阅读说明：本技术 操作超声波电机的方法 (Method of operating an ultrasonic motor ) 是由 弗拉迪米尔·维什涅夫斯基 阿列克谢·维什涅夫斯基 于 2018-04-04 设计创作，主要内容包括：用于操作带有板形式的超声波致动器的超声波电机的方法以及提供用于激励超声波致动器的电激励设备,其中,超声波致动器包括至少四个相同的体积区域,四个相同的体积区域相对于超声波致动器的横切对称平面对称且相对于纵向对称平面对称地布置,并且每个体积区域形成用于形成声驻波的发生器以及用于形成静态弯曲变形的发生器,其中,电激励设备提供至少一个交流电压(U1)和两个静态电压E1、E2,并且至少一个交流电压U1在动态操作模式下同时施加到两个发生器上,以在超声波致动器中形成声驻波,两个静态电压E1、E2在静态操作模式下同时施加到所有发生器上,以形成超声波致动器的静态弯曲变形。(Method for operating an ultrasonic motor with an ultrasonic actuator in the form of a plate and electrical excitation device for exciting an ultrasonic actuator, wherein the ultrasonic actuator comprises at least four identical volume regions which are arranged symmetrically with respect to a transverse symmetry plane and symmetrically with respect to a longitudinal symmetry plane of the ultrasonic actuator and each form a generator for forming an acoustic standing wave and a generator for forming a static bending deformation, wherein the electrical excitation device provides at least one alternating voltage (U1) and two static voltages E1, E2, and at least one alternating voltage U1 is simultaneously applied to both generators in a dynamic operating mode for forming an acoustic standing wave in the ultrasonic actuator, and two static voltages E1, E2 are simultaneously applied to all generators in the static operating mode, to create a static bending deformation of the ultrasonic actuator.)

1. A method of operating an ultrasonic motor comprising the steps of:

Providing an ultrasonic actuator (1) in the form of a plate (2) made of piezoelectric or electrostrictive or magnetostrictive material, the width B of the plate (2) being greater than the thickness D of the plate (2) and less than the length L of the plate (2), and the plate (2) comprising two main faces (13, 14), two side faces (15) extending along the length, and two end faces (16) extending along the width, and comprising a transversal symmetry plane S1 extending perpendicularly to the main faces (13, 14) and the side faces (15) and parallel to the end faces (16), and a longitudinal symmetry plane S2 extending perpendicularly to the side faces (15) and the end faces (16) and parallel to the main faces (13, 14), wherein on at least one of the end faces (16) of the ultrasonic actuator (1) is arranged a friction element (3) for contacting an element (5) to be driven, and the ultrasonic actuator comprises at least four identical volume regions (19, 20, 21, 22), the four identical volume regions (19, 20, 21, 22) being symmetrically arranged with respect to the transversal symmetry plane S1 and symmetrically arranged with respect to the longitudinal symmetry plane S2, each of the volume regions (19, 20, 21, 22) being arranged together with an excitation electrode (27, 38) and a common electrode (28, 39) on and/or in the ultrasonic actuator (1) to form a generator (G1, G2, G3, G4) for forming an acoustic standing wave and a generator (G1, G2, G3, G4) for forming a static bending deformation;

Providing an electrical excitation device (50) delivering one alternating voltage U1 or two alternating voltages U1, U2 and delivering two static voltages E1, E2;

-applying the alternating voltage U1 to the electrodes (27, 28, 38, 39) of two of the four generators G1, G2, G3, G4, or-applying one of the two alternating voltages U1, U2 to the electrodes (27, 28, 38) of two of the generators G1, G2, G3, G4, and-applying the other alternating voltage U1, U2 to the electrodes (27, 28, 38, 39) of the other two generators G2, G2 to form an acoustic standing wave in the ultrasonic actuator in dynamic mode of operation, or-applying one of the two static voltages E2, E2 to the electrodes (27, 28, 38, 39) of two of the four generators G2, and-applying the other static voltage E2, E2 to the electrodes (27, 28, 38, 39) of the two generators G2, and-generating the other two electrodes (27, 28, G2, G2, 28. 38, 39) to create a static bending deformation in the static operation mode.

2. Method according to claim 1, characterized in that in the dynamic operating mode, when the two alternating voltages U1, U2 are applied, one of the two pairs of generators to which one of the alternating voltages U1, U2 is applied forms an acoustic standing wave in the ultrasonic actuator (1) corresponding to the second mode of bending standing waves, and the other of the two pairs of generators to which the other alternating voltage U1, U2 is applied forms an acoustic standing wave in the ultrasonic actuator (1) corresponding to the first mode of acoustic longitudinal standing waves.

3. Method according to claim 1, characterized in that in the dynamic operating mode, when the two alternating voltages U1, U2 are applied, one of the two pairs of generators to which one of the alternating voltages U1, U2 is applied forms an acoustic standing wave in the ultrasonic actuator (1) corresponding to the second mode of bending standing waves, and the other of the two pairs of generators to which the other alternating voltage U1, U2 is applied forms an acoustic standing wave in the ultrasonic actuator (1) corresponding to the first mode of acoustic longitudinal standing waves.

4. The method according to any of the preceding claims, characterized in that the static bending deformation of the ultrasonic actuator (1) takes place in a plane extending substantially parallel to the end face (16).

Technical Field

Background

DE 102005010073B 4 discloses a method for actuating or operating an ultrasonic motor, in which the control of the movement of the element to be driven is achieved by means of an acoustic standing wave generated by an ultrasonic actuator in the form of a rectangular plate and by means of a static bending of the ultrasonic actuator.

In the ultrasonic actuator, an acoustic bending standing wave propagating along its length L and height H, and an acoustic longitudinal standing wave propagating along its length L are generated.

For technical reasons, the thickness B of the piezoelectric plate of the ultrasonic actuator is limited to H/4, so that it is not possible with the ultrasonic motor known from DE 102005010073B 4 to achieve a length of the frictional contact which is greater than H/4. The maximum force that can be generated by the ultrasonic motor and the corresponding mechanical power are limited.

If a higher driving force or higher mechanical power is required, two or more ultrasonic motors connected in parallel or coupled in parallel may be used.

One disadvantage of this coupling, however, is that ultrasonic motors exhibit a wide distribution of operating (resonant) frequencies in practice. This is due to the distribution of the density and hardness of the piezoelectric ceramic during the production of the ultrasonic actuator for technical reasons.

The difference in the operating frequencies of the individual ultrasonic motors results in a reduction in the total power of the parallel ultrasonic motors and in unstable operation due to the transmission or switching of the operating frequency of one motor to the other.

In addition, the use of multiple motors results in higher costs.

Disclosure of Invention

It is therefore an object of the present invention to provide a method of operating an ultrasonic motor, wherein an ultrasonic motor with a higher driving force, a higher mechanical power and a higher operational stability can be achieved compared to methods known in the prior art.

This object is met by a method of operating an ultrasonic motor according to claim 1, wherein the following dependent claims 2 to 4 represent at least advantageous improvements.

The method according to the invention is divided into the following steps.

-providing an ultrasonic actuator (1) in the form of a plate (2) made of piezoelectric or electrostrictive or magnetostrictive material, the width B of the plate (2) being greater than the thickness D of the plate (2) and less than the length L of the plate (2), and the plate (2) comprising two main faces (13, 14), two lateral faces (15) extending along the length, and two end faces (16) extending along the width, and comprising a transversal symmetry plane S1 extending perpendicular to the main faces (13, 14) and the lateral faces (15) and parallel to the end faces (16), and a longitudinal symmetry plane S2 extending perpendicular to the lateral faces (15) and the end faces (16) and parallel to the main faces (13, 14), wherein on at least one end face (16) of the ultrasonic actuator (1) a friction element (3) for contacting the element (5) to be driven is arranged, and the ultrasonic actuator comprises at least four identical volume regions (19, B), 20. 21, 22) arranged symmetrically with respect to the transversal symmetry plane S1 and symmetrically with respect to the longitudinal symmetry plane S2, each volume area (19, 20, 21, 22) being arranged together with the excitation electrodes (27, 38) and the common electrodes (28, 39) on and/or in the ultrasonic actuator (1) to form generators (G1, G2, G3, G4) for forming acoustic standing waves and generators (G1, G2, G3, G4) for forming static bending deformations;

-providing an electrical excitation device (50) delivering one alternating voltage U1 or two alternating voltages U1, U2 and delivering two static voltages E1, E2;

-applying an alternating voltage U1 to the electrodes (27, 28, 38, 39) of two of the four generators G1, G2, G3, G4, or applying one of the two alternating voltages U1, U2 to the electrodes (27, 28, 38) of two of the generators G1, G2, G3, G4, and another alternating voltage U1, U2 is applied to the electrodes (27, 28, 38, 39) of the other two generators G1, G2, G3, G4, to form an acoustic standing wave in the ultrasonic actuator in the dynamic operation mode, alternatively, one of the two electrostatic voltages E1, E2 is applied to the electrodes (27, 28, 38, 39) of two of the four generators G1, G2, G3, G4 and the other electrostatic voltage E1, E2 is applied to the electrodes (27, 28, 38, 39) of the other two generators G1, G2, G3, G4 to form a static bending deformation in the static operation mode.

The dynamic and static modes of operation are performed independently of each other and may preferably be performed continuously such that the dynamic mode of operation is followed by the static mode of operation.

In the dynamic operating mode, either a single alternating voltage U1 is applied simultaneously to two of the four generators G1, G2, G3, G4, or two alternating voltages U1, U2 are each applied to a pair of generators consisting of two interacting generators (i.e., for example, U1 to G1 and G4 and U2 to G2 and G3) to form an acoustic standing wave in the ultrasonic actuator, while in the static operating mode, two static voltages E1, E2 are applied simultaneously to all four generators G1, G2, G3, G4 to form a static bending deformation of the ultrasonic actuator.

It may be advantageous that in the dynamic mode of operation, when applying two alternating voltages U1, U2, each of the two pairs of generators is applied with the same alternating voltage U1, U2, an acoustic standing wave is formed in the ultrasonic actuator, which acoustic standing wave corresponds to a superposition of the second mode of the bending standing wave and the first mode of the longitudinal standing wave.

However, it may also be advantageous that in the dynamic mode of operation, one of the two pairs of generators to which one of the alternating voltages U1, U2 is applied may form an acoustic standing wave in the ultrasonic actuator corresponding to the second mode of the bending standing wave when the two alternating voltages U1, U2 are applied, and the other of the two pairs of generators to which the other alternating voltage U1, U2 is applied may form an acoustic standing wave in the ultrasonic actuator corresponding to the first mode of the acoustic longitudinal standing wave.

It may be advantageous for the static bending deformation of the ultrasonic actuator to occur in a plane extending substantially parallel to the end face.

It may be further advantageous to have the ratio of the length L to the thickness D of the ultrasonic actuator in the range of 3.5 to 4.5.

It is also advantageous to arrange the surface formed by the elliptical path of the points of the friction element, or by the direction of motion of the element to be driven by the ultrasonic motor, perpendicular to the main face of the ultrasonic actuator.

Furthermore, it is advantageous if the generators G1, G2, G3, G4 for forming standing acoustic waves and for forming static bending deformations are each formed by strip-shaped excitation electrodes and strip-shaped common electrodes arranged alternately on both main faces, wherein the strip-shaped electrodes extend parallel to the transverse plane of symmetry S1 and the polarization direction of the piezoelectric material or electrostrictive material or magnetostrictive material arranged between the strip-shaped electrodes is perpendicular to the strip-shaped electrodes.

It is advantageous to make the distance between adjacent strip-shaped electrodes equal to or less than half the thickness D of the ultrasonic actuator.

In addition, it is advantageous if the generator for forming the acoustic standing wave and for forming the static bending deformation is formed by planar excitation electrodes which are spaced apart from one another and arranged on both main faces and by a single planar common electrode which is arranged in the ultrasonic actuator in line with the longitudinal symmetry plane S2 of the ultrasonic exciter, wherein the polarization direction of the piezoelectric material or electrostrictive material or magnetostrictive material arranged between the planar electrodes is perpendicular to the planar electrodes.

In addition, it may be advantageous for the ultrasonic motor to comprise a clamping element for holding the ultrasonic actuator, wherein the clamping element is arranged in the region of a minimum value of the oscillation speed of the acoustic bending standing wave excited in the ultrasonic actuator.

Drawings

The invention is described in more detail by way of examples of embodiment schematically illustrated in the drawings, in which:

FIG. 1: an embodiment of an ultrasonic motor in the form of a linear drive suitable for operation in accordance with the method of the present invention is shown.

FIG. 2: an embodiment of an ultrasonic motor in the form of a rotary drive suitable for operation in accordance with the method of the present invention is shown.

FIG. 3: the geometry of an ultrasonic actuator of an ultrasonic motor adapted to operate in accordance with the method of the present invention is shown.

FIG. 4: an ultrasonic actuator according to fig. 3 is shown with a friction element arranged on one of the front faces.

fig. 5, diagrams 23 to 26: different views of the ultrasonic actuator according to figures 3 and 4 and possible embodiments of the electrodes of the ultrasonic actuator are shown.

Fig. 6, diagram 34 to diagram 37: different views of the ultrasonic actuator according to figures 3 and 4 and additional possible embodiments of the electrodes of the ultrasonic actuator are shown.

Fig. 7, diagram 46: a perspective view of the ultrasonic actuator according to fig. 5 with a friction element arranged on one end face of the front face is shown; drawing 47: a perspective view according to fig. 6 with an ultrasonic actuator arranged on the rear one end face is shown.

Fig. 8, diagram 48: a circuit for operating an ultrasonic actuator according to the method of the invention using a single alternating voltage U1 according to fig. 5 is shown; diagram 49: a block diagram of an electrical excitation device for performing a method according to the invention using a single alternating voltage U1 is shown.

fig. 9, illustration 66 and illustration 67: the maximum deformation state due to the second mode (dynamic operation mode) of the bending standing wave formed in the ultrasonic actuator actuated according to the method of the present invention is shown; diagram 68 and diagram 69: the maximum deformation state due to the first mode (dynamic mode of operation) of the longitudinal standing wave formed in the ultrasonic actuator actuated according to the method of the present invention.

FIG. 10: a graphical representation of possible motion trajectories of points of a friction element of an ultrasonic actuator actuated according to the method of the invention is shown (dynamic mode of operation).

Fig. 11, diagram 73 and diagram 74: the maximum deformation state due to the resulting static bending deformation (static mode of operation) in an ultrasonic actuator actuated according to the method of the present invention is shown.

FIG. 12: a diagram of possible movement trajectories of the points of the friction element of an ultrasonic actuator actuated according to the method of the invention is shown (static operating mode).

Fig. 13, diagram 78: a circuit for operating an ultrasonic actuator according to the method of the invention using two alternating voltages U1 and U2 according to fig. 5 is shown; diagram 79: a block diagram of an electrical excitation device for performing the method according to the invention using two alternating voltages U1 and U2 is shown.

Fig. 14, diagram 83: a circuit for operating an ultrasonic actuator according to the method of the invention using two alternating voltages U1 and U2 according to fig. 5 is shown; wherein each alternating voltage creates a separate standing wave in the ultrasonic actuator; diagram 84: a block diagram of an electrical excitation device for performing the method according to the invention using two alternating voltages U1 and U2 is shown.

Fig. 15, diagram 85: a circuit for operating an ultrasonic actuator according to the method of fig. 6 using a single alternating voltage U1 according to the present invention is shown; diagram 86: a block diagram of an electrical excitation device for performing a method according to the invention using a single alternating voltage U1 is shown.

Fig. 16, diagram 87: a circuit for operating an ultrasonic actuator according to the method of the invention using two alternating voltages U1 and U2 according to fig. 6 is shown; diagram 88: a block diagram of an electrical excitation device for performing the method according to the invention using two alternating voltages U1 and U2 is shown.

Fig. 17, illustration 89: a circuit for operating an ultrasonic actuator according to the method of the invention using two alternating voltages U1 and U2 according to fig. 6 is shown; wherein each alternating voltage creates a separate standing wave in the ultrasonic actuator; diagram 90: a block diagram of an electrical excitation device for performing the method according to the invention using two alternating voltages U1 and U2 is shown.

FIG. 18: an embodiment of an ultrasonic motor in the form of a linear drive suitable for operation in accordance with the method of the present invention is shown.

Detailed Description

Figure 1 shows an embodiment of an ultrasonic motor in the form of a linear drive operating in accordance with the method of the present invention. The ultrasonic motor comprises an ultrasonic actuator 1 in the form of a rectangular piezoelectric plate 2, the ultrasonic actuator 1 having two main faces 13 and 14 with the largest surface area, two side faces 15 extending along the length of the ultrasonic actuator and two end faces 16 extending along the width of the ultrasonic actuator. The friction element 3 is mounted on an end face 16 facing the element 5 to be driven, the friction element 3 being pressed with a force F against the friction surface 4 of the element 5 to be driven by means of the spring element 10.

The element 5 to be driven is embodied as a body 6, the body 6 being mounted slidably in the longitudinal direction in a housing 8 by means of a bearing 7.

The ultrasonic actuator 1 is held in the housing 8 by a clamping element 9.

The contact force F generated by the spring element 10 acts on the ultrasonic actuator 1 through the sound-insulating support 11.

In addition to the rod-shaped element to be driven 5 shown in fig. 1, the element to be driven 5 may also be configured as a plate, a table, or other similar shapes.

The arrow with the reference v indicates the direction of movement of the element 5 to be driven.

Fig. 2 shows a further embodiment of an ultrasonic motor which is suitable for operation in the form of a rotary drive and in the method according to the invention, wherein the element 5 to be driven is configured as a disk-shaped rotating body 12.

The rotating body 12 may also be only a part of a disc, wherein other shapes are also conceivable, such as a ring or a part of a ring, a cylinder or a part of a cylinder, and a sphere or a part of a sphere.

Figure 3 shows the geometry or geometric ratio of an ultrasonic actuator of an ultrasonic motor suitable for operation according to the method of the present invention. The ultrasonic actuator has the shape of a rectangular plate 2, wherein the plate is made entirely of piezoelectric ceramics. The piezoelectric plate 2 has two main faces 13, 14, two side faces 15 and two end faces 16. The plate has a length L, a width B, and a thickness D, wherein the ratio of the length L to the thickness D is between 3.5 and 4.5.

The ratio of the length to the thickness, L/D, determines the position of the resonant frequency, Fp2, of the second mode of the acoustic bending standing wave, which propagates longitudinally with respect to the length, L, and longitudinally with respect to the thickness, D, relative to the resonant frequency, Fp1, of the first mode of the acoustic bending standing wave, which propagates longitudinally with respect to the length, L.

At ratios of L/D between 3.5/4.5, the resonant frequencies Fp2 and Fp1 are adjacent to or coincide with each other.

The width B of the piezoelectric plate 2 is greater than its thickness D and less than its length L.

The plate 2 may be divided by a virtual vertical symmetry plane S1 extending perpendicular to the side faces 15 and parallel to the end faces 16. The symmetry plane S1 divides the length L and the main faces 13, 14 of the board 2 into two equal parts.

In addition, the plate 2 may be divided by an imaginary longitudinal symmetry plane S2 extending perpendicularly to the end face 16 and parallel to the main planes 13, 14. The plane S2 divides the thickness D of the plate and the end face 16 of the plate 2 into two equal parts.

dotted line 17 and dotted line 18 indicate the intersection of the planes of symmetry S1 and S2 with the surfaces 13, 14, 15, 16 of the plate 2. The two planes S1 and S2 divide the plate 2 into four equal-volume zones 19, 20, 21 and 22.

Fig. 4 shows the ultrasonic actuator according to fig. 3, on one of its end faces 16 a friction element 3 is arranged.

The plate 2 of the ultrasonic actuator 1 is divided into four equal or identical volume regions 19, 20, 21 and 22, wherein each volume region together with a respective electrode (not shown in fig. 4) forms a generator G1, G2, G3, G4 to form an acoustic standing wave and to form a static bending deformation. The respective generator G1, G2, G3, G4 may be formed by the total volume of the respective volume region 19, 20, 21, 22 or by only a part of the respective volume region.

The diagrams 23 to 26 in fig. 5 show different views of the ultrasonic actuator according to fig. 3 and 4 and possible embodiments of the electrodes of the ultrasonic actuator.

In these drawings, fig. 23 and 26 show the electrode structures on the side surface 15, and fig. 24 and 25 show the electrode structures on the main surfaces 13 and 14.

Each generator G1, G2, G3 and G4 comprises a strip-shaped excitation electrode 27 and a strip-shaped common electrode 28 arranged on the main face 13 and the main face 14, respectively, of the plate 2, wherein a piezoelectric material or a piezoceramic material is arranged between adjacent strip-shaped electrodes 27, 28, respectively. The arrow with the label p indicates the direction of polarization of the piezoceramic material between the electrodes 27 and 28.

Generator G1 comprises strip-shaped excitation electrodes 27 and strip-shaped common electrodes 28 which are arranged on main surface 13 and can be assigned to volume region 19, and piezoceramic material arranged between strip-shaped common electrodes 27 and 28.

Generator G2 comprises strip-shaped excitation electrodes 27 and strip-shaped common electrodes 28 which are arranged on main surface 13 and can be assigned to volume region 20 of plate 2, and piezoceramic material arranged between electrodes 27 and 28.

Generator G3 comprises strip-shaped excitation electrodes 27 and strip-shaped common electrodes 28 which are arranged on main surface 14 and can be assigned to volume region 21 of plate 2, and piezoceramic material arranged between electrodes 27 and 28.

Finally, the generator G4 comprises strip-shaped excitation electrodes 27 and strip-shaped common electrodes 28 which are arranged on the main face 14 and can be assigned to the volume region 22 of the plate 2, and piezoceramic material arranged between the electrodes 27 and 28.

The strip-shaped excitation electrodes 27 of generator G1 have terminals 29 arranged on side 15, while the strip-shaped excitation electrodes 27 of generator G2 have terminals 30 arranged on the same side 15.

The strip-shaped excitation electrode 27 of generator G3 has a terminal 31 and the strip-shaped excitation electrode 27 of generator G4 has a terminal 32, wherein both the terminal 31 and the terminal 32 are arranged on the same side 15, which side 15 is opposite to the side on which the terminals 29 and 2930 are arranged.

The common strip electrode 28 has terminals 33 arranged on both side faces 15.

All the strip-shaped electrodes 27 and 28 are arranged parallel to the symmetry plane S1, and the polarization direction of the piezoceramic material of the piezoelectric plate 2 between the electrodes 27 and 28 is perpendicular to the electrodes 27 and 28.

The distance k between the adjacent strip-shaped excitation electrodes 27 and the strip-shaped common electrodes 28 is equal to or less than half the thickness D of the piezoelectric plate 2.

The width m of the strip-shaped electrodes 27 and 28 is in the range between 0.1mm and 0.5 mm.

The strip-shaped electrodes 27 and 28 can be applied to the main faces 13 and 14 of the plate 2 during the chemical deposition of nickel, or by vacuum deposition, or by thermal deposition of chromium, copper or nickel, or by ion plasma sputtering of chromium, copper, nickel or gold. The structure of the strip-shaped electrodes 27 and 28 can be produced by laser milling, by lithographic chemical etching, by spraying or in a mask printing process.

The number of strip-shaped electrodes 27 and 28 on the surfaces 13 and 14 is only limited by the technical manufacturing possibilities.

In the generators G1, G2, G3 and G4 with strip-shaped excitation electrodes and common electrodes 27 and 28 according to fig. 5, the piezoelectric coefficient d33 is used to excite the acoustic standing wave in the ultrasonic actuator.

Fig. 6 shows different views of the ultrasonic actuator according to fig. 3 and 4 and a further embodiment of the electrodes of the ultrasonic actuator in diagrams 34 to 37.

Fig. 6 shows a side view of the ultrasonic actuator at 34, a bottom view of the ultrasonic actuator at 35, a top view of the ultrasonic actuator at 36, and a view of the side face 15 disposed opposite to the side face shown at 34 at 37.

In this embodiment of the ultrasonic actuator of the ultrasonic motor according to the present invention, each of the generators G1, G2, G3, and G4 includes a planar excitation electrode 38, a planar common electrode 39, and a piezoceramic material disposed between the electrodes.

The planar excitation electrode 38 is arranged on the main faces 13 and 14 spaced apart from each other, while the planar common electrode 39 is arranged on the inner face 40 of the piezoelectric plate 2 coinciding with the longitudinal symmetry plane S2.

The polarization directions of the piezoelectric material of the ultrasonic actuator are perpendicular to the planar electrodes 38 and 39, respectively.

Generator G1 comprises a planar excitation electrode 38 arranged on main face 13 and assignable to a volume region 19 of plate 2, and a portion of a planar common electrode 39 arranged on inner face 40 and assignable to volume region 19.

Generator G2 comprises a planar excitation electrode 38 arranged on main face 13 and assignable to a volume region 20 of plate 2, and a portion of a planar common electrode 39 arranged on inner face 40 and assignable to volume region 20.

Generator G3 comprises a planar excitation electrode 38 arranged on main face 14 and assignable to a volume region 21 of plate 2, and a portion of a planar common electrode 39 arranged on inner face 40 and assignable to volume region 21.

Generator G4 comprises a planar excitation electrode 38 arranged on main face 14 and assignable to a volume region 22 of plate 2, and a portion of a planar common electrode 39 arranged on inner face 40 and assignable to volume region 22.

Each of the planar excitation electrodes 38 of the generators G1, G2, G3 and G4 comprises an electrical terminal 41, 42, 43 and 44 arranged substantially centrally, while the planar common electrode 39 provides two electrical terminals 45, each of which is arranged on the side face 15.

In the embodiment of the generators G1, G2, G3 and G4 according to fig. 6 with planar excitation electrodes 38 and planar common electrodes 38 and 39, the piezoelectric coefficient d31 is used for the excitation of the acoustic standing wave.

The planar excitation electrodes 38 may be made of a material and may be fabricated according to the techniques previously described for the strip-shaped excitation electrodes and the universal electrodes with respect to fig. 5.

The planar common electrode 39 is located on the inner face 40 and can be produced in an inert gas atmosphere by a synthesis process from copper, silver, palladium or an alloy together with the piezoceramic material of the piezoceramic plate 2. The planar common electrode 39 may also be made of a conductive ceramic material.

The illustration 46 of fig. 7 shows a perspective view of the ultrasonic actuator according to fig. 5 with the friction element 3 arranged on one end face 16 thereof; while illustration 47 of fig. 7 shows a perspective view of the ultrasonic actuator according to fig. 6 with a friction element 3 arranged on one end face 16 thereof. It can be seen that in both cases the friction element 3 is arranged substantially centrally with respect to the thickness D and extends over the entire width B of the ultrasonic actuator 1.

The diagram 48 of fig. 8 shows a circuit for operating the ultrasonic actuator 1 according to fig. 5 with the method according to the invention, wherein the ultrasonic actuator 1 comprises strip-shaped excitation electrodes 27 and strip-shaped common electrodes 28, and the circuit comprises separating capacitors C1, C2, C3 and C4 and separating resistors R1, R2, R3 and R4.

The capacitance of the separation capacitors C1, C2, C3 and C4 is preferably equal to or greater than the capacitance Co of the actuator 1 between the electrodes 27 and 28 of the generators G1, G2, G3 and G4.

The values of the separation resistors R1, R2, R3, and R4 are preferably 5 to 10 times greater than the characteristic resistance Xo of the capacitor Co, where Xo is 1/2pFgCo and Fg is the operating frequency of the ultrasonic motor.

The diagram 49 of fig. 8 shows a block diagram relating to an electrical stimulation device 50 for performing the method according to the invention.

The driver device 50 comprises a single-phase generator 51 for generating an alternating voltage U1 at a terminal 52, a switch 53 having terminals 54, 55 and 56, a generator 57 for generating a static control voltage Es at a terminal 58, linear amplifiers 59 and 60 for the static voltages of terminals 61 and 62, and a controller 63 having an input 64, to which the static voltages E1 and E2 are applied.

All blocks of the excitation device 50 have a common output 65.

The control can be performed in a dynamic mode (dynamic operation mode) as well as in a static mode (static operation mode) by the actuation device 50.

The dynamic single-phase control generator 51 according to fig. 8 or fig. 15 is used to provide an electric single-phase alternating voltage U1 having a frequency Fg which is equal to the frequency Fp2 or to the frequency Fp1 or is arranged between or in the vicinity of these frequencies, respectively.

On the one hand, the voltage U1 is applied to the terminals 29 and 32 of the excitation electrodes 27 of the generators G1 and G4 via the terminal 54 of the switch 53 and the capacitors C1 and C4. On the other hand, the voltage U1 is applied via the common output 65 to the input 33 of the common electrode 28 of the generators G1 and G4.

The voltage U1 dynamically controls the generators G1 and G2, which simultaneously generate in the actuator 1 a second mode of acoustic bending standing waves that propagate longitudinally with respect to the length L and longitudinally with respect to the thickness D (see diagrams 66 and 67 of fig. 9), and a first mode of acoustic longitudinal wave standing waves that propagate longitudinally with respect to the length L (see diagrams 68 and 69 of fig. 9).

The dashed lines of the illustration 66 and the illustration 67 in fig. 9 show the shape of the maximum deformation of the plate 2 when the second mode of the acoustic bending standing wave propagates in the plate 2.

The dashed lines of the illustration 68 and the illustration 69 in fig. 9 show the shape of the maximum deformation of the plate 2 when the first mode of the acoustic longitudinal standing wave propagates in the plate 2.

The superposition of the bending standing wave and the longitudinal standing wave causes the point 70 (and other points) of the friction surface 71 of the friction element 3 to move continuously on an elliptical trajectory 72 in the directions indicated by the arrow and reference Vd, as shown in fig. 10. The shape of the ellipse and its inclination with respect to the friction surface 4 depend on the L/D ratio chosen.

The elliptical locus 72 of the points 70 and the other points forming the surface of the friction element 3 are arranged perpendicularly to the main faces 13 and 14 of the piezoelectric plate 2 of the actuator 1.

Since the friction surface 71 of the friction element 3 is pressed against the friction surface 4 of the element to be driven 5 by the force F, the elliptical trajectory 72 results in a continuous movement of the element to be driven 5 in the direction of the arrow indicated in the + Vd direction.

When switch 53 is actuated into a contact position with terminal 56 (dashed line of diagram 49 in fig. 8), voltage U1 reaches terminals 30 and 31 of electrodes 27 and 28 of generators G2 and G3, which are thereby dynamically energized.

The generators G2 and G3 thus simultaneously generate in the actuator 1 a first mode of an acoustic bending standing wave propagating longitudinally with respect to the length L and longitudinally with respect to the thickness D (see diagrams 66 and 67 of fig. 9), and an acoustic longitudinal standing wave propagating longitudinally with respect to the length L (see diagrams 68 and 69 of fig. 9).

When the switch 53 is actuated, the phase shift between the bending standing wave and the acoustic longitudinal standing wave propagating in the actuator 1 changes by 180 °. This reverses the direction of movement of the point 70 on its trajectory 72, as indicated by the arrow and the reference-Vd. This also reverses the direction of movement of the element 5 to be driven. Then, the member to be driven is moved in the opposite direction designated by the arrow and the reference numeral-Vd.

The direction of movement of the element 5 to be driven (indicated in fig. 1, 2, 10, 12 and 18 by the arrow and the reference V or Vd) extends perpendicularly to the main faces 13 and 14 of the piezoelectric plate 2 of the actuator 1.

In the dynamic operating mode of the method according to the invention, the drive path of the element 5 to be driven is in principle not limited, whereas the minimum drive step of the element 5 to be driven is determined by the surface roughness of the friction surfaces 71 and 4 of the friction element 3 and the element 5 to be driven. Most preferably, the drive steps are between 0.05 and 0.1 microns in length.

The static mode of operation of the method according to the invention is as follows: first, the dynamic operation mode is stopped by moving the switch 53 to the contact position with the terminal 55. In this position of the switch 53, the generators G1, G2, G3 and G4 are no longer dynamically driven because no voltage U1 is applied to the electrodes 27 and 28.

The dynamic voltage generator 57 provides a static control voltage Es at terminal 58 which can vary by a value 0 in the range of + Es to-Es. This voltage is amplified by linear amplifiers 59 and 60.

The quiescent voltage E1 is then applied to terminal 61 of amplifier 59 and varies by a value of 0 in the range of + Es to-Es. An inverted electrostatic voltage E2 is applied to terminal 62 of amplifier 60 and varies in a range between-E to + E.

On the one hand, the voltage E1 reaches the terminals 29 and 30 of the excitation electrode 27 of the generators G1 and G2 via the resistors R1 and R2. On the other hand, the voltage E1 reaches the terminal 33 of the common electrode 28 of the generators G1 and G2 via the common terminal 65.

Furthermore, the voltage E2 reaches, via the resistors R3 and R4, the terminals 29 and 30 of the excitation electrodes 27 of the generators G3 and G4, on the other hand the voltage E2 reaches the terminal 33 of the common electrode 28 of the generators G3 and G4.

The voltages E1 and E2 applied to the generators G1, G2 and G3, G4 of the actuators cause the piezoelectric plate 2 to statically bend or deform, as indicated by the dashed lines in graphs 73 and 74 in fig. 11.

The direction of the static bending is determined by the polarity of voltage E1 with respect to the polarity of voltage E2. The magnitude of the static bending depends on the magnitude of the voltages E1 and E2.

If voltage E1 equals voltage + E and voltage E2 equals voltage-E, then plate 2 bends, as shown in plot 73 of FIG. 11. The point 70 on the friction surface 71 of the friction element 3 moves on the trajectory 75 to the position 76 as shown in fig. 12.

Since the friction surface 71 of the friction element 3 is pressed by the force F against the friction surface 4 of the element 5 to be driven, the displacement of the point 70 into the position 76 causes the element 5 to be driven to translate a distance + d in the direction indicated by the arrow and the reference number + Vs.

When the polarity is changed (E1 equals-E and E2 equals-E), then the plate 2 bends, as shown by plot 74 in FIG. 11. In this case, the point 70 on the friction surface 71 of the friction element 3 moves on the trajectory 75 to the position 77 (see fig. 12).

the displacement of point 70 to position 77 causes the element 5 to be driven to translate a distance-d in the direction indicated by the arrow and the reference-Vs.

In the static operating mode of the method according to the invention, the maximum displacement of + d/-d, i.e. the maximum step size of the element 5 to be driven, is determined by the maximum values of the voltages E1 and E2. The maximum step size may reach values between 0.1 μm and 1 μm.

The minimum step size is determined by the rigidity of the structure of the clamping element 9. It may be in the range of 0.1nm to 1 nm.

The dynamic mode of operation of the method according to the invention can also be achieved by means of two-phase electrical voltages. The diagram 78 and the diagram 79 of fig. 13 show the corresponding circuit and the corresponding block diagram, respectively.

By means of a two-phase control, the generator 80 supplies the terminals 81 and 82 with two alternating voltages U1 and U2 having the same frequency Fg.

The voltages U1 and U2 are offset relative to each other by a phase angle fg +/-90 or by a different angle.

On the one hand, the voltage U1 is applied through the terminal 81 and the capacitors C1 and C4 to the terminals 29 and 32 of the excitation electrodes 27 of the generators G1 and G4, and on the other hand, the voltage U1 reaches the terminal 33 of the common electrode 28 of the generators G1 and G4 through the common terminal 65.

Furthermore, a voltage U2 is applied to the terminals 30 and 31 of the excitation electrodes 27 of the generators G2 and G3 via the terminal 82 and the capacitors C2 and C3, and a voltage U2 reaches the terminal 33 of the common electrode 28 of the generators G2 and G3 through the common terminal 65.

Each of the two pairs of generators G1, G4 and G2, G3 simultaneously generates in the actuator 1 a second mode of acoustic bending standing waves propagating longitudinally with respect to the length L and longitudinally with respect to the thickness D (see diagrams 66 and 67 of fig. 9) and a first mode of acoustic longitudinal standing waves propagating longitudinally with respect to the length L (see diagrams 68 and 69 in fig. 9).

The superposition of the acoustic bending standing wave and the acoustic longitudinal standing wave causes the point 70 of the friction surface 71 of the friction element 3 to move continuously on an elliptical trajectory 72, as shown in fig. 10. This results in the element 5 to be driven being displaced or driven accordingly.

Reversing the phase shift angle fg changes the direction of motion of the element to be driven.

Furthermore, in the method according to the invention, the dynamic mode of operation may be achieved by a two-phase electrical voltage having acoustic standing waves generated independently and simultaneously by two pairs of generators (such as G1 and G3 and G2 and G4). The diagrams 83 and 84 of fig. 14 show the corresponding circuits for this form of excitation.

In this case, the generators G1 and G3 form anti-phase generators, the generators G2 and G4 representing in-phase generators.

A pair of generators G1, G3 generates a second mode of acoustic bending standing waves in the actuator 1 that propagate longitudinally with respect to the length L and longitudinally with respect to the thickness D (see diagrams 66 and 67 of fig. 9). A pair of generators G2, G4 generates a first pattern of acoustic longitudinal standing waves in the actuator 1 that propagate longitudinally with respect to the length L (see diagrams 68 and 69 of fig. 9).

The superposition of the acoustic bending standing wave and the longitudinal standing wave results in a uniform movement of the point 70 of the friction surface 71 of the friction element 3 according to fig. 10 on an elliptical trajectory 72. This results in a driving movement of the element 5 to be driven.

The diagrams 85 and 86 of fig. 15 show a circuit for carrying out the method according to the invention with an ultrasonic actuator 1, wherein the generators G1, G2, G3 and G4 comprise a planar excitation electrode 38 and a planar common electrode 39 according to the diagram 47 in fig. 7. The dynamic operating mode is realized here by an electrical single-phase voltage U1.

The operating principle of the circuit according to fig. 17 is similar to that shown in fig. 8.

The diagrams 87 and 88 of fig. 16 show a circuit for realizing the dynamic operating mode of the method according to the invention by means of two-phase electrical voltages U1, U2, wherein the generators G1, G2, G3, G4 of the ultrasonic actuator 1 comprise a planar excitation electrode 38 and a planar common electrode 39.

The operating principle of the circuit according to fig. 16 is similar to that shown in fig. 13.

The diagrams 89 and 90 of fig. 17 show circuits for implementing the dynamic operating mode of the method according to the invention by means of two-phase electrical voltages U1, U2, in which the generators G1, G3 and G2, G4 are excited independently of one another.

The operating principle of the circuit according to fig. 17 is similar to that shown in fig. 14.

Figure 18 shows an ultrasonic motor adapted to operate according to the method of the invention, comprising an additional ultrasonic actuator 91 in addition to the main ultrasonic actuator 1.

In this motor arrangement, a clamping element 92 fixedly mounted on the motor housing 8 serves to fix the actuator 1 and the actuator 91. The actuator 1 and the actuator 91 are pressed against the clamping element 92 from two opposite sides by means of a stop 93 and a leaf spring 94. At the minimum value of the oscillation speed of the bending standing wave, the stopper 93 contacts the actuator 1 and the actuator 91.

The friction elements 3 of the actuator 1 and the actuator 91 are pressed against the friction surface 4 of the element 5 to be driven by a spring 95, which spring 95 acts on the actuator 1 and the actuator 91 via a lever 96 mounted on an axis 96.

It is thus possible to accurately balance the force F pressing the friction elements 3 of the actuator 1 and the actuator 91 against the friction surface 4 of the element 5 to be driven.