JP6723858B2 - VIBRATION MOTOR CONTROL DEVICE, LENS DEVICE HAVING THE SAME, AND IMAGING DEVICE - Google Patents

Description

The present invention relates to a vibration motor control device, and a lens device and an imaging device having the same.

As a control method of a vibration type motor having a vibrating body formed of a metal elastic body or the like to which an electro-mechanical energy conversion element (piezoelectric element or electrostrictive element) is bonded, and a contact body that makes pressure contact with the vibrating body Various proposals have been made. Patent Document 1 uses a phase difference control that fixes the frequency and changes the phase difference, and uses a frequency control that fixes the phase difference and changes the frequency when the phase difference reaches a prescribed value. A technique for widening the dynamic range of the speed is disclosed.

JP, 2011-067035, A

The technique disclosed in Patent Document 1 discloses a method of widely using the dynamic range of the driving speed of the vibration type motor. In this case, after switching from the phase difference control to the frequency control, even if the frequency is increased or decreased by a fixed amount, the increase or decrease in the driving speed of the vibration type motor is not constant, and the controllability deteriorates. On the other hand, if the frequency for performing the phase difference control is set to a low frequency in order to reduce the influence of the non-linearity of the driving speed on the frequency in the frequency control region, the controllability is likely to decrease in the low speed region. This is because on the lower frequency side than the resonance frequency of the frequency-speed curve, the speed change with respect to the frequency change is large, and the resonance frequency of the frequency-speed curve with a small phase difference is the frequency-speed curve with a large phase difference. This is because it becomes higher than That is, if the frequency during phase difference control is set to a higher frequency, the controllability is degraded due to the influence of the nonlinearity in the frequency control region, and the frequency during phase difference control is reduced to reduce the influence of the nonlinearity in the frequency control region. Is set to the low frequency side, control is performed according to the frequency-speed curve on the low frequency side of the resonance frequency, resulting in unstable operation. As described above, it is difficult to achieve both the controllability of the vibration motor and the stability when the phase difference is low.

Therefore, an object of the present invention is to provide a vibration type motor control device that maintains both a wide dynamic range of driving speed and controllability and stability at the time of low phase difference.

To achieve the above object, the vibration type motor control apparatus of the present invention, the first frequency signal Oyo electric beauty second frequency signal is applied having a phase difference - vibration is excited by the mechanical energy conversion element that a vibrator, the vibration type motor controller for controlling the driving speed of the vibration type motor relatively moving a contact member in contact with the vibrator, the frequency and the phase difference of the first and second frequency signal relationship storing a phase difference determining means for determining the phase difference for the frequency based on the relationship, the frequency of the first and second frequency signals, the phase difference determined on the basis of the frequency between a phase difference determined by the means, based on said control means for controlling the speed of the vibration type motor has, the relationship the phase difference determining means you store the frequency of the vibration type motor - It is characterized in that the relationship between the frequency lower than the resonance frequency in the velocity characteristic and the phase difference is not included.

According to the present invention, it is possible to achieve both controllability and stability at the time of low phase difference while maintaining a wide dynamic range of drive speed.

Configuration diagram of an embodiment of a vibration type motor control device of the present invention FV characteristic curve and FV control line of the first embodiment of the vibration type motor control device of the present invention (A) F-V characteristic curve and F-V control line of the first embodiment of the vibration type motor control device of the present invention, and (B) relationship between frequency and phase difference. (A) F-V characteristic curve and F-V control line of the first embodiment of the vibration type motor control device of the present invention, and (B) relationship between frequency and phase difference. (A) F-V characteristic curve and F-V control line of the second embodiment of the vibration type motor control device of the present invention, and (B) relationship between frequency and phase difference. Vibration type motor speed characteristics Velocity locus for each starting frequency The figure which shows the linear definition in each Example of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Outline of conventional vibration motor control)
The vibration-type motor has a vibrating body formed of a metal elastic body or the like to which an electro-mechanical energy conversion element (piezoelectric element or electrostrictive element) is bonded, and a contact body that comes into pressure contact with the vibrating body. When a plurality of frequency signals having a phase difference are applied to the piezoelectric element, vibration is excited in the vibrating body, and the vibrating body and the contact body move relatively to generate a driving force. The vibration type motor has a method of changing a frequency (hereinafter, also simply referred to as frequency) of a frequency signal applied to the piezoelectric element (hereinafter, referred to as frequency control) and a phase difference between a plurality of frequency signals applied to the piezoelectric element. The drive is controlled by a method of changing (hereinafter, also referred to as a phase difference) (hereinafter, referred to as phase difference control). Since the frequency control and the phase difference control are known, the details are omitted.

As a method of ensuring controllability and widening the dynamic range, conventionally, phase difference control that fixes the frequency and changes the phase difference is used, and after the phase difference reaches a specified value, the phase difference is fixed. Techniques using frequency control to change the frequency are known. FIG. 6 shows the relationship between the driving speed and the frequency and the phase difference in the vibration type motor (hereinafter also referred to as an FV characteristic curve). The horizontal axis represents frequency and the vertical axis represents drive speed. Each curve represents an FV characteristic curve of the vibration type motor when the phase difference is fixed from 10° to 90° and the frequency is changed. In order to improve the controllability, this region is generally set in order to improve controllability because the drive speed changes drastically on the low frequency side below the frequency at which the maximum speed is obtained in each phase difference (hereinafter also referred to as the resonance frequency). There is a tendency to avoid using it for control.

FIG. 7 shows a locus of the driving speed when both the phase difference control and the frequency control are used in the case where the frequency serving as the starting point (hereinafter, the starting frequency) is changed in the speed characteristics of the vibration type motor. FIG. 7 is described similarly to FIG. 6. First, consider a case where the frequency during phase difference control is set to a frequency FresH, which is higher than the resonance frequency Fres with a phase difference of 10°, and frequency control is switched at a phase difference of 90°. In this case, the trajectory of frequency-velocity indicated by the dashed arrow is followed. The dashed arrow has a higher frequency than the resonance frequency Fres even when the phase difference is 10°, so that the control is stable. However, in frequency control after the phase difference of 90° or more, the dashed arrow follows a non-linear locus. That is, in the frequency control region, even if the frequency is increased or decreased by a certain amount, the increase or decrease in the drive speed of the vibration motor is not constant, and the controllability is deteriorated. When the frequency of the phase difference control is set to a frequency FresL that is lower than the frequency FresH in order to reduce the influence of deterioration of controllability due to the non-linearity in the frequency control region, the locus of the driving speed indicated by the solid arrow is traced. The solid arrow makes the frequency control area narrower than the broken arrow, and it is possible to reduce the influence of the nonlinearity of the frequency control. However, the frequency FresL during the phase difference control is lower than the resonance frequency Fres with the phase difference of 10°, and if the frequency is FresL during the phase difference control, the operation of the vibration motor may become unstable at the low phase difference. In general, the resonance frequency in the frequency-speed characteristics of the vibration type motor is lower in the phase difference (phase difference 10° in FIG. 7) in which the speed is lower than in the phase difference (phase difference 90° in FIG. 7) where the high speed is generated. high. For this reason, when the starting frequency is set to a low frequency range, it may be necessary to use a region on the low frequency side of the resonance frequency of the FV characteristic curve for control.

The configuration of the vibration type motor control device in this embodiment is shown in FIG. In the following description, in order to make the present invention easy to understand, only the main parts of the present invention are shown, and the parts that are not the features of the present invention are omitted.

The vibration type motor control device 100 controls driving of the vibration type motor 103.
The frequency determination unit 101 determines the frequencies of a plurality of frequency signals input to the vibration motor 103. As a determination method, for example, it is determined according to the difference between the output of the position detection unit 105 that detects the position of the vibration motor 103 and the output of the target input unit 106. Further, the frequency determines the low frequency side from the starting frequency stored in the starting frequency storage unit 107. The phase difference determination unit 102 determines the phase difference of the plurality of frequency signals according to the frequency determined by the frequency determination unit 101. The detailed determination method will be described later. The output unit 104 (control unit) outputs a plurality of frequency signals to the vibration type motor 103 based on the frequency determined by the frequency determination unit 101 and the phase difference determined by the phase difference determination unit 102.

Next, a method of determining the phase difference in the phase difference determining unit 102 will be described with reference to FIGS. FIG. 2 is a view similar to FIG. 7, showing the relationship between the frequencies of the two frequency signals applied to the vibration type motor and the drive speed, using the phase difference as a parameter.

In the FV characteristic of the vibration type motor, since the slope of the drive speed with respect to the frequency is large on the lower frequency side than the resonance frequency as described above, the controllability is taken into consideration and the region is not used for drive control. Further, when the phase difference becomes large to some extent, the driving speed rapidly decreases at the end on the high frequency side as shown in FIG. 2 (hereinafter, also referred to as “cliff drop”). In consideration of the characteristics, the area is not used for drive control. As described above, by using the region of the FV characteristic curve in which the change of the driving speed is not large with respect to the change of the frequency for the control, it is possible to perform the control with good controllability.

First, the range of phase difference used for control is determined. Here, a case where 0° to 90° is used as the control phase difference range will be described as an example. On the FV characteristic curve having a certain phase difference (here, 90°), the frequency F0 higher than the resonance frequency is shown among the frequencies (F0′, F0) showing the maximum speed V0 in the target control speed range. The point P0 is specified (FIG. 3(A)). A starting frequency Fa2, which is higher than the resonance frequency of the FV characteristic of any phase difference and lower than the high frequency side indicating a cliff, is set, and a point P1 at a driving speed of 0 at the starting frequency Fa2 is set. , And the point P0 on the FV characteristic curve having the predetermined phase difference (90°). It should be noted that the straight lines P0 to P1 do not intersect with the F-V characteristic curve of any phase difference in the region on the lower frequency side than the resonance frequency (for example, when the frequency Fa1 is selected), and the maximum speed Vmax is exhibited. The starting frequency Fa2 is set so as not to intersect with the FV characteristic curve of the phase difference (here, 90°) (for example, when the frequency Fa3 is selected).

The straight lines P1 to P0 thus determined have a linear relationship between the frequency and the driving speed. Therefore, by changing the frequency and controlling the driving speed based on this relationship, High controllability can be realized. Here, in order to change the drive speed on the straight lines P1 to P0 which are the control lines with respect to the change of the frequency, the frequency is adjusted so as to satisfy the relationship between the frequency and the phase difference illustrated in the straight lines of FIGS. It is necessary to control the phase difference in accordance with the change of. Therefore, the relationship between the frequency and the phase difference in the range from the frequency Fa2 to the frequency F0 (driving speed 0 to V0) that satisfies the relationship of the straight lines P1 to P0 that are the control lines (FIG. 3B) is given to the phase difference determining unit 102. Keep it. The relationship between the frequency and the phase difference in FIG. 3B is held in the phase difference determining unit 102 as a relationship such as a table or a mathematical expression, and the phase difference determining unit 102 determines the phase difference output to the vibration type motor according to the frequency. By doing so, the drive speed can be linearly controlled with respect to the frequency input.

It should be noted that the straight lines P1 to P0 shown as the frequency-speed control line in FIG. 3 do not intersect the FV characteristic curve of any phase difference with the region on the lower frequency side than the resonance frequency, Moreover, it may be set so as not to intersect with the FV characteristic curve of the phase difference exhibiting the maximum speed. Since the drive speed and the frequency have a linear relationship, the frequency corresponding to the maximum speed is the lowest frequency in the control frequency range, but the phase difference corresponding to the maximum speed is not necessarily illustrated in FIG. 3(B). As described above, it is not always the maximum phase difference. For example, as illustrated in FIG. 4A, the phase difference of the FV characteristic curve showing the maximum speed (70° in FIG. 4A) shows the maximum speed within the phase difference range used as the control range. If the phase difference of the F-V characteristic curve is not 90° in FIG. 4A, the maximum phase difference does not always occur at the maximum speed V0 in the control range as shown in FIG. 4B. In the case of FIG. 4B, as the frequency is lowered from the starting frequency, the phase difference increases once and then decreases to become the frequency and phase difference corresponding to the maximum speed. Even based on such an FV control line, it is possible to achieve an effect that the frequency and the driving speed can be controlled with a linear relationship with good controllability.

A vibration type motor 103 according to a second embodiment of the present invention will be described with reference to FIG. This embodiment is an embodiment in which the desired maximum speed V0 to the minimum speed cannot be linearly controlled with respect to the frequency due to the FV characteristic of the vibration motor 103.
The configuration of the vibration motor device according to the present embodiment is the same as that of the first embodiment, and therefore will be omitted.

Here, the case where 0° to 90° is used as the range of the phase difference will be described as an example. Of the frequencies (F0', F0) showing the maximum speed V0 on the FV characteristic curve of the phase difference showing the maximum speed (here, 90°) with respect to the maximum speed V0 of the required control range, the resonance frequency A point P0 indicating a higher frequency F0 is identified. Next, the starting frequency, which is higher than the resonance frequency and lower than the high frequency indicating the cliff, is set. Here, the straight lines P0 to P1 connecting the point P1 at the driving frequency of 0 at the starting frequency and the point P0 on the F-V characteristic curve with the phase difference of 90° are from the driving speed 0 to the maximum speed in the following cases. It is possible to control linearly with respect to the frequency up to V0. That is, the straight lines P0 to P1 do not intersect the FV characteristic curve of any phase difference with the region on the lower frequency side of the resonance frequency (when the frequency Fb2 is selected) and exhibit the maximum speed. This is a case where the F-V characteristic curve of the phase difference does not intersect (when the frequency Fb3 is selected). However, in the case of the vibration motor having the FV characteristic of FIG. 5A, since there are no straight lines P0 to P1 that satisfy the above condition, the following frequency-speed control line is adopted.

First, the starting frequency Fb3 is set on the higher frequency side than the resonance frequency of the FV characteristic curve of any phase difference and on the lower frequency side than the high frequency side indicating the cliff drop, and the point P1 of the starting frequency Fb3 is set. The point P2 of the maximum speed at which the straight line from is in contact with the F-V characteristic curve showing the maximum speed and having a phase difference of 90° without crossing is obtained. In most cases, at this point P2, the straight lines P1 and P2 are tangents to the FV characteristic curve showing the maximum speed and having a phase difference of 90°.

From the frequency Fb3 at the point P1 to the frequency Fb1 at the point P2, speed control is performed using this straight line as the FV control line, and from the frequency Fb1 to the frequency F0 indicating the maximum control speed V0, a phase difference of 90° is applied. The V characteristic curve is used as a control line to control the frequency with a constant phase difference (here, 90°).

The FV control line (straight lines P1 and P2, curves P2 and P0) determined in this way has a linear relationship between frequency and drive speed between frequencies Fb3 and Fb1. The relationship between the frequency and the driving speed is not linear between the frequencies Fb1 and F0 (driving speed V1 (first speed) to V0), but it is possible to realize the controllability close to linear in the section of the straight lines P1 and P2. And In addition, the transition between the straight lines P1 and P2 and the curves P2 and P0 is also tangential to the straight lines P1 and P2 and the curves P2 and P0. It enables a smooth transition of. Note that control is required to change the phase difference in accordance with the change in frequency so that the relationship between the frequency and the phase difference illustrated in the control lines P1 to P0 illustrated in FIG. 5A is satisfied. Therefore, the relationship between the frequency and the phase difference (FIG. 5B) in the range from the frequency Fb3 to the frequency F0 (driving speed 0 to V0) that satisfies the relationship between the control lines P1 to P0 is stored in the phase difference determination unit 102 as a table and mathematical expressions. Save as a relationship. The relationship between the frequency and the phase difference in FIG. 5B is held in the phase difference determining unit 102, and the phase difference determining unit 102 determines the phase difference output to the vibration type motor according to the frequency, thereby inputting the frequency. On the other hand, it is possible to control the driving speed linearly on the low speed side and almost linearly on the high speed side.

With this configuration, the control device of the present invention can achieve both controllability and stability at the time of low phase difference while maintaining a wide dynamic range of driving speed.

As the FV control line in the range of the straight lines P1 and P2 of this embodiment, a control line as shown in FIG. 4 of the first embodiment may be adopted.

As described above, by determining the phase difference according to the frequency by the configuration described above, the FV characteristic on the high frequency side of the resonance frequency is used even when the phase difference is low, and the drive speed with respect to the frequency is used in the entire speed control range. It is possible to realize the linear control of, or the control exhibiting a substantially linear characteristic. Therefore, it becomes possible to achieve both controllability and stability at the time of low phase difference. Further, it is possible to widely use the dynamic range of the driving speed by changing the phase difference while changing the frequency from the starting frequency to the low frequency side.

In this embodiment, the phase difference used is 90° (0° to 90°), but the present invention is not limited to this. For example, the effect of the present invention can be obtained even at 80° or 70°.

In the present embodiment, the phase difference is changed from 0° to 90°, but the invention is not limited to this as long as the phase difference can be obtained from low speed to high speed. For example, the effect of the present invention can be obtained even at 90° to 180° or −90° to 0°.

In the present embodiment, the phase difference of the frequency Fb3 is set to 0° in FIG. 5, but the present invention is not limited to this as long as the minimum speed required for the control device can be obtained, and the control speed aiming at the effect of the present invention does not necessarily include 0. There is nothing you have to do. For example, the effect of the present invention can be obtained even if the same curve or straight line as in FIG. 5A is acquired based on the straight line connecting the point P2 with the phase difference of 10° at the frequency Fb3.

In this embodiment, the starting frequency is Fb3, but the starting frequency is not limited to this as long as the above conditions can be satisfied. For example, the intermediate frequency between the resonance frequency of the phase difference of 10° and the frequency Fb3 is set as the starting frequency, and the straight line connecting to the point P2 is the resonance frequency of each phase difference due to the FV characteristic of the vibration motor as in the above condition. The effect of the present invention can be obtained as long as it is a straight line passing through the higher frequency side.

The vibration type motor control device described in the first or second embodiment can be applied as a drive control device for a lens device including a movable optical member and a vibration type motor for driving the movable optical member as driving means. When the movable optical member is the movable lens group, the operation ring, the operation knob, and the like correspond to the target input unit 106, and the target value from the target input unit 106 and the detection value from the detection unit 105 that detects the position of the movable lens group. The frequency is determined by the frequency determination unit 101 based on the difference between and. The determined frequency is input to the phase difference determination unit 102, the phase difference is determined from the stored relationship between the frequency and the phase difference, and the vibration type motor 103 is controlled based on the frequency and the phase difference. become. As a result, it is possible to realize a lens device that can achieve both controllability and stability at the time of low phase difference while maintaining a wide dynamic range of drive speed, which is an effect of the present invention.

Furthermore, the vibrating motor control device described in the first or second embodiment is used to capture a lens device including a movable optical member and a vibrating motor that drives the movable optical member as driving means, and an optical image formed by the lens device. It can be used as a drive control device of an image pickup device having an image pickup element that operates. Also in this case, similarly to the case where the control device of the present invention is applied to the above lens device, the controllability and the stability at the time of the low phase difference are maintained while maintaining the wide dynamic range of the driving speed, which is the effect of the present invention. It is possible to realize an imaging device that can achieve both.

(About the definition of linearity)
The linear control of the drive speed in each embodiment of the present invention will be described in more detail with reference to FIG. In each embodiment of the present invention, the linear control of the drive speed does not need to be strictly mathematically linear, and control for repeating the phase difference control and the frequency control within the range shown by the double-headed arrow and the diagonal line in FIG. May be

The range shown in FIG. 8 is a range having a predetermined width on the low frequency side and the high frequency side with the straight line connecting P0 and P1 as the center. This range is, for example, a range of ±10% or less of the width of the frequency region used around the straight line connecting P0 and P1, and more preferably a range of ±6% or less. More specifically, when the starting frequency is 94 kHz and the frequency at which the maximum speed is obtained is 90 kHz, the range shown in FIG. 8 is a range of ±0.4 kHz around the straight line connecting P0 and P1. Further, the range shown in FIG. 8 may be a range having a predetermined width on the high speed side and the low speed side with the straight line connecting P0 and P1 as the center. For example, it is within a range of ±10% or less of the maximum speed, and more preferably within a range of ±6% or less around the straight line connecting P0 and P1.

The linear control of the drive speed in each embodiment of the present invention qualitatively means the following. That is, when the vibration type motor is used to drive the focus lens and the frequency is changed with the minimum resolution that can be determined by the frequency determination unit, the focus lens ideally drives the focus lens due to the speed fluctuation of the vibration type motor. It means not to deviate from the depth of focus in the case of doing.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof.

100: Vibration type motor control device 102: Phase difference determination unit

Claims (13)

First frequency signal and the electric second frequency signal is applied having a phase difference - and the vibrating body vibrated by mechanical energy conversion element is excited, a relatively a contact body in contact with said vibration member A vibration type motor control device for controlling the drive speed of a vibration type motor to be moved,
Storing a relationship between the frequency and the phase difference between the first and second frequency signals, a phase difference determining means for determining the phase difference for the frequency based on the relationship,
And the frequency of the first and second frequency signals, the control means and the phase difference determined by the phase difference determining means based on the frequency, based on the, to control the speed of the vibration type motor,
Have
The relationship the phase difference determining means you store the frequency of the vibration type motor - not including the relationship between the phase difference and a frequency lower than the resonant frequency in the velocity profile,
A vibration type motor control device characterized by the above. Speed of the vibration type motor the phase difference determining means is based on the relationship you store the vibration of claim 1 speed against frequency, characterized in that that have a range of linear in the control range Type motor controller. Range of said linear vibration motor control device according to claim 2, characterized in including that the minimum speed in the control range. Range of said linear vibration motor controller according possible not including the range from the maximum speed to less than the outermost speed first speed to claim 2 or claim 3, characterized in the said control range .. The phase difference determining means, as the relationship between the phase difference and the frequency in the range up to the first speed from the maximum speed in the control range, the relationship whose frequency varies for a constant phase difference vibration type motor control apparatus according to claim 4, characterized in that you store. Range of said linear vibration motor control device according to the maximum speed to claim 2 or claim 3, characterized in including it in the control range. Frequency of the vibration type motor - the resonant frequency in the rate characteristic, the vibration type according to claim 2, wherein the phase difference is equal to or maximum speed Ru frequency der obtained in conditions that are held constant Motor control device. An optical member movable,
A vibration type motor for driving the optical member,
The vibration type motor control device according to any one of claims 1 to 7, which controls a driving speed of the vibration type motor ,
Lens apparatus characterized by having a. A vibration type motor control device for controlling the speed of a moving member of a vibration type motor to which a first frequency signal and a second frequency signal having a phase difference are applied,
Storing a relationship between the frequencies of the first and second frequency signals and the phase difference, determining the phase difference with respect to the frequency based on the frequency and the relationship,
Controlling the speed based on the frequency and the determined phase difference,
The relationship is configured such that the speed changes linearly with the frequency while the phase difference is changed with the frequency based on the relationship.
A vibration type motor control device characterized by the above. The vibration type motor control device according to claim 9, wherein the frequency is determined based on a position of the moving member and a target position of the moving member. 10. The relationship is configured such that the phase difference changes with the frequency based on the relationship, and the speed changes linearly with the discretely changed frequency. Alternatively, the vibration type motor control device according to claim 10. An optical member,
A vibration type motor for moving the optical member,
The vibration type motor control device according to any one of claims 9 to 11, which controls the speed of a moving member included in the vibration type motor,
A lens device comprising: The lens device according to claim 8 or 12 ,
An imaging element Ru receiving an image formed by the lens apparatus,
An imaging device comprising:

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