CN108681031B - Miniature camera applying stepping ultrasonic motor and control method thereof - Google Patents
Miniature camera applying stepping ultrasonic motor and control method thereof Download PDFInfo
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- CN108681031B CN108681031B CN201810886466.4A CN201810886466A CN108681031B CN 108681031 B CN108681031 B CN 108681031B CN 201810886466 A CN201810886466 A CN 201810886466A CN 108681031 B CN108681031 B CN 108681031B
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- 238000000034 method Methods 0.000 title claims abstract description 12
- 239000000919 ceramic Substances 0.000 claims abstract description 31
- 229920001971 elastomer Polymers 0.000 claims abstract description 7
- 239000000806 elastomer Substances 0.000 claims abstract description 7
- 238000002604 ultrasonography Methods 0.000 claims 2
- 230000005611 electricity Effects 0.000 claims 1
- 230000005284 excitation Effects 0.000 description 11
- 230000006835 compression Effects 0.000 description 9
- 238000007906 compression Methods 0.000 description 9
- 230000008901 benefit Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000005094 computer simulation Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
- G02B7/04—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with mechanism for focusing or varying magnification
- G02B7/09—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with mechanism for focusing or varying magnification adapted for automatic focusing or varying magnification
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
- H02N2/10—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors
- H02N2/101—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors using intermittent driving, e.g. step motors
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Abstract
The invention discloses a miniature camera applying a stepping ultrasonic motor and a control method thereof, wherein the miniature camera applying the stepping ultrasonic motor comprises the following components: the motor base, stator, rotor, lens base and pre-pressing device which are set on the motor base in turn and apply pre-pressing force to the lens base; the stator comprises an elastomer and a piezoelectric ceramic piece, wherein the piezoelectric ceramic piece is arranged on the lower surface of the elastomer and is used for exciting standing wave vibration, and at least two electrodes are arranged on the lower surface of the piezoelectric ceramic piece; at least one contact tooth is arranged on the rotor and is contacted with the upper surface of the elastic body through the contact tooth. The automatic focusing precision of the miniature camera using the stepping ultrasonic motor is improved by controlling the electrodes to be electrified in different modes and utilizing the principle that the node after standing wave superposition is positioned between two nodes before standing wave superposition.
Description
Technical Field
The invention relates to the field of ultrasonic motors, in particular to a miniature camera applying a stepping ultrasonic motor.
Background
In recent years, scholars at home and abroad try to realize the stepping ultrasonic motor by a mode of matching the design of a special mechanical mechanism with an excitation mode. In theory, the single-pulse displacement response of the ultrasonic motor is in the mu m level or even in the nm level, in the prior art, a traveling wave motor is adopted as a common ultrasonic motor, the precision is insufficient, the advantage of high stepping precision of the ultrasonic motor cannot be fully exerted, and therefore the ultrasonic motor cannot be popularized and applied to miniature application scenes such as miniature cameras, and automatic focusing of the miniature cameras cannot be well realized.
Accordingly, the prior art is still in need of improvement and development.
Disclosure of Invention
The invention aims to solve the technical problems that the stepping ultrasonic motor has low stepping precision and cannot be applied to automatic focusing of a miniature camera.
The technical scheme adopted for solving the technical problems is as follows:
a miniature camera employing a stepper ultrasonic motor, comprising: the motor base, stator, rotor, lens base and pre-pressing device which are set on the motor base in turn and apply pre-pressing force to the lens base; the stator comprises an elastomer and a piezoelectric ceramic piece, wherein the piezoelectric ceramic piece is arranged on the lower surface of the elastomer and is used for exciting standing wave vibration, and at least two electrodes are arranged on the lower surface of the piezoelectric ceramic piece; at least one contact tooth is arranged on the rotor and is contacted with the upper surface of the elastic body through the contact tooth.
The miniature camera applying the stepping ultrasonic motor further comprises a lens seat positioned between the pre-pressing device and the rotor; the lens seat is provided with a stand column hole for the stand column to pass through, and the lens seat can slide up and down along the stand column.
The miniature camera applying the stepping ultrasonic motor is characterized in that a first curved surface is arranged on the lower surface of the lens base, and a second curved surface matched with the first curved surface is arranged on the upper surface of the rotor.
The miniature camera using the stepping ultrasonic motor, wherein the first curved surface and the second curved surface are saddle-shaped.
The miniature camera applying the stepping ultrasonic motor is characterized in that a lens is arranged on the lens base.
The miniature camera applying the stepping ultrasonic motor, wherein the pre-pressing device comprises a shell connected with the motor seat and an elastic piece positioned in the shell, and two ends of the elastic piece are respectively contacted with the shell and the lens seat.
The miniature camera using the stepping ultrasonic motor, wherein a photosensitive chip and a photosensitive chip flexible circuit board are arranged at the bottom of the motor seat.
A miniature camera control method using a stepping ultrasonic motor based on the miniature camera using the stepping ultrasonic motor comprises the following steps:
controlling any one electrode of the at least two electrodes to be electrified so as to drive the rotor through any one electrode of the at least two electrodes;
and when the rotation step number of the rotor reaches a first preset value, any two electrodes of the at least two electrodes are controlled to be electrified so as to drive the rotor through any two electrodes of the at least two electrodes.
The method for controlling the miniature camera by using the stepping ultrasonic motor, wherein the step of controlling any one electrode of the at least two electrodes to drive the rotor through any one electrode of the at least two electrodes further comprises:
and after any one electrode in at least two electrodes is controlled to be electrified to drive the rotor, the adjacent electrode is controlled to be electrified to drive the rotor.
The method for controlling the miniature camera by using the stepping ultrasonic motor, wherein when the rotation step number of the rotor reaches a first preset value, controlling any two electrodes of at least two electrodes to be electrified so as to drive the rotor through any two electrodes of at least two electrodes specifically comprises the following steps:
when the number of rotation steps of the rotor reaches a first preset value, any two electrodes in the at least two electrodes are controlled to be electrified with the same voltage so as to drive the rotor through any two electrodes in the at least two electrodes;
and when the rotation step number of the rotor reaches a second preset value, controlling any two electrodes of the at least two electrodes to be electrified with different voltages so as to drive the rotor through any two electrodes of the at least two electrodes.
The beneficial effects are that: because the lower surface of the piezoelectric ceramic piece is provided with at least two electrodes, the rotor can be driven by controlling the at least two electrodes, and the rotor is electrified in different modes by controlling the electrodes, the automatic focusing precision of the miniature camera using the stepping ultrasonic motor is improved by utilizing the principle that the node after standing wave superposition is positioned between two nodes before standing wave superposition.
Drawings
FIG. 1 is a schematic diagram of a first standing wave, a second standing wave, and a first superimposed standing wave in the present invention.
Fig. 2 is a schematic diagram of a first standing wave, a third standing wave, a first superimposed standing wave, and a second superimposed standing wave in the present invention.
Fig. 3 is an exploded view of a miniature camera employing a stepper ultrasonic motor in accordance with the present invention.
Fig. 4 is a schematic structural view of a miniature camera using a stepping ultrasonic motor according to the present invention.
Fig. 5 is a cross-sectional view taken in the direction H-H of fig. 4.
Fig. 6 is a schematic view of a lens mount and a lens according to the present invention.
Fig. 7 is a schematic view of a longitudinal section of a lens mount and a lens in the present invention.
Fig. 8 is a schematic view of a rotor structure in the present invention.
Fig. 9 is a schematic view of the structure of the contact teeth in the present invention.
Fig. 10 is a schematic view of a motor base according to the present invention.
Fig. 11 is a schematic structural view of a stator in the present invention.
FIG. 12 is a computer simulation of a stator exciting a 5-order standing wave in accordance with the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear and clear, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1-12, the present invention provides a miniature camera using a stepping ultrasonic motor, comprising: a motor base 10, a stator, a rotor 30, a lens base 100 and a pre-pressing device for applying pre-pressing force to the lens base 100, which are sequentially arranged on the motor base 10; the stator comprises an elastic body 20 and a piezoelectric ceramic piece 50 which is arranged on the lower surface of the elastic body 20 and is used for exciting standing wave vibration, and at least two electrodes 60 are arranged on the lower surface of the piezoelectric ceramic piece 50; at least one contact tooth 31 is provided on the rotor 30 and is in contact with the upper surface of the elastic body 20 through the contact tooth 31.
Specifically, one electrode is usually used to excite a corresponding standing wave vibration, and a group of electrodes can be used to excite a corresponding standing wave vibration together. Thus, there are two ways of dividing the electrodes, one of which is: a plurality of electrodes are provided, the plurality of electrodes being arranged in sequence, e.g. electrodes 1 Electrode 2 Electrode 3 Electrode 4 Electrode 5 Electrode 6 Electrode 7 Electrode 8 Electrode 9 Sequentially arranged on the piezoelectric ceramic plate; and the second is: provided with a plurality of groups of electrodes, each group of electrodes being uniformly arranged on the piezoelectric ceramic plate, e.g. electrodes 11 Electrode 21 Electrode 31 Electrode 12 Electrode 22 Electrode 32 Electrode 13 Electrode 23 Electrode 33 Electrode 14 Electrode 24 Electrode 34 Sequentially arranged on the piezoelectric ceramic sheet, wherein the electrodes 11 Electrode 12 Electrode 13 Electrode 14 For the first group of electrodes, the electrodes 21 Electrode 22 Electrode 23 Electrode 24 For the second group of electrodes, the electrodes 31 Electrode 32 Electrode 33 Electrode 34 Is the second set of electrodes. The electrodes being divided into groups, eachThe electrodes between the groups are arranged at intervals in this order, and the stepping accuracy of the stepping motor is formed according to the excitation characteristics of the electrodes (this is the characteristics of the electrodes themselves, and therefore, the design needs to be adopted according to actual needs at the time of design). Of course, after dividing the plurality of electrodes into groups, the standing wave vibration can be excited by a single electrode to electrify.
Specifically, the miniature camera using the stepping ultrasonic motor performs stepping operation by adopting the following steps:
the plurality of sets of electrodes on the piezoelectric ceramic sheet 50 are controlled, wherein at least one of the at least two sets of electrodes is energized, and typically, the current is simultaneously energized, so that for stepping, the current is needed to be energized between the sets of electrodes in order to drive the rotor through any one of the electrodes 60.
When the number of rotation steps of the rotor reaches a first preset value, any two adjacent electrodes in the electrodes 60 are controlled to be electrified, and the voltages of the adjacent electrodes can be controlled to be different according to actual needs or a preset scheme, so that the step length of the driving step is controlled, and the rotor is driven through any two adjacent electrodes in the electrodes 60.
The accuracy of the stepper motor can be understood by the fact that if all electrodes are electrodes with the same specification excitation characteristics (although electrodes with different specifications can be used, but the control and design calculation is more complex), the adjacent electrodes can be given a predetermined same excitation voltage according to the excitation characteristics of the electrodes so as to excite a standing wave at a position between the adjacent electrodes, and if the excitation voltage of one of the electrodes is cancelled at this time, the motor can be driven to be stepped above the energized electrodes, so that the accurate stepping displacement of the half-way between the electrodes can be realized by the unit excitation voltage driving. Also, in the drive control, if the excitation voltages of the electrodes on both sides are different, for example, 20% on one side and 80% on the other side, the stepping motor is driven to a position at which the pitch between the two electrodes is approximately one fifth of the pitch on the side of the electrode close to 80%, and at this time, the pitch control of the stepping is not more accurate than the half-way and full-way pitch of one electrode, but still can be realized as a control manner of the stepping motor.
It should be noted that, when the electrode 60 is energized by the single-phase ac control electrode 60, the piezoelectric ceramic plate 50 vibrates and excites a standing wave on the elastic body 20, specifically, excites a standing wave on the driving surface of the elastic body 20. One vibration period of the standing wave is called a first order, and one vibration period comprises a wave crest and a wave trough, the amplitude of the two positions is maximum, and the vibration directions are opposite; one vibration period also comprises two nodes with zero amplitude, a plurality of vibration periods are distributed on the driving surface of the elastic body 20, namely, a plurality of standing waves, and the total number of standing wave nodes on the driving surface of the elastic body 20 is twice the order of the standing waves. The frequency of the single-phase alternating current is consistent with the frequency of the standing wave, and then the standing wave order can be adjusted by changing the frequency of the single-phase alternating current. The amplitude of the standing wave is determined by the voltage of the single-phase alternating current, and the higher the voltage is, the larger the amplitude of the standing wave is, the lower the voltage is, and the smaller the amplitude of the standing wave is.
The standing wave order will be different for electrodes of different specifications, which is a characteristic of the electrode itself, like a vibrating elastic rod, the rod has different vibration order characteristics due to different length, thickness and density, but the standing wave of several orders is selected according to the exciting voltage. That is, although the electrodes may have different order characteristics, the resulting several orders of standing waves that can be formed are dependent on the frequency and amplitude of the excitation. For ease of understanding, the aforementioned elastic rod may be taken as an example, when vibration with different frequencies is used to excite the elastic rod, standing waves with different orders such as first order, second order, third order … … are formed finally, but for a certain elastic rod, the optimal excitation vibration frequency (i.e., resonance frequency) for forming standing waves with different orders such as first order, second order, third order … … is determined. The stepping motor of the invention utilizes the excitation voltage required by standing waves with different orders of the electrodes to control the realization of the stepping function.
In the following, a case where a plurality of electrodes are provided will be described as an example, and a case where a plurality of sets of electrodes are provided may be referred to.
First, before the electrode 60 is energized, the contact teeth 31 are in an initial position, which may be a starting position of the rotation of the rotor 30 or any position. As shown in fig. 1, when any one electrode 60 (denoted as a first electrode) of the at least two electrodes 60 is controlled to be energized, the piezoelectric ceramic plate 50 vibrates, so that a first standing wave 1 (only a vibration waveform at a certain time of the standing wave is shown in fig. 1 and 2 for convenience of description) is excited on the elastic body 20. The contact teeth 31 cannot be stably stopped at the position where the amplitude of the first standing wave 1 is not zero, but can be stably positioned at the node position a of the first standing wave, and thus the contact teeth 31 are displaced from the initial position to the node position a of the first standing wave, that is, the rotor 30 is rotated, and then the stepping operation is ready. The angle at which the rotor 30 rotates is related to the initial position of the contact teeth 31 and is not necessarily rotated by a "pitch angle". Of course, if the initial position of the contact tooth 31 is just the node position a of the first standing wave, the contact tooth 31 is not displaced, that is, the rotor 30 is not rotated.
Next, when the other electrode 60 (denoted as a second electrode) of the at least two electrodes 60 is controlled to be energized, the piezoelectric ceramic plate 50 vibrates, so that the second standing wave 2 excited on the elastic body 20 has its node position B spatially changed with respect to the node position a of the first standing wave, and thus the contact teeth 31 are displaced from the node position a of the first standing wave to the node position B of the second standing wave, that is, the rotation of the rotor 30 continues to perform the stepping operation. The step ultrasonic electrode step may be achieved when each electrode is energized sequentially, for example, when the first electrode and the second electrode are energized sequentially. Normally, the amplitude of the first standing wave 1 is identical to the amplitude of the second standing wave 2, and the contact teeth 31 are rotated from the node position a of the first standing wave to the node position B of the second standing wave, and the angle at which the rotor 30 rotates is a "pitch angle". Of course, the amplitude of the first standing wave 1 and the amplitude of the second standing wave 2 may be different.
More specifically, any two electrodes 60 of the at least two electrodes 60 are controlled to be energized, for example, the first electrode and the second electrode are simultaneously controlled to be energized, a space position difference exists between the electrodes in the rotation direction of the stepper motor, at this time, the first standing wave 1 and the second standing wave 2 are overlapped to form a first overlapped standing wave, a node position C of the first overlapped standing wave is located between a node position a of the first standing wave and a node position B of the second standing wave, the contact teeth 31 are displaced from the node position a of the first standing wave to the node position C of the first overlapped standing wave, at this time, the rotation angle of the rotor 30 is smaller than a step angle, and therefore the stepping accuracy of the rotor 30 is improved. If the amplitude of the first standing wave 1 is identical to the amplitude of the second standing wave 2, the node position C of the first superimposed standing wave is located at an intermediate position between the node position a of the first standing wave and the node position B of the second standing wave, and the rotor 30 is rotated by a half pitch angle.
According to the miniature camera using the stepping ultrasonic motor, as the lower surface of the piezoelectric ceramic plate 50 is provided with the at least two electrodes 60, the rotor 30 can be driven by controlling the at least two electrodes 60, so that the automatic focusing precision of the miniature camera using the stepping ultrasonic motor is improved.
In the embodiment of the present invention, referring to fig. 3, 5, and 8-9, the rotor 30 includes a side plate 33, the side plate 33 has a circular column shape, and the contact teeth 31 are disposed at the bottom of the side plate 33. Specifically, the outer diameters of the side plates 33 are all identical to the outer diameter of the elastic body 20. The contact teeth 31 are in contact with the upper surface of the elastic body 20, and the contact points are distributed at the outer edge of the upper surface of the elastic body 20. The number of the contact teeth 31 may be one or more, and if the number of the contact teeth 31 is plural (typically, the number of the contact teeth 31 is a divisor of the number of nodes, for example, as shown in fig. 12, when the number of nodes is 10, the number of the contact teeth 31 may be 1, 2, 5 or 10), the plurality of the contact teeth 31 are uniformly distributed on the outer edge of the upper surface of the elastic body 20, and preferably, the number of the contact teeth 31 is identical to the number of nodes of the standing wave excited by the electrode 60, a larger driving force can be obtained.
More specifically, the contact teeth 31 are provided with a bottom surface 311 that contacts the elastic body 20 and two first side surfaces 312 in the radial direction of the elastic body 20, the bottom surface 311 and the first side surfaces 312 smoothly transitioning. Of course, the two second side surfaces 313 and the bottom surface 311 of the contact teeth 31 along the circumferential direction of the elastic body 20 may be smoothly transitioned.
In an embodiment of the present invention, referring to fig. 3 to 8, the motor base 10 is provided with a post 18, the lens base 100 is provided with a post hole through which the post 18 passes, and the lens base 100 can slide up and down along the post 18. The lower surface of the lens holder 100 is provided with a first curved surface 110, and the upper surface of the rotor 30 (specifically, the upper surface of the side plate 33) is provided with a second curved surface 37 adapted to the first curved surface 110. The pre-pressing device comprises a shell 43 connected with the motor base 10 and an elastic piece 42 positioned in the shell 43, wherein two ends of the elastic piece 42 are respectively contacted with the shell 43 and the lens base 100.
Specifically, referring to fig. 6-8, the first curved surface 110 and the second curved surface 37 are saddle-shaped, and the saddle-shaped refers to a saddle-shaped with two ends high and two ends low, i.e. two symmetrical concave parts and two symmetrical convex parts. In the initial state, the first curved surface 110 is attached to the second curved surface 37, that is, the concave portion of the side plate 33 is in contact with the convex portion of the lens holder 100, and the convex portion of the side plate 33 is in surface-to-surface contact with the concave portion of the lens holder 100. When the rotor 30 rotates (rotates in the horizontal direction), the lens holder 100 can only slide up and down in the vertical direction and cannot rotate in the horizontal direction, and the first curved surface 110 and the second curved surface 37 cannot be completely attached to each other, so that the lens holder 100 can slide up in the vertical direction until the convex portion of the side plate 33 contacts the convex portion of the lens holder 100, and then the lens holder is in a point-to-point contact state.
More specifically, the lens holder 100 is provided with a lens 200, the bottom of the motor holder 10 is provided with a photosensitive chip 300 and a photosensitive chip flexible circuit board 400 (as shown in fig. 3-5), and the height of the lens 200 relative to the photosensitive chip 300 can be adjusted along with the rotation of the rotor 30, so as to achieve the focusing purpose. The lens 200 is in threaded connection with the lens holder 100, so that the lens 200 and the lens holder 100 can be glued and fixed when the lens 200 is in a zero position.
As shown in fig. 10, of course, four posts 18 are disposed at four corners of the motor base 10. The elastic member 42 is a spring, the four springs are respectively sleeved on the four posts 18, the diameter of the spring is larger than that of the post hole, two ends of the spring are respectively contacted with the housing 43 and the lens holder 100, and the elastic member 42 provides a pre-pressing force for making the lens holder 100 downward. The motor base 10 is provided with a first through hole 19 at a position corresponding to the lens 200, and light can pass through the lens 200 to reach the photosensitive chip 300.
Specifically, the housing 43 may deform the elastic member 42 and apply a pre-compression to the rotor 30, thereby providing the rotor 30 with a pre-compression to the stator. Of course, a pre-compression nut may be disposed, where the pre-compression nut is in threaded connection with the upright 18, specifically, an external thread is disposed on an outer side surface of the upright 18, an internal thread corresponding to the external thread is disposed on an inner side surface of the pre-compression nut, and the magnitude of the pre-compression force of the rotor 30 on the stator can be changed by adjusting the pre-compression nut, so that the pre-compression force is too small, and the output torque is insufficient, and the pre-compression force is too large, so that the amplitude of the standing wave of the stator is greatly reduced, and the output torque is still insufficient. There are optimal pre-pressure values in different miniature cameras using stepper ultrasonic motors and different use scenarios.
As shown in fig. 11, the elastic body 20 is generally annular, and the piezoelectric ceramic plate 50 is also annular and fixedly disposed on the lower surface of the elastic body 20. The outer diameter of the piezoelectric ceramic plate 50 is consistent with the outer diameter of the elastic body 20, and the inner diameter of the piezoelectric ceramic plate 50 is larger than or equal to the inner diameter of the elastic body 20, namely, the piezoelectric ceramic plate 50 is distributed on the outer edge of the elastic body 20. Each electrode 60 has a fan shape, and the size and shape of each electrode 60 may be the same or different, and in this embodiment, the size and shape of each electrode 60 are the same. Of course, each electrode 60 may take other shapes, such as a ring. The electrodes 60 are uniformly distributed on the lower surface of the piezoelectric ceramic plate 50. The outer edge of the elastic body 20 is deformed under the driving of the piezoelectric ceramic plate 50, and the inner edge of the elastic body 20 is not deformed. As shown in fig. 12, the outer edge of the elastic body 20 is deformed to form a 5-order standing wave, the vibration amplitude of the outer edge of the elastic body 20 is large, and the vibration of the inner edge is small, so that the vibration does not substantially occur. The lower surface of the electrodes 60 is provided with a motor flexible circuit board 90 (as shown in fig. 3-5), and each electrode 60 is connected to a power source (not shown) through the motor flexible circuit board 90.
The invention also provides a preferred embodiment of a miniature camera control method using a stepping ultrasonic motor based on the miniature camera using the stepping ultrasonic motor:
the miniature camera control method based on the miniature camera using the stepping ultrasonic motor and using the stepping ultrasonic motor comprises the following steps:
step S100, controlling any one electrode 60 of the at least two electrodes 60 to be energized, so as to drive the rotor 30 through any one electrode 60 of the at least two electrodes 60.
Specifically, before the electrode 60 is energized, the contact teeth 31 are in an initial position, where the initial position may be a starting position of the rotation of the rotor 30, or may be any position. When any one electrode 60 (denoted as a first electrode) of the at least two electrodes 60 is controlled to be energized, the piezoelectric ceramic plate 50 vibrates, so that the first standing wave 1 is excited on the elastic body 20. The contact teeth 31 cannot be stably stopped at the position where the amplitude of the first standing wave 1 is not zero, but can be stably positioned at the node position a of the first standing wave, and thus the contact teeth 31 are displaced from the initial position to the node position a of the first standing wave, that is, the rotor 30 is rotated, and then the stepping operation is ready. The angle at which the rotor 30 rotates is related to the initial position of the contact teeth 31 and is not necessarily rotated by a "pitch angle". Of course, if the initial position of the contact tooth 31 is just the node position a of the first standing wave, the contact tooth 31 is not displaced, that is, the rotor 30 is not rotated.
Step S100 further includes:
when any one electrode 60 of the at least two electrodes 60 is controlled to be electrified to drive the rotor 30, the adjacent electrode 60 is controlled to be electrified to drive the rotor 30.
Specifically, the single-phase ac control electrode 60 is used to apply power, but two-phase ac or multi-phase ac may be used. When two electrodes 60 are used, the two electrodes 60 are energized sequentially in accordance with the distribution position, i.e. twoThe poles 60 are alternately energized to continue the stepwise rotation of the rotor 30. When a plurality of electrodes 60 (two or more electrodes 60) are used, the plurality of electrodes 60 are sequentially energized according to the distribution position, so that the rotor 30 is continuously rotated in a stepwise manner. For example, a 5-order standing wave has 10 nodes, which can divide 360 ° into 36 °, while each electrode 60 can produce a corresponding 5-order standing wave, and has a corresponding 10 nodes, and since 9 electrodes 60 have a spatial position difference on the elastic body 20, the 9 electrodes 60 can continue to divide 36 ° into 4 °, so that the minimum rotation angle that can be obtained when 9 electrodes 60 are energized in sequence is 4 °. Of course, the electrodes may not be energized sequentially 1 After energizing, the counter electrode 6 When the current is applied, the rotation angle of the rotor 30 is 20 °, and the purpose of this embodiment is to reduce the rotation angle of the rotor 30, so that a sequential current application method is adopted.
When the other electrode 60 (denoted as a second electrode) of the at least two electrodes 60 is controlled to be energized, the piezoelectric ceramic plate 50 vibrates, so that the second standing wave 2 excited on the elastic body 20 changes in node position B with respect to node position a of the first standing wave, and thus the contact teeth 31 are displaced from the node position a of the first standing wave to the node position B of the second standing wave, that is, the rotation of the rotor 30 continues to perform the stepping operation. The step-by-step ultrasonic electrode 60 can be achieved when the first electrode and the second electrode are energized sequentially. The contact teeth 31 are rotated by a "pitch angle" from the node position a of the first standing wave to the node position B of the second standing wave, at which time the rotor 30 rotates. Of course, the amplitude of the first standing wave 1 and the amplitude of the second standing wave 2 may not be identical, and the angle of each rotation of the contact teeth 31 may be different.
And step 200, when the number of rotation steps of the rotor 30 reaches a first preset value, any two electrodes 60 of the at least two electrodes 60 are controlled to be electrified so as to drive the rotor 30 through any two electrodes 60 of the at least two electrodes 60.
Specifically, step S200 specifically includes:
and step S210, when the rotation step number of the rotor 30 reaches a first preset value, controlling any two electrodes 60 of the at least two electrodes 60 to be electrified with the same voltage so as to drive the rotor 30 through any two electrodes 60 of the at least two electrodes 60.
Specifically, the first predetermined value may be preset, and may be an integer of 0, 1, 2 to n. The first predetermined value being 0 here means that step S100 is not performed and step 200 is directly performed. When any two electrodes 60 of the at least two electrodes 60 are controlled to be energized with the same voltage, for example, as shown in fig. 2, the first electrode and the second electrode are simultaneously controlled to be energized, at this time, the first standing wave 1 and the second standing wave 2 are superimposed to form a first superimposed standing wave, the node position C of the first superimposed standing wave is located at a midpoint position (as shown in fig. 1) between the node position a of the first standing wave and the node position B of the second standing wave, the contact teeth 31 are displaced from the node position a of the first standing wave to the node position C of the first superimposed standing wave, at this time, the angle at which the rotor 30 is rotated is smaller than one step angle, and therefore the stepping accuracy of the rotor 30 is improved. When the two electrodes 60 are energized with the same voltage, the amplitude of the first standing wave 1 and the amplitude of the second standing wave 2 are identical, and the standing waves formed by the two electrodes have a spatial position difference due to the different spatial positions of the first electrode and the second electrode, so that the node position A of the first standing wave and the node position B of the second standing wave do not coincide. Since the amplitude of the first standing wave 1 and the amplitude of the second standing wave 2 are identical, the node position C of the first superimposed standing wave is located at an intermediate position between the node position a of the first standing wave and the node position B of the second standing wave. Here, in order to reduce the rotation angle of the rotor 30, after the first electrode is controlled to position the contact tooth 31 at the node position a of the first standing wave in step S100, the first electrode and the electrode adjacent to the first electrode are simultaneously controlled, and at this time, the rotation angle of the rotor 30 is half the pitch angle (half the pitch angle is 2 ° calculated by 5 steps of standing waves and 9 electrodes) with respect to the node position a of the first standing wave. Of course, it is also possible to control two non-adjacent poles, for example, after the pole 1 is controlled to stop the rotor at the corresponding node position, the poles 1 and 4 are controlled simultaneously (corresponding to the adjacent poles 2 and 3 being controlled simultaneously), and at this time, the angle of rotation of the rotor 30 is 1.5 step angles (1.5 step angles are 6 ° calculated by 5-step standing waves and 9 poles).
And step 220, when the number of rotation steps of the rotor 30 reaches a second preset value, controlling any two electrodes 60 of the at least two electrodes 60 to be electrified with different voltages so as to drive the rotor 30 through any two electrodes 60 of the at least two electrodes 60.
Specifically, the second predetermined value may be preset, and may be an integer of 0, 1, 2 to n. The second predetermined value being 0 here means that step S210 is not performed and step 220 is directly performed. When any two electrodes 60 of the at least two electrodes 60 are controlled to be energized with different voltages (the different voltages herein refer only to the different amplitudes of the voltages and the same frequencies), for example, the first electrode and the second electrode are simultaneously controlled to be energized, at this time, the first electrode excites the first standing wave 1, and the second electrode excites the third standing wave 3. The first standing wave 1 and the third standing wave 3 are overlapped to form a second overlapped standing wave, the amplitude of the third standing wave 3 is smaller than that of the first standing wave 1, the node position E of the second overlapped standing wave is located between the node position A of the first standing wave and the node position D of the third standing wave, the contact teeth 31 are displaced from the node position A of the first standing wave to the node position E of the second overlapped standing wave, at the moment, the rotating angle of the rotor 30 is smaller than half a step angle, and therefore the stepping precision of the rotor 30 is further improved. When the two electrodes 60 are energized with different voltages, the amplitude of the first standing wave 1 and the amplitude of the third standing wave 3 are not uniform, for example, the amplitude of the third standing wave 3 is half of the amplitude of the first standing wave 1. Since the spatial positions of the first electrode and the second electrode are different, the standing waves formed by the first electrode and the second electrode have a spatial position difference, and of course, the node position A of the first standing wave and the node position D of the third standing wave do not coincide. Since the amplitude of the first standing wave 1 and the amplitude of the third standing wave 3 are inconsistent, and the amplitude of the third standing wave 3 is smaller than the amplitude of the first standing wave 1, the node position E of the second superimposed standing wave is located between the node position a of the first standing wave and the node position D of the third standing wave (as shown in fig. 2), specifically, the node position E of the second superimposed standing wave is located between the node position a of the first standing wave and the node position C of the first superimposed standing wave, and the angle at which the rotor 30 rotates is smaller than half the pitch angle. Of course, if the amplitude of the first standing wave 1 is smaller than the amplitude of the third standing wave 3, and the node position E of the second superimposed standing wave is located between the node position C of the first superimposed standing wave and the node position D of the third standing wave, the angle of rotation of the rotor 30 is larger than half the pitch angle and smaller than one pitch angle, and the amplitude of the standing wave can be set as needed, so that the angle of rotation of the rotor 30 can be controlled. Of course, in order to reduce the rotation angle of the rotor 30, two adjacent electrodes are controlled simultaneously, and when the amplitude of the third standing wave 3 is smaller than that of the first standing wave 1, the rotation angle of the rotor 30 is between 0 ° and half of the pitch angle (calculated by 5-step standing waves and 9 electrodes, and the rotation angle of the rotor 30 is a certain angle between 0 ° -2 °). Of course, two non-adjacent electrodes can also be controlled simultaneously.
In order to further reduce the angle of rotation of the rotor 30, the order of the standing wave excited by the piezoelectric ceramic plate 50 to vibrate the standing wave may be increased or the number of electrodes may be increased.
In summary, the present invention provides a miniature camera using a step ultrasonic motor and a control method thereof, where the miniature camera using the step ultrasonic motor includes: the pre-pressing device is sequentially arranged on the stator, the rotor and the lens seat on the motor seat and is used for applying pre-pressing force to the lens seat; the lower surface of the stator is provided with a piezoelectric ceramic plate, and the lower surface of the piezoelectric ceramic plate is provided with at least two electrodes; at least one contact tooth is arranged on the rotor and is contacted with the upper surface of the elastic body through the contact tooth. The automatic focusing precision of the miniature camera using the stepping ultrasonic motor is improved by controlling the electrodes to be electrified in different modes and utilizing the principle that the node after standing wave superposition is positioned between two nodes before standing wave superposition.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (9)
1. A miniature camera employing a stepper ultrasonic motor, comprising: the motor base, stator, rotor, lens base and pre-pressing device which are set on the motor base in turn and apply pre-pressing force to the lens base; the stator comprises an elastomer and a piezoelectric ceramic piece, wherein the piezoelectric ceramic piece is arranged on the lower surface of the elastomer and is used for exciting standing wave vibration, and at least two electrodes are arranged on the lower surface of the piezoelectric ceramic piece; at least one contact tooth is arranged on the rotor and is contacted with the upper surface of the elastomer through the contact tooth;
wherein the at least two electrodes are controlled by the following steps:
controlling any one electrode of the at least two electrodes to be electrified so as to drive the rotor through any one electrode of the at least two electrodes;
when the number of rotation steps of the rotor reaches a first preset value, controlling any one electrode of the at least two electrodes and an electrode adjacent to the electrode to conduct electricity with the same voltage so as to drive the rotor through any one electrode of the at least two electrodes and the electrode adjacent to the electrode;
and when the rotation step number of the rotor reaches a second preset value, controlling any one electrode of the at least two electrodes and the electrode adjacent to the electrode to electrify different voltages so as to drive the rotor through any one electrode of the at least two electrodes and the electrode adjacent to the electrode.
2. The miniature camera using a stepper ultrasonic motor according to claim 1, wherein a post is provided on the motor mount, the lens mount is provided with a post hole through which the post passes, and the lens mount is slidable up and down along the post.
3. The miniature camera employing a step ultrasonic motor according to claim 2, wherein a lower surface of the lens mount is provided with a first curved surface, and an upper surface of the rotor is provided with a second curved surface adapted to the first curved surface.
4. A miniature camera employing a stepper ultrasound motor as defined in claim 3, wherein said first curved surface and said second curved surface are saddle-shaped.
5. The miniature camera employing a stepper ultrasound motor of claim 2, wherein a lens is disposed on the lens mount.
6. The miniature camera using a stepper ultrasonic motor according to claim 2, wherein said pre-pressing means comprises a housing connected to said motor mount and an elastic member located in said housing, both ends of said elastic member being respectively in contact with said housing and said lens mount.
7. The miniature camera using a stepper ultrasonic motor according to claim 1, wherein a photosensitive chip and a photosensitive chip flexible circuit board are arranged at the bottom of the motor base.
8. A control method of a miniature camera using a step ultrasonic motor, based on the miniature camera using a step ultrasonic motor according to claim 1.
9. The method of claim 8, wherein the step of controlling any one of the at least two electrodes to be energized to drive the rotor through any one of the at least two electrodes further comprises:
and after any one electrode of the at least two electrodes is controlled to be electrified to drive the rotor, the other electrodes of the at least two electrodes are controlled to be electrified to drive the rotor.
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