FR2495400A1 - MOTOR DEVICE NOT HAVING VERY HIGH SENSITIVITY - Google Patents

Abstract

The invention relates to high-sensitivity and high-speed motor devices. It relates to a device comprising a deformable sleeve 10 carrying a piezoelectric ring 15 on which are mounted electrodes 16. The sleeve 10 has teeth 12 forming an internal crown and a rotor 20 having teeth 22 and placed in the sleeve. The differential excitation of the piezoelectric elements by the electrodes 16 causes the sleeve 10 to be placed in an elliptical form, the ellipse rotating and causing the rotation of the rotor 20. Application to motor devices for adjusting the mirrors of the lasers. (CF DRAWING IN BOPI)

Description

The present invention relates to a precision motor device

  operating at high speed, this

  the term "high speed" means, for example, a vi-

  input speed of several million revolutions per minute and an output speed of several tens of thousands

of revolutions per minute.

  Obtaining precise movement and movement is a problem that continues to arise in many technical areas. This problem is complicated

  significantly when the movements and movements

  to take place at high speed (in a certain

  gangster). An example of an application is the positioning

  the movement, movement and deformation of

  mirrors of a laser. Such a mirror usually has to trans-

  put an extremely parallel beam (coplanar wave fronts). Undesirable disturbances of the fronts

  are caused for example by the turbulence

  mospheric or by the variations of density in

  the laser cavity, as well as structural vibrations

  ture. These disturbances occur frequently at a frequency

  high (bandwidth included in the range of

  hertz and beyond). A corrective mechanical movement acts

  the mirror must be able to follow these high frequency movements. A correction movement must have

  frequency and speed and it must be sufficient

accurately.

  The invention relates to a new technique for obtaining movements and displacements

  at high speed and with great precision.

  More specifically, the invention relates to a

  positive precision motor having high speed.

  It also concerns the improvement of

  positive harmonic drive in a way that allows

  operates at a high speed and with high accuracy

  sion, in particular by implementing a new technique

  than powering the motor device.

  More specifically, the invention uses a t495400 annular arrangement of piezoelectric bending elements placed on a deformable corrugated sleeve cooperating with

  a fluted rotor or pinion, according to a harmonious

  that, the teeth of the pinion being chosen accordingly. Bending elements have electrodes that are excited

  by the signals of a suitable generator. When working

  the generator electrically excites some bending elements in one direction and the others in the other

  so that the fluted sleeve takes an elliptical shape.

  Thus, the grooved sleeve and the rotor cooperate at the small axis of the ellipse but do not cooperate at the level

  of the main axis. The feed pattern is changed progressively

  so that the elliptical deformation turns. Lors-

  that the ellipse made a turn, the rotor turned from an angle

  dependent on the gear ratio. This motor device pre-

  the advantage of allowing a very large rotation

  velocity of the elliptical deformation of the sleeve (i.e.

  animation design), the limits being fixed by the electronic components used for the creation

  signals and the resonance of the structure of the

  piezoelectric devices used. A particular advantage of this motor device is that it has no effects

  counter-electromotive force. These effects limit much

  the sensitivity of electromagnetic

  c. The electromagnetic device is essentially of the step-by-step type, a step being given by a change

  of the excitation pattern of the bending elements. A change

  The regular peripheral device of this drawing, for example under the control of sinusoidal excitation voltages, causes a continuous shifting movement so that any particular position can be reached instantaneously and can be maintained. As far as the step-by-step mode is concerned, the number

  different steps per turn is given by the number of

  bending forces multiplied by the gear ratio; the

  report is for example of the order of a few hundred.

  Such a motor device can obviously operate in a very precise manner and at a very high speed, as described

3 2495400

  for illustrative purposes in the remainder of this memoir.

  Other features and advantages of the

  will become apparent from the following description,

  with reference to the appended drawing in which: - Figure 1 is a perspective of a device

  motor according to an advantageous embodiment of the invention.

  tion; FIG. 2 is an enlarged frontal elevation of a portion of the driving device of FIG. 1; and FIGS. 3 and 4 are diagrams illustrating the elliptical deformation of a portion of the device of FIGS. 1 and 2, showing how the orientation of the deformation changes.

  FIG. 1 represents a tube or sleeve 10 de-

  This tube or sleeve is formed of a suitable elastic material and is flexible, that is to say that the sleeve can undergo a flexible deformation and can pass for example 'a profile

  circular to an elliptical profile. Apart from this distortion

mation, the sleeve 10 is fixed.

  The front end of the sleeve has teeth 12 of

  grinding cooperating with teeth 22 of a rotor 20 with the-

  what they are in. Unlike sleeve 10, the

  rotor 20 is not flexible or deformable. According to one

  usual characteristic of harmonic motor devices, the rotor has one or more teeth more or less than

  the pinion formed in the sleeve, two for example.

  The sleeve 10 carries, outside, several piezoelectric bending elements. These comprise a common ceramic ring 15 which itself carries several

  external electrodes 16, for example about twenty. The man

  chon 10 forms a common internal electrode. Each element

  bending is thus defined by a segment of the year

  piezoelectric water 15 and the adjacent electrodes, forming a pair of electrodes arranged opposite one another.

  of the assembly 16 and the other of the sleeve 10. The piezo ring

  electrical is bonded to the sleeve 10 and the electrodes.

  All the electrodes are connected to a signal generator 18, transmitting excitation signals to the electrode faces of the set of flexural elements;

  a pair of electrodes comprises an electrode 16 and the man-

  chon 10. The signal generator 18 transmits for example

  oscillations at a particular frequency which is exactly

  the same for all the electrodes but whose phase differences differ, as described below with reference to the fast scan mode. The generator 18 can also transmit displacement signals in steps such as the

  signals applied to different electrodes have

different causes.

  The piezoelectric device 15 as a whole ensures the elliptical deformation of the sleeve 10 in the vicinity

  of the fluted portion formed by the teeth 12. This deform-

  elliptical mating causes the teeth to engage 12

  placed near the minor axis of the ellipse with the juxtail teeth

  taposées 22 of the rotor while the teeth 12 which are for example along the major axis of the ellipse, are separated

rotor and the pinion he is carrying.

  The elliptical deformation of the sleeve 10 is due to the electrical potentials applied at any time to the electrodes and their particular polarity. FIG. 3 represents, for example, in exaggerated form the deformation of the sleeve 10. In addition, the polarities disposed near the external electrodes indicate the polarities of the signals applied (radially) to the piezoelectric ring. A positive polarity at the outer electrodes tends to radially push the sleeve inward while a negative polarity tends to repel the sleeve.

  sleeve radially outward. Excitations

  parts of the ring 15 provoke a

  overall elliptical formation of this ring and the sleeve 10. When the polarities of certain electrodes are

  modified, the ellipse changes (turns) with respect to

  its axis, as shown in Figure 4. This change

  The orientation arrangement of the elliptical deformation changes the co-operating pattern of the sleeve and rotor teeth and tends to cause angular displacement of the rotor in the same direction as rotation of the ellipse. After a complete "turn" of the ellipse (the sleeve 10 does not rotate itself), the stator and rotor co-operating pattern has moved one tooth and the rotor has rotated from the

  corresponding elementary angular distance.

  In fast scan mode, if the frequency of the applied AC voltage is called f, the ellipse

  takes a turn for two cycles, that is to say that it turns

  do not at a speed f / 2. In addition, the ellipse rotates continuously and the rotor 20 rotates at a frequency given by

  the speed reduction of the harmonic motor device.

  If n is the number of teeth of the sleeve and the rotor has n + 1 teeth, the number of rotations of the rotor per unit of time corresponding to the frequency is equal to f / 2n.

  The resonant frequency of this piezo ring

  ceramic 15, supported by the sleeve 10 and the rotor 20, may be close to the resonance frequency of a single bending element in the form of a segment of the piezoelectric ring and adjacent electrodes. For example, the piezoceramic ring may be formed of the "Gulton" material G1512. A ring with a diameter of 50.8 mm

  and carrying 20 electrodes at a resonant frequency

  calculated crawl of 188 kHz. This frequency, when

  chooses it as the working frequency of the piezo ring

  electric, corresponds to an input rotation speed slightly less than 6 million rpm

  the ellipse. If n is equal to 200, the rotor can thus perform

  kill 28,200 rpm. The particular advantage of this high speed device is due to the fact that the movement takes place in precise synchronism with the exciter field because there is

  no counter-electromotive force as in the provisions

  electromagnetic drugs. This means that the rotor can drive an actuating device with very precise positions, set by the input signal to

6 2495400

  a high frequency equivalent to a high speed of

  and at a high frequency of clock exhaust.

  The input speeds are so high that the output speeds can still be high, so that they can give the desired precision in a wide bandwidth. This behavior is obtained in particular when the device operates in step mode, but also in fast scan mode when the alternative excitation is interpreted as an excitation for a particular number

  of cycles well measured. The rotor stops in any po-

desired.

  In the step-by-step mode, the resonance frequency of the corresponding modes is equal to one tenth of that of the

  fast scanning mode, ie 9400 steps per second. The pre-

  Step-by-step accuracy is due to the construction and does not depend on a reaction for setting the position and / or speed. The activation device placed on the output side, connected to the rotor-20, follows the movement

of it in open loop.

  A single step may be considered as a change in the excitation in which the four "boundaries" between the positively and negatively excited electrodes are shifted (rotated) by a pair of electrodes. In the case of 20 bending elements, one step corresponds to a rotation of 180. If n represents the expected reduction in the speed of the motor device, 20n represents the number

  of step that can present the device by rotation of the rotor.

  If n is equal to 200, the device can therefore have -

  4000 steps per revolution of the rotor. In addition, the device can

change direction with each step.

  With regard to the speed of the actuating device, it can be assumed that each rotation step

  rotor 20 equates to a linear displacement of the

  tif of activation of 5.08.10-5 mm. In step mode, the speed of the actuator is therefore 188,000 x 5.8 × 10 = 9.55 mm / s. In fast scanning mode, the speed is 10 times higher, ie 95.5 mm / s. It must be remembered that two cycles of the excitation voltage are

necessary by "turning" the sleeve.

  The voltage variations applied to electro-

  respective ones involved in a single step pattern change shall not be step type but shall have a gradual variation so that acceleration and deceleration are determined when the fast scan and step modes are combined . The last wave of a train of alternative signals must thus decrease

  If the resonance conditions are observed

  the fast scan and step modes can be combined, a determined sequence of an alternating cycle in fast scan mode forming a large step causing displacement of the motor device by a determined number of steps

  but with the frequency of the sweeping mode

pide.

  It is understood that the invention has not been

  as a preferred example and that any technical equivalence may be

  constituent elements without departing from its scope.

8 - 2495400

Claims (6)

  1. Motor device with high sensitivity and high speed, characterized in that it comprises   an annular internal ring gear and deformed   ble (10), a plurality of annularly arranged piezoelectric bending elements (15, 16), a control device (18) connected to the piezoelectric elements to deform and cause elliptical deformation or substantially elliptical crown, and a rotor element (20) provided with a toothing   the number of teeth (22) of the rotor differing from the   1 to 2 of the teeth of the ring of 1 or 2, the toothing of the rotor cooperating with the ring along a small axis of the ellipse but being separated the l9ng from a major axis of the ellipse so well when rotating the ellipse due to a change in the excitation pattern caused by the control device, the rotor rotates in synchronism with the rotation of the ellipse.   2. Device according to claim 1, characterized in that the piezoelectric elements have a ring   common piezoelectric (15) and separate electrodes (16).   3. Device according to claim 1, characterized in that the control device comprises a signal generator (18) connected to the electrodes (16) of the elements.   piezoelectric and transmitting alternating signals   at the same frequency but with different phase shifts.   4. Device according to claim 1, characterized in that the control device comprises a signal generator (18) transmitting a signal sequence having   different levels to the electrodes of the piezo elements   electric. 5. Motor device of great sensitivity and high speed, characterized in that it comprises   an elastic sleeve (19) having a crown internally, and 9 2495400   piezoelectric bending devices (15,   16) placed on the sleeve and intended to be excited indi-   vidually so that they cause an elliptical deformation of the sleeve, a change in the excitation pattern of the piezoelectric devices causing a change of orientation of the ellipse, the inner ring of the sleeve cooperating with an external toothing of a rotor along of   small axis but not along the long axis of the ellipse.   6. Device according to claim 1, characterized in that the control device (18) transmits at each instant a pattern of signals to the piezoelectric elements with successively different patterns so that the excitation of the piezoelectric devices varies from one to another. drawing to the next.