameters related to phase differences and a frequency conversion unit 113 that calculates parameters related to frequencies. Further, the parameter acquisition unit 111 includes a phase difference-frequency determination unit 114 that outputs a signal related to one parameter of the phase difference and the frequency from outputs of the phase difference conversion unit 112 and the frequency conversion unit 113.

  The control unit 21 includes, for example, a digital device such as a CPU and a PLD (including ASIC), and an element such as an A / D converter.

  The drive unit 22 includes an AC voltage generation unit 119 configured to generate an AC voltage based on the output of the parameter acquisition unit 111, a current detection circuit 102, and a boost unit 116 that applies the amplified AC voltage to the piezoelectric element 101. Have. The AC voltage generation unit 119 includes a pulse signal generation unit 107 that generates a pulse signal based on the output of the phase difference-frequency determination unit 114, and a switching circuit 108 that generates an AC voltage according to the output of the pulse signal generation unit 107. Have.

  The drive unit 22 will be described in more detail. FIG. 1B is a view showing a drive unit of the vibration type actuator of the present invention.

  The pulse signal generation means 107 outputs A-phase and B-phase pulse signals that operate at a driving frequency according to a control signal (not shown). The switching circuit 108 is configured by, for example, a so-called H-bridge circuit, and the switching element is ON / OFF controlled by a pulse signal to output an AC voltage. The rectangular pulse signal is adjusted by PWM (pulse width modulation) control so that a desired AC voltage amplitude can be obtained in the pulse width (pulse duty).

  The switching circuit 108 is connected to the power source 105 via a resistor 106, and the current supplied from the power source is detected when the vibration actuator is driven by detecting the voltage across the resistor 106. Therefore, the power consumed by the vibration type actuator is obtained from the current detected by the current detection circuit 102 and the voltage of the power source 105.

  That is, the current detection circuit 102 only needs to be able to detect the amount of current. For example, the current detection circuit 102 can have a configuration including an operational amplifier and can detect a potential difference between two input terminals of the operational amplifier. The current detection circuit 102 may have an A / D converter in consideration of signal transmission with the control unit 21. The current detection circuit 102 is configured to detect current at least during the characteristic detection period. Further, the current may be detected during the driving period.

  The two-phase AC voltage is boosted to a desired voltage by a booster circuit having an inductor 103 and a transformer 104. The boosted AC voltage is converted from a rectangular shape to a SIN waveform by the filter effect and applied to the piezoelectric element 101. The vibration type actuator can control the speed by the frequency, amplitude, phase difference and the like of the AC voltage applied to the piezoelectric element 101.

  Note that the control unit and the drive unit are not only configured by one element or circuit, but may be configured by a plurality of elements or circuits. In addition, any element or circuit may execute each process.

<Each pulse signal in the characteristic detection period and main drive period>
FIG. 1C shows the waveforms of the A-phase and B-phase pulse signals and the AC voltage after boosting during the characteristic detection period. The characteristic detection period is set so that the phases of the A-phase and B-phase pulse signals are the same. The phase of the AC voltage applied to the piezoelectric element is the same, and an AC voltage having the same phase is input to the piezoelectric element. As a result, substantially only vibration in the direction perpendicular to the contact surface that comes into contact with the driven body (the push-up direction) is generated in the vibrating body.

  At this time, since feed vibration in the driving direction does not substantially occur, the vibration type actuator can be brought into a stopped state (a state in which the driven object is not relatively moved in the driving direction). The stop state can be confirmed by detecting the position or speed using an encoder or the like, as will be described later, with the position detecting means or the speed detecting means. That is, the stop state is a state in which the change in the relative position between the driving object and the vibrating body is equal to or lower than the lower limit value of the position detection unit or the speed detection unit, or a value set to be regarded as a stop state. If the frequency is swept with the two drive voltages in the same phase, the power based on the frequency can be detected while the vibration actuator is stopped.

  In the present embodiment, the case where the AC voltages having the same phase and the same phase are input to the piezoelectric element has been described above, but the vibration actuator control device of the present invention, and The control method is not limited to this. Since the vibration type actuator only needs to be stopped, the phase difference between the A-phase and B-phase pulse signals is preferably in the range of −10 ° to + 10 °. Note that, as described above, only the vibration in the direction perpendicular to the contact surface (the push-up direction) is excited by the vibrating body, so that the phase of the A-phase and B-phase pulse signals is the same (the phase difference is 0 °). Is more preferable.

  Further, in the characteristic detection period, the vibration type actuator may be stopped by adjusting the value of the voltage amplitude in the AC voltage. By reducing the voltage amplitude, it is possible to reduce the component in the driving direction (feeding direction) of the vibration excited in the contact portion of the vibrating body with the driven body.

  FIG. 1 (d) shows an example of the A-phase and B-phase pulse signals during this driving period and the waveform of the AC voltage after boosting. Here, an example is shown in which the phases of the A-phase and B-phase pulse signals are set to differ by 90 degrees during the main drive period. Pushing vibration and feed vibration are generated in the vibrating body, and the relative position of the vibrating body and the driven body changes. In this drive period, the drive speed can be controlled by changing the phase difference and the frequency.

  FIG. 5 shows the speed of the vibration-type actuator when the frequency is swept in the present drive period and the characteristic detection period with respect to the plate-type vibrating body shown in FIGS. 2 (a) to 2 (d). It is a figure which shows the measurement result of power. FIG. 5A shows the result of the speed (drive speed) of the vibration type actuator. Here, the driving speed was measured using an optical encoder (not shown) that detects the relative speed of the driven body and the vibrating body.

  The frequency sweep time in this driving period was 50 ms, the phase difference between the A phase and B phase pulse signals was 90 degrees, and the pulse width was 30%. On the other hand, the frequency sweep time in the characteristic detection period was 10 ms, the phase difference between the A phase and B phase pulse signals was 0 degree, and the pulse width was 12%. Here, the frequency sweep time refers to a time during which the frequency of the AC voltage applied to the vibrating body during driving gradually changes. As a result, during this driving period, the maximum speed of relative movement between the vibrating body and the driven body was 200 mm / s or more, whereas the speed detected by the optical encoder during the characteristic detection period was zero.

  From this, it can be seen that the vibration type actuator was stopped even if the frequency was swept. As shown in FIG. 5C, the vibration during the main drive period is an elliptical motion, whereas the characteristic detection period is substantially free of feed vibration and only a push-up vibration is generated. By causing the push-up vibration, the power peak can be detected even when the vibration type actuator is in a stopped state.

  FIG. 5B shows the measurement result of power when the frequency is swept. During the characteristic detection period, the vibration type actuator is in a stopped state, but a push-up vibration is generated, so that a peak is seen in the electric power. That is, a power curve can be obtained in the same manner as in this driving period. Therefore, by detecting the power or current when the frequency is swept by the pulse signal in the characteristic detection period, it is possible to detect a change in the resonance frequency due to the temperature environment and individual differences.

  Next, a specific method of correcting the startup frequency using the power detection result during frequency sweep will be described.

  FIG. 6 shows a method for detecting the change in the resonance frequency due to the environmental temperature with electric power.

  FIG. 6A is a result of measuring the impedance characteristics of the vibrating body in a room temperature environment and a −20 ° C. environment with respect to the plate-type vibrating body shown in FIGS. 2A to 2D. Yes, the horizontal axis represents frequency, and the vertical axis represents power corresponding to the mechanical arm current of the vibrating body. Here, the electric power corresponding to the mechanical arm current of the vibrating body is obtained based on the amount of current supplied from the power source to the vibration type actuator. Specifically, the potential difference between the power supply and the switching circuit is detected.

  Strictly speaking, a loss occurs in the output of the power source by a switching circuit, a booster circuit, or the like before being applied to the vibrating body, but the mechanical arm current is dominant in the current supplied from the power source to the vibration type actuator. Therefore, the electric power corresponding to the mechanical arm current of the vibrating body can be obtained by obtaining the amount of current supplied from the power source to the vibration type actuator.

  As shown in FIG. 6A, due to the influence of the temperature characteristics of the piezoelectric element, the electric power shifts to 700 Hz for the peak vibration and 800 Hz for the feed vibration, and shifts to a high frequency. Thus, the resonance frequency of the two vibrations used for driving changes in the same manner depending on the temperature. That is, when the resonance frequency of the push-up vibration increases when the temperature changes, the resonance frequency of the feed vibration also increases. When the resonance frequency of the push-up vibration decreases, the resonance frequency of the feed vibration also decreases. .

  FIG. 6B shows characteristics (power characteristics) of frequency and power supply power in the vibration type actuator. For example, the resonance frequency fm0 is shifted to the high frequency side fm1 due to a change in the environmental temperature, and the power characteristics are also changed to reflect the change in the mechanical arm current of the vibrating body.

  The present invention corrects the frequency (for example, start-up frequency) of the AC voltage during the main drive by using the change in the power characteristics. For the frequency of the alternating voltage when the electric power reaches a predetermined value, the difference between the environments such as two temperatures is obtained. The predetermined value may be, for example, power corresponding to peak power or driving frequency. Since there is the above-mentioned correlation between the change in power and the change in resonance frequency due to the difference between the two environmental temperatures, the frequency correction amount in the AC voltage is obtained by obtaining the power or current at the two environmental temperatures. Can do.

  A specific example of the correction will be described. For example, frequency sweep is performed in a room temperature environment, and the current detection circuit 102 is used to acquire the frequency at which the power becomes W1, which is the power corresponding to the activation frequency (f0). Similarly, frequency sweep is performed even in a low temperature environment, and the frequency at which the power is W1 is acquired (f1). Since it is considered that the driving speed is the same if the power is the same, if the starting frequency is corrected to f1 in the low temperature environment, the driving performance of the vibration type actuator similar to that in the normal temperature environment can be obtained.

  The power for acquiring the frequency may be other than W1, and for example, the frequency to be obtained may be set to a frequency corresponding to the power peak Wp. Here, the frequency at which the power becomes Wp during the frequency sweep is fm0 in the normal temperature environment and fm1 in the low temperature environment, and fm0 and fm1 are resonance frequencies at the respective environmental temperatures. Therefore, it is also possible to directly detect a change in resonance frequency.

  Therefore, based on the result of the current detected by the current detection circuit 102, the frequency acquisition unit 117 obtains the frequency of the vibration actuator when the power reaches a predetermined (for example, peak frequency) power.

  The correction amount acquisition unit 118 calculates the correction amount from the first frequency obtained by the frequency acquisition unit 117 at the first temperature and the second frequency obtained by the frequency acquisition unit 117 at the second temperature. it can. Here, the second frequency may be stored in advance by the correction amount acquisition unit 118 as data.

  Based on the correction amount acquired by the correction amount acquisition unit 118, the parameter acquisition unit 111 sets an AC voltage parameter. Here, for example, a frequency is set as a parameter.

  In FIG. 1 (a) and the above description, the frequency acquisition unit 117, the correction amount acquisition unit 118, and the parameter acquisition unit 111 have been described separately. For example, based on the result of the current detection circuit 102, processing may be performed in the CPU without distinction of processes, and parameter values may be output.

  In addition, in the case of a frequency sweep that decreases the frequency, if the frequency becomes smaller than the resonance frequency, a current suddenly flows through the vibration actuator, which may lead to failure or control failure of the vibration actuator, deterioration of drive efficiency, etc. is there. Therefore, the lower limit frequency of the main drive period of the vibration actuator may be corrected based on the correction amount of the starting frequency. In this case, by correcting the lower limit frequency of this driving period to a value larger than fm0 in a normal temperature environment and a value larger than fm1 in a low temperature environment, excessive current flows beyond the resonance frequency. Can be prevented.

  FIG. 7 is a flowchart showing a control sequence of the characteristic detection period and the main drive period.

  The control of the characteristic detection period includes step 1 to step 4, and the control of the driving period includes step 5 to step 7.

  Characteristic detection is started when the vibration actuator is stopped. First, parameters of the A-phase and B-phase pulse signals are determined by the parameter acquisition unit 111 as pulse signals for characteristic detection. At this time, the phase difference is set so as to be a value between −10 ° and + 10 ° (the most effective when 0) (step 1). Next, the control unit 21 sweeps the frequency of the AC voltage applied to the piezoelectric element 101 from the high frequency side to the low frequency side within a predetermined range (step 2). The range for sweeping the frequency is not particularly limited, but it is preferable to sweep from a frequency higher than the startup frequency in the normal temperature environment in a range including the resonance frequency.

  Next, in the frequency sweep process of Step 2, a frequency f1 reaching a predetermined power is acquired based on the output of the current detection circuit 102 (Step 3). Based on f1, the parameter acquisition unit 111 corrects the start-up frequency from f0 in the previous main drive period to f1 (step 4).

  After the characteristic detection is completed, parameters for the pulse signal for main driving are set (step 5). When the main driving is started, the main driving AC voltage generated based on the main driving pulse signal is input to the piezoelectric element. During the actual driving of the vibration actuator, an AC voltage having a frequency, phase difference, and amplitude, which is obtained based on the target position or speed, the relative speed or relative position between the driven object and the vibration actuator, is input to the piezoelectric element. (Step 8).

  If it is necessary to readjust the starting frequency after the actual driving stop of the vibration type actuator (step 9), the process returns to step 1 again. Whether the readjustment is necessary is determined based on a change in the control performance of the vibration type actuator, such as a deviation amount of the detected speed (1b) with respect to the target speed (position), a stop accuracy with respect to the target precision, and a change in electric power.

  The start of characteristic detection when the vibration actuator is stopped may be set to be performed automatically immediately after the vibration actuator is turned on, and may be set by inputting an external command signal before starting the main drive. It may be set to be displayed. Moreover, it is good also as a structure switched from this drive.

<Experimental result: Peak detection when the pulse width is changed>
FIG. 8 shows measurement results of power when the pulse width of the pulse signal is changed.

  The power characteristics when the pulse width was changed by 5% from 30% to 10% were measured. FIG. 8A shows the result of this driving period. The frequency sweep time was 50 ms, and the phase difference between the A-phase and B-phase pulse signals was 90 degrees. As the pulse width is reduced, the amplitude of the AC voltage applied to the piezoelectric element decreases, and the amplitude of the elliptical motion decreases with a constant ellipticity ratio. As a result, the frequency corresponding to the power peak shifts to the high frequency side.

  FIG. 8B shows the result of the characteristic detection period. The frequency sweep time was 10 ms, and the phase difference between the A phase and B phase pulse signals was 0 degree. Since the push-up vibration amplitude in the figure becomes smaller according to the pulse width, the frequency corresponding to the power peak shifts in the same manner as in the present drive period. Thus, there is a strong correlation between the power characteristics during the main drive period and the characteristic detection period.

  However, the power characteristics of the vibration type actuator do not always show a correlation between this driving period and other states. FIG. 8C shows data for comparison with the present invention, in which the pulse signal phase difference between the A phase and the B phase is set to 180 degrees so that only feed vibration occurs. In this case, the power peak cannot be accurately detected, and no correlation is observed with the main driving period. Therefore, it is not possible to obtain a correction amount for the change in the resonance frequency of the vibrating body by detecting the change in the frequency at which the power reaches a peak or the frequency at which the predetermined power is reached.

  From the above, by using the means of the present invention focusing on the relationship between the change in the frequency corresponding to the peak of power when driving the vibration type actuator in the state of only the thrust vibration and the change in the resonance frequency of the vibrating body, It was confirmed that the change of resonance frequency can be detected effectively.

<Experimental results: pulse width and peak frequency>
FIG. 9 shows the frequency and frequency difference at which the power of the vibration actuator peaks when the pulse width is changed. Hereinafter, the frequency of the pulse type signal in which the power of the vibration type actuator exhibits a peak is defined as the power peak frequency, and the difference between the power peak frequency in the main driving period and the characteristic detection period is defined as the power peak frequency difference.

  In FIG. 9A, the horizontal axis represents the pulse width of the pulse signal, the left vertical axis represents the power peak frequency between the main driving period and the characteristic detection period, and the right vertical axis represents the power peak frequency difference between the main driving period and the characteristic detection period. . From the figure, there is a strong correlation between the power peak frequency in the main driving period and the characteristic detection period. The power peak frequency difference is 1.3 kHz on average and falls within a variation of ± 100 Hz. That is, the startup frequency can be corrected with an accuracy of ± 100 Hz by detecting the power peak frequency during the characteristic detection period.

  Furthermore, it is also possible to directly detect the power peak frequency during the main drive period by selecting the pulse width during the characteristic detection period. For example, the power peak frequency with a pulse width of 30% in this driving period is 87 kHz, and if the pulse width in the characteristic detection period is set to 12%, 87 kHz can be detected in the same manner. 9A and 9B show the waveforms of the pulse signals in the characteristic detection period when the pulse width is changed. FIG. 9B shows the setting of 30% pulse width, and FIG. 9C shows the setting of 15% pulse width.

<Experimental result: Power detection example>
FIG. 10 shows changes in driving speed due to differences in environmental temperature and measurement results of power characteristics during the characteristic detection period.

  FIG. 10A shows the detection result of the speed with respect to the frequency during this driving period. The frequency sweep time is 50 ms, the phase difference between the A phase and the B phase is 90 degrees, and the pulse width is 50%. The velocity peak in the -10 ° C environment is shifted to 600 Hz in the high range with respect to the 25 ° C environment. Also in the measurement of the power supply power during the main drive period, the power peak frequency is similarly shifted to a high range by changing from 25 ° C. to −10 ° C. FIG. 10B shows the result of power measurement during the characteristic detection period. The frequency sweep time was 10 ms, the phase difference between the A phase and the B phase was 0 degree, and the pulse width was 25%.

  Here, the power value for detecting the frequency was set to 0.4 W. This is determined in consideration of the power peak speed of 1.0 W during the main drive period since the power during the characteristic detection period is 0.4 times the main drive period. As a result, it was detected from the shift of the frequency of the power peak during the characteristic detection period that the resonance frequency was changed by 600 Hz when the environmental temperature was changed from 25 ° C. to −10 ° C. Therefore, in the −10 ° C. environment, the control may be performed by correcting the starting frequency to the 600 Hz high frequency side from the case of 25 ° C.

  Based on this result, the correction amount obtained by detecting the power or current corresponding to the power consumed by the vibration type actuator during the characteristic detection period and acquiring the frequency should be used as the correction amount for the characteristic change of the vibration type actuator during actual driving. I was able to confirm.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. This embodiment is an application example to a vibration type actuator using traveling waves. Similarly to the first embodiment, the control device and the control method according to the present embodiment can be applied to a lens driving mechanism of a camera that is an optical apparatus, but is not limited thereto.

<Traveling wave type actuator>
FIG. 11 shows a configuration of a vibration type actuator using traveling waves.

  FIG. 11A is a perspective view showing a part of the vibration type actuator 1. The vibration type actuator 1 includes a vibration body 3 having an electromechanical energy conversion element 5 such as a piezoelectric element and an elastic body 4, and a driven body 2. Each member has an annular shape in the θ direction in the figure. When a two-phase alternating voltage is applied to the electromechanical energy conversion element 5, a traveling wave is generated in the vibrating body 3, and the driven body 2 that contacts the vibrating body 3 rotates relative to the vibrating body by friction drive. To do.

  FIG. 11B is a perspective view showing the elastic body 4. On the side of the elastic body 4 that contacts the driven body 2, a plurality of protrusions 6 and grooves 7 are alternately provided as shown in FIG. In the example of FIG. 11B, 32 pieces are provided for each circumference. By providing such a projection 6, the amplitude of the traveling wave can be increased at the contact portion with the driven body 2 (the tip portion of the projection 6), and a sufficient rotational driving force can be obtained.

<Description of standing wave vibration and traveling wave vibration>
FIG. 12 shows a pulse signal during a characteristic detection period and a standing wave vibration in a vibration type actuator using a traveling wave. FIG. 12A shows a pulse signal and a vibration waveform in the characteristic detection period, and the phases of the A-phase and B-phase pulse signals are the same. Assuming that the period of the pulse signal is T, the state of the vibration waveform generated at the time every T / 4 is schematically shown as t0, t1, t2, and t3. The horizontal axis is the position in the circumferential direction. As described above, a state in which vibration in the Z direction is steadily generated at the same position is referred to as standing wave vibration, and since the driving force is not generated in the rotation direction, the actuator is stopped.

  On the other hand, FIG. 12B shows the pulse signal and the vibration waveform during the driving period, and the phase difference between the A-phase pulse signal and the B-phase pulse signal is 90 degrees. During this driving period, traveling wave vibration in which the vibration peak moves in the circumferential direction is generated, and a driving force can be generated in the rotational direction.

  In this way, by setting the pulse signal for the characteristic detection period and causing standing wave vibration, it is possible to measure power while the vibration type actuator is in a stopped state, and to detect frequency changes due to changes in environmental temperature. . Standing wave vibration is also vibration in a direction perpendicular to the contact surface of the vibrating body that contacts the driven body. The specific start-up frequency correction means and control sequence are the same as those in the first embodiment, and a description thereof will be omitted.

(Third embodiment)
In the first and second embodiments, the example in which the control device for the vibration type actuator is used for driving an autofocus lens of the imaging apparatus has been described, but the application example of the present invention is not limited to this. For example, as shown in FIG. 13, it can also be used to drive a lens or an image sensor during camera shake correction. FIG. 13A is a plan view (top view) illustrating the appearance of the imaging device 60. FIG. 13B is a schematic diagram of the internal structure of the imaging device 60.

  The imaging device 60 is generally composed of a main body 61 and a lens barrel 62 that can be attached to and detached from the main body 61. The main body 61 includes an image pickup device 63 such as a CCD sensor or a CMOS sensor that converts an optical image formed by the light passing through the lens barrel 62 into an image signal, and a camera control microcomputer that controls the overall operation of the image pickup apparatus 60. 64. In the lens barrel 62, a plurality of lenses L such as a focus lens and a zoom lens are arranged at predetermined positions.

  The lens barrel 62 incorporates an image blur correction device 50. The image blur correction device 50 includes a disk member 56 and a vibrating body 205 provided on the disk member 56, and includes a disk member. An image blur correction lens 65 is disposed in a hole formed at the center of 56. An image sensor may be arranged on the optical axis of the image blur correction lens 65.

  The image blur correction device 50 is arranged so that the image blur correction lens 65 can be moved in a plane orthogonal to the optical axis of the lens barrel 62. In this case, by driving the vibrating body 205 using the control device 20 of the present invention, the vibrating body 205 and the disk member 56 move relative to the driven body 201 fixed to the lens barrel, and the correction lens. Is driven.

  Further, the control device for the drive type actuator of the present invention can also be used for driving the lens holder for moving the zoom lens. Therefore, the control device for the mold actuator according to the present invention can be mounted not only on the imaging device but also on the interchangeable lens.

  Further, the control device for the vibration type actuator shown in the first and second embodiments can be used for driving the automatic stage. For example, as shown in FIG. 14, it can be used for driving an automatic stage of a microscope.

  The microscope of FIG. 14 includes an imaging unit 70 that includes an imaging device and an optical system, and an automatic stage 71 that is provided on a base and includes a stage 72 that is moved by a vibration actuator. An object to be observed is placed on the stage 72 and an enlarged image is taken by the imaging unit 70. When the observation range is wide, the stage 72 is moved by driving the vibration type drive actuator using the control device 20 of the first or second embodiment. As a result, the object to be observed is moved in the X and Y directions in the figure, and a large number of captured images are acquired. A computer (not shown) can combine captured images and acquire a single image with a wide observation range and high definition.

  By using the control device for the vibration type actuator described in the first or second embodiment, these driving objects corresponding to the change in the resonance frequency of the vibration type actuator due to the change in the environmental temperature without using the temperature sensor. Can be realized. Further, when the vibration type actuator is exchanged and used, it can cope with the difference in resonance frequency due to the individual difference of the vibration type actuator to be used, compensate for the individual difference, and can move the driven object stably.

DESCRIPTION OF SYMBOLS 102 Current detection circuit 117 Frequency acquisition part 118 Correction amount acquisition part 111 Parameter acquisition part 119 AC voltage generation means

Claims (22)

Current detection means for detecting current in the characteristic detection period;
A frequency acquisition unit for acquiring a frequency at which the current reaches a predetermined current based on the output of the current detection means;
A first parameter acquisition unit that acquires an AC voltage parameter using a correction amount based on an output of the frequency acquisition unit;
AC voltage generating means for generating the AC voltage input to the vibration type actuator based on the output of the first parameter acquisition unit;
Have
During the characteristic detection period, vibration in a direction perpendicular to the contact surface is excited in a contact portion of the vibration body of the vibration actuator with the driven body, and the vibration actuator is in a stopped state. Control device for vibration type actuator.   2. The vibration type actuator control device according to claim 1, wherein the current detection unit is provided between a power source and the AC voltage generation unit.   The control of the vibration type actuator according to claim 1, further comprising a booster circuit to which an output of the AC voltage generation means is input, and an output of the booster circuit being input to the vibration type actuator. apparatus.   4. The control of the vibration type actuator according to claim 1, wherein the predetermined current is a current at which a power obtained from the current detected by the current detection unit reaches a peak. 5. apparatus.   5. The vibration type actuator control device according to claim 1, wherein the current detection unit obtains a current by detecting a potential difference. 6.   The vibration type actuator control device according to claim 1, wherein the parameter is a frequency.   The vibration according to claim 1, wherein the first parameter acquisition unit is configured to acquire the parameter using the correction amount during a characteristic detection period. Type actuator control device. Command value generation means,
A PID calculation unit to which the output of the command value generation means is input;
8. The vibration type actuator according to claim 1, further comprising a second parameter acquisition unit configured to acquire an AC voltage parameter during the main driving period based on an output of the PID calculation unit. Control device.   9. The vibration type actuator control device according to claim 1, wherein the vibration type actuator is configured to generate two bending vibration modes. A control device for a vibration type actuator according to any one of claims 1 to 9,
A vibration actuator driven by a control device of the vibration actuator;
A vibration device comprising: A control device for a vibration type actuator according to any one of claims 1 to 9,
A vibration actuator driven by a control device of the vibration actuator;
A lens driven by driving the vibration type actuator;
Replacement lens with A control device for a vibration type actuator according to any one of claims 1 to 9,
A vibration actuator driven by a control device of the vibration actuator;
A lens driven by the vibration actuator;
An image sensor provided on the optical axis of the lens;
An imaging apparatus comprising: A control device for a vibration type actuator according to any one of claims 1 to 9,
A vibration actuator driven by a control device of the vibration actuator;
An image sensor driven by the vibration actuator;
A lens in which the image sensor is provided on the optical axis;
An imaging apparatus comprising: A control device for a vibration type actuator according to any one of claims 1 to 9,
A vibration actuator driven by a control device of the vibration actuator;
A stage driven by the vibration actuator;
Automatic stage with In the characteristic detection period,
A vibration is detected in a state in which an alternating voltage is applied so that vibration in a direction perpendicular to the contact surface is excited and stopped in a contact portion of the vibration body of the vibration type actuator with the driven body,
Based on the detected current, correct the parameter of the AC voltage applied to the vibration type actuator,
During this driving period,
A control method of a vibration type actuator, wherein an AC voltage having the corrected parameter is applied to the vibration type actuator.   16. The method for controlling a vibration type actuator according to claim 15, wherein the correction of the parameter is performed based on a current when the power consumed by the vibration type actuator becomes a peak power in the detected current. .   17. The method for controlling a vibration type actuator according to claim 15, wherein the phase difference of the AC voltage is a value between −10 ° and + 10 ° during the characteristic detection period.   The method of controlling a vibration type actuator according to claim 15 or 16, wherein the voltage amplitude of the AC voltage is adjusted so that the vibration type actuator is stopped during the characteristic detection period.   The method for controlling a vibration type actuator according to any one of claims 15 to 18, wherein a starting frequency is adjusted based on a pulse width for adjusting a voltage amplitude of the AC voltage.   The method for controlling a vibration type actuator according to any one of claims 15 to 19, wherein the characteristic detection period is provided immediately after power-on.   The vibration type actuator control method according to any one of claims 15 to 19, wherein the characteristic detection period is provided before the start of the main driving.   The method for controlling a vibration type actuator according to any one of claims 15 to 21, wherein the corrected parameter is a starting frequency of the vibration type actuator.

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