JP6448406B2 - Vibrating actuator, control method therefor, and optical instrument - Google Patents

Description

  The present invention relates to a vibration type actuator such as an ultrasonic motor, a control method therefor, and an optical apparatus.

  Ultrasonic motors have the characteristics of small size, light weight, high speed drive, and silent drive, and are used in lens barrels of image pickup apparatuses. Patent Document 1 discloses an ultrasonic motor for linear drive. This ultrasonic motor is composed of a rectangular diaphragm on which a piezoelectric element is fixed and a friction member that comes into contact with a contact portion provided on the diaphragm. Due to the vibration generated by the piezoelectric element, an elliptical motion is generated at the tip of the protrusion provided on the diaphragm. The diaphragm obtains a driving force by this elliptical motion and moves relative to the friction member. The piezoelectric element has two polarization regions, and the phase difference of the input voltage to each polarization region is controlled (phase difference control method). As a result, the locus of the elliptical motion of the tip of the protrusion changes, so that the moving speed of the diaphragm can be controlled.

JP 2004-88815 A

In the phase difference control method, by controlling the phase difference of the input voltage to the two polarization regions of the piezoelectric element, the speed of the diaphragm is controlled by changing the locus of the elliptical motion of the tip of the protrusion. In the frequency control method, the speed is controlled by controlling the driving frequency. The advantage of the phase difference control method compared to the frequency control method is that it can be driven in a low speed region. However, in the phase difference control method, the driving force is small in the phase difference region where the phase difference is near 0 ° or 180 °. For this reason, the drive state may become unstable or there may be a region where the drive stops, that is, a dead zone. If there is a dead zone, there is a possibility that desired control characteristics cannot be obtained due to the dead zone in the control system of the ultrasonic motor.
An object of the present invention is to improve controllability in driving a vibration type actuator.

  An apparatus according to the present invention is a vibration type actuator using a vibration member and a piezoelectric element fixed to the vibration member, and a friction member that contacts the vibration member and moves relative to the vibration member; Control means for acquiring relative position information of the vibration member with respect to the friction member and controlling driving of the piezoelectric element. The piezoelectric element has a plurality of polarization regions, and the control means controls the phase difference in the first phase difference region when controlling the phase difference between voltages applied to the plurality of polarization regions. First control to be set and second control to set the phase difference in a second phase difference region having a narrower range than the first phase difference region are performed.

  According to the present invention, controllability can be improved in driving the vibration type actuator.

It is a figure showing an example of composition of an ultrasonic motor concerning a 1st embodiment of the present invention. It is explanatory drawing of the vibration state of the ultrasonic motor which concerns on 1st Embodiment. It is a figure showing roughly the linear drive concerning a 1st embodiment. It is explanatory drawing of the phase difference control of the ultrasonic motor which concerns on 1st Embodiment. It is a figure for demonstrating the locus | trajectory of the elliptical motion which concerns on 1st Embodiment. It is a figure which shows the structural example of the drive device which concerns on embodiment of this invention. It is explanatory drawing of the phase difference area | region which concerns on 1st Embodiment. It is a figure for demonstrating the phase difference control at the time of the drive stop which concerns on 1st Embodiment. It is explanatory drawing of the phase difference area | region which concerns on 2nd Embodiment. It is a figure for demonstrating the influence of the inclination of the linear drive device which concerns on 3rd Embodiment. It is a figure for demonstrating the phase difference control at the time of the drive stop in a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each embodiment, the mechanism and the operation will be described by exemplifying an ultrasonic motor as a vibration type actuator. Ultrasonic motors can be used in electronic devices that require a small, lightweight and wide driving speed range, such as lens driving devices. The present invention can be applied to an optical device (lens device, imaging device, etc.) that drives an optical member such as a lens by a vibration actuator. An ultrasonic motor as one embodiment includes a rectangular diaphragm and a friction member that moves relative to the diaphragm. In this specification, the long side direction of the diaphragm is defined as the X direction, and the short side direction is defined as the Y direction. Further, the normal direction (thickness direction) of the substantially rectangular surface of the diaphragm is defined as the Z direction. In the Z direction, the direction from the diaphragm toward the friction member is defined as + Z direction, and the opposite direction is defined as -Z direction.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram for explaining a basic configuration of an ultrasonic motor 10 according to the present embodiment. 1A is a plan view and FIG. 1B is a front view. 1C and 1D are side views when viewed from different directions. FIG. 1E is a bottom view. The ultrasonic motor 10 includes a diaphragm 1 and a piezoelectric element 2.

  The diaphragm 1 is a vibrating member having a rectangular flat plate portion. Protrusions 1a and 1b are provided on the flat plate portion at a predetermined interval in the X direction. About protrusion part 1a, 1b, you may integrally mold with a flat plate part by drawing, and you may fix another member to a flat plate part by adhesion | attachment. A piezoelectric element 2 that vibrates at a high frequency is fixed to the diaphragm 1.

  As shown in FIG. 1A, the piezoelectric element 2 has two polarization regions 2a and 2b polarized in the same direction. The polarization region 2a is assigned to the A phase, and the polarization region 2b is assigned to the B phase. The A phase and the B phase are two phases when a two-phase voltage having a phase difference is input to the piezoelectric element 2 from an external power source (not shown). The piezoelectric element 2 has a non-polarized region 2c, and the region 2c is an electrode portion used as a ground that is conducted from the entire surface electrode on the back surface 2e of the piezoelectric element 2 via the electrode in the region of the side surface 2d. is there.

  Connection portions 1c and 1d extending in the X direction are provided on the short sides of the rectangular surface of the diaphragm 1, respectively. The connecting portions 1c and 1d move in synchronization with the diaphragm 1 and are directly or indirectly connected to a diaphragm holding member to be described later. The connecting portions 1c and 1d are provided in a portion where the displacement is small in the vibration of the vibration plate 1 and the piezoelectric element 2, and the rigidity is sufficiently weak, so that the connecting portions 1c and 1d are designed in a shape that does not hinder vibration. Accordingly, the connecting portions 1 c and 1 d hardly affect the vibration of the diaphragm 1 and the piezoelectric element 2.

By applying an AC voltage in which the phase difference between the A phase and the B phase is changed from −90 ° to + 90 ° to the piezoelectric element 2, high-frequency vibration is generated. The vibration plate 1 is excited by the following natural vibration modes by high-frequency vibration of the piezoelectric element 2.
A primary natural vibration mode (hereinafter referred to as a first mode) related to bending vibration in the short side direction (Y direction) of the diaphragm 1.
A secondary natural vibration mode (hereinafter referred to as a second mode) related to bending vibration in the long side direction (X direction) of the diaphragm 1.
The protrusions 1a and 1b are in the vicinity of the antinode of the first mode (see X in FIG. 1 (E)) and in the vicinity of the node in the second mode (see Y1 and Y2 in FIG. 1 (E)). Is provided. Each position indicated by Y1 and Y2 in FIG. 1E is symmetrical with respect to the center line Y0 in the Y direction.

  The aspect of vibration will be described with reference to FIG. FIG. 2 is a schematic diagram illustrating an example of vibration when an AC voltage obtained by delaying the phase of the B phase by about 90 ° with respect to the A phase is applied to the piezoelectric element 2. FIG. 2A shows an example of the waveform of each AC voltage of the A phase and the B phase. The horizontal axis represents time T, and the vertical axis represents voltage V. Time points P1 to P4 indicated by arrows indicate time points with different phases for the A phase and the B phase, respectively. At the time point P1, the A phase voltage is a positive value and the B phase voltage is a negative value, and at the time point P2, the A phase voltage and the B phase voltage are positive values. At the time point P3, the A phase voltage is a negative value and the B phase voltage is a positive value, and at the time point P4, the A phase voltage and the B phase voltage are negative values. That is, the phase A voltage and the phase B voltage have the same sign relationship at the time points P2 and P4, and the phase A voltage and the phase B voltage have the opposite sign relationship at the time points P1 and P3. 2B, 2C, and 2D correspond to FIGS. 1B, 1C, and 1D, respectively. 2B is a view when viewed from the Y direction, FIG. 2C is a view when viewed from the X direction, and FIG. 2D is a view from the opposite side of FIG. 2B in the X direction. FIG. These figures show the vibration state at each time point Q1 to Q4 having a predetermined time delay with respect to each time point P1 to P4 indicated by arrows in FIG. In FIG. 2, the piezoelectric element 2 and the connecting portions 1c and 1d are omitted for simplification of illustration.

When voltages having the same sign are applied as the A phase voltage and the B phase voltage (for example, P2 and P4 shown in FIG. 2A), the same expansion and contraction occurs in the A phase and the B phase. Thus, the first mode is excited, the protrusion 1a as indicated by Z ₁ in FIG. 2 (C), the amplitude in the Z direction of the distal end portion of 1b is maximized. On the other hand, when voltages having different signs are applied as the A-phase voltage and the B-phase voltage (for example, P1 and P3 shown in FIG. 2A), expansion and contraction in opposite directions occurs between the A-phase and the B-phase. Thus, the second mode is excited, the amplitude in the X direction of the distal end portion of the protrusion 1a, 1b as indicated by X ₁ in FIG. 2 (B) is maximized. When an AC voltage is applied to the piezoelectric element 2 by delaying the phase of the B phase by about 90 ° with respect to the A phase, elliptical motions as shown in the figure are generated at the tips of the protrusions 1a and 1b, respectively. Since the tips of the protrusions 1a and 1b are in contact with a friction member described later (see FIG. 3: reference numeral 3), friction between the friction member and the protrusions 1a and 1b caused by the elliptical motion of the protrusions 1a and 1b occurs. The diaphragm 1 obtains a driving force. That is, the diaphragm 1 relatively moves in the + X direction (right direction is the positive direction) shown in FIG.

  Further, when an AC voltage is applied to the piezoelectric element 2 by advancing the phase of the B phase by about 90 ° with respect to the A phase, the elliptical motion in the direction opposite to the elliptical motion generated by the vibration state shown in FIG. Will occur. Therefore, the diaphragm 1 obtains a driving force by the friction between the friction member and the protrusions 1a and 1b, which is generated by the elliptical motion of the protrusions 1a and 1b. That is, the diaphragm 1 relatively moves in the −X direction (the left direction is a negative direction) opposite to the arrow in the X direction shown in FIG.

  Next, the configuration of the linear drive device 20 using the ultrasonic motor 10 will be described with reference to FIG. The linear drive device 20 is used in a mechanism unit that moves an optical member along the optical axis direction in, for example, a photographing lens device and an imaging device. FIG. 3 is a schematic view of the linear drive device 20. FIG. 3A is a front view when viewed from the traveling direction of the ultrasonic motor 10. In FIG. 3A, the direction orthogonal to the paper surface is the X direction, the horizontal direction is the Y direction, and the vertical direction is the Z direction. FIG. 3B is a cross-sectional view taken along line AA shown in FIG. In FIG. 3B, the direction orthogonal to the paper surface is the Y direction, the left-right direction is the X direction, and the up-down direction is the Z direction.

  The piezoelectric element 2 shown in FIG. 3 is fixed to the diaphragm 1. The protrusions 1 a and 1 b of the diaphragm 1 are pressed against and contact the friction member 3. By driving the piezoelectric element 2, high-frequency vibration is generated in the diaphragm 1, and the diaphragm 1 can move relative to the friction member 3 in the X direction. The diaphragm holding member 4 moves in synchronization with the diaphragm 1. The diaphragm holding member 4 supports the diaphragm 1 with the coupling parts 1c and 1d in the first support part 4a. In the present embodiment, the diaphragm support member 4 is provided with two first support portions 4a. The diaphragm holding member 4 rotatably supports the roller 41 at the second support portion 4b. The roller 41 rotates and slides on the back surface of the friction member 3, that is, the surface opposite to the contact surface with the protrusions 1a and 1b. In the present embodiment, the number of rollers 41 is 2, and the second support portions 4b are provided at four locations corresponding to them. The roller 41 is a rolling member provided to reduce sliding resistance during driving. The mechanism using not only this embodiment but a rolling roller etc. may be sufficient.

  The pressure spring 42 is an urging member for pressing the diaphragm 1 against the friction member 3. One end portion 42 a of the pressure spring 42 is in contact with the piezoelectric element 2, and the other end portion 42 b is in contact with the diaphragm holding member 4. Since the protrusions 1a and 1b are pressed against the friction member 3 by the pressure applied by the pressure spring 42, as shown by the arrows in FIG. 2, the driving for moving the diaphragm holding member 4 in the + X direction by the driving force by the elliptical motion Power is obtained.

With reference to FIG. 4, the phase difference control method in the present embodiment will be described. FIG. 4 shows a state of vibration when an AC voltage having a small phase difference between the B phase and the B phase is applied to the piezoelectric element 2. FIG. 4A corresponds to FIG. 2A and shows the phase relationship between the A phase and the B phase. The horizontal axis t represents time, and the vertical axis v represents voltage. In FIG. 4A, the phase difference between the B phase voltage and the A phase voltage is small. Each vibration state shown in FIGS. 4B to 4D corresponds to the vibration state described in FIGS. 2B to 2D. _{X 2} shown in FIG. 4 (B), the protrusion 1a, represents the amplitude in the X direction of the distal end portion of 1b, _{Z 2} shown in FIG. 4 (C), in the Z direction of the distal end portion of the protrusion 1a, 1b Represents amplitude.

When the phase difference between the A phase and the B phase is around 0 °, compared to the case of FIG. 2, there is almost no time for applying voltages having different signs as the A phase and the B phase. For this reason, the amplitude of the second mode, that is, the amplitude in the movement direction (X ₂ shown in FIG. 4B) is reduced. As a result, an elliptical motion as shown in FIG. 4B occurs at the tips of the protrusions 1a and 1b, so that the diaphragm 1 relatively moves in the X direction at a low speed.

FIG. 5 shows the locus of elliptical motion generated at the tip of the protrusions 1a and 1b. The horizontal axis is the X axis, and the vertical axis is the Z axis. FIG. 5A shows a circular locus when the phase difference between the input voltages of the A phase and the B phase (hereinafter referred to as θ) is 90 °. FIG. 5B shows a case of “0 ° <θ <90 °” and shows an elliptical trajectory that is longer in the Z direction than in the X direction. FIG. 5C shows a case where “90 ° <θ <180 °”, and shows an elliptical trajectory that is longer in the X direction than in the Z direction. In each figure, A _Z1 , A _Z2 , and A _Z3 indicate the pressure direction of the diaphragm 1, that is, the amplitude in the Z direction, respectively. A _X1 , A _X2 , and A _X3 indicate the movement direction of the diaphragm 1, that is, the X direction. Each amplitude is shown.

As shown in FIG. 5B, in the case of “0 ° <θ <90 °”, the amplitude in the pressurizing direction is larger than in the case of FIG. 5A (θ = 90 °), The amplitude in the moving direction is reduced. That is, A _Z2 > A _Z1 and A _X2 <A _X1 . Further, as shown in FIG. 5C, when “90 ° <θ <180 °”, the amplitude in the pressurizing direction is smaller than in the case of FIG. 5A (θ = 90 °). Thus, the amplitude in the moving direction is increased. That _is, the _{A Z3 <A Z1 ,A X3> A} X1. Thus the amplitude A _X of the moving direction of the phase difference θ is smaller than 90 ° is small, the speed is reduced. That is, the diaphragm 1 can be controlled at a low speed by controlling the phase difference θ. On the other hand, when the phase difference θ is larger than 90 °, the amplitude _{AZ in the} pressurizing direction gradually decreases. In this case, if the amplitude _AZ in the pressurizing direction is smaller than the surface roughness between the tip portions of the protrusions 1a and 1b and the friction member, the diaphragm 1 cannot be driven. The amplitude _{AZ in the} pressing direction is sufficiently larger than the surface roughness of the tip portions of the protrusions 1a and 1b and the friction member, which is a necessary condition for enabling the diaphragm 1 to be driven. In order to satisfy this condition, it is necessary to determine the range of the phase difference θ. In the present specification, the range of the phase difference θ is described as being −90 ° to + 90 °.

Generally, in an ultrasonic motor, speed control is performed by controlling an input voltage and frequency. In control at low speed, if the input voltage or frequency is decreased, the amplitude _{AZ of the} elliptical motion in the pressurizing direction is decreased, and finally it cannot be driven. As described above, in the speed control based on the input voltage and the frequency, there is a certain dead zone in the low speed region. On the other hand, at a rate controlled by the phase difference, by varying the previously described phase difference theta, amplitude A _Z and the amplitude A _X in the moving direction of the pressing direction of the elliptical motion is changed, respectively. That is, it is possible to reduce the amplitude A _X of size to some extent maintaining the as the moving direction of the amplitude A _Z of the pressing direction. As a result, it is possible to drive at a lower speed than speed control using the input voltage and frequency as parameters. Therefore, the speed control based on the phase difference is more advantageous for the control in the low speed region.

  As described above, in the ultrasonic motor 10, elliptical motion is generated in the protrusions 1 a and 1 b of the vibration plate 1 due to high-frequency vibration, so that the vibration plate 1 can move relative to the friction member 3. The speed control of the diaphragm 1 can be performed by controlling the phase difference between the input voltages of the A phase and the B phase.

Below, with reference to FIG. 6, the drive device 30 of the ultrasonic motor 10 is demonstrated. FIG. 6 is a block diagram illustrating a configuration example of the driving device 30.
The position detector 51 detects the relative position of the diaphragm 1 and outputs a detection signal to the position deviation calculator 61 of the phase difference controller 52. The position detection unit 51 includes, for example, an optical encoder and the like, and detects position information of the diaphragm 1. The type of detection means and the measurement principle in the position detector 51 are not limited. The phase difference control unit 52 controls the phase difference of the input voltage to the polarization regions 2 a and 2 b of the piezoelectric element 2 in accordance with the position information detected by the position detection unit 51. The phase difference control unit 52 controls the phase difference so that the position detected by the position detection unit 51 approaches the target position. The phase difference is a phase difference between voltages respectively input from the external power source (not shown) to the polarization regions 2a and 2b of the piezoelectric element 2. The phase difference control unit 52 performs feedback control.

A positional deviation calculation unit 61 of the phase difference control unit 52, the position information x detected by the position detection unit 51, and the target position information x _t from a controller (not shown) is inputted, the position deviation e of both information (= x _t -x) is output. The position deviation e is input to the PID compensator 62 and a control signal is output. The PID compensator 62 includes a compensator having proportional (P), integral (I), and differential (D) calculation functions. The operation results of each compensator are added and output. The control signal output from the PID compensator 62 is sent to the drive waveform generator 63. The drive waveform generator 63 generates a two-phase drive waveform signal having a phase difference θ corresponding to the input control signal. The drive waveform signal generated by the drive waveform generator 63 is supplied to the ultrasonic motor 10 (specifically, the polarization regions 2a and 2b of the piezoelectric element 2), so that the diaphragm 1 is driven at a predetermined speed. The The acceleration calculation unit 55 and the attitude difference detection unit 56 will be described in the later-described embodiments.

The phase difference control method and problems will be described below with reference to the comparative example of FIG. FIG. 11 is a graph showing the positional deviation e and the phase difference θ of the diaphragm 1 when reaching the target position in the comparative example. In FIG. 11A, the horizontal axis represents time t, and the vertical axis represents position deviation e. In FIG. 11B, the horizontal axis indicates time t, and the vertical axis indicates the phase difference θ. In FIG. 11, the times are indicated by t ₁₁ , t ₁₃ ^* , t ₁₂ , and t ₁₁ , and have a relationship of “t ₁₁ <t ₁₃ ^* <t ₁₂ <t ₁₃ ”. In FIG. 11 (A), the a position deviation _{e 11} at time _{t 11,} shows the position deviation _{e 13} at time _{t 13,} and _{"e 11> e 13".} In FIG. 11 (B), the phase difference theta ₁₁ at time _{t 11,} shows a phase difference theta ₁₂ at time _{t 12,} and "θ ₁₁ <θ _12".

According to the position x of the diaphragm 1 closer to the target position _{x t,} the position deviation e ₍₌ x t -x) is reduced. Along with this, the control signal output from the PID compensator 62 also becomes small, so the phase difference θ becomes small. When the phase difference θ decreases as the position deviation e is decreased, the amplitude A _X of the moving direction becomes smaller in the elliptical motion of the tip of the protrusion 1a, 1b. As a result, when the driving force becomes small, the driving of the ultrasonic motor becomes unstable. Therefore, insufficient driving force when the phase difference theta reaches theta ₁₁ at time t ₁₁ the movement of diaphragm 1 is stopped halfway. In this case, the position x of the diaphragm 1 does not reach the target position x _t, the positional deviation e ₁₁ becomes residual. The control signal output from the PID compensator 62 increases, and the phase difference θ increases accordingly. After diaphragm 1 which starts driving again when the phase difference at time t ₁₂ theta reaches the theta _12, the positional deviation e ₁₃ at time t ₁₃ corresponding to the settling time is less than the target position deviation. Thus, when the driving force decreases as the phase difference θ decreases, the driving of the ultrasonic motor becomes unstable. When the ultrasonic motor is stopped before the position deviation e becomes equal to or less than the target position deviation, it takes “t ₁₂ −t ₁₁ ” time to drive again.

A graph indicated by a dotted line in FIG. 11 shows a case where the diaphragm 1 reaches the target position deviation without stopping on the way. The time corresponding to the settling time in this case is shown as t ₁₃ ^* . In the solid line graph, as can be seen from the comparison with the dotted line graph, the settling time until the position deviation e becomes equal to or less than the target position deviation becomes longer (t ₁₃ ^* <t ₁₃ ).
As described above, in the phase difference control of the comparative example, the driving may become unstable due to the influence of the dead zone in the driving in the low speed region, and a desired control characteristic may not be obtained. Therefore, as a solution, the phase difference control method of the present embodiment will be described with reference to FIGS.

FIG. 7 is a diagram for explaining a phase difference region used in the phase difference control method of the present embodiment. For convenience of explanation, FIG. 7A will be described only when the diaphragm 1 is driven in the + X direction. Θ ₁₁ shown in FIG. 7 is a phase difference at time t ₁₁ as in FIG. As described above, the speed of the diaphragm 1 is maximized when the phase difference is 90 °, and the diaphragm 1 stops when the phase difference is 0 °. A phase difference region A shown in FIG. 7A has a range of 0 ° to θ ₁₁ and is a region where the driving of the ultrasonic motor becomes unstable. Since the phase difference θ gradually increases according to the position deviation e at the start of driving, the ultrasonic motor does not stop. On the other hand, there is a problem that driving becomes unstable when driving is stopped.

In the case of the present embodiment, control is performed using the first phase difference region B at the start of driving. The phase difference region B is a region where the phase difference is 0 ° to 90 °. On the other hand, during driving stop, without using a phase difference retardation region C from the phase difference 0 ° to the phase difference lower limit theta ₁ is "θ _1> θ _{11" (0 ° ~θ 1), θ} 1 ~ A phase difference region D of 90 ° is used. The range of the second phase difference region D is narrower than that of the first phase difference region B, and the phase difference control unit 52 performs phase difference control using the phase difference in the phase difference region of θ _{1 to} 90 °. That is, the phase difference control unit 52 includes a first phase difference region B and a second phase difference region D having a narrower range than the first phase difference region B as the phase difference regions. The phase difference region B is used, and the second phase difference region D is used when driving is stopped.

Next, with reference to FIG. 7B, control including the case of moving the diaphragm 1 in the −X direction will be described. When the diaphragm 1 is moved in the −X direction, a phase difference in a region where the phase difference θ is negative is used. For this reason, the speed of the diaphragm 1 becomes maximum when the phase difference is −90 °, and the diaphragm 1 stops when the phase difference is 0 °. As described in FIG. 7 (A), the phase difference is 0 region of ° through? ₁ is not used, in the same manner, the phase difference does not use a region of 0 ° through? _1. That is, a range where the absolute value of the phase difference is smaller than the lower limit value is excluded. Therefore, when the driving is stopped, the phase difference region C that is not used is in the range of −θ _{1 to} θ ₁ , and the second phase difference region D that is used is the range of −90 ° to −θ _{1 and} the range of θ _{1 to} 90 °. It becomes a range.

FIG. 8 illustrates the positional deviation e and the phase difference θ of the diaphragm 1 when the target position is reached in the phase difference control of the present embodiment. In FIG. 8A, the horizontal axis represents time t, and the vertical axis represents position deviation e. In FIG. 8B, the horizontal axis represents time t, and the vertical axis represents the phase difference θ. In FIG. 8, the relationship between time t ₁ and time t ₂ is “t ₁ <t ₂ ”. Positional deviation _{e 1} at time _{t 1,} the target position deviation _{e t} shown in FIG. 8 (A), the position difference theta ₁ at time _{t 1} shown in FIG. 8 (B).

Position deviation e in accordance with the position x of the diaphragm 1 closer to the target position _{x t (= x t} -x) is reduced. Along with this, the control signal output from the PID compensator 62 also becomes small, so the phase difference θ becomes small. Phase difference theta at time t ₁ is, after reaching the phase difference theta ₁ which is the lower limit, the phase difference theta not less than theta _1, constant until time t ₂ while the theta _1. For this reason, the diaphragm 1 moves at a substantially constant speed with the phase difference θ ₁ , and the positional deviation e becomes smaller. At time t ₂ has elapsed time, position deviation e is smaller than the target position deviation e _t, polarized regions 2a of the piezoelectric element 2 at this time, the voltage input to 2b stops. That is, when the position deviation e calculated from the position information detected by the position detection unit 51 and the target position becomes smaller than a predetermined value (= target position deviation _et ), the voltages to the polarization regions 2a and 2b Input stops. Thus, the diaphragm 1 is stopped at a position corresponding to the small positional deviation e from the target position deviation e _t.

In the present embodiment, the phase difference control is performed using the phase difference region D without using the phase difference region C having a small phase difference, which may cause unstable driving of the ultrasonic motor at a low speed. . Therefore, the ultrasonic motor can be driven stably. That is, the ultrasonic motor before the positional deviation e is less than the target position deviation e _t has never stopped, settling time is shortened. As described above, by using the second phase difference region D in which the specific phase difference region C including the phase difference zero is excluded from the first phase difference region B (range of −90 ° to 90 °). The effect of the dead zone can be removed by driving in the low speed region. Therefore, controllability in the low speed region is improved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. This embodiment is different from the first embodiment in that the range of the second phase difference region D is changed according to the acceleration of the diaphragm 1. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals as those already used, and the detailed description thereof will be omitted and mainly the differences will be described. Omitting such description is the same in the embodiments described later.

  When the diaphragm 1 is moving, the force generated in the diaphragm 1 is the driving force generated by the high frequency vibration generated in the diaphragm 1 and the inertial force generated by the movement of the diaphragm 1. It is the added gravity. When the inertial force is large, the diaphragm 1 is less likely to stop even when the driving force is smaller than when the inertial force is small. For this reason, when the inertial force increases, that is, when the acceleration is large, the diaphragm 1 is difficult to stop. Therefore, in this case, control is performed to narrow the range of the phase difference region C that is not used.

  In the present embodiment, the drive device 30 includes an acceleration calculation unit 55 (see FIG. 6). The acceleration calculation unit 55 acquires position information from the position detection unit 51 and calculates an acceleration associated with the relative movement of the diaphragm 1 and the friction member 3. The acceleration information calculated by the acceleration calculation unit 55 is sent to the position deviation calculation unit 61.

FIG. 9 is a diagram for explaining a phase difference region used in the phase difference control of the present embodiment. FIG. 9A shows a phase difference region when the acceleration a is smaller than a predetermined acceleration threshold (denoted as a _sh ), and FIG. 9B shows a case where the acceleration a is greater than or equal to the predetermined acceleration threshold a _sh. The phase difference region is shown.

When the acceleration a calculated by the acceleration calculating unit 55 is less than the acceleration threshold, as shown in FIG. 9 (A), the phase difference region C with a range of - [theta] _1A through? _1A is not used, -90 ° A second phase difference region D having a range of ˜−θ _{1A and} a range of θ _1A ˜90 ° is used. Further, when the acceleration a is equal to or greater than a predetermined acceleration threshold value, as shown in FIG. 9 (B), the retardation regions C having a range of - [theta] _1B through? _1B are not used, -90 ° through? _A second phase difference region D having a range of _{1B and} a range of θ _{1B to} 90 ° is used. In this case, “θ _1B <θ _1A ” is satisfied, and the range of the phase difference region C is smaller and the range of the phase difference region D is larger in FIG. 9B than in FIG. 9A. That is, it is a feature of this embodiment that the range of the second phase difference region D is changed according to the magnitude of the acceleration a of the diaphragm 1 calculated by the acceleration calculation unit 55.

After the phase difference θ reaches the lower limit value θ ₁ when the drive is stopped, the ultrasonic motor moves at a substantially constant speed with the phase difference θ ₁ . Therefore, if the range of retardation region is not used is large, i.e., it increases the speed of the diaphragm 1 when the lower limit value theta ₁ is greater. Positional deviation e is the diaphragm 1 is stopped by stopping the voltage input at the stage it becomes smaller than the target position deviation e _t. For this reason, when the speed of the diaphragm 1 is large, there is a possibility that the stopping accuracy is lowered. When the range of the second phase difference region D is fixedly set, in order to drive the ultrasonic motor stably regardless of the magnitude of the acceleration a, the range of the second phase difference region D is set in advance. It needs to be small. On the other hand, in the present embodiment, the range of the second phase difference region D is changed according to the magnitude of the acceleration a, and an appropriate setting process is performed. Thus, when the acceleration a is large because the rate of the vibration plate 1 immediately before stopping by reducing the lower limit theta ₁ is slow, there is an advantage of improving the stopping accuracy.

In this embodiment, the acceleration a of the diaphragm 1 and the acceleration threshold value a _sh are compared, and one of the two lower limit values θ _1A and θ _{1B in} the phase difference region is selected and set depending on the magnitude relationship. However, the present invention is not limited to this, and a process of setting any one of three or more lower limit values according to a comparison result between the acceleration of the diaphragm 1 and a plurality of acceleration threshold values may be used. Alternatively, the phase difference region may be set using the phase difference lower limit value θ _1C that is linearly related to the acceleration a. That is, _{"θ 1C = k 1 × a +} l 1 " _(k 1, _{l 1} is a constant) using the theta _1C calculated from the relational expression, a second phase difference excluding the range of - [theta] _1C through? _1C Region D is set. More commonly used theta _1C calculated from the function theta _1C acceleration a (a). Thereby, since the range of the suitable phase difference region D can be set according to the acceleration a of the diaphragm 1, the stop accuracy can be further improved.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the present embodiment, the difference from the first embodiment is that the range of the second phase difference region D is changed according to the inclination and the moving direction of the diaphragm 1.

  A case where the moving direction of the diaphragm 1 is inclined with respect to the horizontal direction will be described with reference to FIG. In FIG. 10, the vertical direction is defined as the V direction, and the horizontal direction orthogonal to the V direction is defined as the H direction. The Z direction and the X direction are directions inclined at predetermined angles with respect to the V direction and the H direction, respectively. FIG. 10A shows a linear drive device based on the case where the X direction which is the moving direction of the diaphragm 1 is inclined with respect to the horizontal direction H, that is, the state where the moving direction of the diaphragm 1 is the horizontal direction H. Shows a state in which it is rotated by an angle G around the Y axis. In this state, the angle formed by the X direction that is the moving direction of the diaphragm 1 and the horizontal direction H is G.

10B-1 and 10B-2 are explanatory diagrams of the velocity vector and the gravity vector of the diaphragm 1 in the state of FIG. 10C-1 and 10C-2 are explanatory diagrams of the velocity vector and the gravity vector of the diaphragm 1 in a state in which the linear drive device rotates in the direction opposite to the state of FIG. . This state is a state in which the linear drive device is rotated by an angle of −G around the Y axis. A speed vector indicating the speed and moving direction of the diaphragm 1 is denoted by d. The horizontal velocity vector of the velocity vector d marked d _H, mark the vertical velocity vector and d _V.

  The drive device 30 according to the present embodiment includes an attitude difference detection unit 56 (see FIG. 6) that detects the inclination of the diaphragm 1 with respect to the direction of gravity. The attitude difference detection unit 56 includes, for example, an acceleration sensor, and detects how much the diaphragm 1 is inclined with respect to the direction of gravity by measuring gravitational acceleration. Note that the posture difference detection unit 56 only needs to be able to detect the tilt of the diaphragm 1, and the type of detection means and the measurement principle are not limited. The attitude difference detection unit 56 outputs the detected information about the tilt of the diaphragm 1 to the position deviation calculation unit 61. The position deviation calculator 61 calculates a velocity vector d from the tilt of the diaphragm 1 detected by the attitude difference detector 56 and the speed of the diaphragm 1 calculated by the acceleration calculator 55.

Figure 10 (B-1) and (B-2) shows a case where vertical velocity vector _{d V} of the diaphragm 1 is positive. In this case, as shown in FIG. 10 (B-2), the gravity vector g is applied to the diaphragm 1 in the negative direction in the vertical direction, that is, in the −V direction, and in the opposite direction to the moving direction of the diaphragm 1. It acts components _{g X} of the gravity vector. A component g _Z represents a gravity vector component acting in the Z direction. Figure 10 (C-1) and (C-2), shows a case vertical velocity vector _{d V} of the diaphragm 1 is negative. In this case, as shown in FIG. 10 (C-2), a gravity vector g is added to the diaphragm 1 in the negative direction in the vertical direction, that is, in the −V direction, and the gravity vector is moved in the same direction as the moving direction of the diaphragm 1. The component gX of _X works.

During the movement of the diaphragm 1, the force generated in the diaphragm 1 is applied to the driving force due to the high-frequency vibration generated in the diaphragm 1, the inertial force generated by the movement of the diaphragm 1, and the diaphragm 1. Gravity. And vertical velocity vector d _V of the diaphragm 1 is a positive, easily stopped when the gravity component is added in the opposite direction to the moving direction of the diaphragm 1. For this reason, control for increasing the lower limit value (denoted as θ _1D ) of the phase difference and narrowing the range of the second phase difference region D is performed. Meanwhile, a negative vertical velocity vector d _V of the diaphragm 1 is less likely to stop if the gravity component is applied in the same direction as the movement direction of the diaphragm 1. For this reason, the lower limit value of the phase difference (denoted as θ _1E ) is set to be smaller than the lower limit value θ _1D (θ _1E <θ _1D ), and the second phase difference region D is widened.

In this embodiment, if the vertical velocity vector d _V of the diaphragm 1 is positive, the range of the second retardation region D is set relatively narrow. On the other hand, the vertical velocity vector d _V be a negative, the range of the second retardation region D is set relatively large. By changing the range of the second phase difference region D according to the inclination of the vibration plate 1 with respect to the direction of gravity, stable driving is performed with respect to the change in posture of the vibration plate 1.

When the range of the second phase difference region D is fixedly set, the range of the second phase difference region D is increased in advance in order to drive stably regardless of the tilt angle G of the diaphragm 1. It is necessary to keep. On the other hand, in the present embodiment, the range of the second phase difference region D is appropriately set according to the tilt angle G of the diaphragm 1. Therefore, when the vertical velocity vector d _V of the diaphragm 1 is negative, the speed of the vibration plate 1 immediately before stopping by reducing the lower limit theta ₁ of the phase difference becomes slow, thus improving the stopping accuracy .

In the present embodiment, to determine the positive and negative vertical velocity vector d _V of the diaphragm was set by selecting one of two lower limit theta _1D and theta _1E in retardation region. Not only this but the process which compares the gravity component with respect to the moving direction of the diaphragm 1 with a some threshold value, and sets any 3 or more lower limit values according to a comparison result may be sufficient. Alternatively, the phase difference region may be set using the phase difference lower limit value θ _1F that is linearly related to the tilt angle G of the diaphragm 1. That is, the range of the second phase difference region D is set using θ _1F calculated from the relational expression “θ _1F = k ₂ × G + l ₂ ” (k ₂ and l ₂ are constants). More commonly used theta _1F calculated from the function theta _1F tilt angle G _(G). Thereby, since the suitable phase difference area | region D can be set according to the inclination angle G of the diaphragm 1, a stop precision can be improved more.
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 1 Diaphragm 2 Piezoelectric element 3 Friction member 4 Diaphragm holding member 10 Ultrasonic motor 20 Linear drive device 52 Phase difference control part

Claims (8)

A vibration type actuator using a vibration member and a piezoelectric element fixed to the vibration member,
A friction member that contacts the vibration member and moves relative to the vibration member;
Control means for acquiring relative positional information of the vibrating member with respect to the friction member and controlling driving of the piezoelectric element;
The piezoelectric element has a plurality of polarization regions,
When the control means controls a phase difference between voltages applied to the plurality of polarization regions, a first control for setting the phase difference in a first phase difference region; and the first phase difference region A vibration type actuator that performs second control for setting the phase difference in a second phase difference region having a narrower range.   2. The vibration type actuator according to claim 1, wherein the control unit performs the first control when driving is started and performs the second control when driving is stopped.   The control means changes the range of the second phase difference region based on acceleration information in the relative movement between the vibration member and the friction member, which is calculated using the position information. The vibration type actuator according to claim 1 or 2.   3. The vibration type actuator according to claim 1, wherein the control unit changes a range of the second phase difference region based on information on an inclination of the vibration member with respect to a gravitational direction.   The range of the second phase difference region is a range obtained by excluding a range where the phase difference or the absolute value of the phase difference is smaller than a lower limit value from the range of the first phase difference region. 5. The vibration type actuator according to any one of 1 to 4.   6. The vibration member according to claim 1, wherein the vibration member is a vibration plate having a flat plate portion and a protrusion portion provided on the flat plate portion, and the protrusion portion is in contact with the friction member. The vibration type actuator described. A vibration type actuator according to any one of claims 1 to 6,
An optical apparatus, wherein an optical member is driven by the vibration actuator. A vibrating member;
A piezoelectric element having a plurality of polarization regions fixed to the vibrating member;
A friction member that contacts the vibration member and moves relative to the vibration member;
A control method of a vibration type actuator comprising control means for acquiring relative position information of the vibration member with respect to the friction member and controlling driving of the piezoelectric element,
The control means obtaining relative positional information of the vibration member with respect to the friction member;
The control means includes a control step of controlling a phase difference between voltages applied to the plurality of polarization regions, respectively.
The control step includes
Performing a first control to set the phase difference in a first phase difference region;
A method for controlling a vibration type actuator, comprising: performing a second control for setting the phase difference in a second phase difference region having a narrower range than the first phase difference region.

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