Vibration type driving device, apparatus, driving control device and method

Abstract

The present invention provides a vibration-type driving device, an apparatus, a driving control device and a method. The vibration-type driving device can maintain stable driving performance and controllability. The vibration-type driving device includes: a vibration-type actuator, which includes a vibrator and a contact body; and a driving control device. The driving control device applies a two-phase AC voltage to an energy conversion element of the vibrator through a driving part, converts the control amount based on the feedback control of the relative position / speed into a phase difference between the two-phase AC voltage, and outputs the phase difference to the driving part by using the phase difference of the first quadrant or the second quadrant of the coordinate (in the first direction) and the phase difference of the third quadrant or the fourth quadrant (in the second direction) for relative movement, wherein the vertical axis is SINθ, the horizontal axis is COSθ, and θ is the phase difference.

Description

Technical Field

[0001] The present invention relates to a control method of a vibration-type actuator including a vibrator and a contact body that move relative to each other, a drive control device, and a vibration-type driving device and apparatus including the vibration-type actuator. Background Art

[0002] A vibration type actuator is a non-electromagnetic drive actuator that causes vibration in a vibrator by applying an alternating voltage to an electrical-mechanical energy conversion element such as a piezoelectric element constituting the vibrator, and outputs vibration energy as mechanical motion. For example, Japanese Patent Publication No. 2001-157473 describes a vibration type actuator that excites progressive vibration (hereinafter referred to as "traveling wave") in a vibrator and frictionally drives a contact body in contact with the vibrator.

[0003] The vibration type actuator described in Japanese Patent Publication No. 2001-157473 has the following structure: the vibrator has an annular elastic body, a protrusion group with a comb-shaped shape is formed on one side of the elastic body in the axial direction (thickness direction), and the annular contact body is arranged to contact the friction material bonded to the upper surface of each protrusion. The annular piezoelectric element is bonded to the other side of the elastic body in the axial direction, and a pattern electrode is formed on the piezoelectric element. The pattern electrode is equally divided into four times the order corresponding to the order of the vibration mode excited in the annular part of the vibrator, and a substantially sinusoidal alternating voltage with a phase shift of 90° over time is applied to each electrode in turn. In this case, when an alternating voltage with a frequency close to the natural frequency of the vibration mode to be excited is applied to the pattern electrode, the elastic body is resonated by the bending moment applied to the elastic body through the expansion and contraction of the piezoelectric element. Since the vibration modes to be excited in the vibrator are the same but the phases are different, the vibrations are combined and thus a traveling wave is formed.

[0004] When the vibration type actuator is driven, the speed at which the vibrator and the contact body move relative to each other can be controlled by adjusting the frequency, amplitude, and phase difference of the AC voltage to be applied to the piezoelectric element. An example of a method of reducing the relative movement speed while maintaining a predetermined vibration amplitude includes a method of generating a standing wave by reducing the phase difference between the two-phase AC signals from 90°. According to this control, high-precision control can be performed without a dead zone, and therefore, stable operation can be performed.

[0005] However, in the technology described in Japanese Patent Gazette No. 2001-157473, due to long-term use, there are multiple parts with different vibration amplitudes depending on the position distributed on the contact surface between the contact body and the vibrator, so there is a problem of inconsistent friction state. Since the inconsistency of the friction state causes the difference in the wear rate of the friction surface, the flatness of the friction surface decreases, and thus the driving performance or controllability decreases. Since the maximum displacement position of the vibration amplitude does not change, wear occurs at a specific part of the vibrator, and thus the contact surface pressure of the contact body on the vibrator becomes uneven. Therefore, the driving performance or controllability decreases. If the contact surface between the contact body and the vibrator has irregularities, the rotation synchronized with the relative rotation operation of the contact body to the vibrator is uneven, and therefore, there is a concern that the rotation accuracy will decrease. Summary of the invention

[0006] The present invention provides a control method of a vibration-type actuator, a drive control device, a vibration-type drive device, and an apparatus capable of maintaining stable drive performance and controllability even when the vibration-type actuator is used for a long period of time.

[0007] Therefore, the present invention provides a vibration type driving device, which includes: a vibration type actuator, which includes a vibrator and a contact body that move relative to each other; and a drive control device, which is configured to control the drive of the vibration type actuator, wherein the vibrator has an electrical-mechanical energy conversion element, and the drive control device includes: a driving part, which is configured to apply a two-phase AC voltage to the electrical-mechanical energy conversion element; a detection unit, which is configured to detect the relative position or relative speed between the vibrator and the contact body; a conversion unit, which is configured to convert a control amount based on feedback control of the relative position or relative speed into a phase difference between the two-phase AC voltage; and an output unit, which is configured to output a phase difference to the driving part by using a phase difference in the first quadrant or the second quadrant of a coordinate for driving relative movement in a first direction, and by using a phase difference in the third quadrant or the fourth quadrant of the coordinate for driving in a second direction opposite to the first direction, wherein the phase difference is represented by θ, and SINθ is taken on the vertical axis in the coordinate, and COSθ is taken on the horizontal axis in the coordinate.

[0008] According to the present invention, even when the vibration type actuator is used for a long period of time, stable driving performance and controllability can be maintained.

[0009] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a block diagram of a vibration type driving apparatus according to an embodiment of the present invention.

[0011] FIG. 2A to FIG. 2C is a diagram for describing the configuration of a vibration-type actuator.

[0012] Figure 3 : is a graph showing the relationship between the driving frequency, the phase difference, and the rotation speed of the contact body in the vibration type actuator.

[0013] Figure 4A and Figure 4B It is a diagram showing the contact state and the driving state between the contact body and the vibrator.

[0014] Figure 5A and Figure 5B It is a graph used to describe the relationship between the vibration amplitude and the phase difference between the AC voltage.

[0015] FIG. 6A to FIG. 6C : is a graph showing the comparison between the phase difference control of the prior art and the phase difference control of the first embodiment.

[0016] 7A to 7D is a diagram for describing the output of the phase difference-frequency determination unit.

[0017] Figure 8 is a schematic diagram showing the relationship between the phase difference and the driving direction during low-speed driving.

[0018] Fig.9A and Fig. 9B 2 is a schematic diagram showing a scenario in which the waveforms of the two-phase AC voltage during low-speed driving are switched according to the driving direction.

[0019] Fig.10 is a flowchart for describing a drive control method for a vibration-type actuator.

[0020] Fig.11A and Fig. 11B Is used to describe Fig.10 A flowchart diagram of the beneficial effects of the control performed.

[0021] Fig. 12A and Fig. 12B It is a circuit diagram of the driving part and a diagram for describing the pulse signal.

[0022] Fig.13A and Fig. 13B is a diagram for describing phase difference control according to the second embodiment.

[0023] Fig.14A and Fig. 14B is a graph showing the relationship between relative position, phase difference, and time in the drive control method according to the second embodiment.

[0024] Fig.15A and Fig. 15Bis a diagram for describing phase difference control according to the third embodiment.

[0025] Fig.16A and Fig. 16B is a diagram showing an example of an apparatus including a vibration-type driving device. DETAILED DESCRIPTION

[0026] Now, the present invention will be described in detail below with reference to the accompanying drawings showing embodiments of the present invention. In the following description, it is assumed that a vibration type driving device includes a vibration type actuator and a driving control device that controls the vibration type actuator.

[0027] Figure 1 1 is a block diagram showing a schematic configuration of a vibration-type driving device 15 according to an embodiment of the present invention. The vibration-type driving device 15 includes a driving control device 12, a vibration-type actuator 13, and a position detection unit 14. The driving control device 12 includes a control unit 10 and a driving part 11. The control unit 10 includes a command value generating unit 101, a control amount calculating unit 102, a voltage adjusting unit 107, a subtractor 108, a phase difference-frequency control unit 109, and a driving direction detecting unit 110. The phase difference-frequency control unit 109 includes a phase difference converting unit 103, a frequency converting unit 104, a phase difference quadrant changing unit 105, and a phase difference-frequency determining unit 106. The driving part 11 includes an AC signal generating unit 111 and a boost circuit 112. The vibration-type actuator 13 includes a vibrator 131 and a contact body 132. The position detection unit 14 detects a relative position r between the vibrator 131 and the contact body 132. The position detection unit 14 may be included in the driving control device 12.

[0028] The control unit 101 generates a signal including information for controlling the driving of the vibrator 131. Specifically, the command value generating unit 101 generates a command value (hereinafter, simply referred to as a "command value") for each time of the relative position r when the vibration-type actuator 13 is driven according to a predetermined speed curve, and outputs the generated command value to the subtractor 108. In this case, the command value generating unit 101 generates, for example, one command value for each control sampling, and outputs the generated command value. Figure 1 As shown, the control sampling, for example, represents a cycle as follows, from obtaining the deviation e to immediately before the deviation e is obtained again by inputting an AC voltage to the vibrator 131 and detecting the relative position r performed by the position detection unit 14. Feedback control of the drive (relative position r) of the vibration type actuator 13 is performed in this cycle. The generation of the command value is not limited to the method for obtaining the command value based on the relative position r. A method for detecting the relative speed between the vibrator 131 and the contact body 132 and obtaining the command value from the detected relative speed can be used.

[0029] As described below, in the present embodiment, the rotation drive type that drives the contact body 132 to rotate is used as the vibration type actuator 13. Therefore, in the present embodiment, the relative position r represents the rotation angle of the contact body 132 relative to the vibrator 131. The relative speed between the vibrator 131 and the contact body 132 is the rotation speed of the contact body 132 relative to the vibrator 131. In the following description, the relative speed between the vibrator 131 and the contact body 132 is referred to as "the rotation speed of the contact body 132". The driving direction of the contact body 132 is clockwise (CW direction (first direction)) or counterclockwise (CCW direction (second direction)). The command value generating unit 101 outputs the generated command value to the driving direction detecting unit 110. The driving direction detecting unit 110 detects the driving direction (CW direction or CCW direction) according to the command value, and outputs the detected driving direction to the phase difference quadrant changing unit 105.

[0030] The subtractor 108 calculates the deviation e by calculating the difference between the relative position r detected by the position detection unit 14 and the command value generated by the command value generation unit 101. The control amount calculation unit 102 calculates the control amount u using the deviation e through a PID compensator or the like, and outputs the calculated control amount to the phase difference-frequency control unit 109. It should be noted that the PID compensator adds the outputs of compensators having proportional (P), integral (I), and differential (D) functions, and is generally used to construct a stable control system with high accuracy by compensating for the phase delay or gain of the control target.

[0031] In the phase difference-frequency control unit 109, the phase difference conversion unit 103 and the frequency conversion unit 104 convert the control amount u into a phase difference θ and a frequency ν, which are operating parameters of the AC voltage to be applied to the piezoelectric element of the vibrator 131. The frequency conversion unit 104 outputs the generated frequency ν to the phase difference-frequency determination unit 106. The phase difference conversion unit 103 outputs the generated phase difference θ to the phase difference quadrant changing unit 105.

[0032] Information indicating the driving direction of the contact body 132 is input from the driving direction detection unit 110 to the phase difference quadrant changing unit 105. The phase difference quadrant changing unit 105 performs a phase difference shift, which will be described below, as needed by using the phase difference θ and the information about the driving direction obtained from the driving direction detection unit 110, and outputs the phase difference as a phase difference θs to the phase difference-frequency determining unit 106. The phase difference-frequency determining unit 106 controls the rotation speed of the contact body 132 by using the frequency ν and the phase difference θs.

[0033] The AC signal generating unit 111 generates a two-phase AC signal (to be described in detail) based on the phase difference θs and the frequency ν from the phase difference-frequency determining unit 106 and the pulse width information from the voltage adjusting unit 107. The boosting circuit 112 generates an AC voltage obtained by boosting the AC signal from the AC signal generating unit 111 to a desired voltage value, and applies the generated AC voltage to the piezoelectric element of the vibrator 131. Therefore, a predetermined vibration is excited in the vibrator 131, and a thrust is applied from the vibrator 131 to the contact body 132. Therefore, the vibrator 131 and the contact body 132 move relative to each other.

[0034] The position detection unit 14 includes a position sensor (not shown) attached to the contact body 132 or the vibrator 131. The relative position r detected by the position sensor is fed back to the control amount calculation unit 102, and therefore, the feedback control of the drive of the vibration type actuator 13 is performed so as to comply with the command value. Although the drive control device 12 in the present embodiment has a structure that drives the piezoelectric element included in the vibrator 131 with two phases, the present invention is not limited thereto. The drive control device can also be applied to the drive of such a vibration type actuator, which includes a vibrator that drives the piezoelectric element with two phases or more phases.

[0035] It should be noted that the control unit 10 is composed of, for example, a digital device such as a CPU, a PLD (including an ASIC) or an element such as an A / D converter. In the driving part 11, the AC signal generating unit 111 is composed of, for example, a CPU, a function generator or a switching circuit. The boost circuit 112 is composed of, for example, a coil or a transformer. The control unit 10 and the driving part 11 may not be composed of one element or circuit. The control unit and the driving part may be composed of a plurality of elements or circuits, and each process may be performed by any element or circuit.

[0036] FIG. 2A to FIG. 2C 1 is a diagram for describing a schematic configuration of the vibration-type actuator 13 . Figure 2A 1 is a three-dimensional diagram of a vibrator 131 and a contact body 132 constituting a vibration-type actuator 13. Both the vibrator 131 and the contact body 132 have an annular shape and are coaxially arranged. In a state where the contact body is rotatably supported around an axis, the contact body 132 contacts the vibrator 131 in an axial direction. The vibrator 131 includes an elastic body having an annular shape and in contact with the contact body 132. The vibrator 131 includes an annular piezoelectric element (electrical-mechanical energy conversion element) bonded to a surface of the elastic body opposite to a surface in contact with the contact body 132. It should be noted that in Figure 2A A portion of the contact body 132 is shown cut away.

[0037] Figure 2B1 is a plan view showing an electrode pattern of a piezoelectric element constituting the vibrator 131. The electrode pattern of the piezoelectric element is formed so that the number of waves of the traveling wave generated in the vibrator 131 is four waves during one rotation. However, the number of traveling waves is not limited to four waves. Figure 2B In the figure, "A" represents the A phase, the letter with a "-" above "A" represents the A' phase, "B" represents the B phase, and the letter with a "-" above "B" represents the B' phase.

[0038] Figure 2C 1 is a cross-sectional view showing a schematic structure of a vibration-type actuator 13. In the vibration-type actuator 13, a vibrator 131 is fixed to a housing 133 by screws or the like, and an output shaft 211 is rotatably supported on the housing 133 by a ball bearing 136. A pressurizing spring 138 causes the contact body 132 to pressurize the vibrator 131, and transmits the rotation of the contact body 132 to the output shaft 211. An AC voltage is applied to the piezoelectric element of the vibrator 131 by using a drive control device 12. As a result, the contact body 132 rotates, and thus, the rotational position of the contact body 132 relative to the vibrator 131 changes relatively. When the contact body 132 rotates, the output shaft 211 rotates by the pressurizing spring 138. The output shaft 211 is connected to a drive mechanism 16 of various devices or equipment through a mechanism not shown. Therefore, the drive mechanism 16 operates by receiving the rotational output of the output shaft 211. It should be noted that the vibration-type actuator that can be drive-controlled by the drive control device 12 is not limited to Figure 2C The construction shown in .

[0039] Figure 3 1 is a diagram showing the relationship between the driving frequency and phase difference in the vibration-type driving device 15 and the rotation speed of the contact body 132 in the vibration-type actuator 13. Phase difference control for changing the phase difference is performed in an area with low rotation speed (low-speed area), and frequency control for changing the driving frequency is performed in an area with high rotation speed (high-speed area). Switching is performed between phase difference control and frequency control according to the feedback control amount. In the phase difference control during low-speed driving, the frequency is fixed, and the phase difference is operated in the range of 0° to 90°. In the frequency control during high-speed driving, the phase difference is fixed to 90°, and the frequency is operated. It should be noted that in this specification, "degree" as a unit representing the phase difference is represented by "°".

[0040] Compared with frequency control, phase difference control can achieve stable driving in the low speed range. Figure 4A and Figure 4B As described, the phase difference control has a disadvantage in suppressing wear because amplitude unevenness is caused in the vibrator 131. In contrast, the frequency control has an advantage in suppressing wear because amplitude unevenness is hardly caused in the vibrator 131.

[0041] The principle of changing the quadrant by phase difference shift as characteristic control in the drive control device 12 will be described in conjunction with an example of a case where the phase difference between two-phase drive signals to be applied to the A phase and the B phase is shifted. Figure 4A and Figure 4B 1 and 2 are diagrams showing a contact state between a vibrator 131 and a contact body 132 in the vibration-type actuator 13 and a driving state of the vibration-type actuator 13 . Figure 4A The state that the phase difference is set to 30 ° (first quadrant) and the vibration type actuator 13 is driven at a low speed is shown. In this case, during one rotation (the range of 0 degrees to 360 degrees), the maximum displacement (position a and position c in the figure) and the minimum displacement (position b and position d in the figure) of the vibration amplitude appear at eight positions. Specifically, the rotation positions of 0deg, 45deg, 90deg, 135deg, 180deg, ... are the maximum displacement positions (position a and position c). It should be noted that in this specification, "degree" as a unit representing each rotation position of the vibrator 131 is represented by "deg". Each rotation position of the vibrator 131 can be represented as 0deg to 360deg in the circumferential direction.

[0042] In this case, the rotation speed of the contact body 132 is controlled to be maintained at a constant speed. Therefore, as the driving time becomes longer, there is a difference in the amount of wear between the maximum displacement position and the minimum displacement position of the vibration in the vibrator 131. This is because, depending on the size of the vibration at the contact portion between the vibrator 131 and the contact body 132, there is a difference in the amount of sliding. Therefore, there is a difference in the amount of wear between the maximum displacement position and the minimum displacement position, and thus uneven wear is caused in the vibrator 131. As a result, a good contact state cannot be maintained, so the driving performance is reduced. It should be noted that the driving direction of the contact body 132 when the phase difference is -30° (fourth quadrant) is opposite to the driving direction when the phase difference is 30° (first quadrant), but the maximum displacement position and the minimum displacement position of the vibration are the same as the case where the phase difference is 30° (first quadrant).

[0043] Figure 4B 1 shows the driving state when the phase difference of 30° in the first quadrant is shifted by only 180° to -150° in the third quadrant. In this state, the driving direction of the contact body 132 is Figure 4A The situation is the opposite, but the rotation speed is the same. Figure 4AIn this case, the maximum displacement position and the minimum displacement position of the vibration are switched. That is, the position a and the position c, which are the maximum displacement positions of the vibration amplitude when the phase difference is 30°, become the minimum displacement positions of the vibration amplitude of the vibrator 131 when the phase difference is -150°. Specifically, when the phase difference is -150°, the rotation positions 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, ... become the minimum displacement positions.

[0044] As described above, by adjusting the phase difference between the AC voltages, the maximum displacement position and the minimum displacement position of the vibration caused in the vibrator 131 can be switched to each other. By periodically shifting the phase difference, the uneven wear of the vibrator 131 is reduced. As a result, the driving performance of the vibration-type actuator 13 can be suppressed from being degraded. It should be noted that the case where the shift amount of the phase difference is 180° has been described above.

[0045] Figure 5A and Figure 5B is a diagram showing the relationship between the phase difference between the AC voltages induced in the vibrator 131 and the vibration amplitude. Figure 5A represents the vibration amplitude at the position of the vibrator 131 when the phase difference between the AC voltages is set to a predetermined value within the range of 0° to 90° in the first quadrant.

[0046] When the phase difference is 0°, a standing wave with a traveling wave component of zero (0) is generated. That is, only vibration in the direction in which the vibrator 131 and the contact body 132 are pressurized is caused, and the difference between the maximum displacement and the minimum displacement is the largest. As the phase difference between the AC voltages increases, the difference between the maximum displacement and the minimum displacement decreases. When the phase difference is 90°, the vibration amplitudes at all positions of the vibrator 131 are equal. That is, an ideal traveling wave is generated, and the vibration amplitude becomes constant at all positions of the vibrator 131.

[0047] Figure 5B represents the vibration amplitude at the position of the vibrator 131 when the phase difference between the AC voltages is set to a predetermined value within the range of -180° to -90° in the third quadrant. Figure 5A situation, in Figure 5B The maximum displacement position and the minimum displacement position of the standing wave amplitude are switched. Figure 5A The situation is the opposite. In the case of a phase difference of -180°, a standing wave is obtained, and the difference between the maximum displacement and the minimum displacement of the vibration is the largest. In the case of a phase difference of -90°, the vibration amplitude becomes constant.

[0048] Next, a drive control method according to the first embodiment performed by the drive control device 12 will be described. FIG. 6A to FIG. 6C1 is a diagram showing a comparison between the phase difference control according to the prior art and the phase difference control according to the first embodiment (the operation of the phase difference quadrant changing unit 105). FIG. 6A to FIG. 6C In FIG. 1 , regarding the phase difference θ, the vibration amplitude is schematically represented by coordinates having COSθ and SINθ on the horizontal axis and the vertical axis, respectively.

[0049] Fig. 6A : is a diagram for describing the phase difference control of the prior art. With respect to COSθ, the maximum displacement position and the minimum displacement position of the vibration are switched according to the sign of the phase difference, and with respect to SINθ, the driving direction of the contact body 132 is changed according to the sign of the phase difference. The phase difference θ is divided into four quadrants. In the prior art, the first quadrant and the fourth quadrant are used for control. In this case, the two quadrants are switched according to the driving direction (CW direction, CCW direction), but the maximum displacement position and the minimum displacement position of the vibration amplitude do not change.

[0050] Figure 6B : is a schematic diagram for describing an example of phase difference control according to the first embodiment. In this example, in the drive in the CW direction, the phase difference θ of the first quadrant is used as the phase difference θs (phase difference θs=θ), and in the drive in the CCW direction, the phase difference θs=-(180-θ) of the third quadrant is used. The phase difference θs=-(180-θ) is obtained by the phase shift of the phase difference θ, and the maximum displacement position and the minimum displacement position of the vibration amplitude are switched between the first quadrant and the third quadrant. Therefore, when the drive in the CW direction and the drive in the CCW direction are repeatedly performed, the maximum displacement position and the minimum displacement position of the vibration amplitude are switched with each other according to the driving direction, so that the uneven wear in the vibrator 131 can be reduced.

[0051] Figure 6C : is a diagram for describing another example of phase difference control according to the first embodiment. In this example, the phase difference θs=(180-θ) of the second quadrant obtained by phase shifting is used for driving in the CW direction, and the phase difference θs=-θ of the fourth quadrant is used for driving in the CCW direction. Figure 6B In the case of the vibration amplitude, the maximum displacement position and the minimum displacement position are switched between the second quadrant and the fourth quadrant. Therefore, when the driving in the CW direction and the driving in the CCW direction are repeated, the maximum displacement position and the minimum displacement position of the vibration amplitude are switched with each other according to the driving direction, so that uneven wear in the vibrator 131 can be reduced. It should be noted that in this embodiment, the maximum displacement position and the minimum displacement position of the vibration amplitude are switched between the second quadrant and the fourth quadrant. Figure 6B or Figure 6C , or you can periodically switch to use Figure 6B and Figure 6C drive control method.

[0052] FIG. 7A to FIG. 7D is a diagram for describing the output of the phase difference-frequency determination unit 106 . Fig. 7A : is a diagram showing the output based on the phase difference and frequency of the control amount, wherein the control amount is taken on the horizontal axis, the phase difference is taken on the left vertical axis, and the frequency is taken on the right vertical axis. The area where the absolute value of the control amount is less than the predetermined value is the phase difference control area, and the area where the absolute value of the control amount is greater than the predetermined value is the frequency control area. Control using the phase difference and control using the frequency are switched according to the control amount. Figure 6B The method shown is applicable to the phase difference control area. That is, the rotation speed of the contact body 132 is controlled by fixing the driving frequency to the upper frequency limit, changing the phase difference in the range of 0° to +90° in the first quadrant in the CW direction driving, and changing the phase difference in the range of -180° to -90° in the third quadrant obtained by phase shifting in the CCW direction driving. In the frequency control area, the rotation speed of the contact body 132 is controlled by fixing the phase difference to the lower limit or the upper limit and changing the driving frequency between the upper frequency limit and the lower frequency limit (for example, between 53kHz and 51kHz).

[0053] Figure 7B The rotation speed of the contact body 132 based on the control amount is shown, wherein the horizontal axis represents the control amount and the vertical axis represents the rotation speed of the contact body 132. It should be noted that in this specification, the rotation angle per second as a unit representing the rotation speed of the contact body 132 is represented by "deg / s". Phase difference control is performed in an area (low-speed drive area) where the rotation speed is -30deg / s to +30deg / s (5rpm or less), and frequency control is performed in other areas (high-speed drive areas). It should be noted that when the phase difference is 0°, -180° and +180°, the rotation speed is zero (0). At the same time, control is performed in the frequency control so that the amplitude of the traveling wave changes. Through this control, the phase difference and frequency are set so that the speed is as linear as possible relative to the control amount.

[0054] Figure 7C is a diagram for describing phase difference control in the normal mode, and Fig.7D is a diagram for describing phase difference control in the phase shift mode. Fig. 7A ) can be seen from the drive control method of using an output obtained by combining the output in the normal mode when the control amount is positive and the output in the phase shift mode when the control amount is negative.

[0055] Figure 81 is a schematic diagram showing the relationship between the driving direction and the phase difference during the low-speed driving (specifically, 1 deg / s) performed by the driving control device 12. The rotation speed of the contact body 132 is controlled by using the phase difference in the range of 0° to 90° in the first quadrant in the CW direction and the phase difference in the range of -180° to -90° in the third quadrant obtained by phase shifting in the CCW direction. The phase difference is continuously updated and slightly changed so that the rotation speed of the contact body 132 is controlled to 1 deg / s (= 0.2rpm) during driving. For example, assuming that the average value of the phase difference is set to +30°, the phase difference is controlled to, for example, +27°, 29°, 32°, 28°, ... for each control cycle. In this example, at the time point when the rotation position of the contact body 132 reaches 360 degrees, the control is switched to the drive in the CCW direction. Thereafter, feedback control is performed using the phase difference in the third quadrant obtained by phase shifting. For example, assuming that the average value of the phase difference is -150°, the phase difference is controlled to be, for example, -152°, -149°, -146°, -153°, etc. for each control cycle.

[0056] The drive control in this embodiment is characterized in that the phase difference obtained by the phase shift corresponding to the driving direction is not a fixed value, but changes continuously according to the feedback control amount, and the maximum displacement position and the minimum displacement position of the vibration are switched with each other according to the quadrant selection performed by the phase shift.

[0057] Fig.9A and Fig. 9B 1 is a schematic diagram showing a scenario in which the waveform of the two-phase AC voltage during low-speed driving of the vibration-type actuator 13 by the drive control device 12 is switched according to the driving direction. Fig.9A An example of the prior art is shown, and Fig. 9B An example according to the present invention is shown. As an example, in Fig. 9B : shows an A-phase voltage signal (dashed line) and a B-phase voltage signal (solid line) when the vibration-type actuator is driven with a phase difference of +30° in the CW direction and with a phase difference of −150° in the CCW direction.

[0058] like Fig.9A and Fig. 9B For example, when the driving direction is suddenly reversed, the vibration excited in the vibrator 131 may be unstable at the moment of switching the phase difference, and therefore, there is a concern that the driving sound becomes louder. Therefore, it is desirable to avoid continuous phase shifting during driving, and it is desirable to provide a stop area before and after the phase shift (phase shifting is performed within the stop area).

[0059] Fig.101 is a flowchart for describing a drive control method of the vibration type actuator 13 by the drive control device 12. The control unit 10 (CPU constituting the control unit 10) executes a predetermined program, thereby realizing the operation of each part of the vibration type drive device 15. Fig.10 The S number in represents the process (step).

[0060] In step S101, the control unit 10 sets the target position and speed of the contact body 132. Subsequently, it is assumed in this example that the control unit 10 performs a reciprocating operation by repeatedly performing the drive in the CW direction (S1) and the drive in the CCW direction (S2). S1 and S2 are performed in a random order. One of the control of S1 and the control of S2 can be continuously performed according to the operation required by the drive mechanism 16. That is, the process of S1 is used in the rotation drive of the contact body 132 in the CW direction, and the process of S2 is used in the rotation drive of the contact body in the CCW direction.

[0061] The processing of S1 will be described in detail. In step S102, the control unit 10 turns on the driving pulse and applies the AC voltage from the driving part 11 to the piezoelectric element of the vibrator 131 constituting the vibration type actuator 13. Therefore, the driving of the contact body 132 in the CW direction is started. In step S103, the control unit 10 performs PID calculation by using the deviation of the position or speed. In step S104, the control unit 10 obtains the phase difference θ according to the feedback control amount. In step S105, the control unit 10 outputs the phase difference θs=θ (first quadrant) to the driving part 11. In step S106, the control unit 10 determines whether the contact body 132 reaches the target position. When it is determined that the contact body 132 reaches the target position ("Yes" in step S106), the control unit 10 causes the processing to proceed to S2 (step S201) after a predetermined stop time, and when it is determined that the contact body 132 does not reach the target position ("No" in step S106), the control unit 10 returns the processing to step S103.

[0062] Next, the processing of S2 will be described in detail. In step S201, the control unit 10 turns on the driving pulse and applies the AC voltage from the driving part 11 to the vibration type actuator 13 (the piezoelectric element of the vibrator 131). Therefore, the driving of the contact body 132 in the CCW direction is started. In step S202, the control unit 10 performs PID calculation by using the deviation of the position or speed. In step S203, the control unit 10 obtains the phase difference θ according to the feedback control amount. In step S204, the control unit 10 outputs the phase difference θs=-(180-θ) (third quadrant) to the driving part 11. In step S205, the control unit 10 determines whether the contact body 132 reaches the target position. When it is determined that the contact body 132 reaches the target position ("Yes" in step S205), the control unit 10 ends this processing after a predetermined stop time, and when it is determined that the contact body 132 does not reach the target position ("No" in step S205), the control unit 10 returns the processing to step S202.

[0063] Fig.11A and Fig. 11B Is used to describe when Fig.10 Flowchart showing the advantageous effects of the present invention obtained when driving control of a vibration-type actuator is performed. Fig.11A and Fig. 11B The results obtained by checking the change in the surface shape of the friction contact portion of the vibrator 131 before and after the durability test, and the results obtained by measuring the flatness of the friction contact portion at positions of 0 deg to 360 deg in the circumferential direction are shown. The durability test was performed by reciprocating operation of one rotation at 1 deg / s for about 24 hours.

[0064] Fig.11A It is shown that when the drive control method of the prior art is used ( Fig. 6A ). After the durability test, based on the shape change of the contour lines 401 and 402 obtained by connecting the predetermined height position (about 2.1 μm) from the reference surface, the change of the friction contact surface forming 18 peaks was identified, and thus a significant decrease in flatness was identified. In this example, the vibrator 131 was driven by a traveling wave using the ninth mode. In the standing wave in this case, the maximum displacement position of the vibration amplitude theoretically appears at 18 positions in one cycle. Therefore, it can be said that Fig.11A The results match the theoretical values. After the durability test of the vibration type actuator, the speed characteristics, torque performance and torque efficiency are greatly reduced.

[0065] Fig. 11B It shows that when Fig.10 Flowchart using Figure 6B. When the contour lines 403 and 404 connecting the predetermined height position (about 2.1 μm) from the reference plane are compared, it can be seen that no significant shape change is observed even after the durability test and good flatness is maintained. It should be noted that the speed characteristics, torque performance, and torque efficiency equivalent to those before the durability test are obtained after the durability test of the vibration-type actuator.

[0066] Next, the configuration of the driving section 11 suitable for performing the driving control method according to the first embodiment will be described. Fig. 12A : is a circuit diagram of the driving section 11 . The AC signal generating unit 111 of the driving section 11 includes a pulse signal generating circuit 117 that generates a pulse signal, and a switch circuit 116 (H-bridge circuit) that is switched by the pulse signal from the pulse signal generating circuit 117 . Fig. 12B 1 is a diagram for describing a pulse signal generated by the pulse signal generating circuit 117. The pulse signal generating circuit 117 outputs an A+ pulse and an A- pulse having a phase difference of 180° from the A+ pulse to the switch circuit 116 according to a control signal from the control unit 10.

[0067] The switch circuit 116 generates an AC voltage by switching the voltage of the DC power supply 115 (turning it on or off) through a switch element according to a pulse signal from a pulse signal generating circuit 117. At this time, the pulse width (duty cycle) of the pulse signal is adjusted according to the control signal so that the desired AC voltage amplitude is obtained through PWM (pulse width modulation) control. The AC voltage output from the switch circuit 116 is boosted to the desired voltage by a boost circuit 112 composed of a coil 113 and a transformer 114. The AC voltage whose waveform is converted from a square waveform to a SIN waveform by a filter effect is output from the boost circuit 112 and applied to the piezoelectric element of the vibrator 131.

[0068] The AC voltage corresponding to one phase generated by using the A+ pulse and the A- pulse has been described. Since an AC voltage corresponding to another phase is similarly generated by the B+ pulse output from the pulse signal generating circuit 117 and the B- pulse whose phase is 180° different from the B+ pulse, its description will be omitted. It should be noted that the phase difference θ obtained by the feedback control in the drive control device 12 represents the phase difference between the A+ pulse and the B+ pulse. Fig. 12B A+ and B+ pulses are shown with phase shifts of 90°.

[0069] According to the present invention, by converting the feedback control amount based on position or speed into the phase difference of multiple quadrants and switching the quadrants, driving is performed while switching the maximum displacement position and the minimum displacement position of the traveling wave with each other. Therefore, uneven wear caused in the vibrator can be suppressed, and therefore, the performance of the vibration type actuator can be suppressed from decreasing over time. Therefore, the vibration type actuator can be maintained at high driving performance for a long time, and good controllability can be maintained.

[0070] Next, description will be given of a drive control method according to the second embodiment performed by the drive control device 12. The operation of the phase difference quadrant changing unit 105 is different between the first embodiment and the second embodiment. Fig.13A and Fig. 13B is used by using FIG. 6A to FIG. 6C The same coordinates are used to describe a diagram of phase difference control (operation of the phase difference quadrant changing unit 105 ) according to the second embodiment. Fig.13A 1 is a schematic diagram showing a drive control method using all quadrants from the first quadrant to the fourth quadrant. In the drive control method according to the second embodiment, the normal mode of the first quadrant or the phase shift mode of the second quadrant is used in the rotation drive in the CW direction, and the phase shift mode of the third quadrant or the normal mode of the fourth quadrant is used in the rotation drive in the CCW direction.

[0071] Fig. 13B is a schematic diagram showing control for switching between normal mode and phase shift mode. Fig. 6A The figure is the same. A phase difference θs=θ (first quadrant) is used in the rotation drive in the CW direction, and a phase difference θs=-θ (fourth quadrant) is used in the rotation drive in the CCW direction. In the phase shift mode, a phase difference θs=180-θ (second quadrant) obtained by phase shift is used in the rotation drive in the CW direction, and a phase difference θs=-(180-θ) (third quadrant) obtained by phase shift is also used in the rotation drive in the CCW direction. It should be noted that the maximum displacement position and the minimum displacement position of the vibration amplitude do not change in the normal mode, and the maximum displacement position and the minimum displacement position of the vibration amplitude do not change in the phase shift mode. The maximum displacement position and the minimum displacement position of the vibration amplitude switch with each other between the normal mode and the phase shift mode.

[0072] Therefore, the uneven wear of the vibrator 131 can be suppressed by switching between the normal mode and the phase shift mode at an appropriate time so that the maximum displacement position and the minimum displacement position are switched with each other, so that the driving frequency in the normal mode and the driving frequency in the phase shift mode are equal to each other. The switching between the driving in the normal mode and the driving in the phase shift mode can be performed at the time of turning on or off the driving, or can be performed based on the driving direction, driving distance (rotation angle), driving time, or the number of driving times.

[0073] Shown above Figure 7C shows the phase difference control area in normal mode, the above Fig.7D The phase difference control region in the phase shift mode is shown. The drive control method according to the second embodiment is characterized in that a method of outputting the phase difference θ in the phase difference control region is switched between the normal mode and the phase shift mode.

[0074] Fig.14A and Fig. 14B Graphs showing the relationship between the rotational position, the phase difference, and the time until the contact body 132 reaches the target position in the drive control method according to the second embodiment. In these examples, the normal mode is used in the drive in the CW direction, and the phase shift mode is used in the drive in the CCW direction.

[0075] Fig.14A The time variation of the phase difference θ is shown, which changes according to the command value, the rotational position or the feedback control amount of the deviation e in the normal mode. In this example, the time t1, t2 and t3 will be focused on to describe the present drive control. After the start-up by the phase difference control, the phase difference is fixed (in this example, approximately +90°), followed by frequency control, and the time reaches time t1. In the period from time t1 to time t2, control is performed with a phase difference θs=θ (first quadrant). The period from time t2 to time t3 is the period of the return operation after overshooting. The sign of the phase difference during the return operation is negative (-), that is, control is performed with a phase difference θs=-θ (fourth quadrant). At time t3, the command value reaches the target position, and control is performed again with a phase difference θs=θ (first quadrant).

[0076] Fig. 14BThe time variation of the phase difference θ is shown, which changes according to the command value, the rotational position or the feedback control amount of the deviation e in the phase shift mode. Also in this example, the focus will be on times t1, t2 and t3 to describe the present drive control. After the start-up by the phase difference control, the phase difference is fixed (in this example, approximately -90°), followed by frequency control, and the time reaches time t1. In the period from time t1 to time t2, control is performed with a phase difference θs=-(180-θ) (third quadrant). The period from time t2 to time t3 is the period of the return operation after the overshoot. During the return operation, control is performed with a phase difference θs=180-θ (second quadrant). At time t3, the command value reaches the target position, and control is performed again with a phase difference θs=-(180-θ) (third quadrant).

[0077] As described above, in the second embodiment, control is performed by using the phase difference θ based on the change of the feedback control amount and combining the normal mode using the phase difference of the first quadrant and the fourth quadrant and the phase shift mode using the phase difference of the second quadrant and the third quadrant by phase difference shift. The maximum displacement position and the minimum displacement position of the amplitude of the traveling wave caused in the vibrator are switched with each other, and therefore, uneven wear in the vibrator can be suppressed. As a result, the vibration type actuator can be maintained at high driving performance for a long time, and good controllability can be maintained.

[0078] Next, description will be given of a drive control method according to the third embodiment performed by the drive control device 12. The operation of the phase difference quadrant changing unit 105 is different between the first and second embodiments and the third embodiment. Fig.15A and Fig. 15B 1 is a diagram for describing the phase difference control (operation of the phase difference quadrant changing unit 105) according to the third embodiment. In the phase difference control according to the third embodiment, during driving in the same direction, the normal phase difference and the phase difference obtained by shifting the phase difference (normal mode and phase shift mode) are switched.

[0079] Fig.15A is shown for use with FIG. 6A to FIG. 6C and Fig.13A and Fig. 13BSchematic diagram of control for switching between rotational drive in the CW direction and rotational drive in the CCW direction in a similar manner. In the rotational drive in the CW direction, a phase difference θs=θ (first quadrant) and a phase difference θs=(180-θ) (second quadrant) are used. Therefore, during driving, the maximum displacement position and the minimum displacement position are switched with each other. At the same time, in the rotational drive in the CCW direction, a phase difference θs=-(180-θ) (third quadrant) and a phase difference θs=-θ (fourth quadrant) are used. In this case as well, during driving, the maximum displacement position and the minimum displacement position of the vibration amplitude are switched with each other.

[0080] An example of a specific method for switching the phase difference θs during driving includes the following method: in the case of driving in the CW direction, whenever a predetermined driving time is passed, the phase difference θ in the first quadrant and the phase difference (180-θ) in the second quadrant are switched. The predetermined driving time in this case can be changed according to the speed. Whenever the contact body 132 is driven by a predetermined rotation angle, the phase difference can be switched. For example, there is a method as follows: the phase difference is switched when the position sensor detects that the contact body reaches half of the target position. Alternatively, the phase difference can be switched at a time when a predetermined driving time has passed. For example, there is a method as follows: the phase difference is switched when the timer detects half of the predicted arrival time for the target position of the contact body.

[0081] In the case of this drive control method, since the driving direction does not change during driving but the maximum displacement position and the minimum displacement position of the vibration switch with each other, there is a concern that the driving state becomes unstable at the timing when the maximum displacement position and the minimum displacement position switch with each other. Fig. 15B , the waveforms of the A+ pulse and the B+ pulse when the phase switches from 180° to 0° during driving are shown. Fig. 15B As shown, a pulse component with a double period is generated at the timing of switching the phase difference (quadrant). As a result, an AC voltage with a frequency different from the driving frequency is instantaneously applied to the vibration type actuator 13. Therefore, there is a concern that the driving sound will increase or an abnormal current will be generated. Therefore, in the drive control method according to the third embodiment, it is expected that the number of switching between the normal phase difference and the phase difference obtained by the phase shift during driving is small.

[0082] Next, an example of an apparatus including a vibration-type drive device will be described. Fig. 16 is a diagram showing a schematic configuration of an image pickup apparatus 600 including a vibration-type drive device 15. In the image pickup apparatus 600, it is possible to perform image pickup by driving a tripod head 602 to rotate by a vibration-type actuator 13 and rotating a camera 601 fixed to the tripod head 602 so that the image pickup direction is a predetermined direction. Fig. 16B1 is a diagram showing a partial structure of a rotation driving device 650 constituting the MFP. In this example, the transfer drum 651 can be driven to rotate by connecting the transfer drum 651 to the output shaft 211 of the vibration-type actuator 13.

[0083] The vibration-type driving device 15 according to the present embodiment is not limited to application to these examples, and can be applied to various devices including components that need to be positioned or moved by the drive of the vibration-type actuator 13. For example, in a camera device, the vibration-type driving device can be applied to a mechanism that drives a focusing lens or a zoom lens connected to a contact body in the direction of the optical axis. The vibration-type driving device can be applied to a driving mechanism of a joint part in an industrial or medical multi-joint robot. In particular, the present invention is applicable to a device that requires drive control of a vibration-type actuator (which needs to be driven at a low speed).

[0084] Other embodiments

[0085] The embodiments of the present invention may also be implemented by reading and executing computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more completely referred to as a "non-transitory computer-readable storage medium") to perform one or more functions in the above-mentioned embodiments, and / or a computer of a system or device including one or more circuits (e.g., an application-specific integrated circuit (ASIC)) for performing one or more functions in the above-mentioned embodiments, and the embodiments of the present invention may be implemented by, for example, reading and executing the computer executable instructions from the storage medium by the computer of the system or device to perform one or more functions in the above-mentioned embodiments, and / or controlling the one or more circuits to perform one or more functions in the above-mentioned embodiments. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessing unit (MPU)), and may include a network of separate computers or separate processors to read and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, a hard disk, a random access memory (RAM), a read-only memory (ROM), a memory of a distributed computing system, an optical disk (such as a compact disc (CD), a digital versatile disc (DVD), or a Blu-ray disc (BD) TM ), flash memory devices, memory cards, etc.

[0086] The embodiments of the present invention may also be implemented by providing software (program) for performing the functions of the above-described embodiments to a system or device via a network or various storage media, and a computer or a central processing unit (CPU) or a microprocessing unit (MPU) of the system or device reads and executes the program.

[0087] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0088] This application claims the benefit of Japanese Patent Application No. 2018-182377, filed September 27, 2018, which is hereby incorporated by reference herein in its entirety.

Claims

1. A vibration type driving device, comprising: a vibration type actuator including a vibrator and a contact body that move relative to each other; as well as a drive control device configured to control the drive of the vibration-type actuator, wherein the vibrator has an electrical-mechanical energy conversion element, and The drive control equipment includes: a driving section configured to apply a two-phase AC voltage to the electrical-mechanical energy conversion element; a detection unit configured to detect a relative position or a relative speed between the vibrator and the contact body; a conversion unit configured to convert a control amount of feedback control based on the relative position or relative speed detected by the detection unit into a phase difference between two-phase AC voltages; and An output unit is constructed to output a phase difference to a driving part by using a phase difference in a first quadrant or a second quadrant of a coordinate for driving relative movement in a first direction, and by using a phase difference in a third quadrant or a fourth quadrant of the coordinate for driving in a second direction opposite to the first direction, wherein the phase difference is represented by θ, and SINθ is taken on the vertical axis in the coordinate, and COSθ is taken on the horizontal axis in the coordinate.

2. The vibration type driving device according to claim 1, wherein: Between the phase difference in the first quadrant and the phase difference in the fourth quadrant, the maximum displacement position and the minimum displacement position of the vibration amplitude induced in the vibrator do not change, Between the phase difference in the second quadrant and the phase difference in the third quadrant, the maximum displacement position and the minimum displacement position of the vibration amplitude induced in the vibrator do not change, and Between the phase difference in the first quadrant and the phase difference in the second quadrant, the maximum displacement position and the minimum displacement position of the vibration amplitude induced in the vibrator are switched to each other.

3. The vibration type driving device according to claim 1, wherein: The phase difference in the first quadrant is θ, the phase difference in the second quadrant is (180°-θ), the phase difference in the third quadrant is -(180°-θ), and the phase difference in the fourth quadrant is -θ.

4. The vibration type driving device according to claim 1, wherein The output unit uses the phase difference of the first quadrant for driving in the first direction, and uses the phase difference of the third quadrant for driving in the second direction.

5. The vibration type driving device according to claim 1, wherein The output unit uses the phase difference of the second quadrant for driving in the first direction, and uses the phase difference of the fourth quadrant for driving in the second direction.

6. The vibration type driving device according to claim 1, wherein: The output unit switches between a mode of using the phase difference of the first quadrant for driving in the first direction and the phase difference of the fourth quadrant for driving in the second direction, and a mode of using the phase difference of the second quadrant for driving in the first direction and the phase difference of the third quadrant for driving in the second direction.

7. The vibration type driving device according to claim 1, wherein: The output unit switches between the phase difference in the first quadrant and the phase difference in the second quadrant during driving in the first direction, and switches between the phase difference in the third quadrant and the phase difference in the fourth quadrant during driving in the second direction, based on the driving time of the vibration-type actuator or the relative driving distance between the vibrator and the contact body.

8. The vibration type driving device according to claim 1, wherein The drive control device includes a control unit configured to perform phase difference control for operating the phase difference in a region where the absolute value of the control amount is less than a predetermined value, and to perform frequency control for operating the frequency of the AC voltage in a region where the absolute value of the control amount is greater than a predetermined value.

9. The vibration type driving device according to claim 1, wherein: The phase difference in the first quadrant is set within the range of 0° to +90°.

10. A vibration-type driving device, comprising: a vibration type actuator including a vibrator and a contact body that move relative to each other; as well as a drive control device configured to control the drive of the vibration-type actuator, wherein the vibrator has an electrical-mechanical energy conversion element, and The drive control equipment includes: a driving section configured to apply a two-phase AC voltage to the electrical-mechanical energy conversion element; a detection unit configured to detect a relative position or a relative speed between the vibrator and the contact body; and a control unit configured to control a phase difference between two-phase AC voltages through feedback control based on a relative position or relative speed detected by the detection unit, and The control unit operates the phase difference so that the maximum displacement position and the minimum displacement position of the vibration amplitude induced in the vibrator are switched to each other according to any one of the direction of relative movement, the relative position between the vibrator and the contact body, and the driving time of the vibration type actuator.

11. A drive control device, comprising: The vibration type drive device according to any one of claims 1 to 10; as well as A member positioned by driving of a vibration-type actuator included in the vibration-type driving device.

12. A drive control device for a vibration type actuator, in which a vibrator including an electrical-mechanical energy conversion element and a contact body move relative to each other, the drive control device comprising: a driving section configured to apply a two-phase AC voltage to the electrical-mechanical energy conversion element; a detection unit configured to detect a relative position or a relative speed between the vibrator and the contact body; a conversion unit configured to convert a control amount of feedback control based on the relative position or relative speed detected by the detection unit into a phase difference between two-phase AC voltages; as well as An output unit is constructed to output a phase difference to a driving part by using a phase difference in a first quadrant or a second quadrant of a coordinate for driving relative movement in a first direction, and by using a phase difference in a third quadrant or a fourth quadrant of the coordinate for driving in a second direction opposite to the first direction, wherein the phase difference is represented by θ, and SINθ is taken on the vertical axis in the coordinate, and COSθ is taken on the horizontal axis in the coordinate.

13. A drive control method for a vibration type actuator, in which a vibrator including an electrical-mechanical energy conversion element and a contact body move relative to each other, the drive control method comprising: Detecting the relative position or relative speed between the vibrator and the contact body; converting a control amount of feedback control based on the relative position or relative speed detected in the detection into a phase difference between two-phase AC voltages to be applied to the electrical-mechanical energy conversion element; as well as The phase difference in the first or second quadrant of the coordinate is used for driving relative movement in a first direction, and the phase difference in the third or fourth quadrant of the coordinate is used for driving in a second direction opposite to the first direction, wherein the phase difference is represented by θ, and SINθ is taken on the vertical axis of the coordinate and COSθ is taken on the horizontal axis of the coordinate.

Images