JP6671883B2 - Vibration type actuator control device and control method, vibration device, replacement lens, imaging device, and automatic stage - Google Patents

Description

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

  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 comes into pressure contact with the vibration body. The vibration-type motor is a non-electromagnetic drive type configured to generate high-frequency vibration in an electro-mechanical energy conversion element by applying an AC voltage to the element and take out the vibration energy as continuous mechanical movement. Motor.

  The control device for a 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 vibrator. The vibration type actuator can control the speed by the frequency, amplitude, phase difference, etc. of an AC voltage applied to the piezoelectric element, and is used for, for example, autofocus driving of a camera. Autofocus driving requires high-precision positioning control, and for example, position feedback control using a position sensor is performed.

  At the time of control, it is the object to be driven by utilizing the fact that 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 a higher frequency side. Drive the lens at high or low speed. Here, since the resonance frequency of the vibration type actuator changes depending on the environmental temperature, the characteristics of the driving speed (the relative speed between the vibrating body and the driven body) with respect to the driving frequency change. Therefore, when control is performed without correcting the drive parameters, the control performance may be impaired due to the environmental temperature.

  The following methods have been proposed to solve the above problems.

  Japanese Patent Application Laid-Open No. H11-163873 uses a means for detecting an environmental temperature such as a temperature sensor to control a reference frequency of a drive voltage based on data of a frequency correction amount corresponding to an environmental temperature stored in advance.

Patent No. 5391595

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

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

In one embodiment of the present invention,
During the characteristic detection period,
A current is detected in a state where an AC voltage is applied so that a vibration in a direction perpendicular to the contact surface is excited at a contact portion between the driven body and the driven body in the vibrating body of the vibration type actuator, and is in a stopped state,
Based on the detected current, correct the parameter of the AC voltage applied to the vibration type actuator,
In this driving period,
The present invention relates to a method of 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, a drive frequency can be corrected by detecting a change in resonance frequency due to an environmental change of a vibration type actuator without using a temperature sensor. Further, it is possible to cope with variations in individual differences.

FIG. 2 is a diagram illustrating a vibration type actuator having a vibration type actuator and its control device, a driving unit of the control device, and a pulse signal according to the first embodiment of the present invention. It is a figure explaining the drive principle of a vibration type actuator of a linear drive type. FIG. 3 is a diagram illustrating a driving mechanism of a lens of a lens barrel. FIG. 7 is a diagram illustrating characteristics of frequency and actuator speed depending on a difference in environmental temperature. FIG. 9 is a diagram illustrating measurement results of speed and power when the frequency is swept in a main driving period and a characteristic detection period. It shows a method of detecting a change in resonance frequency due to environmental temperature with electric power. 5 is a flowchart illustrating a control sequence of a characteristic detection period and a main drive period. It is a measurement result of the power when the pulse width of the pulse signal is changed. It shows a peak frequency and a frequency difference when the pulse width is changed. It shows a change in driving speed due to a difference in environmental temperature and a measurement result of power characteristics during a characteristic detection period. 9 shows a vibration-type actuator using a traveling wave according to a second embodiment of the present invention. FIG. 9 shows a pulse signal during a characteristic detection period in a vibration type actuator using a traveling wave and standing wave vibration. It is the top view which shows the external appearance of the imaging device which is an example of application of the control apparatus of this invention, and the schematic diagram of an internal structure. It is a figure showing the appearance of the microscope which is an example of application of the control device of the present 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 having an elastic body to which an electro-mechanical energy converting element such as a piezoelectric element and an electro-mechanical energy converting element are joined, A driven body whose relative position to the vibrating body changes. A plurality of AC voltages (driving voltages) having different phases are applied to the electro-mechanical energy conversion element, respectively, to generate a vibration wave in the elastic body. The elastic body generates an elliptical motion in a driving part (a contact part with the driven body) of the elastic body due to the generated vibration wave, and the relative position between 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, an annular vibration-type actuator used for rotating a photosensitive drum of a copying machine or a transfer belt of an image forming apparatus, for example, and forms a traveling wave on a vibrating body to change the relative position between the vibrating body and the driven body. The present invention can be applied to an annular vibration type actuator. Further, the present invention can be applied to a vibration type actuator used for zoom drive and auto focus drive of a camera lens. In the vibration type actuator, for example, primary bending vibrations in two directions orthogonal to the friction surface of the elastic body (the contact surface between the vibration body and the driven body) are excited and superimposed at a time phase of π / 2. This is a rod-shaped vibration-type actuator that generates a spheroidal motion on a friction surface.

  In the present invention, the driving direction refers to a direction of relative movement between the vibrating body and the driven body that is parallel to a 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 the friction surface of the driven body.

  In addition, driving the vibration-type actuator refers to a state in which a driving voltage is input to the vibration-type actuator so that vibration is excited in the electro-mechanical energy conversion element. Including period.

  The characteristic detection period is a period in which information is obtained on whether or not there is a change in the speed characteristics of the vibration type actuator due to a change in the resonance frequency of the vibration type actuator, and how the information has changed. The main driving period is a period in which a driving AC voltage for moving a driving target is input to the electro-mechanical energy conversion element. During the characteristic detection period, a vibration in a thrust direction (a direction perpendicular to the contact surface) is excited at a contact portion of the vibrating body of the vibration type actuator with the driven body, and the vibration type actuator is in a stopped state. During the main drive period, elliptical motion is excited in the contact portion.

  The starting frequency refers to the frequency of the AC voltage input to the vibration-type actuator at the start of driving of the vibration-type actuator.

(First embodiment)
<Principle explanation of vibrator>
FIG. 2 is a diagram illustrating the driving principle of the linear drive type vibration type 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 AC voltage to the piezoelectric element 204, two vibration modes as shown in FIGS. 2C and 2D are generated, and the driven body 201 that comes into pressure contact with the protrusion 202 is moved in the direction of the arrow. Let it.

  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 has an electrode region divided into two in the longitudinal direction. The polarization directions in the respective electrode regions are the same (+). Of the two electrode regions of the piezoelectric element 204, an AC voltage (VB) is applied to an electrode region located on the right side of FIG. 2B, and an AC voltage (VA) is applied to an electrode region located on the left side of FIG. . Assuming that VB and VA are frequencies near the resonance frequency of the first vibration mode and AC voltages having the same phase, the entire piezoelectric element 204 (two electrode regions) expands at one moment, and at another moment. Will shrink.

  As a result, the vibration in the first vibration mode (hereinafter, thrust-up vibration) shown in FIG. Further, when VB and VA are frequencies near the resonance frequency of the second vibration mode and AC voltages whose phases are shifted by 180 °, at a certain moment, the right electrode region of the piezoelectric element 204 shrinks and the left The electrode area extends. At another moment, the relationship is reversed. As a result, vibration in the second vibration mode (hereinafter referred to as feed vibration) shown in FIG.

  Thus, by combining the two vibration modes, the driven body 201 is driven in the direction of the arrow in FIG. Further, the generation ratio between the first vibration mode and the second vibration mode can be changed by changing the phase difference of the AC voltage input to the equally divided electrodes. 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 that is an optical device 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 of a lens which is a driving object using the vibration type actuator of the present embodiment includes a vibrating body, a driven body, and a first guide arranged in parallel, which slidably holds the driven body. A bar and a second guide bar are provided. The relative movement force is generated between the vibrating body and the second guide bar in contact with the protruding part of the elastic body due to the elliptical motion generated on the protruding part of the vibrating body by applying a driving voltage to the electro-mechanical energy conversion element. Let it. Thus, the driven body is configured to be movable along the first and second guide bars in the driving direction (here, a direction parallel to the direction in which the second guide bar extends).

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

  Both ends of each 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 with each other. The lens holder 302 includes a cylindrical holder portion 302a, a holding portion 302b that holds and fixes the vibrating body 205 and the pressing magnet 305, and a first guide portion 302c that engages with the first guide bar 303 to function as a guide. Have.

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

  The protrusion of the elastic body comes into pressure contact with the second guide bar 304 and functions as a second guide. Since the second guide portion forms a guide mechanism using a magnetic attraction force, the vibrating body 205 and the guide bar 304 may be separated from each other due to external force or the like. Has been dealt with. That is, a countermeasure is made so that the lens holder 302 returns to a desired position by the falling-off preventing portion 302d provided in the lens holder 302 hitting 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 driving force drives the lens holder.

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

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

  Here, the normal temperature environment and the low temperature environment are in a temperature range such as 15 ° C. to 30 ° C. and −15 ° C. to 0 ° C., for example. Comparing the frequency at which the predetermined starting speed is reached with the ambient temperature, a difference between f0 and f1 occurs. In the case of controlling the speed in the range of the starting frequency f0 to fm0 in a normal temperature environment, it is desirable to control the speed in the range of the starting frequency f1 to fm1 in a low temperature environment. If the starting frequency can be adjusted according to the change 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 control device for a vibration-type actuator according to the present invention and a vibration device having the control device will be described with reference to the drawings.

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

  Therefore, 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 the relative speed between the vibrating body and the driven object. Further, the relative speed between the vibrating body and the driven object is determined from the relative position between the vibrating body and the driven 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 driving unit 22, and a power supply 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 means 109 is configured to output a command value relating to position and speed, and the PID calculation unit 110 is configured to obtain a control amount based on a difference between the command value and the output of the relative speed detection means. ing.

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

  The parameter acquisition unit 111 is configured to acquire a parameter of the AC voltage 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. During the characteristic detection period, the parameter obtaining unit 111 obtains a parameter of the AC voltage using the correction amount based on the output of the frequency obtaining unit (based on the output of the correction amount obtaining unit 118). The parameter of the AC voltage is obtained based on the output of the arithmetic unit 110.

  The parameter acquisition unit 111 includes 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. It may have a parameter operation unit. 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 driving period. Further, the parameter acquiring unit 111 may be a single parameter acquiring unit having the functions of the two parameter acquiring 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 a parameter relating to a phase difference, and a frequency conversion unit 113 that acquires a parameter relating to a frequency. In addition, the parameter acquisition unit 111 includes a phase difference-frequency determination unit 114 that outputs a signal relating to one of the phase difference and frequency parameters from the outputs of the phase difference conversion unit 112 and the frequency conversion unit 113.

  The control unit 21 is configured by digital devices such as a CPU and a PLD (including an ASIC), and elements 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 boosting 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 driving unit of the vibration type actuator according to the present invention.

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

  The switching circuit 108 is connected to a power supply 105 via a resistor 106. By detecting a voltage between terminals of the resistor 106, a current supplied from the power supply when the vibration actuator is driven is detected. 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 supply 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 may be configured to include an operational amplifier and configured to detect a potential difference between two input terminals of the operational amplifier. Further, the current detection circuit 102 may include an A / D converter in consideration of signal transmission with the control unit 21. The current detection circuit 102 is configured to be able to detect a current at least during a characteristic detection period. Further, the configuration may be such that the current can be detected during the main 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 rectangle into a SIN waveform by a filter effect and applied to the piezoelectric element 101. The speed of the vibration type actuator can be controlled 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 may be configured not only from one element or circuit, but also from a plurality of elements or circuits. Further, each element may be executed by any element or circuit.

<Pulse signals during the characteristic detection period and the main drive period>
FIG. 1C shows the waveforms of the A-phase and B-phase pulse signals and the boosted AC voltage 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 same applies to the phase of the AC voltage applied to the piezoelectric element, and the AC voltage having the same phase is input to the piezoelectric element. As a result, substantially only the vibration in the direction (thrust-up direction) perpendicular to the contact surface that comes into contact with the driven body is generated in the vibrating body.

  At this time, since the 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 a position or a speed using an encoder or the like with a position detecting unit or a speed detecting unit as described later. That is, the stopped state is a state in which a change in the relative position between the driven object and the vibrating body is equal to or lower than the lower limit of the position detecting unit or the speed detecting unit or a value set as a stop state. If the frequency is swept in a state where the phases of the two drive voltages are the same, power based on the frequency can be detected with the vibration type actuator stopped.

  In the present embodiment, the case where the phase of the A-phase and the B-phase pulse signals are the same and the AC voltage having the same phase is input to the piezoelectric element has been described above, but the control device of the vibration-type actuator of the present invention, and The control method is not limited to this. The phase difference between the A-phase and B-phase pulse signals is preferably in the range of −10 ° to + 10 ° since the vibration-type actuator only needs to be able to be in the stopped state. As described above, since only the vibration in the direction perpendicular to the contact surface (thrust direction) is excited by the vibrating body, when the phases of the A-phase and B-phase pulse signals are the same (the phase difference is 0 °), Is more preferred.

  Further, during the characteristic detection period, the value of the voltage amplitude of the AC voltage may be adjusted to bring the vibration type actuator into a stopped state. By reducing the voltage amplitude, it is possible to reduce the component in the driving direction (feed direction) of the vibration excited at the contact portion of the vibrating body with the driven body.

  FIG. 1D shows an example of the waveforms of the A-phase and B-phase pulse signals and the boosted AC voltage during the main driving period. 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. Raising vibration and feed vibration occur in the vibrating body, and the relative position between the vibrating body and the driven body changes. In the main driving period, the driving 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 during the main drive period and the characteristic detection period for the plate-type vibrator shown in FIGS. 2A to 2D. 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. The drive speed was measured using an optical encoder (not shown) that detects the relative speed between the driven body and the vibrating body.

  The frequency sweep time during this drive 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 during 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 the main drive period, the maximum speed of the 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.

  This indicates that the vibration type actuator was stopped even when the frequency was swept. As shown in FIG. 5C, the vibration during the main drive period is an elliptical motion, whereas during the characteristic detection period, there is substantially no feed vibration and only a thrust vibration is generated. By causing the thrust vibration, a power peak can be detected even when the vibration type actuator is in a stopped state.

  FIG. 5B shows the measurement result of the power when the frequency is swept. During the characteristic detection period, the vibration-type actuator is in the stopped state, but thrust-up vibration occurs, so that a peak is seen in the electric power. That is, a power curve can be obtained as in the main 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 or individual differences.

  Next, a description will be given of a specific method of correcting the starting frequency using the detection result of the power during the frequency sweep.

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

  FIG. 6A shows the results of measuring the impedance characteristics of the vibrating body shown in FIGS. 2A to 2D in a normal temperature environment and a −20 ° C. environment with respect to the vibrating body having a plate-shaped piezoelectric element. The horizontal axis indicates frequency, and the vertical axis indicates electric power corresponding to the mechanical arm current of the vibrating body. Here, the power corresponding to the mechanical arm current of the vibrating body is obtained based on the amount of current supplied from the power supply to the vibrating actuator. Specifically, the potential difference between the power supply and the switching circuit is detected.

  Strictly, the output of the power supply causes a loss due to a switching circuit, a boosting circuit, and the like before being applied to the vibrating body, but the mechanical arm current is dominant in the current supplied from the power supply to the vibration type actuator. Therefore, by determining the amount of current supplied from the power supply to the vibration-type actuator, it is possible to obtain power corresponding to the mechanical arm current of the vibrating body.

  As shown in FIG. 6A, due to the influence of the temperature characteristic of the piezoelectric element, the electric power shifts to a high frequency at 700 Hz at the peak in the thrust vibration and 800 Hz at the peak in the feed vibration. As described above, the resonance frequencies of the two vibrations used for driving change in the same manner depending on the temperature. That is, when the resonance frequency of the thrust vibration increases when the temperature changes, the resonance frequency of the thrust vibration also increases, and when the resonance frequency of the thrust vibration decreases, the resonance frequency of the thrust 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 shifts to the higher frequency side fm1 due to a change in the environmental temperature, and the power characteristic also changes reflecting the aforementioned change in the mechanical arm current of the vibrating body.

  The present invention corrects the frequency (for example, the starting frequency) of the AC voltage at the time of the main drive using the change in the power characteristics. For the frequency of the AC voltage when the power reaches a predetermined value, a difference between two environments such as temperature is obtained. The predetermined value may be, for example, peak power or power corresponding to the drive frequency. Since the change in power and the change in resonance frequency due to the difference between the two environmental temperatures have the above-mentioned correlation, it is necessary to obtain the power or current at the two environmental temperatures to obtain the correction amount of the frequency in the AC voltage. Can be.

  A specific example of the correction will be described. For example, a frequency sweep is performed in a normal temperature environment, and the frequency at which the power becomes W1, which is power corresponding to the starting frequency, is obtained using the current detection circuit 102 (f0). Similarly, a frequency sweep is performed even in a low-temperature environment, and a frequency at which the power becomes W1 is obtained (f1). It is considered that the driving speed will be the same if the power is the same. Therefore, if the starting frequency is corrected to f1 in a 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 the frequency corresponding to the power peak Wp. Here, the frequency at which the power becomes Wp during the frequency sweep is fm0 in a normal temperature environment and fm1 in a low temperature environment, and both fm0 and fm1 are resonance frequencies at respective environmental temperatures. Therefore, it is also possible to directly detect a change in the resonance frequency.

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

  From the first frequency obtained by the frequency obtaining unit 117 at the first temperature and the second frequency obtained by the frequency obtaining unit 117 at the second temperature, the correction amount obtaining unit 118 obtains the correction amount. it can. Here, the second frequency may be held in advance by the correction amount acquisition unit 118 as data.

  Based on the correction amount obtained by the correction amount obtaining unit 118, the parameter obtaining unit 111 sets a parameter of the AC voltage. Here, for example, a frequency is set as a parameter.

  In FIG. 1A 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, but the processes need not be separately performed as the respective steps. For example, a configuration may be employed in which processing is performed in the CPU without discrimination between steps based on the result of the current detection circuit 102, and parameter values are output.

  Also, in the case of a frequency sweep in which the frequency is reduced, if the frequency becomes lower than the resonance frequency, a current suddenly flows through the vibration-type actuator, which may lead to a failure or uncontrollability of the vibration-type actuator, deterioration of drive efficiency, and the like. is there. Therefore, the lower limit frequency of the main driving period of the vibration type actuator may be corrected based on the correction amount of the starting frequency. In this case, the lower limit frequency of the main drive period is similarly corrected to be a value larger than fm0 in a normal temperature environment and larger than fm1 in a low temperature environment, so that an 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 Steps 1 to 4, and the control of the main drive period includes Steps 5 to 7.

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

  Next, in the frequency sweeping step of step 2, a frequency f1 that reaches a predetermined power is obtained based on the output of the current detection circuit 102 (step 3). Based on the f1, the parameter acquisition unit 111 corrects the starting frequency from f0 in the last main driving period to f1 (step 4).

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

  After the main drive of the vibration type actuator is stopped (step 9), if it is necessary to readjust the starting frequency, the process returns to step 1 again. The necessity of the readjustment is determined based on a change in the control performance of the vibration type actuator, such as a deviation amount of the detection speed (1b) from the target speed (position), a stop accuracy with respect to the target accuracy, and a change in power.

  The start of the characteristic detection in the stopped state of the vibration type actuator may be set to be automatically performed immediately after the power supply of the vibration type actuator is turned on, and may be performed by inputting a command signal from outside before starting the actual driving. It may be set to be performed. Further, a configuration for switching from the main driving may be adopted.

<Experimental results: Example of peak detection when pulse width is changed>
FIG. 8 shows a measurement result of the 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 the main driving period, in which 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 is reduced, and the amplitude of the elliptical motion is reduced at a constant elliptic ratio. As a result, the frequency corresponding to the peak of the power shifts to the higher frequency side.

  FIG. 8B shows the result of the characteristic detection period, in which 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 amplitude of the push-up vibration shown in the figure decreases in accordance with the pulse width, the frequency corresponding to the peak of the power shifts in the same manner as in the main driving period. Thus, there is a strong correlation between the power characteristics in the main drive period and the power detection period.

  However, the power characteristics of the vibration type actuator do not always show a correlation between the main 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 as to generate only the feed vibration. In this case, the power peak cannot be detected with high accuracy, and there is no correlation with the main driving period. Therefore, it is not possible to obtain a correction amount for a change in the resonance frequency of the vibrating body by detecting a change in the frequency at which the power reaches a peak or a frequency at which the power reaches a predetermined power.

  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 the power and the change in the resonance frequency of the vibrating body when the vibration type actuator is driven in the state of only the thrust vibration, It was confirmed that the change of the resonance frequency could be detected effectively.

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

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

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

<Experimental result: Power detection example>
FIG. 10 shows a change in drive speed due to a difference in environmental temperature and a measurement result of power characteristics during a characteristic detection period.

  FIG. 10A shows the detection result of the speed with respect to the frequency during the main driving period. The frequency sweep time was 50 ms, the phase difference between the A phase and the B phase was 90 degrees, and the pulse width was 50%. The speed peak in the -10 ° C environment is shifted by 600 Hz to a higher frequency than the 25 ° C environment. Similarly, in the measurement of the power supply power during the main driving period, the power peak frequency shifts to a higher range by changing from 25 ° C. to −10 ° C. FIG. 10B shows the power measurement results 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. Since the power during the characteristic detection period is 0.4 times that of the main drive period, the power is determined in consideration of the peak power of 1.0 W during the main drive period. As a result, from the shift of the frequency of the power peak during the characteristic detection period, it was possible to detect that the resonance frequency had changed by 600 Hz by changing the environmental temperature from 25 ° C. to −10 ° C. Therefore, in the -10 ° C. environment, the start frequency may be corrected to be higher by 600 Hz than in the case of 25 ° C. and controlled.

  From 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 obtaining the frequency should be used as the correction amount of the characteristic change of the vibration type actuator during the main drive. It was confirmed that it could be done.

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

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

  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 electro-mechanical energy conversion element 5, a traveling wave is generated in the vibrating body 3, and the driven body 2 that comes into contact with the vibrating body 3 rotates relatively to the vibrating body by friction driving. I do.

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

<Explanation of standing wave vibration and traveling wave vibration>
FIG. 12 shows a pulse signal and a standing wave vibration during a characteristic detection period in a vibration type actuator using a traveling wave. FIG. 12A shows a pulse signal and a vibration waveform during 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 states of the vibration waveforms generated at time intervals of T / 4 are simulated as t0, t1, t2, and t3. The horizontal axis is the position in the circumferential direction. Such a state in which vibration in the Z direction constantly occurs at the same position is referred to as standing wave vibration, and since no driving force is generated in the rotation direction, the actuator is stopped.

  On the other hand, FIG. 12B shows a pulse signal and a vibration waveform in the main driving period, and the phase difference between the A-phase and B-phase pulse signals differs by 90 degrees. In the main driving period, traveling wave vibration in which the peak of the vibration moves in the circumferential direction occurs, and a driving force can be generated in the rotating direction.

  As described above, by setting the pulse signal in the characteristic detection period to cause the standing wave vibration, the power can be measured while the vibration type actuator is stopped, and the frequency change due to the change in the environmental temperature can be detected. . The standing wave vibration is also a vibration in a direction perpendicular to a contact surface of the vibrating body that contacts the driven body. The specific means for correcting the starting frequency and the 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 of the vibration type actuator is used for driving the lens for autofocus of the imaging device 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 be used for driving a lens or an image sensor at the time of camera shake correction. FIG. 13A is a plan view (top view) illustrating an 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 generally includes a main body 61 and a lens barrel 62 that is detachable from the main body 61. The main body 61 includes an imaging element 63 such as a CCD sensor or a CMOS sensor that converts an optical image formed by light passing through the lens barrel 62 into an image signal, and a camera control microcomputer that controls the overall operation of the imaging device 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 has a built-in 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. 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 drive type actuator control device of the present invention can be used for driving a lens holder for moving a zoom lens. Therefore, the control device of the mold actuator of the present invention can be mounted not only on the imaging device but also on the replacement lens.

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

  The microscope in FIG. 14 includes an imaging unit 70 having a built-in imaging element and an optical system, and an automatic stage 71 provided on a base and having a stage 72 moved by a vibration type actuator. The object to be observed is placed on the stage 72, and an enlarged image is captured 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 observed object is moved in the X direction and the Y direction in the figure, and a large number of captured images are obtained. By using a computer (not shown), the captured images are combined to obtain a single high-definition image with a wide observation range.

  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 a temperature sensor. Can be realized. Further, when the vibration type actuator is replaced and used, it is possible to cope with a difference in resonance frequency due to an individual difference of the vibration type actuator to be used, compensate for the individual difference, and stably move the driven object.

102 Current detection circuit 117 Frequency acquisition unit 118 Correction amount acquisition unit 111 Parameter acquisition unit 119 AC voltage generation means

Claims (19)

In the characteristic detection period, a state where a vibration in a direction perpendicular to the contact surface is excited at a contact portion of the vibrating body of the vibration type actuator with the driven body, and an AC voltage is applied so that the vibration type actuator is stopped. A current detecting means for detecting a current while changing the frequency of the AC voltage ;
A frequency acquisition unit that acquires a frequency at which a current or power consumption reaches a peak or a predetermined value based on an output of the current detection unit,
AC voltage generating means for generating the AC voltage input to the vibration-type actuator using a correction amount based on the output of the frequency acquisition unit in the main drive period,
A control device for a vibration-type actuator, comprising:   The control device according to claim 1, wherein the current detection unit is provided between a power supply and the AC voltage generation unit.   3. 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 unit is input, wherein an output of the booster circuit is input to the vibration-type actuator. 4. apparatus.   The control device for a vibration-type actuator according to any one of claims 1 to 3, wherein the current detection means obtains a current by detecting a potential difference.   5. The control device for a vibration-type actuator according to claim 1, wherein a parameter is acquired using the correction amount during a characteristic detection period. 6. Command value generation means,
A PID calculation unit to which an output of the command value generation unit is input,
The control device for a vibration-type actuator according to any one of claims 1 to 5, further comprising: a parameter acquisition unit configured to acquire a parameter of an AC voltage in a main driving period based on an output of the PID calculation unit. .   The control device for a vibration-type actuator according to any one of claims 1 to 6, 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 7,
A vibration-type actuator driven by a control device for the vibration-type actuator,
A vibration device comprising: A control device for a vibration-type actuator according to any one of claims 1 to 7,
A vibration-type actuator driven by a control device for the vibration-type 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 7,
A vibration-type actuator driven by a control device for the vibration-type actuator,
A lens driven by the vibration-type actuator;
An image sensor provided on the optical axis of the lens;
An imaging device comprising: A control device for a vibration-type actuator according to any one of claims 1 to 7,
A vibration-type actuator driven by a control device for the vibration-type actuator,
An imaging element driven by the vibration-type actuator;
A lens in which the image sensor is provided on an optical axis;
An imaging device comprising: A control device for a vibration-type actuator according to any one of claims 1 to 7,
A vibration-type actuator driven by a control device for the vibration-type actuator,
A stage driven by the vibration-type actuator;
Automatic stage equipped with. During the characteristic detection period,
The frequency of the AC voltage is changed in a state where the vibration in the direction perpendicular to the contact surface is excited at the contact portion of the vibrating body of the vibration type actuator with the driven body and the AC voltage is applied so as to be in a stopped state. Together with the current,
Current or power consumption during the characteristic detection period, to detect a peak or a frequency reaching a predetermined value,
In this driving period,
A method of controlling a vibration-type actuator, wherein an AC voltage having a frequency corrected based on the detected peak or a frequency at a predetermined value is applied to the vibration-type actuator.   14. The method according to claim 13, wherein during the characteristic detection period, the phase difference of the AC voltage is a value between -10 degrees and +10 degrees.   14. The method according to claim 13, 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 according to any one of claims 13 to 15, wherein the starting frequency is adjusted based on a pulse width for adjusting a voltage amplitude of the AC voltage.   The method according to any one of claims 13 to 16, wherein the characteristic detection period is provided immediately after power-on.   The method according to any one of claims 13 to 16, wherein the characteristic detection period is provided before starting the main driving.   19. The method according to claim 13, wherein the corrected frequency is a starting frequency of the vibration type actuator.

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