LT6981B - Piezoelectric sliding-rotary motion drive - Google Patents

Abstract

The invention discloses a high-precision piezoelectric actuator that provides independent rotational and sliding motion of the rotor or sliding motion of the flat slider in a plane. The piezoelectric drive comprises a piezoelectric actuator (1) consisting of an elastic double elliptical-shaped stator (6), four multilayer piezoelectric transducers (7) arranged two in each elliptical-shaped vibration transducer (11, 12) in the direction of the major ellipse axis and a rigid frictional contact element (9) attached to the elastic bridge (10) that connects the two elliptical-shaped vibration transducers. The contact element is in the sliding contact with the preloaded rotor that can be implemented as a cylindrical rod (3) or a plate-shaped slider (13). Rotary - sliding motion of a cylindrical rod or sliding motion of the slider in a plane is obtained when multilayer piezoelectric transducers are excited by two electrical signals having a frequency equal to one of the resonant frequencies of the stator bending oscillations and a phase difference of π/2. The rotational motion of the cylindrical rod (3) is generated when two piezoelectric transducers located on the same side of the mounting plate (8) are excited by an electrical signal of the same phase, while the sliding motion is obtained when two piezoelectric transducers (7) located in the same elliptical-shaped vibration transducer (11, 12) are excited by an electrical signal of the same phase. The displacement resolution of the drive is increased when piezoelectric actuator (1) is excited by two asymmetric electrical signals with a frequency close to one of the resonant frequency of bending oscillations of the stator (6).

Description

FIELD OF THE INVENTION

The invention belongs to the fields of electro-mechanical, mechatronic systems and robotics. It is an actuator designed to create high-precision multi-function rotary and sliding motion systems, including reverse, and can be applied in precise angular and linear positioning systems, such as optical filter and laser beam positioning systems, as well as precision positioning systems for specimens and other objects.

STATE OF THE ART

With the rapid development of precision positioning, optics and microscopy systems, the aim is to increase their resolution and accuracy. When developing multi-functional precision multi-degree-of-freedom positioning systems, the problem is how to reduce the number of gears and the volume they occupy. The application of classical electromagnetic actuators in a multi-functional positioning system is limited due to the design features related to the fact that the electromagnetic actuator of the actuator creates a movement of one degree of freedom, which complicates the integration of actuators in multi-functional positioning systems with several degrees of freedom. One of the research directions is associated with the development of multi-functional piezoelectric actuators and actuators with several degrees of freedom, in which the rotary and sliding movement of the drive chain is not created by the electromagnetic principle, but by transforming electrical energy into high-frequency mechanical vibrations and linear or rotational displacement of the drive chain. By controlling the amplitudes of the mechanical oscillations of the actuator, it is possible to achieve the movement of the drive chain with nanometric precision of several degrees of freedom. This makes it possible to simplify the design of the drive, reduce the dimensions of mechatronic systems, increase the functionality of devices and create integrated mechatronic positioning systems.

A well-known piezoelectric actuator is described in the patent CN104967358A which provides the possibility to create rotary and sliding movement of the rod using the inertial operating principle. The actuator consists of a piezoelectric tube-shaped actuator with electrodes on the outer and inner surfaces. The outer electrode is divided across the tube into two equal parts, while the inner electrode of the tube is solid. One of the outer electrodes of the piezoelectric tube is additionally divided spirally in order to induce rotational deformations of the tube along the axis of the tube. Other actuator electrodes are used to excite longitudinal deformations of the tube. The elastic rod is placed along the axis of the piezoelectric tube and anchored at the free ends in anchoring mechanisms. In order to create a sliding movement of the drive chain, two sawtooth electrical signals with a phase difference of π are applied to the inner and outer electrodes of the piezoelectric tube, resulting in a sliding movement of the actuator's drive chain due to the asymmetric longitudinal mechanical vibrations of the piezoelectric actuator. In order to create a rotary movement of the drive chain, a single saw-shaped electrical signal is used, which is fed to a spirally divided electrode, thus exciting rotary mechanical vibrations of the actuator, which create rotary movements of the drive chain through anchoring mechanisms. The drive has a complex design, the principle of operation is based on low-efficiency vibration modes, the drive does not provide for the possibility of operation in step mode, and the dynamic characteristics of the rotary movement are limited by the characteristics of the interaction between the actuator and the drive chain.

Patent CN102843063B describes a piezoelectric actuator for rotary sliding motion. The drive structure consists of a rectangular bar stator with a threaded cavity formed along the stator. The outer surfaces of the rectangle are covered with eight piezoelectric plates polarized along the thickness of the plates. The gear drive link is a rod with an external thread screwed into a threaded cavity in the stator. Two harmonic electrical signals with a phase difference of π/2 are used to excite the drive. In order to obtain rotational-sliding displacements of the active part, the excitation signals are connected to the corresponding piezoelectric plates, and the frequency of the excitation signals is selected to coincide with the second bending deformation mode of the stator. When exciting the drive with this principle, the stator is deformed in two different directions, thus creating oscillations of the running wave, thus creating a rotary - sliding motion of the drive chain of the drive. The translational-rotational resolution of this drive is influenced by the pitch and precision of the threaded connection between the stator and the drive chain. Also, the design of this gear allows to obtain only synchronous rotary - sliding movement of the drive chain. In addition, non-systematic movement errors are possible in the drive due to the backlash of the threaded connection.

Patent CN106100437A describes a piezoelectric sliding motion actuator consisting of a flexible stator consisting of two diamond-shaped actuators connected in series by a high-stiffness coupling. In the short axes of the actuators, multi-layer piezoelectric transducers are fixedly installed. The free ends of the drive stator are secured immovably, and a contact surface is formed at the point of connection of the two diamond-shaped actuators, which contacts the rectangular slider. The friction force between the contact surface of the stator and the slider is regulated by an elastic ellipse-shaped spring, the stiffness of which is changed using a threaded drive. The operation of the drive is based on the inertial principle, when by exciting the piezoelectric transducers with two saw-shaped electric signals with a phase difference of π, a friction force of different magnitude is created between the stator and the slider, and thus the step sliding movement of the slider is generated. Reverse sliding motion is obtained by reversing the phases of electrical signals. The drive is characterized by the fact that the displacement amplitudes of the piezoelectric transducers and the pushing force of the slider are increased using diamond-shaped actuators. However, the drive does not provide for the possibility of creating a rotary slider motion and a plate-shaped slider sliding motion in the plane.

ESSENCE OF THE INVENTION

The purpose of the invention is to increase the performance, displacement resolution, dynamic characteristics and expand the functional possibilities of the piezoelectric actuator.

The aim of the invention is achieved by the fact that in the piezoelectric actuator consisting of a double-ellipse-shaped elastic stator, on the long axis of which four multilayer piezoelectric transducers are installed, connected to each other by a mounting plate into a single structure, on the outer surface of which a rigid contact element is fixed in the connecting bridge of the ellipses, and slidingly pressed driving links having in the form of a cylindrical rod or a flat slider, mechanical vibrations of the piezoelectric actuator are generated in the contact zone, which are transformed into rotation or displacement of the actuator's drive chain during frictional contact.

The rotational and linear speed of the drive link and the dynamic characteristics and performance of the piezoelectric actuator are increased due to the fact that in the elliptic actuator, the longitudinal oscillations of multilayer piezoelectric transducers excited by two harmonic electrical signals with a phase difference of π/2 are transformed into stator bending oscillations with amplitudes greater than multilayer piezoelectric transducers and resonant traveling wave oscillations are generated, and the location of the contact rigid element is selected on the elastic bridge connecting two elliptical oscillators, and the position of the piezoelectric actuator mounting plate is aligned with the short axis of the ellipses to reduce the vibration damping of the contact area due to the actuator in the case of rigid mounting, therefore, the amplitudes of vibrations in the contact zone of the drive link are increased.

The displacement resolution and accuracy of the rotary and sliding movement of the piezoelectric actuator drive chain is increased by exciting the multilayer piezoelectric transducers with two asymmetric electric signals with a frequency close to the resonant frequency of the traveling wave and a phase difference of π/2, resulting in a step motion of the drive chain whose resolution is directly dependent from the strength of the electrical signal and is equal to the resolution of the smallest generated step.

The functional capabilities of the piezoelectric actuator are expanded when a double ellipse on the surface of the stator, in which the contact element is fixed, separately excites the vibrations of the traveling wave in the longitudinal and transverse directions of the stator, as a result of which elliptical trajectories of the contact point movement are generated, the main axes of which are perpendicular to each other. Therefore, depending on the excitation scheme of the multilayer piezoelectric transducers, rotational or sliding displacements of the rod-shaped drive chain or flat slider displacements in the plane in two perpendicular directions are obtained. The independent movement of the sliding and rotary drive chain is obtained when the traveling wave oscillations of the actuator are excited in the longitudinal and transverse directions by non-matching frequencies of electrical signals.

In order to create an independent sliding or rotary motion of the driving circuit in the resonant mode, the phase difference of the excitation signals must be π/2, and the frequency is chosen to coincide, respectively, with the first transverse or longitudinal bending vibration mode of the double elliptical stator, and the excitation order of the piezoelectric transducers is chosen to coincide with the vibrational phases and directions of the bending strain modes.

DESCRIPTION OF DRAWINGS

The figures in the drawings are provided as an indication of the possible implementation of the invention and are not intended to limit the scope of the invention. None of the drawings and graphs presented should be considered as limiting, but only as examples of possible embodiments of the invention.

Fig. 1 a, b Principle diagram of a piezoelectric rotary-sliding motion drive:

- isometric piezoelectric rotary-sliding drive, view with rod;

- isometric view of a piezoelectric rotary-sliding actuator, with a flat slider;

(c) - exploded view of piezoelectric rotary-sliding actuators, rod view;

(d) - exploded view of piezoelectric rotary-sliding actuators, view with flat slider.

Fig. 2 a, b Schematic diagram of a piezoelectric ellipse-shaped actuator:

(a) - isometric view of the piezoelectric ellipse actuator;

(b) - expanded view of the piezoelectric ellipse actuator;

Fig. 3 Piezoelectric rotary-sliding drive excitation scheme;

Fig. 4 Bending vibration modes of the piezoelectric ellipse actuator used to obtain the motions of the drive chain;

(a) is the transverse bending mode used to obtain the rotary motion of the rod-shaped drive link;

(b) is the longitudinal bending mode used to obtain the sliding motion of the drive link;

DRAWINGS - description of marked objects

- piezoelectric elliptical actuator;

- piezoelectric actuator fastening screws;

- cylindrical rod;

- sleeve;

- drive mounting body, when the drive link is a cylindrical rod;

- double elliptical stator;

- multilayer piezoelectric transducer;

- mounting plate of the piezoelectric ellipse actuator;

- rigid frictional contact element;

- elastic bridge;

,12 - elastic elliptical vibration transducers;

- flat slider;

- drive mounting housing when the drive link is a flat slider;

- switchers of electrical excitation signals;

- two-channel electric signal generator.

DETAILED DESCRIPTION OF THE INVENTION

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

Detailed description of the drive. The piezoelectric rotary-sliding motion actuator consists of a piezoelectric elliptical actuator (1) and a spring-loaded actuator drive link, which can be realized as a cylindrical rod (3) or a flat slider (13). Elliptical piezoelectric actuator (1) consists of a stator (6), which consists of two identical elastic elliptical vibration transducers (11, 12), connected to each other by two elastic bridges (10), and four multilayer piezoelectric transducers (7), arranged in two in each vibration transducer (11, 12), ellipses in the direction of the long axis and one end rigidly fixed in the stator (6), and the other end elastically attached to the mounting plate (8), which is also used to mount the piezoelectric actuator (1) in the drive mounting body (5, 14). In the center or near the elastic bridge (10) of the piezoelectric actuator (1), a rigid frictional contact element (9) is fixed, to which the drive link of the actuator is slidably pressed, which can be a cylindrical rod (3) or a flat slider (13). The parts (10, 11, 12) of the double-elliptical stator (6) form a one-piece structure and are made of a solid elastic material such as steel or bronze.

The piezoelectric actuator is rigidly fixed in the housing (5, 14) with screws (2). The cylindrical rod (3) is fixed in the same body (5) using bushings (4), which ensure the sliding and rotating movements of the cylindrical rod (3). The flat slider (13) is placed on four supports in the housing.

Description of the operation of the piezoelectric actuator. The rotary movement of the cylindrical rod (3) or the linear displacement of the flat slider (13) in the direction of the long axis of the stator (6) is obtained when two harmonic electrical signals are supplied to the multilayer piezoelectric transducers (7) of the piezoelectric actuator (1) from the electrical signal generator (16), whose phase difference is π/2, and the frequency f is equal to the resonant frequency of one of the even bending modes of the stator (6), so that the multilayer piezoelectric transducers located on one side of the piezoelectric actuator mounting plate (8) are excited by a harmonic electrical signal of the same phase, which as a result, traveling wave vibrations are formed in both elliptical vibration transducers (11, 12) in the longitudinal direction, and the high-stiffness contact element (9) begins to move along an elliptical trajectory and contacts the spring-loaded cylindrical rod (3) or flat slider (13) and due to friction forces between the drive link surface and the contg the actuating element (9) receives the rotary movement of the cylindrical rod (3) or the sliding movement of the flat slider (13).

The sliding motion of the cylindrical rod (3) or the linear displacement of the flat slider in the direction perpendicular to the long axis of the ellipse is obtained when the multilayer piezoelectric transducers (7) are excited so that a harmonic signal of the same phase is fed to two multilayer piezoelectric transducers located in the same oscillator (11 , 12), as a result of which oscillations of the traveling wave are formed in the elastic bridge (10) and the rigid frictional contact element (9) begins to move along an elliptical trajectory, the direction of the long axis of which coincides with the longitudinal axis of the cylindrical rod (3). The reverse movement of the cylindrical rod (3) or the flat slider (13) in both directions is obtained by exchanging the phases of the electrical signals. In order to obtain stepwise rotary or sliding motions of a cylindrical rod (3) or a flat slider (13), multilayer piezoelectric transducers (7) are excited by two asymmetric pulsed electrical signals with a frequency close to the resonant frequency of the traveling wave and a phase difference of π/2.

Claims (3)

Piezoelectric rotary-sliding motion actuator, which includes a piezoelectric elliptical actuator (1), consisting of a double elliptical stator (6), multilayer piezoelectric transducers (7) and a rigid frictional contact element (9), differing in that the stator (6) has two elliptical the vibration transducers (11, 12) are interconnected by two elastic bridges (10), and a rigid frictional contact element (9) is placed on the outer surface of one of the elastic bridges (10). The drive according to claim 1, but differs in that the location of the elastic bridges (10) is selected so that the axis of symmetry of the bridge intersects the short axes of both elliptical vibration transducers (11, 12), and the resonant frequency of the even bending vibration mode of the bridges coincides with one of the ellipses at the resonant frequency of the bending vibrations of the shape vibration transducers (11, 12). The drive according to claim 1, but differs in that a rigid frictional contact element (9) is placed on the outer surface of the elastic bridge (10) of the piezoelectric actuator (1), to which a cylindrical rod (3) or a flat slider (13) is slidably pressed, and elliptical the movement trajectories of the contact element are obtained by exciting multilayer piezoelectric transducers (7) with two electrical signals whose phase difference is equal to π/2.