Vibration-type actuator control apparatus and method, drive apparatus, and storage medium

Abstract

This invention provides a control device and method for a vibration-type actuator, a drive device, and a storage medium. A control device for a vibration-type actuator that moves a vibrating body and a contact body, wherein vibration is excited in the vibrating body using an electromechanical energy conversion element, and the contact body is in relative contact with the vibrating body, the control device comprising: a generation unit configured to generate a multiphase drive signal with a phase difference applied to the electromechanical energy conversion element; and a detection unit configured to detect the actual position of a movable unit including the vibrating body or the contact body. The generation unit sets the phase difference based on the deviation between the actual position of the movable unit and a target position. Compared to after the movable unit begins to move with a change in the target position, the generation unit makes the rate of change of the phase difference of the relative deviation from when the movable unit stops until when the movable unit begins to move larger.

Description

Technical Field

[0001] This invention relates to the control of vibration actuators. Background Technology

[0002] Some vibration actuators excite vibration in a vibrating body by applying two drive signals with a phase difference to an electromechanical energy conversion element, thereby generating elliptical motion of a protrusion on the vibrating body, and causing relative movement between the vibrating body and a contact body in contact with the protrusion. The moving speed of the movable unit, which is either the vibrating body or the contact body, can be changed by altering the phase difference between the two drive signals.

[0003] Japanese Patent Application Publication No. 2016-152746 discloses a method for suppressing the decrease in controllability of a vibration-type actuator in the low-speed range by setting the phase difference outside the dead zone, wherein the movable unit stops due to the insufficient phase difference and the resulting insufficient driving force in the low-speed range within the dead zone.

[0004] Due to changes in the attitude of the vibrating actuator, environmental variations (e.g., temperature), and time-varying factors, the phase difference and its width within the dead zone fluctuate. Therefore, regardless of these fluctuations in the dead zone, it is necessary to suppress the decrease in controllability. Summary of the Invention

[0005] This invention provides control devices, etc., that can achieve good controllability in phase difference control of vibration actuators.

[0006] According to one aspect of the invention, a control device for a vibration actuator moves a vibrating body and a contact body, wherein vibration is excited in the vibrating body using an electromechanical energy conversion element, and the contact body is in relative contact with the vibrating body. The control device includes: a generation unit configured to generate a multiphase drive signal with a phase difference applied to the electromechanical energy conversion element; and a detection unit configured to detect the actual position of a movable unit including the vibrating body or the contact body. The generation unit sets the phase difference based on the deviation between the actual position of the movable unit and a target position. Compared to after the movable unit begins to move with a change in the target position, the generation unit makes the rate of change of the phase difference relative to the deviation greater from when the movable unit stops until when the movable unit begins to move; or compared to after the movable unit begins to move, the generation unit makes the rate of increase of the phase difference greater from when the movable unit stops until when the movable unit begins to move; and when the movable unit begins to move and accelerates, the generation unit first decreases the rate of increase and then increases the rate of increase.

[0007] According to another aspect of the present invention, a driving device includes the control device described above, the vibration actuator described above, and a driven member driven by the vibration actuator.

[0008] The control method corresponding to the aforementioned control device also constitutes another aspect of the present invention. A storage medium storing a program that causes a computer to execute the control method also constitutes another aspect of the present invention.

[0009] A control method for a vibration actuator, the vibration actuator moving a vibrating body and a contact body, wherein vibration is excited in the vibrating body using an electromechanical energy conversion element, and the contact body is in relative contact with the vibrating body. The control method includes the following steps: generating a multiphase drive signal with a phase difference applied to the electromechanical energy conversion element; and detecting the actual position of a movable unit including the vibrating body or the contact body. The generation step sets the phase difference based on the deviation between the actual position of the movable unit and a target position. Compared to after the movable unit begins to move as the target position changes, the generation step makes the rate of change of the phase difference with respect to the deviation larger from when the movable unit stops until when the movable unit begins to move; or compared to after the movable unit begins to move, the generation step makes the rate of increase of the phase difference larger from when the movable unit stops until when the movable unit begins to move; and if the movable unit begins to move and accelerates, the generation step first decreases the rate of increase and then increases the rate of increase.

[0010] A storage medium storing a program that enables a computer to execute the control method described above.

[0011] Other features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0012] Figure 1 This is a block diagram illustrating the electrical structure of a vibration-type actuator drive system according to an embodiment of the present invention.

[0013] Figure 2 This is a flowchart illustrating the control process of the vibration actuator according to this embodiment.

[0014] Figure 3 This is a schematic diagram showing the mechanical structure of a vibration actuator.

[0015] Figure 4A and Figure 4B The driving signal applied to the piezoelectric element is shown.

[0016] Figure 5A and Figure 5BThis is a schematic diagram showing an elastic body in a deformed state.

[0017] Figure 6A and Figure 6B This is a schematic diagram showing an elastic body in another deformation state.

[0018] Figure 7A and Figure 7B This is a schematic diagram showing an elastic body in another deformation state.

[0019] Figure 8A and Figure 8B This is a schematic diagram showing an elastic body in another deformation state.

[0020] Figure 9 The movement trajectory of the protrusion of the elastomer is shown.

[0021] Figure 10 The relationship between the phase difference θ and the velocity V of the vibration actuator is shown.

[0022] Figure 11 The control block of the vibration actuator drive system is shown.

[0023] Figure 12 The proportional gain of the vibration actuator drive system is shown.

[0024] Figure 13 The temporal change of the position of the movable unit according to this embodiment is shown.

[0025] Figure 14 The time variation of the deviation according to this embodiment is shown.

[0026] Figure 15 The time variation of the proportional gain according to this embodiment is shown.

[0027] Figure 16 The time variation of the phase difference according to this embodiment is shown.

[0028] Figure 17 This illustrates another time variation of the phase difference according to this embodiment.

[0029] Figure 18 An example of a drive device including a vibration actuator is shown. Detailed Implementation

[0030] A description of embodiments of the present invention will now be given with reference to the accompanying drawings.

[0031] Figure 1The electrical configuration of a vibration actuator drive system 1 according to an embodiment of the present invention is shown. The drive system 1 includes a vibration actuator 2 and a control device 3 for controlling the drive of the vibration actuator 2. The vibration actuator 2 includes a first piezoelectric element 310 and a second piezoelectric element 320. Each of the first piezoelectric element 310 and the second piezoelectric element 320 is an electromechanical energy conversion element that displaces upon receiving a voltage. The specific structure of the vibration actuator 2 will be described later.

[0032] The control device 3 includes a position command unit 100, a position detection unit 200, and a drive signal generation unit (generation unit) 400. The position command unit 100 instructs the target position Xt and target velocity Vt of the movable unit in the vibration actuator 2 (described later). The position detection unit (detection unit) 200 acquires the current position (actual position) Xa of the movable unit. The drive signal generation unit 400 uses the instruction from the position command unit 100 and the current position Xa of the movable unit acquired from the position detection unit 200 to generate multiphase (two-phase) drive signals (voltage signals) required for the movable unit to reach the target position Xt at the target velocity Vt. These two-phase drive signals are each applied to a corresponding one of the first piezoelectric element 310 and the second piezoelectric element 320.

[0033] Although the driving signal is a voltage signal in this embodiment, it can also be a current signal. Although two piezoelectric elements are used in this embodiment, three or more piezoelectric elements can be used, or three or more phase driving signals can be applied to the three or more piezoelectric elements.

[0034] Figure 2 The flowchart illustrates the control processing of the vibration actuator 2. The drive signal generation unit 400 includes a computer, such as a CPU, and executes the processing according to a computer program.

[0035] In step S01, the drive signal generation unit 400 obtains the target position Xt and target velocity Vt of the movable unit from the position command unit 100.

[0036] In step S02, the drive signal generation unit 400 acquires the current position Xa of the movable unit detected by the position detection unit 200.

[0037] In step S03 (generation step), the drive signal generation unit 400 uses the target position Xt and target velocity Vt of the movable unit obtained from the position command unit 100 and the current position Xa of the movable unit obtained from the position detection unit 200 to generate a two-phase drive signal. At this time, the drive signal generation unit 400 sets (controls) the phase difference between the two-phase drive signals based on the deviation between the current position Xa and the target position Xt (i.e., based on the deviation itself or the value obtained from the deviation), so that the moving speed of the movable unit can be the target velocity Vt.

[0038] In step S04 (application step), the drive signal generation unit 400 applies the two-phase drive signal generated in step S03 to the first piezoelectric element 310 and the second piezoelectric element 320. Thus, the movable unit of the vibration actuator moves towards the target position Xt while accelerating towards the target velocity Vt.

[0039] Figure 3 The mechanical structure of the vibration actuator 2 is schematically shown. The first piezoelectric element 310 and the second piezoelectric element 320 are attached to the elastic body 500, which is a vibrating body, via the mating surfaces 311 and 321, respectively, by adhesion or the like.

[0040] Connectors 511 and 512, provided on the elastomer 500, are respectively fixed to protrusions 711 and 712 provided on the retaining member 700 by adhesion or the like. Thus, the elastomer 500 is fixed to the retaining member 700. The retaining member 700 is fixed to a fixing member (not shown). The first piezoelectric element 310, the second piezoelectric element 320, the elastomer 500, and the retaining member 700 form a fixing portion that remains stationary when the movable unit in the vibration actuator moves.

[0041] The compression spring 800 is a compression spring with its first end in contact with the retaining member 700 and its second end in contact with at least one of the first piezoelectric element 310 and the second piezoelectric element 320, thereby applying spring force (compression force) to the elastic body 500 in the Y direction, which is the compression direction.

[0042] The pressure spring 800 can be a spring other than a compression spring, or the pressure can be applied to the elastomer 500 by means other than a spring (such as magnetic force).

[0043] The elastic body 500, having received applied pressure, makes pressurized contact with the friction member 600, which serves as the contact body. The elastic body 500 has two protrusions 521 and 522. The front end of each protrusion is the portion that contacts the friction member 600. The friction member 600 constitutes at least a portion of the movable unit of the vibration-type actuator. That is, only the friction member 600 can be the movable unit, or the movable unit can include the friction member 600 and a component (not shown) that moves or is linked with the friction member 600.

[0044] When a two-phase drive signal with a frequency near the resonant frequency of the elastomer 500 is applied to the first piezoelectric element 310 and the second piezoelectric element 320 by the drive signal generation unit 400, vibration is excited to the elastomer 500, and elliptical motion, as indicated by arrow A, occurs at the front ends of the protrusions 521 and 522. The elliptical motion is propagated by friction to the friction member 600, which is in pressurized contact with the front ends of the protrusions 521 and 522, causing the movable unit including the friction member 600 to move (translate) in the X direction, which is the direction of movement.

[0045] Although this embodiment describes a movable unit including the friction member 600 moving relative to a fixed portion including the elastic body 500, the movable unit including the elastic body can also move relative to the fixed portion including the friction member 600. That is, the elastic body and the contact member can move relative to each other.

[0046] Figure 4A and Figure 4B Examples of drive signals applied to the first piezoelectric element 310 and the second piezoelectric element 320 are shown. The horizontal axis represents time t, and the vertical axis represents the voltage V, which is the value of the drive signal. Two-phase drive signals 900 and 901 are periodic signals with amplitude Va and period Ta, respectively, and are applied to the first piezoelectric element 310 and the second piezoelectric element 320. Although the drive signal 901 applied to the second piezoelectric element 320 has the same waveform as the drive signal 900 applied to the first piezoelectric element 310, its phase is shifted by θ. That is, the two-phase drive signals 900 and 901 have a phase difference θ. The term "same waveform" as used herein means not only that the waveforms are completely identical, but also that the waveforms are slightly different within a range that does not affect the drive of the vibration actuator, or that the waveforms can be considered substantially the same.

[0047] In this embodiment, when a positive voltage is applied, the first piezoelectric element 310 and the second piezoelectric element 320 extend in an in-plane direction parallel to the bonding surfaces 311 and 321, respectively, and contract in a thickness direction orthogonal to the bonding surfaces 311 and 321. When a negative voltage is applied, the first piezoelectric element 310 and the second piezoelectric element 320 contract in the in-plane direction and extend in the thickness direction, respectively.

[0048] Figures 5A to 8B The deformation states of the first piezoelectric element 310, the second piezoelectric element 320, and the elastomer 500 are shown when drive signals 900 and 901 are applied to the first piezoelectric element 310 and the second piezoelectric element 320. Figure 5A , Figure 6A , Figure 7A and Figure 8A It shows Figure 3 The cross section along line BB of the vibration actuator shown in the figure. Figure 5B , Figure 6B , Figure 7B and Figure 8B It shows from and Figure 3 The first piezoelectric element 310, the second piezoelectric element 320, and the elastomer 500 are viewed from the same direction.

[0049] In these figures, arrows 531a, 531b, 531c, and 531d represent the movement of the tip of protrusion 521. Similarly, arrows 532a, 532b, 532c, and 532d represent the movement of the tip of protrusion 522. The black dots indicate the positions of the tips of protrusions 521 and 522 when no voltage is applied to the first piezoelectric element 310 and the second piezoelectric element 320 and the elastomer 500 is not deformed. The positions of the arrow tips are the positions of the tips of protrusions 521 and 522 when voltage is applied to the first piezoelectric element 310 and the second piezoelectric element 320 and the elastomer 500 deforms.

[0050] Figure 5A and Figure 5B It shows in Figure 4A and Figure 4B The deformation states of the first piezoelectric element 310, the second piezoelectric element 320, and the elastomer 500 at time t1. At time t1, positive and negative voltages are applied to the first piezoelectric element 310 and the second piezoelectric element 320, respectively. Therefore, the first piezoelectric element 310 extends in the in-plane direction, and the second piezoelectric element 320 contracts in the in-plane direction. At this time, since the elastomer 500 maintains its original size, it bends and deforms, and the non-jointing surface 312 on the side opposite to the joining surface 311 in the first piezoelectric element 310 becomes convex. The non-jointing surface 322 of the second piezoelectric element 320 becomes concave. Thus, as shown respectively... Figure 5B As indicated by arrows 531a and 532a, the tips of protrusions 521 and 522 move to the right. At time t1, the voltage difference between the first piezoelectric element 310 and the second piezoelectric element 320 becomes maximum. The rightward movement of protrusions 521 and 522 is also maximum at this point.

[0051] Figure 6A and Figure 6B It shows in Figure 4A and Figure 4B The deformation state of the first piezoelectric element 310, the second piezoelectric element 320, and the elastomer 500 at time t2. At time t2, a positive voltage is applied to both the first piezoelectric element 310 and the second piezoelectric element 320. Both the first piezoelectric element 310 and the second piezoelectric element 320 extend in the in-plane direction. At this time, since the elastomer 500 maintains its original size, the elastomer 500 bends and deforms, and the non-jointing surfaces 312 and 322 are convex surfaces. Thus, respectively as Figure 6B As indicated by arrows 531b and 532b, the tips of protrusions 521 and 522 move upward. At time t2, the sum of the voltages applied to the first piezoelectric element 310 and the second piezoelectric element 320 becomes maximum. Therefore, the amount of upward movement of each tip of protrusions 521 and 522 is also maximum.

[0052] Figure 7A and Figure 7B It shows in Figure 4A and Figure 4B The deformation states of the first piezoelectric element 310, the second piezoelectric element 320, and the elastomer 500 at time t3 are shown. At time t3, a negative voltage and a positive voltage are applied to the first piezoelectric element 310 and the second piezoelectric element 320, respectively. Therefore, the first piezoelectric element 310 contracts in the in-plane direction, and the second piezoelectric element 320 extends in the in-plane direction. At this time, since the elastomer 500 maintains its original size, it bends and deforms, the non-jointing surface 312 becomes concave, and the non-jointing surface 322 becomes convex. As a result, as shown below... Figure 7B As indicated by arrows 531c and 532c, the tips of protrusions 521 and 522 move to the left. At time t3, similar to time t1, the voltage difference between the first piezoelectric element 310 and the second piezoelectric element 320 becomes maximum. Therefore, the leftward movement of the tips of protrusions 521 and 522 is also maximum.

[0053] Figure 8A and Figure 8B It shows in Figure 4A and Figure 4B The deformation state of the first piezoelectric element 310, the second piezoelectric element 320, and the elastomer 500 at time t4. At time t4, a negative voltage is applied to both the first piezoelectric element 310 and the second piezoelectric element 320. Therefore, both the first piezoelectric element 310 and the second piezoelectric element 320 contract in the in-plane direction. At this time, since the elastomer 500 maintains its original size, the elastomer 500 bends and deforms, and the non-jointing surfaces 312 and 322 are concave. As a result, respectively as Figure 8BAs indicated by arrows 531d and 532d, the tips of protrusions 521 and 522 move downwards. At time t4, as at time t2, the sum of the voltages applied to the first piezoelectric element 310 and the second piezoelectric element 320 becomes maximum. Therefore, the downward movement of the tips of protrusions 521 and 522 also becomes maximum.

[0054] Therefore, by applying periodic drive signals 900 and 901 to the first piezoelectric element 310 and the second piezoelectric element 320, the front ends of protrusions 521 and 522 are repeatedly... Figure 5B , Figure 6B , Figure 7B and Figure 8B The movement shown is an elliptical motion.

[0055] Figure 9 An example of the movement trajectory of the respective front ends of protrusions 521 and 522 in elliptical motion is shown. The horizontal and vertical axes represent the trajectories of the protrusions 521 and 522 in elliptical motion. Figure 3 The positions of the front ends of protrusions 521 and 522 in the X and Y directions are shown. When the phase difference θ between drive signals 900 and 901 is a first phase difference, the front ends of protrusions 521 and 522 move to positions 550a, 550b, 550c, and 550d at times t1, t2, t3, and t4. This movement cycle repeats to perform elliptical motion, thereby depicting an elliptical trajectory. When the phase difference θ between drive signals 900 and 901 is a second phase difference greater than the first phase difference, the front ends of protrusions 521 and 522 move to positions 551a, 551b, 551c, and 551d at times t1, t2, t3, and t4, and this movement cycle repeats to perform elliptical motion, thereby depicting an elliptical trajectory 541.

[0056] When the phase difference θ is the first phase difference and the second phase difference, respectively, the tips of protrusions 521 and 522 separate from the friction member 600 in the Y direction from positions 550a and 551a via positions 550b and 551b to positions 550c and 551c, so the friction member 600 does not move. Subsequently, the tips of protrusions 521 and 522 move from positions 550c and 551c via positions 550d and 551d to positions 550a and 551a, pushing the friction member 600 in the Y direction while moving by amounts 560 and 561 in the X direction. At this time, the friction member 600 also moves by the same amount in the X direction. The amounts 560 and 561 of movement of the tips of protrusions 521 and 522 in the X direction are the amplitudes of the elliptical motion in the X direction within one cycle of drive signals 900 and 901, and will be referred to as the feed amplitude in the following description. The amount of movement 570 and 571 of the front ends of protrusions 521 and 522 in the Y direction within one cycle of drive signals 900 and 901 (i.e., the amplitude of elliptical motion in the Y direction) will be referred to as the drive amplitude.

[0057] The friction member 600 can be continuously moved in the X direction by repeatedly generating feed amplitudes 560 and 561 at the front end of protrusions 521 and 522 in each cycle of drive signals 900 and 901.

[0058] When the feed amplitude is equal, the shorter the period Ta of the drive signal, the higher the moving speed of the friction member 600. With the same period Ta, the larger the feed amplitude 560, the higher the moving speed of the friction member 600. Since the movement of the friction member 600 does not involve the driving amplitude, the larger the driving amplitude, the greater the power loss.

[0059] As the phase difference θ approaches Ta / 2, the difference between the applied voltages at times t1 and t3 increases, while the sum of the absolute values ​​of the applied voltages at times t2 and t4 decreases. The feed amplitude increases and drives the amplitude to decrease. When the phase difference θ becomes Ta / 2, times t1 and t3 correspond to Ta / 4 and 3Ta / 4, respectively, and the difference between the applied voltages at these times becomes the maximum of 2Va. Times t2 and t4 correspond to Ta / 2 and Ta, respectively, and the sum of the applied voltages at these times becomes 0. The feed amplitude becomes the maximum and drives the amplitude to zero.

[0060] As the phase difference θ approaches 0, the difference between the applied voltages at times t1 and t3 decreases, while the sum of the absolute values ​​of the applied voltages at times t2 and t4 increases. The feed amplitude decreases, and the driving amplitude increases. When the phase difference θ becomes 0, times t1 and t3 correspond to 0 and Ta / 2, respectively, and the difference between the applied voltages at these times becomes zero. Times t2 and t4 correspond to Ta / 4 and 3Ta / 4, respectively, and the sum of the applied voltages at these times becomes a maximum of 2Va. Therefore, the feed amplitude becomes 0, and the driving amplitude becomes maximum.

[0061] exist Figure 9 In the process, when the phase difference θ between drive signals 900 and 901 is close to 0, the tips of protrusions 521 and 522 move to trace an elliptical trajectory 540 with a small feed amplitude 560. When the phase difference θ between drive signals 900 and 901 is close to Ta / 2, the tips of protrusions 521 and 522 move to trace an elliptical trajectory 541 with a large feed amplitude 561. Therefore, by changing the phase difference θ, the magnitude of the feed amplitude can be changed, and thus the amount of movement and speed of the friction member 600 can be altered.

[0062] Figure 10An example of the relationship between the phase difference θ and the moving speed V of the friction member 600 is shown. The horizontal axis represents the phase difference θ, and the vertical axis represents the moving speed V. Line 601 represents the moving speed V for each phase difference θ. As shown in this figure, when the phase difference θ is less than phase difference θA and greater than phase difference θB, the moving speed V decreases and increases as the phase difference θ decreases and increases, respectively. On the other hand, when the phase difference θ is between phase difference θA and phase difference θB, the moving speed V is always 0, that is, even if the phase difference θ changes, the friction member 600 remains stationary.

[0063] like Figure 9 As shown, when the phase difference θ is small, the feed amplitude 560 decreases and the driving amplitude 570 increases. If the driving amplitude becomes too large, the frictional force generated between the tips of the protrusions 521 and 522 and the friction member 600 decreases, and the feed amplitude 560 at the tips of the protrusions 521 and 522 is not transmitted to the friction member 600. Therefore, as Figure 10 As shown, in the region where the phase difference θ is small (θA to θB), the moving speed V remains 0 even if the phase difference θ changes. This phase difference region is called the dead zone. The phase difference corresponding to the dead zone and its width change due to various factors such as changes in the posture of the vibrating actuator 2 (the device on which the vibrating actuator 2 is installed), changes in the environment (e.g., temperature), and changes over time.

[0064] Figure 11 The structure of the proportional control in the drive signal generation unit 400 is shown. The drive signal generation unit 400 calculates the deviation (Xt-Xa) based on the target position Xt obtained from the position command unit 100 and the actual position Xa obtained from the position detection unit 200. Then, the product P(Xt-Xa) is calculated by multiplying the deviation (Xt-Xa) by the proportional gain P. The drive signal generation unit 400 sets the phase difference θ between drive signals 900 and 901 to P(Xt-Xa) to generate drive signals 900 and 901, and applies them to the first piezoelectric element 310 and the second piezoelectric element 320 of the vibration actuator 2.

[0065] Figure 12 It shows Figure 11 The proportional gain P is set as shown. The horizontal axis represents the actual velocity Va of the friction member 600, and the vertical axis represents the proportional gain P. The actual moving velocity Va of the friction member 600 can be calculated by the drive signal generation unit 400 based on the actual position Xa detected by the position detection unit 200.

[0066] like Figure 12As shown, the proportional gain P is set to change according to the magnitude of the actual moving speed Va. More specifically, when the friction member 600 is in a stopped state where the actual moving speed Va is 0, the proportional gain P is set to its maximum value (first value) Pc + Pu. The proportional gain P decreases as the magnitude of the actual moving speed Va |Va| increases according to P = (Pu - Pc)(1 - |Va| / Vth) + Pc, and is set to a constant value (second value) Pc when |Va| exceeds a threshold (predetermined speed) Vth.

[0067] Although this embodiment changes the proportional gain P based on the actual moving speed Va, the present invention is not limited to this embodiment, and for example, the proportional gain P can be changed based on the target speed Vt. While this embodiment discusses proportional control of the vibration actuator 2, the present invention is not limited to this embodiment, and various controls such as integral control and derivative control can be performed. In integral and derivative control, the phase difference is set based on the integral value of the deviation, which is a value corresponding to the deviation, or the product of the deviation value and the integral or derivative gain.

[0068] Figure 13 , Figure 14 , Figure 15 , Figure 16 and Figure 17 The changes in position X (target position Xt and actual position Xa), deviation (Xt-Xa), proportional gain P, phase difference θ, and actual moving speed Va (vertical axis) of the friction member 600 in this embodiment with respect to each time t (horizontal axis) are shown respectively.

[0069] exist Figure 13 In the diagram, the target position Xt, indicated by the solid line, is located at the stop position from time 0 to time t5, and represents the position after time t5 where the movement is at a constant speed. The actual position Xa1, indicated by the dashed line, is the actual position of the friction member 600 in this embodiment (this actual position is relative to...). Figure 10 The relationship between the phase difference θ and the moving speed V shown is used to set... Figure 11 and Figure 12 The proportional control and proportional gain are shown, and the time change of the response position relative to the target position Xt is shown. The actual position Xa2, indicated by the dotted line, is... Figure 11 The actual position of the friction member 600 in the conventional example where the proportional gain P in the control is always constant at Pc is shown, and the time change of the response position relative to the target position Xt is shown.

[0070] Figures 14 to 17 The deviation (Xt-Xa1), proportional gain P1, phase difference θ1, and actual moving speed Va1, shown by the solid lines, illustrate this. Figure 11 and Figure 12The time variations of the values ​​in the proportional control and proportional gain settings are shown. The deviation (Xt-Xa2), proportional gain P2, phase difference θ2, and actual movement speed Va2, indicated by the dashed lines, illustrate the time variations of these values ​​in the above conventional example.

[0071] In this embodiment and the conventional example, when the target position Xt begins to change at time t5, both the deviations (Xt-Xa1) and (Xt-Xa2) increase according to the change in the target position Xt. Since the actual moving speed V1 is 0 at time t5, the proportional gain P1 in this embodiment is the maximum value Pc+Pu. On the other hand, the proportional gain P2 in the conventional example is always constant at Pc. Therefore, in the phase differences θ1 and θ2, which are set as the products of proportional gains P1 and P2 and deviations (Xt-Xa1) and (Xt-Xa2), the increase in phase difference θ1 is greater than the increase in phase difference θ2. In this embodiment, the phase difference θ1 reaches the phase difference θB at time t6 earlier, which is when the friction member 600 begins to move.

[0072] As a result, Figure 13 As shown, in this embodiment, the friction member 600 begins to move at time t6 earlier than in the conventional example. On the other hand, in the conventional example, the phase difference θ2 reaches the phase difference θB at time t7, which is later than time t6, and the friction member 600 begins to move. Therefore, since the friction member in this embodiment begins to move earlier than the friction member in the conventional example, the traceability of the friction member 600 to the target position Xt is improved.

[0073] like Figure 14 As shown, the friction member 600 starts moving at time t6 in this embodiment and at time t7 in the conventional example, and the increase in deviation (Xt-Xa1) and deviation (Xt-Xa2) gradually decreases. Figure 15 As shown, in this embodiment, when the friction member 600 starts moving from time t6, the proportional gain P1 decreases as the actual moving speed Va1 increases, and becomes constant as the proportional gain Pc at time t8 when the moving speed V1 reaches the threshold Vth.

[0074] In this embodiment, as Figure 16 As shown, from time t6 to time t8, the rate of increase of the deviation (Xt-Xa1) decreases and the proportional gain P1 also decreases. Therefore, the rate of increase (rate of change) of the phase difference θ1, which is their product, gradually decreases. After time t8, although the rate of increase of the deviation (Xt-Xa1) still decreases, the proportional gain P1 becomes constant. Therefore, the rate of increase of the phase difference θ1 temporarily increases at time t8, and thereafter the rate of increase of the phase difference θ1 decreases as the deviation (Xt-Xa1) decreases.

[0075] On the other hand, in the conventional example, the proportional gain P2 is constant, so the rate of increase of the phase difference θ1 decreases as the rate of increase of the deviation (Xt-Xa2) decreases.

[0076] As described above, in this embodiment, after the friction member 600 begins to move, the phase difference θ1 changes to have an inflection point θ1i. More specifically, after the friction member 600 begins to move, the rate of increase (rate of change) of the phase difference θ1 decreases at one point, and then the rate of increase of the phase difference θ1 increases until the actual moving speed Va1 of the friction member 600 approaches the target speed, and when the actual moving speed Va1 becomes closer to the target speed, the rate of increase of the phase difference θ1 decreases.

[0077] As described above, in this embodiment, the rate of change of the phase difference θ1 of the relative deviation (Xt-Xa1) up to the point where the friction member 600 begins to move is greater than the rate of change after the friction member 600 begins to move. Therefore, the rate of increase of the phase difference θ1 immediately after the target position Xt begins to change is greater than that in the conventional example, and the phase difference θ1 can cross the dead zone and quickly reach the phase difference θB at which the friction member 600 begins to move. Thus, the trackability of the friction member 600 to the target position Xt can be improved. In this embodiment, the proportional gain P1 is gradually reduced as the actual moving speed Va1 increases, so the phase difference θ1 does not change abruptly, allowing the friction member 600 to move smoothly and stably.

[0078] In this embodiment, the proportional gain P1 is reduced only in the low-speed range after the friction member 600 begins to move (up to time t8). In the high-speed range where oscillations may occur in the vibration actuator 2 when the proportional gain P1 is large, the proportional gain P1 can be set to the same as in the conventional example, and stable control can be achieved. This embodiment changes the proportional gain P1 based on the actual moving speed Va1, and even if the dead zone changes due to the above factors and the phase difference θB at which the friction member 600 begins to move changes, good controllability can be maintained in phase difference control.

[0079] Figure 18 The image-capturing device (camera) is shown as a drive device including a vibration actuator 2 and a control device 3. The fixing part of the vibration actuator 2 (which includes a first piezoelectric element 310, a second piezoelectric element 320, an elastomer 500 and a retaining member 700) is fixed to the fixing member F in the image-capturing device.

[0080] On the other hand, the lens holding member H is fixed to the friction member 600 of the vibration actuator 2, and the lens holding member H holds the lens L as a driven member. The movable unit includes the friction member 600, the lens holding member H, and the lens L. The lens holding member H is guided by the guide member G in the optical axis direction (object side and image side).

[0081] An image sensor S, such as a CCD sensor or a CMOS sensor, is provided on the image side of the lens L to capture an optical image formed by light incident from the object side and passing through the lens L.

[0082] When two-phase drive signals 900 and 901 are applied from the control device 3 to the first piezoelectric element 310 and the second piezoelectric element 320 to excite vibration in the elastic body 500, the lens L is driven in the optical axis direction via the friction member 600. This allows for focusing of the optical image formed on the camera sensor S. For example, when photographing a moving object, the control device 3 ensures good tracking and controllability of the vibration actuator 2, enabling good focus tracking of the moving object. Magnification can be achieved by moving the lens L to change the camera angle.

[0083] Although a camera device has been described, embodiments of the present invention may include various drive devices that drive the driven member by a vibration actuator.

[0084] This embodiment can provide good controllability in phase difference control of vibration actuators.

[0085] Other embodiments

[0086] The embodiments of the present invention can also be implemented by providing software (programs) that perform the functions of the above embodiments to a system or device via a network or various storage media, and the computer or central processing unit (CPU) or microprocessor unit (MPU) of the system or device reads out and executes the program.

[0087] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims will be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A control device for a vibration actuator, wherein the vibration actuator causes a vibrating body and a contact body in contact with the vibrating body to move relative to each other, and the vibration is excited by an electromechanical energy conversion element in the vibrating body, the control device comprising: A generation unit is configured to generate a multiphase drive signal with a phase difference applied to the electromechanical energy conversion element; as well as A detection unit is configured to detect the actual position of a movable unit, including the vibrating body or the contact body. The characteristic is that the generating unit sets the phase difference based on the deviation between the actual position and the target position of the movable unit. Specifically, compared to after the movable unit begins to move as the target position changes, the generating unit makes the rate of change of the phase difference relative to the deviation larger from when the movable unit stops until when the movable unit begins to move.

2. The control device according to claim 1, characterized in that, The generation unit sets the phase difference based on the product of the gain and a value corresponding to the deviation between the actual position and the target position of the movable unit. Specifically, compared to after the movable unit begins to move as the target position changes, the generating unit makes the gain larger from when the movable unit stops until when the movable unit begins to move.

3. The control device according to claim 2, characterized in that, The generating unit sets the gain to a first value when the movable unit is stopped. Wherein, after the movable unit starts to move, the generating unit decreases the gain from the first value as the moving speed of the movable unit increases.

4. The control device according to claim 3, characterized in that, After the moving speed has increased to the predetermined speed, the generating unit maintains the gain at a constant second value lower than the first value.

5. The control device according to claim 1, characterized in that, Compared to after the movable unit begins to move, the generating unit makes the rate of increase of the phase difference greater from when the movable unit stops until when the movable unit begins to move, and when the movable unit begins to move and accelerates, the generating unit first decreases the rate of increase and then increases the rate of increase.

6. The control device according to claim 1, characterized in that, In the vibration actuator, the portion of the vibrating body that contacts the contacting body undergoes elliptical motion due to the vibration, and the amplitude of the movable unit in the direction of movement changes according to the phase difference during the elliptical motion.

7. A control device for a vibration actuator, the vibration actuator causing a vibrating body and a contact body in contact with the vibrating body to move relative to each other, wherein vibration is excited in the vibrating body using an electromechanical energy conversion element, the control device comprising: A generation unit is configured to generate a multiphase drive signal with a phase difference applied to the electromechanical energy conversion element; as well as A detection unit is configured to detect the actual position of a movable unit, including the vibrating body or the contact body. The characteristic is that the generating unit sets the phase difference based on the deviation between the actual position and the target position of the movable unit. Specifically, compared to after the movable unit begins to move, the generating unit makes the rate of increase of the phase difference greater from when the movable unit stops until when the movable unit begins to move; and when the movable unit begins to move and accelerates, the generating unit first decreases the rate of increase and then increases the rate of increase. In the vibratory actuator, the portion of the vibrating body that contacts the contacting body undergoes elliptical motion due to the vibration, and the amplitude of the movable unit in the direction of movement changes according to the phase difference during the elliptical motion.

8. A driving device, comprising: The control device according to any one of claims 1 to 7; Vibration actuator; as well as A driven member driven by the vibration actuator.

9. A control method for a vibration actuator, wherein the vibration actuator causes a vibrating body and a contact body in contact with the vibrating body to move relative to each other, and the vibration is excited by an electromechanical energy conversion element in the vibrating body, the control method comprising the following steps: Generate a multiphase drive signal with a phase difference applied to the electromechanical energy conversion element; as well as The detection includes the actual position of the movable unit, including the vibrating body or the contact body. The characteristic is that the generation step sets the phase difference based on the deviation between the actual position and the target position of the movable unit. Specifically, compared to after the movable unit begins to move as the target position changes, the generating step results in a larger rate of change of the phase difference relative to the deviation from when the movable unit stops until when the movable unit begins to move.

10. A control method for a vibration actuator, wherein the vibration actuator causes a vibrating body and a contact body in contact with the vibrating body to move relative to each other, and the vibration is excited by an electromechanical energy conversion element in the vibrating body, the control method comprising the following steps: Generate a multiphase drive signal with a phase difference applied to the electromechanical energy conversion element; as well as The detection includes the actual position of the movable unit, including the vibrating body or the contact body. The characteristic is that the generation step sets the phase difference based on the deviation between the actual position and the target position of the movable unit. Specifically, compared to after the movable unit begins to move, the generating steps result in a larger rate of increase of the phase difference from when the movable unit stops until when the movable unit begins to move, and when the movable unit begins to move and accelerates, the generating steps first decrease the rate of increase and then increase the rate of increase.

11. A computer program product comprising a program that, when executed by a computer, implements the steps of the control method according to claim 9 or 10.

12. A computer-readable storage medium storing a program that, when executed by a computer, implements the steps of the control method according to claim 9 or 10.

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