LT6867B - Piezoelectric rotary-sliding motion drive - Google Patents

Abstract

The invention discloses a flat piezoelectric drive which generates a rotational or sliding movement of a rotor along an axis. The piezoelectric drive consists of four rectangular metal plates (1) tightly connected by trapezoidal beams (18). Four piezoceramic plates (2), polarized in the thickness direction, are glued to the flat top and bottom surfaces of each metal plate. A circular hole (21) is made at the point of junction of the trapezoidal beams, and a double-sided rotor (6, 7) is spring-loaded against the upper and lower surfaces of the hole, or a high-stiffness rod (14) is mounted perpendicularly, by which a slider (13) moves. The beams (18) acts as waveguides by transmitting and transforming the bending oscillations of piezoelectric bimorph plates into the rotational or sliding motion of the rotor or slider, respectively. The rotary or sliding type of motion can be obtained by using different modes of bending oscillations of the actuator, which is excited by harmonic or asymmetric waveform electrical signals. Three excitation schemes can be used to excite the rotational movement, and one scheme can be used for the sliding movement. Changing the phases of the excitation signals results a reverse motion of rotor or slider. The piezoelectric drive can be adapted for mounting on a printed circuit board or can be integrated in mechatronics devices where the mounting volume of the motor is limited.

Description

FIELD OF THE INVENTION

The invention belongs to the fields of electro-mechanical, mechatronic systems and robotics. It is a device designed to develop high-precision multifunctional, compact rotary and sliding actuators, including reversible, and can be used in precision positioning systems such as optical lenses, filter positioning or laser beam guidance systems.

BACKGROUND OF THE INVENTION

With the rapid development of precision positioning or optical systems, mechatronic components must provide high positioning accuracy and take up less and less volume in the overall design of the system. Modern electronic components are easily reduced, so most of the drive volume consists of electromagnetic motors and drives, which are usually installed separately from electronic control systems due to relatively large drive dimensions, electromagnetic noise or design features. One of the research directions is related to the development of a new type of small-volume, multifunctional piezoelectric actuators, in which the rotational and sliding motion of the output circuit is generated not by the electromagnetic field, but by high-frequency mechanical vibrations of the stator. This simplifies the design of the drive, reduces the dimensions of mechatronic systems, increases electromagnetic noise, increases the functionality of the devices and creates integrated mechatronic systems.

A known piezoelectric actuator is described in CN101572505A (published in 2009) which is capable of asynchronously generating rotational or sliding motion in two different modes. There are two different gear connection methods for each operating mode. The piezoelectric drive consists of a square plate with a round hole in the center, two piezoelectric rings attached to both sides of the stator. The electrodes of the piezoelectric rings are divided into four equal parts, and there are four wedge-shaped contact zones at the bottom of the stator. The rotational motion of the drive is generated by excitation of the wave-type oscillations running in the stator. Due to the friction between the stator and the rotor, the excited mechanical vibrations create a rotational movement of the rotor. In order to obtain a sliding motion, stationary wave-type oscillations are excited in the drive stator, which are transmitted to wedge-shaped contact zones which, in contact with the output circuit, push it. The piezoelectric actuator has a limited range of displacement due to the principle of operation used to obtain the sliding motion, and the dynamic characteristics of the rotational motion are limited by the characteristics of the interaction between the stator and the rotor.

U.S. Pat. The outer electrodes of the piezoelectric rings mounted on both surfaces of the actuator are divided into four equal parts. A rod with an external thread is inserted in the center of the actuator, which together with the actuator forms a threaded drive. A four-phase electrical signal generator is used to excite the actuator, the phases of adjacent voltage signals differ by π / 2. The principle of operation of the drive is based on the excitation of the traveling wave type oscillations in the center of the actuator, which create the rotational movements of the threaded rod. Thanks to the threaded connection between the actuator and the rod, a sliding movement is also obtained. The direction of the sliding motion depends on the direction of propagation of the traveling wave. The drive creates a synchronous rotational and sliding motion, the direction of which can be changed by changing the phase values of the excitation signals via π. Due to the threaded connection between the actuator and the rod, the sliding and rotating movements are interrelated, which limits the application of such a drive.

JP2009219281A (published 2009) describes a piezoelectric actuator with two degrees of freedom that produces rotational and sliding motion of the output circuit. The drive consists of a hollow cube or octagonal parallelepiped actuator with a round hole in the center. Four or more piezoelectric plates mounted on the outer surface of the actuator, which, when exposed to electrical signals, generate mechanical vibrations of the traveling or standing wave type. Output circuit - the cylinder is placed in a hole in the center of the actuator. The oscillations generated in the actuator hole are transmitted to the output circuit, resulting in a sliding or rotational motion of the output circuit. Motion control requires six control signals with different frequencies and phases. This complicates the electronic control design of the drive. Also, the clamping force between the actuator and the output circuit cannot be adjusted dynamically, which limits the dynamic characteristics of such a drive.

SUMMARY OF THE INVENTION

The aim of the invention is to increase the dynamic characteristics, reliability, accuracy and expand the functionality of the piezoelectric drive.

The object of the invention is achieved in that a piezoelectric actuator consisting of a flat elastic bending oscillator consisting of four bimorph piezoelectric plates tightly connected by trapezoidal rods in a continuous structure and excited by a harmonic or asymmetric electric signal is excited which are transformed into rotor rotation. The rotational speed of the rotor, and thus the shaft, and the dynamic characteristics of the drive are increased by trapezoidal rods, which transform and increase the bending oscillations of the bimorph plates into contact zone rotations, and by notches vibrations amplitudes of the contact zone.

To increase the rotor speed, the passive layer of the piezoelectric actuator is made of a high mechanical quality rigid material and the rod length is selected to be a quarter of the wavelength of the rod bending oscillations.

The functionality of the piezoelectric actuator is extended and its reliability is enhanced by the rotor rotation using several different forms and frequencies of bending oscillations of the actuator, excited by the same generator of four-phase harmonic signals with π / 2 adjacent phases, but with different excitation schemes. which differ in that in the bimorph plate the phase of the excitation signal of the piezoelectric elements arranged in a row closer to the center is shifted by π.

When the electrodes of a piezoelectric bimorph actuator are excited by an asymmetric electrical signal with a frequency close to the bending oscillation mode of the piezoelectric actuator, the rotor is rotated in stepless mode with unlimited angular displacement and one lowest generated step resolution.

In order to extend the functionality of the piezoelectric drive, a high-stiffness rod is rigidly attached to the actuator center perpendicular to the plane of the actuator, on which a spring-loaded slider is placed. oscillation modes so that the oscillations in the perpendicular plane of bending are induced in the plates.

DESCRIPTION OF THE DRAWINGS

The drawings are provided as a reference to a possible embodiment of the invention and are not intended to limit the scope of the invention. None of the accompanying drawings and diagrams should be construed as limiting, but merely as exemplary embodiments of the invention.

Fig. 1 a, b Schematic diagram of piezoelectric drive:

(a) an exploded view of a rotary mode piezoelectric drive;

(b) an isometric view of a piezoelectric drive;

Fig. 2 a, b Schematic diagram of piezoelectric drive:

(a) an exploded view of a piezoelectric actuator operating in a sliding mode;

(b) an isometric view of a piezoelectric actuator operating in a sliding mode;

Fig. 3 Directions of polarization of piezoelectric plates:

(a) - top view;

(b) - bottom view.

Fig. 4 a, b Excitation scheme for a piezoelectric actuator operating in an out-of-plane bending oscillation mode:

(a) - top view;

(b) - bottom view.

Fig. 5 a, b Excitation scheme for rotary piezoelectric actuators excited by a harmonic signal in an in-plane bending oscillation mode:

(a) - top view;

(b) - bottom view.

Fig. 6 a, b Excitation scheme for rotary piezoelectric actuators excited by an asymmetrical signal in an in-plane bending oscillation mode:

(a) - top view;

(b) - bottom view.

Fig. 7 a, b Excitation scheme for piezoelectric actuator:

(a) - top view;

(b) - bottom view.

Fig. 8 a, b, c, d Piezoelectric actuator bending oscillation modes used for rotor rotation:

(a) - in - plane bending oscillation mode, using the excitation scheme shown in Figure 5;

(b) - the mode of bending oscillations in the perpendicular plane (angle, when the plate bends with respect to the axis of transverse symmetry and the excitation scheme shown in Figure 4 is used);

(c) - out-of-plane mode of bending, when the plate is bent with respect to the longitudinal axis of symmetry and the excitation scheme shown in Figure 4 is used.

Fig. 9 Piezoelectric actuator bending oscillation mode used to obtain the sliding motion of a slider. Excitation scheme used Figure 7.

DRAWINGS - description of marked objects actuator elastic plate with notches (piezoelectric actuator base, stator);

piezoelectric plates;

drive mounting housing (printed circuit board);

actuator mounting location;

rotor compression spring;

axis with hemispherical rotor;

hemispherical rotor;

rotor compression spring retainer;

compression spring retainer mounting bolts;

the contact zone between the hole of the piezoelectric actuator and the rotor;

piezoelectric actuator;

hyperelastic hollow cylinder;

one side of the slider;

high stiffness rod;

the direction of polarization of the piezoelectric plate directed away from the plane;

four-phase harmonic signal generator;

a two-phase asymmetric signal generator;

elastic trapezoidal rod;

rectangular notches in the axes of longitudinal symmetry of the elastic plates;

rectangular notches in the axes of transverse symmetry of the elastic plates;

circular hole in the center of the actuator in trapezoidal bars of rectangular notch elastic mounting bar

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the rotary-sliding motion piezoelectric drive is described with reference to the drawings, but the technical implementation of the piezoelectric drive is not limited as shown. Various modifications and improvements to the implementation method are possible.

Detailed drive description. The rotary-sliding piezoelectric actuator (Fig. 1) consists of a piezoelectric actuator (11) consisting of four resilient plates (1) connected by an elongated trapezoidal rod (18) at an angle of 90 ° to a single structure and thin piezoelectric plates which are polarized in the thickness direction and adhered to the upper and lower flat surfaces of the elastic plates (1) so that the polarization directions (15) of the piezoelectric plates (2) on the upper and lower surfaces are opposite (Fig.3). In order to reduce the stiffness of the piezoelectric actuator (11) and increase the oscillation amplitudes of the contact zone (10), a rectangular notch (19, 20) is formed in each elastic plate (1) along its longitudinal and transverse axis of symmetry. Additional rectangular cutouts (22) are also made in the elastic trapezoidal rods (18).

A round hole (21) is formed in the center of the actuator (11) to accommodate a first hemispherical rotor (7) having a diameter larger than the hole (17) and an axle with a rigidly mounted second hemispherical rotor (6) of the same size. The spherical (or conical) surfaces of both rotors (6) and (7) slip into contact with the edges of the round hole (21) of the actuator, thereby forming a contact area (10) between the actuator and the rotor. The first rotor (7) and the axle with the second rotor (6) are assembled in one system and pressed against the hole (21) by an edge spring (5) mounted on the axle (6) and locked by a lock (8), the position of which on the shaft is fixed by the fastener with bolts (9) which are pressed firmly against the axle and, due to the frictional force between the axle and the bolt, lock the position of the lock (8) on the axle. The clamping force of the rotor sides (6) and (7) can be varied by changing the position of the clamp spring (8) on the shaft. The piezoelectric actuator is rigidly mounted in the housing (3) at the appropriate mounting points (4) via short mounting rods (23), the length of which is chosen to isolate the propagation of vibrations into the housing.

The actuator parts (1, 18) can be made of a solid elastic material such as steel or bronze. In order to obtain the maximum oscillation amplitudes of the contact zone (10) and to increase the efficiency of the piezoelectric drive and the rotational speed of the rotor (6, 7), the lengths and widths of the notches (19, 20, 22) can be changed and the length of the rods (18) bending oscillation wavelength.

In order to extend the functionality of the piezoelectric actuator (Fig. 2), a high-stiffness rod (14) is rigidly fixed in the center of the piezoelectric actuator (11) at a hole perpendicular to the plane of the actuator, on which a slider consisting of two equally cut halves 13 ), which are pressed against the rod (14) by a cylindrical tube (12) made of hyperelastic material. The slider (13) can move along the rigid rod (14) in step mode when the electrodes of the actuator piezoelectric plates (2) are connected to an asymmetric signal generator (17) whose signal frequency is close to one of the bending oscillation modes of the plates (1) so that the plates would generate oscillations in a bending perpendicular plane (Fig.9).

Description of drive operation. There are four operating modes (variants) in the described drive. Three modes are used to obtain the rotational movement of the rotor and one option to obtain the sliding movement of the slider along the rigid rod.

operating variant. The first operating variant is illustrated in Figs. 1, 5, 8a. After applying to the electrodes of the piezoelectric elements (2), divided into four groups, a four-phase harmonic electrical signal with a phase difference π / 2 (Fig.5) and a frequency equal to one of the oscillations of the bending plane in the actuator (Fig. 8a) mechanical vibrations in the bending plane of the plates (1) are induced, which are transformed by means of elastic rods (18) into rotational movements of the hole (21) in the actuator plane, which are further transmitted to the double-sided rotor (6, 7). The rotational movement of the rotor (6, 7) is formed by the frictional force between the contact of the rotor surface and the actuator (11), all points of the annular surface of which move in elliptical trajectories in the plane of the actuator. The direction of rotation of the rotor (6, 7) is reversed when the electrical signals supplied to the electrodes of the piezoelectric elements (2) of the two opposite elastic plates (1) of the actuator are reversed. This variant of the piezoelectric drive allows a high rotor speed to be achieved.

operating variant. The second operating variant is illustrated in Figs. 1, 4, 8b, 8c. After applying to the electrodes of the piezoelectric elements (2), divided into four groups, a four-phase harmonic electrical signal with a phase difference π / 2 (Fig.4) and a frequency equal to the oscillation shape of one of the actuator plates in a bending perpendicular plane (Fig. 8b, 8c). ), the actuator induces mechanical oscillations of the plates (1) in a bending perpendicular plane, which are transformed into spatial elliptical movements of the points of the actuator contact zone (10) by means of elastic rods (18) which rotate the rotor (6, 7) about vertical. axis. The direction of rotation of the rotor (6, 7) is reversed when the electrical signals supplied to the electrodes of the piezoelectric elements (2) of the two opposite elastic plates (1) of the actuator are reversed. This version of the piezoelectric drive allows high rotor speed and torque to be achieved.

operating variant. The third operating variant is illustrated in Figs. 1, 6, 8a. Periodic asymmetrical rotational oscillations in the contact zone of the hole (21) are obtained by applying from the signal generator (17) the electrodes of the piezoelectric elements (2) divided into two groups an asymmetric two opposite phase signal (Fig. 6) with a frequency f close to the even bending of the actuator plates. in the plane of the oscillation form. Since the actuator (11) is slidably and sprungly connected to the rotor (6, 7) by a spring (5), the rotor rotates in a directional step mode with unlimited angular travel and a resolution of one of the smallest generated steps. The direction of rotation of the rotor (6, 7) is changed by reversing the phases of the asymmetric signal. This operating variant results in a high rotor rotation resolution.

operating variant. The fourth operating variant is illustrated in Figs. 2, 7, 9. The piezoelectric elements (2) are divided into two groups by applying an asymmetric two-phase signal (Fig. 7) to the electrodes, the frequency f of which is close to the oscillation mode in the bending plane of the elastic plate (1) (Fig. 9) and the phase difference is π, asymmetric longitudinal oscillations are generated in the high stiffness rod (14), which cause periodic stepwise sliding movements of the slider along the rod (14) with a resolution of one of the smallest generated steps. The direction of movement of the slider (13) is changed by reversing the phases of the asymmetric signal. Using this variant of operation, a high resolution of the sliding rotational movement of the slider (13) is obtained.

Claims (6)

A piezoelectric rotary-sliding actuator comprising a stator of four resilient plates (1) connected to each other at an angle of 90 ° and a circular hole (21) formed in the center of the connection with a contact zone and a rotating half-spherical half-spherical 7) with a spring clamping system (5, 8, 9) - piezoelectric excitation elements (2) glued to the upper and lower surface of the flat part of the plates (1) - characterized in that four elastic trapezoidal rods (18) are used to connect the elastic plates, in which one end is connected to the plates (1) and at the other end all the rods are connected to each other and perform the function of oscillating waveguides of the elastic plates (1) by transforming the bending oscillations of the plates into rotational movements of rotors (6, 7). The drive according to claim 1, characterized in that the length of the elastic rods (18) is selected to be a quarter of the wavelength of the bending oscillations of the rod, and the frequency of the bending oscillations of the rods coincides with the bending frequency of the elastic plates. Drive according to Claim 1, characterized in that a four-phase electrical signal with a phase difference of π / 2 is used to excite the rotation of the rotor (6, 7) and the frequency is equal to the bending plane of the resilient plate (1) or the bending perpendicular to the actuator (11). ) in the plane for the resonant frequency, and the direction of rotation of the rotor (6, 7) is changed by changing the phases of two signals with a phase difference π through π. The drive according to claim 1, characterized in that asymmetric signals are applied to excite the rotation of the rotor (6, 7) to the electrodes of the piezoelectric elements (2), the frequency of which is selected close to one of the oscillation modes in the bending plane of the plates (1). bending oscillations are induced. Drive according to Claim 1, characterized in that a high-stiffness rod (14) with a slidably pressed slider (13) is fixed rigidly in the center of the hole (21) in the center of the piezoelectric actuator (11) so that the slider can move longitudinally. The drive according to claim 5, characterized in that the movements of the slider along the rod (14) are obtained by asymmetric signals of the generator (17) applied to the electrodes of the piezoelectric elements (2) at a frequency close to one of the oscillations , so as to generate bending oscillations in the actuator (11).