JP2010193633A - Jogging mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress occurrence of noise at the time of driving by a burst wave drive signal, and to allow jog feeding in submicron order. <P>SOLUTION: The jogging mechanism includes a fixed stage 1, a moving body 3 which is movable and supported by the fixed stage 1, an ultrasonic motor 6 which moves the moving body 3 and the fixed stage 1 in a relative manner, and a control device 9 for outputting a drive signal of the ultrasonic motor 6. Here, the drive signal of the ultrasonic motor 6 means the drive signals of two kinds, having the same frequency and different phases. The two kinds of drive signals are different in maximum amplitude at jog driving and maximum amplitude at normal driving. At the time of jog driving, the maximum amplitude of one drive signal is different from that of the other drive signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fine movement mechanism provided with an ultrasonic motor.

  When using a microscope for observation of a fine structure, an XY stage is used to move an observation target to a target position. The XY stage is required to have a fine driving performance, high-speed operation, and stability at rest with a feed resolution equal to or higher than that of the structure to be observed.

  Since the ultrasonic motor has advantages such as being small and highly responsive and not requiring energization when stopped, various apparatuses that employ the ultrasonic motor as an actuator for the XY stage have been proposed. For example, Patent Document 1 proposes an apparatus that employs an ultrasonic motor as an actuator for an XY stage for a microscope.

  As an example of the ultrasonic motor, there is a rectangular parallelepiped linear drive ultrasonic motor configured by a laminated piezoelectric body having two kinds of electrodes. In this ultrasonic motor, two driver elements (so-called feet), which are components of the ultrasonic motor, rotate by applying alternating wave signals (bending vibration signal and longitudinal vibration signal) having different phases to two types of electrodes. Then, by causing the action of kicking the mating member, the mating member is moved relative to the ultrasonic motor.

FIG. 6 is a diagram schematically showing an example of a stage moving mechanism provided with such a linear drive type ultrasonic motor.
In the example shown in the figure, an ultrasonic vibrator (hereinafter simply referred to as “vibrator”) made of a laminated piezoelectric material having a bending vibration electrode 101 (101a, 101b, 101c, 101d) and a longitudinal vibration electrode 102. In an ultrasonic motor 106 having 105 and two driver elements 104 (104a, 104b), a longitudinal vibration signal which is a sine wave signal is applied to the longitudinal vibration electrode 102, and the longitudinal vibration signal is applied to the bending vibration electrode 101. When a bending vibration signal that is a sine wave signal having a phase difference of 90 ° is applied, the movable body (stage) 108 moves along the guide 107.

  In the figure, the sign “+” or “−” of the bending vibration electrode 101 and the longitudinal vibration electrode 102 indicates the polarization direction of the piezoelectric body. For example, when a positive voltage is applied to the electrode, the piezoelectric body of the “+” sign electrode portion is deformed to extend in the longitudinal direction, and the piezoelectric body of the “−” sign electrode portion is shrunk in the longitudinal direction. Deform. Therefore, when a sinusoidal signal is applied to the bending vibration electrode 101, bending deformation vibration as schematically shown in FIG. 7A is excited, and when a sinusoidal signal is applied to the longitudinal vibration electrode 102. Longitudinal vibration extending and contracting in the longitudinal direction as schematically shown in FIG. In FIGS. 4A and 4B, dotted arrows indicate the deformation direction of the piezoelectric body, and solid arrows indicate the movement direction of the driver element 104. In this way, when the phases of the two types of vibrations are simultaneously shifted by 90 ° and excited simultaneously, the driver element 104 becomes a vibration that draws an elliptical locus (see the dotted line in the same figure) as shown by the arrow in FIG. At this time, the frictional force is reduced by the vertical component of the force generated when the driver element 104 contacts the movable member 108, and the movable member 108 is moved by the force of the horizontal component.

  By the way, in recent years, the observation magnification has been increased by the miniaturization of observation objects such as semiconductor line width observation and biomolecule observation, and the fine resolution mechanism for positioning the observation sample requires a submicron order drive resolution. It has become.

  On the other hand, the operation of the ultrasonic motor is greatly influenced by the driving frequency, the driving voltage, and the contact surface state, and the reproducibility is particularly poor in micro driving. Therefore, many attempts have been made to improve the controllability by defining the step movement amount using a burst wave as the control signal of the ultrasonic motor. For example, Patent Document 2 proposes a driving method using a signal having a burst waveform portion intermittently as a method of increasing the driving resolution of the ultrasonic motor and increasing the stop position accuracy. However, when such a drive signal is applied to the ultrasonic motor, as schematically shown in FIG. 8, the start (startup) and end (stop) of the burst waveform portion (see 111 and 112 in the figure). ) Produces a sound similar to a metal sound, which makes the operator uncomfortable. Therefore, in order to suppress the generation of this sound, for example, in Non-patent Document 1, when a burst waveform signal is applied, as shown schematically in FIG. Until then, a method of increasing or decreasing the amplitude stepwise or continuously over time has been proposed.

JP 2005-265996 A JP 2001-161081 A

Actuator Handbook for Precision Control, Japan Industrial Technology Association, Solid Actuator Study Group / Edition, p.596-p.602

  In order to perform micro-drive using such a burst waveform signal, it is necessary to reduce the number of burst waveform waveforms. On the other hand, in order to prevent the generation of sound, the burst waveform signal is reduced to a certain time (several millimeters). Second order) must be applied. According to an experiment by the applicant of the present patent application (hereinafter simply referred to as “the present application”), the amplitude of the burst waveform signal is gradually changed over 2 milliseconds at the beginning and end of the burst waveform signal. Otherwise, the generated sound was not suppressed. In this experiment, the frequency of the signal of the burst waveform is about 80 kHz. For example, in this case, as schematically shown in FIG. 10, even if the number of waveforms at the maximum amplitude is set to 1, The total signal application time is 4 (2 + 2) milliseconds, and the number of burst waveforms is 300 or more. Further, the moving amount of the movable body at this time was about 2 μm. With such a burst waveform signal, it is difficult to achieve submicron order fine movement even if the generated sound can be suppressed.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a fine movement mechanism equipped with an ultrasonic motor capable of suppressing the generation of sound and performing fine movement feed in the order of submicrons when driven by a burst wave drive signal. To do.

  In order to achieve the above object, a fine movement mechanism according to a first aspect of the present invention includes a fixed base, a movable body supported to be movable with respect to the fixed base, and the movable body and the fixed base relative to each other. An ultrasonic motor to be moved, and a control device that outputs a drive signal of the ultrasonic motor, wherein the drive signal of the ultrasonic motor is two types of drive signals having the same frequency and different phases, Each of the two types of drive signals has a maximum amplitude at the time of fine movement and a maximum amplitude at the time of normal drive, and at the time of fine movement, the maximum amplitude of one drive signal and the maximum amplitude of the other drive signal are different. It is characterized by being different.

  The fine movement mechanism according to a second aspect of the present invention is the above-described first aspect, wherein the ultrasonic motor has a rectangular parallelepiped shape that generates elliptical vibration at a contact position with a driven body using bending vibration and longitudinal vibration. The two types of drive signals are both burst-wave drive signals, and one drive signal is a flexural vibration signal that excites the flexural vibration, and the other drive signal is the It is a longitudinal vibration signal that excites longitudinal vibration.

  The fine movement mechanism according to a third aspect of the present invention is the fine movement mechanism according to the second aspect, wherein the maximum amplitude of the longitudinal vibration signal is larger than the maximum amplitude of the bending vibration signal during fine movement driving. .

  The fine movement mechanism according to a fourth aspect of the present invention is the fine vibration mechanism according to the second or third aspect, wherein each of the longitudinal vibration signal and the bending vibration signal has a maximum amplitude during fine movement driving higher than a maximum amplitude during normal driving. It is small.

  According to the present invention, in the fine movement mechanism provided with the ultrasonic motor, it is possible to suppress the generation of sound and to perform fine movement feeding on the order of submicron when driven by the burst wave drive signal.

It is a perspective view which shows typically the whole structure of the fine movement mechanism which concerns on 1st Embodiment. (a) is a partial top view of the fine movement mechanism according to the first embodiment, and (b) is a side view of (a). (a) is a top view of the ultrasonic motor, and (b) is an AA ′ cross-sectional view of (a). (a), (b), (c) is a figure which shows typically an example of the drive signal which a control apparatus outputs to an ultrasonic motor (vibrating body) at the time of fine movement drive. It is a figure which shows experimental data. It is a figure which shows typically an example of the stage moving mechanism provided with the linear drive type ultrasonic motor. (a) is a diagram schematically showing a state when bending deformation vibration is excited, and (b) is a diagram schematically showing a state when longitudinal vibration is excited. It is a figure which shows typically an example of the signal which has a burst waveform part intermittently. It is a figure explaining the method of increasing or decreasing an amplitude in steps or continuously over time. It is a figure which shows typically an example of the signal of a burst waveform when the number of waveforms at the time of a maximum amplitude is 1.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view schematically showing the overall configuration of the fine movement mechanism according to the first embodiment of the present invention. 2 (a) is a partial top view of the fine movement mechanism, and FIG. 2 (b) is a side view of FIG. 2 (a). FIG. 4A is also a partial perspective view of the fine movement mechanism.

  In the fine movement mechanism according to the present embodiment shown in FIGS. 1 and 2 (a) and 2 (b), a guide 2 comprising a ball circulation type guide rail 2a and a guide block 2b is mounted on the fixed base 1. Yes. The guide 2 is composed of two guide blocks 2b and one guide rail 2a as shown in FIG. 2 (a). The guide rail 2a is fixed to the fixed base 1, and the guide block 2b is a movable body. A certain moving body 3 is fixed. Below the moving body 3, two side members 4 are fixed in parallel to the guide rail 2a, in contact with the guide block 2b, and symmetrically with the guide rail 2a interposed therebetween.

The moving body 3 is supported so as to be movable in one axial direction together with the guide block 2b and the side surface member 4.
One of the side members 4 is provided with a sliding member 5 made of a hard material such as ceramic.

  An ultrasonic motor 6 is fixed to the fixed base 1 so as to contact and press the sliding member 5. The ultrasonic motor 6 is an example of an ultrasonic actuator that moves the moving body 3 and the fixed base 1 relative to each other, and generates elliptical vibration at a contact position with the driven body using bending vibration and longitudinal vibration. An ultrasonic vibrator (hereinafter simply referred to as “vibrator”) 12 which is a rectangular parallelepiped vibrator to be described later is included.

  A scale 7 is provided on the other side surface of the movable body 3 where the sliding member 5 is provided, and an encoder 8 is disposed at a position where the pattern of the scale 7 can be detected. It is fixed. The encoder 8 is a displacement sensor that detects the relative positional relationship between the moving body 3 and the fixed base 1.

  Here, it is desirable that the arrangement interval of the guide blocks 2 b be equal to or greater than the maximum movement amount of the moving body 3. By setting such an arrangement interval, even if the moving body 3 moves, the pressing position of the ultrasonic motor 6 is kept within the arrangement interval of the guide block 2b.

A control device 9 that acquires position information from the encoder 8 and drives the ultrasonic motor 6 based on the position information is connected to the encoder 8 and the ultrasonic motor 6.
FIG. 3A is a top view of the ultrasonic motor 6, and FIG. 3B is a cross-sectional view taken along the line AA 'of FIG.

  In the ultrasonic motor 6 shown in FIGS. 4A and 4B, the holding member 11 is a holding mechanism that holds the vibrating body 12 with respect to the fixed base 1, and is made of a metal material such as aluminum. ing. Further, the holding member 11 has a thin plate spring portion 14 (portion indicated by hatching in FIG. 1A) formed by providing a notch hole portion 13 by wire electric discharge machining or the like. A thick portion 14a that does not act as a spring is formed in the center of the thin plate spring portion 14, and the thick portion 14a and the vibrating body 12 are bonded to each other with a high hardness adhesive such as a ceramic adhesive. At this time, the thin leaf spring portion 14 and the vibrating body 12 are configured to be provided close to each other in parallel. Further, the bonding position of the vibrating body 12 is near the center of the bonding surface of the vibrating body 12.

  In the vibrating body 12, two protrusions 15 (15 a and 15 b) as drive elements are provided on the surface opposite to the surface to which the thick portion 14 a of the holding member 11 is bonded. The protrusion 15 is made of, for example, a material such as polyacetal containing reinforcing fibers, a material made of a resin having a relatively small friction coefficient, or a material such as ceramic. The holding member 11 is fixed to the fixing base 1 with screws through fixing screw holes 16 (16a, 16b) in a state where both of the protrusions 15 are in contact with the sliding member 5. At this time, it is desirable that the pressing force to the movable body 3 side is in the vicinity of zero in a state where there is almost no deflection of the thin leaf spring portion 14. In FIG. 1, the fixing screw holes 16 and screws for fixing the holding member 11 to the fixing base 1 are omitted.

  In addition, the holding member 11 is formed with a female screw. Specifically, as shown in FIG. 3B, the thick portion 14a can be pressed by screwing a plunger 17 having a male screw formed on the outer periphery. ing. Although not shown, a coil spring is built in the plunger 17, and a pressing force is generated when the tip member 17a is pushed. For this reason, the pressing force according to the movement amount of the tip member 17a of the plunger 17 is loaded on the thick portion 14a. At this time, the vibrating body 12 is also pressed against the sliding member 5 together with the protrusion 15.

4A, 4B, and 4C schematically show examples of drive signals output from the control device 9 to the ultrasonic motor 6 (vibrating body 12) during fine movement driving (also referred to as “micro driving”). FIG.
In this example, it is assumed that the amplitude of the drive signal is increased or decreased by changing the voltage.

  As shown in FIG. 6A, the vibrating body 12 has the same configuration as that of the vibrator 103 shown in FIG. 6 and includes bending vibration electrodes 21 (21a, 21b, 21c, 21d). It consists of a laminated piezoelectric material having an electrode 22 for longitudinal vibration. The control device 9 uses a bending vibration signal and a longitudinal vibration signal (detailed in FIGS. 4B and 4C) as shown in FIG. The moving body 3 can be finely moved by applying (described later). At this time, as in the case of the driver element 104 shown in FIG. 6, the protrusion 15 is vibrated so as to draw a locus of an ellipse (see the dotted line in FIG. 4A) shown in FIG. The frictional force is reduced by the vertical component of the force generated when contacting the sliding member 6, and the sliding member 6 (moving body 3) is moved by the force of the horizontal component.

  Here, the bending vibration signal is a burst-wave drive signal (hereinafter simply referred to as “burst signal”) that excites the vibrating body 12, and the longitudinal vibration signal is a burst signal that causes the vibrating body 12 to excite longitudinal vibration. These two types of burst signals are signals having the same frequency and different phases, and the beginning and end of each signal are controlled so that the amplitude changes with time. In addition, the two types of burst signals are controlled such that the maximum amplitude of each signal is smaller than that during normal driving, and one signal has a smaller maximum amplitude than the other signal. By such control, the vibration amplitude of the ultrasonic motor 6 can be reduced even if the number of burst signal waveforms (the number of waveforms for one period is 1) is large. Fine feed is possible on the order.

  In the example shown in (a), (b), and (c) of the figure, both the flexural vibration signal and the longitudinal vibration signal have an amplitude from 0 to the maximum amplitude over a time of several milliseconds at the beginning of the signal. The amplitude is controlled to change stepwise or continuously from the maximum amplitude to zero over a time of several milliseconds at the end of the signal. Further, as shown in detail in FIGS. 2B and 2C, the maximum amplitude (Va) of the bending vibration signal and the maximum amplitude (Vb) of the longitudinal vibration signal are both the maximum amplitude during normal driving ( Vdef) and the maximum amplitude (Va) of the flexural vibration signal that is one signal is controlled to be smaller than the maximum amplitude (Vb) of the longitudinal vibration signal that is the other signal. That is, the maximum amplitudes of the flexural vibration signal and the longitudinal vibration signal are controlled so that Vdef> Vb> Va. Note that the maximum amplitude (Vdef) during normal driving is the same for both the flexural vibration signal and the longitudinal vibration signal.

  Further, in the longitudinal vibration signal, the maximum amplitude reduction amount at the time of fine movement driving with respect to the normal driving time is Vdef−Vb, and in the bending vibration signal, the maximum amplitude reduction amount at the time of fine movement driving relative to the normal driving time is Vdef−Va, In the example shown in (a), (b), and (c) of the figure, the ratio k of the maximum amplitude reduction amount of the longitudinal vibration signal to the bending vibration signal is 50% (k = (Vdef−Vb) / (Vdef). -Va) * 100 = 50). In this case, if the maximum amplitude (Vdef) at the time of normal driving is 100 and the maximum amplitude (Va) of the flexural vibration signal at the time of fine movement is 50, the maximum amplitude (Vb) of the longitudinal vibration signal at the time of fine movement is 75.

  In the examples shown in (a), (b), and (c) of the figure, the ratio k of the maximum amplitude reduction amount of the longitudinal vibration signal to the bending vibration signal is set to 50%. Therefore, as apparent from the experimental data shown in FIG. 5 described later, it was considered desirable to control the ratio k of the maximum amplitude reduction amount to be 25% or more.

FIG. 5 is a diagram showing the experimental data.
In the figure, the horizontal axis indicates the voltage value corresponding to the maximum amplitude of the burst signal whose maximum amplitude is changed, and the vertical axis indicates the movable body per one output of the respective burst signals of the bending vibration signal and the longitudinal vibration signal. The movement amount of 3 is shown. The marks “◆”, “■”, “▲”, “◇”, and “□” in the figure indicate that the ratio k of the maximum amplitude reduction amount of the longitudinal vibration signal to the flexural vibration signal is 0% and 25%, respectively. Data when 50%, 75%, and 100% are shown.

  The case where the ratio k is 0% indicates the case where the maximum amplitude of the longitudinal vibration signal at the time of fine movement driving is kept at the time of normal driving (Vb = Vdef, where Vdef> Va). The case where k is 100% indicates a case where the maximum amplitude of the longitudinal vibration signal at the time of fine movement driving is the same as the maximum amplitude of the bending vibration signal at the time of fine movement driving (Vb = Va, where Vdef> Va). .

  As is clear from the experimental data shown in the figure, when the ratio k of the maximum amplitude reduction amount of the longitudinal vibration signal to the flexural vibration signal is 0%, that is, when the longitudinal vibration signal is not changed compared with that during normal driving. Even if the voltage applied to the flexural vibration signal is 0, a movement amount of about 1.5 μm is obtained, and submicron order fine movement is impossible (refer to the mark “◆” in the figure). Experimental results were obtained. However, as the ratio k of the maximum amplitude reduction amount of the longitudinal vibration signal with respect to the bending vibration signal is increased, this phenomenon is improved, and when the ratio k is 25% or more, submicron order fine movement is possible (in the figure). (See “■”, “▲”, “◇”, “□”)).

  Although not shown, when the ratio k of the maximum amplitude reduction amount of the longitudinal vibration signal to the bending vibration signal is 100% or more, that is, the maximum amplitude of the longitudinal vibration signal is equal to or greater than the maximum amplitude of the bending vibration signal. In some cases, an experimental result has been obtained that the movement amount change with respect to the voltage change becomes large, and that the fine movement resolution becomes low when the voltage resolution is considered to be fixed.

  Therefore, at the time of fine movement driving, the maximum amplitude of the longitudinal vibration signal and the bending vibration signal is controlled to be smaller than those at the time of normal driving, and preferably the maximum amplitude of the longitudinal vibration signal with respect to the bending vibration signal. An experimental result was obtained that the best mode is that the reduction ratio k is 25% or more and less than 100%, more preferably 75%.

  Accordingly, in the two types of driving burst signals whose maximum amplitude is controlled to be smaller than that during normal driving, the maximum amplitude of the flexural vibration signal, which is one of the burst signals, is increased from 0, thereby moving the moving body 3. Since the amount also increases from 0 and the increase in the movement amount is gradual, the fine movement amount can be easily adjusted (the fine movement resolution is improved), and the fine movement drive can be stably obtained.

  In the present embodiment, as described above, the amplitudes of the bending vibration signal and the longitudinal vibration signal are changed by changing the voltage. Thus, the voltage change determines an increase in amplitude at the beginning of the signal, a decrease in amplitude at the end of the signal, and a maximum amplitude value. In this case, it is possible to increase and decrease the amplitude at the beginning and end of the signal by various methods such as a method of changing the voltage linearly or a method of changing it sinusoidally. The effect of suppressing the generation of sound from the vicinity of 2.5V begins to appear, and if the voltage change per millisecond is 1V or less, the generation of sound is greatly suppressed. The amount of voltage change at the end portion is preferably 2.5 V / msec or less, more preferably 1 V / msec or less.

  As described above, according to the fine movement mechanism according to the present embodiment, it is possible to suppress the generation of sound when driven by a burst signal and to perform fine movement feeding on the order of submicrons. Therefore, in the micro drive of the linear drive type ultrasonic motor, it is possible to reduce the instability due to the motor contact state and parameters while suppressing noise and achieve stable micro positioning.

The fine movement mechanism according to this embodiment can also be applied to, for example, an XY stage for a microscope.
Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and changes may be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Fixing base 2 Guide 3 Moving body 4 Side member 5 Sliding member 6 Ultrasonic actuator 7 Scale 8 Encoder 9 Control device 11 Holding member 12 Vibrating body 13 Notch hole portion 14 Thin plate spring portion 15 Protrusion portion 16 Fixing screw hole 17 Plunger 101 Electrode for bending vibration 102 Electrode for longitudinal vibration 103 Laminated piezoelectric body 104 Driver 105 Ultrasonic vibrator 106 Ultrasonic motor 107 Guide 108 Movable body 111, 112 Burst waveform section

Claims (4)

A fixed base;
A movable body supported movably with respect to the fixed base;
An ultrasonic motor for relatively moving the movable body and the fixed base;
A control device for outputting a drive signal of the ultrasonic motor;
Have
The drive signals of the ultrasonic motor are two types of drive signals having the same frequency and different phases, and each of the two types of drive signals has a different maximum amplitude during fine movement driving and maximum amplitude during normal driving. And, at the time of fine movement driving, the maximum amplitude of one drive signal is different from the maximum amplitude of the other drive signal.
A fine movement mechanism characterized by that. The ultrasonic motor has a rectangular parallelepiped vibrator that generates elliptical vibration at a contact position with a driven body using bending vibration and longitudinal vibration,
The two types of drive signals are both burst-wave drive signals, and one drive signal is a flexural vibration signal that excites the flexural vibration, and the other drive signal excites the longitudinal vibration. Signal
2. The fine movement mechanism according to claim 1, wherein: At the time of fine movement driving, the maximum amplitude of the longitudinal vibration signal is larger than the maximum amplitude of the bending vibration signal,
The fine movement mechanism according to claim 2, wherein: Each of the longitudinal vibration signal and the flexural vibration signal has a maximum amplitude at the time of fine movement driving smaller than a maximum amplitude at the time of normal driving,
The fine movement mechanism according to claim 2 or 3, wherein