JP2015144557A - Drive control method of ultrasonic motor and drive control device of ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive control method and device of an ultrasonic linear motor which can perform fine drive of 0.1 μm or less, secure speed stability in a low speed region, and stability of motor characteristics, perform ultrafine feeding and ultrafine positioning in nano order, is small in size, and has high output and high durability.SOLUTION: There is provided a drive control method of an ultrasonic motor which controls telescopic vibration and bending vibration independently from each other, and applies sawtooth waveform DC voltage or rectangular DC voltage with different rise times and fall times to an electrode for telescopic drive and an electrode for bending drive independently from each other. There is also provided a drive control device of an ultrasonic motor which controls telescopic vibration and bending vibration independently from each other, and includes a voltage control unit for applying sawtooth waveform DC voltage or rectangular DC voltage with different rise times and fall times of voltage to the electrode for telescopic drive and the electrode for bending drive independently from each other.

Description

  The present invention relates to an ultrasonic motor drive control method and an ultrasonic motor drive control apparatus. In particular, the present invention relates to a drive control method and a drive control apparatus for an ultrasonic motor in which electrodes on a piezoelectric vibrator are arranged independently in polarization regions of bending vibration and stretching vibration, and the stretching vibration and bending vibration are controlled independently. .

  With the rapid development of electronic and information technology, there is a need for further miniaturization and higher integration of precision parts, and an ultra-precision positioning device that can handle nano-order inspection and ultra-fine processing is becoming necessary. . Ultrasonic motors using piezoelectric vibrators have been developed as means for realizing such an ultra-precision positioning device and ultra-fine feed. Since this ultrasonic motor uses the resonance phenomenon of a piezoelectric element, it is more efficient than an impact drive actuator, can output high power, and is excellent in that the structure is relatively simple and can be miniaturized. .

  The basic structure of an ultrasonic motor is composed of a vibrator and a moving body. The frictional contact portion at the tip of the vibrator is pressed against the moving body, and the frictional contact portion of the vibrator is subjected to both stretching and bending operations. The moved elliptical motion is performed, and the moving body is moved while the frictional contact portion is intermittently pressed against the moving body.

Prior arts related to ultrasonic motors include those disclosed in Patent Documents 1 to 3 by the present applicants. In Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-155760), an electrode region for exciting bending vibration and an electrode region for exciting stretching vibration are arranged in a piezoelectric element so that each vibrator can be controlled individually. This method can eliminate variations in speed and dead zone as compared with those in which each electrode is controlled simultaneously.
Further, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2010-041777), a leaf spring using a buckling phenomenon is employed as a spring means for pressing the piezoelectric vibrator against the moving body, so that the pressing load is constant in a certain displacement region. By realizing this non-linearity and driving in this constant load region, it is possible to reduce the change in the applied pressure due to wear of the frictional contact portion and to improve the durability. Patent Document 3 (Japanese Patent Application Laid-Open No. 2008-054407) describes a laminated piezoelectric ultrasonic motor vibrator in which a plurality of thin piezoelectric elements are laminated, and a predetermined voltage is applied to an electrode region that excites stretching vibration. This is applied to excite stretching vibration, and the bending vibration is adjusted by changing the voltage applied to the electrode region for exciting the bending vibration, thereby controlling the moving speed of the moving body.

JP 2011-155760 A JP 2010-041777 A JP 2008-054407 A

  Since the ultrasonic motor has instability in low-speed driving, complicated control is required for precise positioning of the nano-order. Moreover, many points to be improved are left, such as motor performance changing due to wear of the friction member. For example, when micro drive is performed by resonance with an ultrasonic motor that performs independent control of stretching vibration (longitudinal vibration) and flexural vibration, there is a problem of start-up time until steady vibration, and the input time is as in micro drive. When the movement is short, transient vibration during startup becomes dominant, and it becomes difficult to perform micro-driving at 0.1 μm or less.

  The present invention has been made to solve the above-described problems, and can be driven minutely of 0.1 μm or less, can ensure speed stability in a low speed range and stability of motor characteristics, and is ultrafine in nano-order. It is an object of the present invention to provide a drive control method and apparatus for an ultrasonic linear motor that can perform feeding and ultrafine positioning, and is small, high output, and high durability.

  According to the present invention, the following ultrasonic motor drive control method [1] to [5] and [6] drive control apparatus are provided.

(Corrected according to claims)
[1] In a drive control method for an ultrasonic motor that independently controls expansion and contraction vibrations and bending vibrations, sawtooth wave-like waveforms having different rise times and fall times independently of the extension drive electrodes and the bending drive electrodes. A drive control method for an ultrasonic motor, wherein a DC voltage or a rectangular DC voltage is applied.

[2] The ultrasonic motor drive control method according to [1], wherein a sawtooth wave-like DC voltage having a different rise time and fall time is applied independently to each of the expansion drive electrode and the bending drive electrode.

[3] The drive control method for an ultrasonic motor according to the above item 2, wherein the rising time of the applied voltage is longer than the falling time.
3. The drive control apparatus for an ultrasonic motor according to item 2, wherein the rising time of the applied DC voltage is longer than the falling time.

[4] The drive control method for an ultrasonic motor according to item 3 above, wherein a rising time of the applied voltage is 5000 μs or more and a falling time is 5 μs or less.
[5] The drive control method for an ultrasonic motor according to [1], wherein a rectangular DC voltage (voltage OFF time of 5 μsec or less) is applied independently to each of the extension drive electrode and the bending drive electrode.

[6] In an ultrasonic motor drive control device that independently controls expansion and contraction vibrations and bending vibrations, a sawtooth wave-like DC voltage having a different rise time and fall time independently of the extension drive electrode and the bending drive electrode. Or a drive control device for an ultrasonic motor, comprising a voltage control unit for applying a rectangular DC voltage.

  According to the drive control method and drive control apparatus for an ultrasonic motor according to the present invention, a minute drive of 0.1 μm or less is possible, speed stability in a low speed range, stability of motor characteristics can be ensured, and nano order Ultra fine feed and ultra fine positioning are possible. Furthermore, the present invention can realize a small, high output and high durability ultrasonic motor.

It is a schematic top view of the vibrator | oscillator of the ultrasonic motor applied to this invention. It is the side view (a) and schematic cross-sectional view (b) which showed the holding mechanism part of the piezoelectric vibrator of the ultrasonic motor which concerns on the Example of this invention which applies a sawtooth wave-like DC voltage. It is a figure which shows the relationship between the displacement of the vibrator | oscillator of an ultrasonic motor which has a holding mechanism part shown in FIG. 2, and applied pressure. It is a figure which shows the standard of the time of the voltage ON area | region in the drive control method of the ultrasonic motor by the Example of this invention. It is a figure which shows the standard of the time of the voltage OFF area | region in the drive control method of the ultrasonic motor by the Example of this invention. It is a figure which shows the rising and falling state of the sawtooth voltage in the drive control method of the ultrasonic motor by the Example of this invention. It is a figure which shows the slider movement characteristic at the time of giving only a bending displacement to the vibrator | oscillator of an ultrasonic motor. It is a figure which shows the slider movement characteristic at the time of inputting the sawtooth-wave-like DC voltage to the vertical drive electrode and the bending drive electrode by independent control in the drive control method of the ultrasonic motor according to the present invention. It is a figure which shows the slider movement characteristic by the Example of this invention which inputs rectangular DC voltage independently to a longitudinal drive electrode and a bending drive electrode.

  Next, various embodiments of the present invention will be described with reference to the drawings. First, an example of an ultrasonic motor vibrator applied to the embodiment will be described with reference to FIG. 1. A plurality of rectangular thin plate-like inorganic or organic piezoelectric materials are laminated to form a laminated piezoelectric element. The bending vibration electrodes 7 and 8 and the stretching vibration electrode 9 are arranged on the laminate. The bending vibration electrodes 7 and 8 have their outer edges 7a and 8a adjacent to the long side portion 1a of the rectangular plate-like piezoelectric element 1 in parallel, and the inner edges 7b and 8b are curves along a contour line of a predetermined strain. In the upper surface of the piezoelectric element 1, connection portions 7c and 8c with external electrodes are formed at the position of the long side portion 1a. The electrode on the lower surface of the piezoelectric element 1 is connected to an external electrode different from the external electrode connected to the upper surface. The secondary bending vibration is excited by driving the electrodes 7 and 8 paired on each surface in opposite phases.

  In the stretching vibration electrode 9, the rectangular plate-shaped piezoelectric element is disposed at the same central position on both the upper surface and the lower surface, the electrode outer side portion 9 a is adjacent to the long side portion 1 a of the element 1 on the upper surface side, and the other side of the element 1 A connecting portion 9c with the external electrode is formed on the long side portion 1b. On the lower surface of the element 1, the electrode outer portion is connected to another external electrode at the long side portion 1 a of the element 1, and the lower electrode is adjacent to the other long side portion 1 b of the element 1. In addition, the stretching vibration electrode 9 is curved along the curved portions of the bending vibration electrodes 7 and 8 with a space between the bending vibration electrodes 7 and 8 so as to ensure sufficient insulation. To form. The rectangular plate piezoelectric element may be a single-layer piezoelectric element as well as a laminated body.

  As shown in FIGS. 2A and 2B, the piezoelectric vibration element as described above is held in the frame-shaped support member 11 via the leaf spring 3 so as not to be in direct contact with the support member 11. The The piezoelectric vibration element 1 has a friction contact portion 2 at the tip exposed from the support member 11, and this portion frictionally contacts a moving body (not shown) to give a moving operation to the moving body. The leaf spring 3 supports the vibrator 1 on both sides on the upper end side (friction contact portion side) and both sides on the lower end side of the vibrator 1. Reference numeral 4 denotes a fixing member for fixing the leaf spring 3 to the vibrator 1 and is fixed to both upper and lower sides of the vibrator 1. In this example, the upper and lower four leaf springs 3 are configured as buckling parallel leaf springs, and the vibrator 1 is displaced by the pressing force acting on the frictional contact portion 2 of the vibrator 1 against the moving body. When this occurs, a buckling phenomenon occurs in the leaf spring 3 in a certain displacement region, and exhibits a non-linear spring displacement-pressure force characteristic. FIG. 3 shows the relationship between the displacement (mm) of the vibrator and the applied pressure (N) at this time. In the figure, line A is the case of the buckled parallel leaf spring, and line B in the figure is the case of a normal coil spring in which the displacement and the applied pressure are in a proportional relationship. As shown in FIG. 3, by driving in the region S where the pressing force of the line A does not change, it is possible to eliminate a change in the pressing force due to wear of the friction contact portion, and to maintain stable motor characteristics. .

Next, in the ultrasonic motor as described above, the ON / OFF mode of the voltage applied to the vibrator will be described.
In the case of an ultrasonic motor, the voltage is applied to the vibrator in an intermittent ON / OFF form. By such an intermittent ON / OFF operation of the voltage, the moving body in contact with the vibrator is moved. When the voltage is ON, the vibrator needs to feed and drive the slider without generating any slip. When the voltage is OFF, the vibrator is in its original position due to the involvement of the spring means described above. Returning to step S2, the moving body is moved while repeating this operation. Here, it is necessary that slip occurs between the vibrator and the moving body when the vibrator returns. In the present invention, the drive control is performed in a voltage mode in which no slip occurs when the voltage is on and the slip works effectively when the voltage is off.

As described above, in this type of ultrasonic motor for fine feed, when driving by resonating expansion and contraction vibration and bending vibration by independent control, the startup time until steady vibration is important. In this case, the transitional vibration during start-up becomes dominant in the movement while the input time is short, and the minute driving becomes difficult.
In the present invention, in view of this problem, the ultrasonic motor drive control device is controlled by setting the ON / OFF time for applying a sawtooth wave or rectangular wave voltage to the vibrator within an appropriate range.

Next, a case where a sawtooth voltage is applied (embodiment 1) will be described in detail with reference to FIGS.
A laminated piezoelectric element plate was prepared by laminating 50 layers of rectangular lead zirconate titanate (PZT) plates having a thickness of 0.08 mm, a length of 30 mm, and a width of 7.6 mm. The shape shown in FIG. And the expansion / contraction primary vibration electrode (9) and the bent secondary vibration electrode (7, 8) were formed. The expansion / contraction primary vibration electrode is a cross shape having a length of 29.6 mm and has a size of 41% of the area of the piezoelectric element. Each of the electrodes for bending secondary vibration has a length of 11.72 mm and a width of 3.02 mm, and two pairs have 14% of the area of the piezoelectric element. An ultrasonic motor vibrator was manufactured by adhering a stator (made of zirconia, 1 mmφ pin shape) serving as a friction contact portion to the center of the short side.

  Alumina zirconia is used as the sliding plate, and a sawtooth wave-like (25 msec / wave) DC voltage with different rise time and fall time is independently applied to the extension drive electrode and the bending drive electrode of the vibrator. FIG. 4 shows a guideline for the time in the voltage ON region in the drive control method of the ultrasonic motor to which the voltage is applied. 70 V (longitudinal voltage, fixed) was applied to the expansion / contraction driving electrode, and 0 to 80 V (bending voltage) was applied in a variable manner to the bending driving electrode.

  In the voltage ON region, if the voltage is increased within a rise time of 13 μsec (μs) or less, a slip occurs, and the moving body is not effectively driven. Above this time, no slip occurs until 250 μs (point A in FIG. 4), but there is an overlap of moving bodies due to the early (short) voltage ON time. In order to prevent the occurrence of overlap and slip, it has been found that the voltage should be turned on over a time of 5000 μs (point B in FIG. 4) or more.

  FIG. 5 shows a guideline for the time in the voltage OFF region in this ultrasonic motor drive control method. In the voltage OFF region, when the voltage is dropped over 5 μs (μs) or more, slip between the moving body and the vibrator hardly occurs, and a phenomenon that the moving body returns with the vibrator is observed. In FIG. 5, A indicates a point where slip occurs (5 μs or less), and B indicates a point where the slip hardly occurs and a return phenomenon is observed (5 to 25 μs).

  Therefore, in this embodiment 1, as shown in FIG. 6, the voltage is turned on over 5000 μs or more (A in the figure) when the voltage is turned on, and as soon as possible when the voltage is turned off. Specifically, it has been confirmed that a minute driving of 0.1 μm or less is possible by voltage control in which the voltage is turned OFF in a time of 5 μs or less.

  FIG. 7 is a diagram showing slider movement characteristics when the vibrator of the ultrasonic motor is driven only by bending displacement by application of a bending drive electrode. In the case of driving only by bending displacement by applying only the bending drive electrode, no slip occurs when the voltage is OFF, and there is a difficulty in minute displacement operation. Although a slight displacement is possible only by bending vibration, voltage must be continuously applied to the bending drive electrode in order to keep it in a restrained state (because the moving body returns to its original position when the voltage is turned off). This makes it impossible to take advantage of the ultrasonic motor's power consumption of 0 V at rest.

  On the other hand, by performing both the bending driving and the expansion / contraction driving by independent control, as shown in FIG. 8, it is possible to finely move the moving body by 0.1 μm or less with a lower voltage and a smaller moving amount. In addition, the part of the code | symbol A in FIG. 7 is a part where the moved mobile body returns, and such a state has not arisen in FIG.

Next, a case where a rectangular voltage is applied (embodiment 2) will be described.
As in the first embodiment, the expansion and contraction primary vibration electrode and the bending secondary vibration electrode having the rectangular shape and arrangement shown in FIG. 1 are formed, and a stator (made of alumina, 4 mmφ cylindrical shape) is bonded to the center of the short side. Thus, a vibrator for an ultrasonic motor was produced. 99 Alumina is used as the sliding plate, and a rectangular DC voltage (25 ms / wave, voltage OFF time of 5 μsec or less) is independently applied to the extension driving electrode and the bending driving electrode of the vibrator. 80 V (longitudinal voltage, fixed) was applied to the expansion / contraction driving electrode, and 0 to 80 V (bending voltage) was applied in a variable manner to the bending driving electrode. The result is shown in FIG. From FIG. 9, it was confirmed that a minute movement amount of 0.1 μm or less can be achieved in the range of the bending voltage of 5 to 10V.

DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 2 Friction contact part 3 Leaf spring (buckling parallel leaf spring)
4 Fixing member 7, 8 Electrode for bending vibration 9 Electrode for stretching vibration 11 Support member

Claims (6)

  In an ultrasonic motor drive control method that controls stretching vibration and bending vibration independently, a sawtooth wave-like DC voltage having a different rise time and fall time independently for each of the extension drive electrode and the bending drive electrode, Alternatively, a drive control method for an ultrasonic motor, wherein a rectangular DC voltage is applied.   The ultrasonic motor drive control method according to claim 1, wherein a sawtooth wave-like DC voltage having a different rising time and falling time is applied to each of the extension driving electrode and the bending driving electrode.   The ultrasonic motor drive control method according to claim 2, wherein a rising time of the applied voltage is made longer than a falling time.   The ultrasonic motor drive control method according to claim 3, wherein a rising time of the applied voltage is set to 5000 μs or more and a falling time is set to 5 μs or less.   The ultrasonic motor drive control method according to claim 1, wherein a rectangular DC voltage (voltage OFF time of 5 μsec or less) is applied independently to each of the extension drive electrode and the bending drive electrode.   In an ultrasonic motor drive control device that independently controls stretching vibration and bending vibration, a sawtooth wave-like DC voltage with different rise time and fall time, or a rectangular wave, independently from each other, the stretching drive electrode and the bending drive electrode. A drive control apparatus for an ultrasonic motor, comprising a voltage control unit for applying a DC voltage having a shape.

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