LT7111B - High-power piezoelectric rotary drive - Google Patents

Abstract

The invention is intended to create a high-power piezoelectric drive, allowing to achieve high torque, speed and stability of operation under high loads. The piezoelectric drive consists of a flexible ring-shaped stator (6), in which trapezoidal teeth (7) are arranged on both sides of the ring, with notches (8) formed in the horizontal axis of symmetry, and piezoelectric elements (9) are arranged between the teeth (7). Disk-shaped rotors (2) are pressed against the upper and lower double-sided trapezoidal teeth (7) in a spring-loaded manner through rigid friction elements (10), which are rotated by affecting the piezoelectric elements (9) with one or two electric harmonic signals, the frequency of which is matched to the resonant frequency of longitudinal vibrations of the flexible ring (6). When exciting the drive with two harmonic signals, their phase difference must be π/2. When excited by a single electrical signal, only one of the piezoelectric element groups (18, 19) is activated, while the other is left passive. By changing the harmonic signals to a sawtooth or rectangular signal, and combining the piezoelectric package groups (18, 19) into a common group, the inertial drive operating principle is obtained.

Description

FIELD OF THE INVENTION

The invention belongs to the fields of electro-mechanical, mechatronic systems and robotics. The design of the drive, its composition and operating principle can be applied in the creation of high-precision and high-power rotary motion systems, such as gyroscopic or spatial positioning systems, designed to control the position of objects in space or in a plane. Gyroscopic and other positioning systems created using these drives are applicable to the control, determination and adjustment of the spatial or planar position of small Earth satellites or other objects in a continuous cycle.

STATE OF THE ART

Small Earth satellites are increasingly used in communication, communications and other research areas, which creates a need for extremely precise control, adjustment and maintenance of the spatial or planar position of these objects. To achieve this goal, high-reliability, precision and high-power drives and actuators are used, which, depending on their scope of application, have strict requirements for mass and installation volume. In order to meet these requirements, piezoelectric drives and motors are increasingly used. Currently, several technical solutions and patents are known that propose and solve these technical problems.

Patent EP0449048A1 describes a piezoelectric rotary motion drive based on multilayer piezoelectric transducers. The drive structure consists of multilayer piezoelectric transducers, which are evenly distributed around a wavy rotor. Cylindrical tips or cylindrical rolling elements are mounted on the free ends of the transducers, which are pressed against the wavy rotor by friction. In order to obtain a rotary motion of the rotor, the piezoelectric multilayer transducers are affected by an excitation voltage, as a result of which longitudinal displacements of the transducers are created, which are converted through the tips of the transducers and the uneven rotor into a radial force that acts on the rotor and creates a rotary motion of the rotor. The drive is excited by a constant voltage, which is applied to the piezoelectric transducers at time intervals defined by the waviness of the rotor. Reversible actuator motion can be obtained by changing the excitation sequence of the piezoelectric multilayer transducers.

US patent US5955820A describes a piezoelectric ring-shaped rotary actuator. The actuator structure consists of a piezoelectric ring, on the upper and lower planes of which elastic cross-shaped asymmetric structures raised from the plane of the ring are attached. The lower, asymmetric structure is fixed stationary, and a rotor is pressed against the upper part of the structure by friction. The actuator operation is based on the radial vibration modes of the piezoelectric ring being excited by a harmonic electrical signal, which is fed to the upper and lower electrodes of the piezoelectric ring. By exciting the radial vibration mode of the piezoelectric ring, radial vibrations of the entire structure are created, which, thanks to the asymmetric structures and the method of mounting the drive, create radial, bending and longitudinal vibrations of the asymmetric structure, which create an elliptical motion trajectory in the contact zone of the stator and rotor, therefore, during contact, rotational motion of the rotor is created through the friction force.

Patent US6628045B2 describes a piezoelectric ring-shaped rotary actuator. The actuator consists of an elastic ring, on which rectangular teeth are formed on one side, to the tops of which a disk-shaped rotor is pressed by friction, and a piezoelectric ring is mounted on the other side of the elastic ring, the electrode of which is divided into equal parts. The operation of the actuator is based on the excitation of a traveling wave in the ring using bending vibrations, which are excited by two harmonic signals with a phase difference of π/2. When the vibrations of the traveling wave in the ring are excited, elliptical motion trajectories are formed at the tops of the teeth, which create a rotational motion of the rotor through friction. The geometric parameters of the teeth are selected so that they increase the amplitudes of the bending vibrations of the ring and ensure a higher rotor rotation speed and torque. The height of the teeth is directly proportional to the generated rotational speed of the drive, but when the drive is loaded with a greater force, the stator teeth begin to slip, which results in a decrease in the rotational speed and torque of the drive, increased wear of the contact area, and reduced reliability of the drive.

ESSENCE OF THE INVENTION

The essence and purpose of this invention is to increase the torque, speed, operating stability, reliability and expand the functional capabilities of a piezoelectric rotary motion drive.

The object of the invention is achieved by arranging trapezoidal teeth on the upper and lower surfaces of the elastic ring in a piezoelectric ring-shaped rotary motion drive, thus forming a double-sided trapezoidal tooth, and their location on the elastic ring is selected so as to coincide with the longitudinal oscillations excited in the annular stator, and the distance between the axes of symmetry of the teeth is equal to the wavelength of the longitudinal oscillations. The piezoelectric elements are permanently mounted between the trapezoidal teeth on the upper and lower ring surfaces so that the polarization directions of the elements located next to each other in the same plane are opposite and directed along the thickness of the elements. The piezoelectric elements located on the upper and lower ring surfaces have opposite polarization directions.

The torque of the drive is increased due to longitudinal resonant vibrations excited in the stator ring, which ensure the conversion of electrical energy into mechanical energy and stable operation at high engine loads, and due to the double-sided disk-shaped rotor, on the contact surface of which a ring made of a friction-resistant high-rigidity material, for example AI2O3, is fixedly mounted. The rotor rotation speed is increased due to the notch formed in the double-sided trapezoidal teeth. The length of the notch must not exceed 2/3 of the tooth width itself, which increases the amplitude of the oscillations of the tops of the trapezoidal teeth and reduces the total height of the drive.

The stability of the drive operation is increased by using trapezoidal teeth, the long base of which is placed on an elastic ring, which reduces their tripping under high axial loads. The functional capabilities of the drive are expanded by applying different excitation schemes and methods of individual piezoelectric elements or their groups.

DESCRIPTION OF DRAWINGS

Here and below, the rotary motion drive is described with reference to the drawings, but the technical implementation of the drive is not limited to the presented method. Various modifications and improvements to the method of implementation are possible.

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

(a) - isometric view of a piezoelectric rotary motion actuator;

(b) - exploded view of the piezoelectric rotary motion drive;

Fig. 2 a, b Schematic diagram of the stator of a piezoelectric rotary motion drive:

(a) - isometric view of the stator of a piezoelectric rotary motion drive;

(b) - exploded view of the stator of the piezoelectric rotary motion drive;

Fig. 3 a, b Excitation diagram of a piezoelectric rotary motion drive;

(a) - top view;

(b) - bottom view;

Fig. 4 Distribution diagram of double-sided trapezoidal teeth;

Fig. 5 Vibration modes of a rotary motion drive:

DRAWINGS - description of marked objects

- piezoelectric rotary motion actuators;

- disc-shaped rotor;

- compression spring;

- nut;

- shaft;

- elastic ring;

- double-sided trapezoidal tooth;

- notch;

- piezoelectric element;

- rigid frictional contact element;

- stator retaining ring;

- slider;

- piezoelectric reciprocating motion actuators;

- elastic square-shaped rod;

- signal generator;

- signal switching device;

- direction of polarization of piezoelectric elements;

- the first group of piezoelectric elements;

- second group of piezoelectric elements;

DETAILED DESCRIPTION OF THE INVENTION

Here and below, the drive is described with reference to the drawings, but the technical implementation of the drive is not limited to the methods presented. Various modifications and improvements to the implementation methods are possible.

Detailed description. The piezoelectric rotary motion drive consists of a resilient ring-shaped stator (1), in which radially arranged double-sided trapezoidal teeth (7), interconnected indestructibly forming a common ring-shaped statohaus (1) structure, and two disc-shaped rotors (2) pressed by a spring. A notch (8) is formed in the horizontal axis of symmetry of each double-sided trapezoidal tooth (7), which allows reducing the height of the double-sided trapezoidal teeth (7). Rigid friction contact elements (10) are placed on the upper and lower planes of the double-sided trapezoidal teeth (7). The friction elements (10) are in direct contact with two disc-shaped rotors (2), which are connected to the drive shaft (5). The rotor pressing force is changed via a pressure spring (3) by changing the vertical position of the nut (4) on the shaft (5). The average diameter of the elastic ring (6) of the statohaus drive (1) is selected so as to satisfy the condition D = nC/πί (where D is the average diameter of the elastic ring; n is an integer; C is the propagation velocity of the longitudinal vibration wave of the ring; f is the resonant frequency of the drive). Double-sided trapezoidal teeth (7) are placed in the longitudinal vibration lobes of the ring (6), and their height together with the height of the ring (6) is selected so as to be equal to or close to the half-wavelength of the bending vibrations. A notch (8) is formed in the horizontal axis of symmetry of the double-sided trapezoidal teeth (7), the length of which is selected so as not to exceed 2/3 of the total width of the tooth. On the upper and lower surfaces of the stator ring (6) of the piezoelectric rotary motion drive, piezoelectric elements (9) are mounted between the double-sided trapezoidal teeth (7), the polarization directions of the adjacent elements of which are opposite and directed along the thickness of the elements. The piezoelectric elements (9) located on the upper and lower surfaces of the ring have opposite polarization directions. The fastening of the piezoelectric rotary motion drive is realized using a stator fastening ring (11), which is indestructibly connected to the stator (1) in the nodal zones of longitudinal vibrations, and the fastening ring (11) itself is rigidly connected to other structural parts of the drive. When forming the rotary motion drive, two disk-shaped rotors (2) are slidably pressed against the rigid friction contact elements (10), which are interconnected by a shaft (5). The clamping force is formed by a clamping spring (3), the clamping force created by which is adjusted by changing the vertical position of the nut (4).

Description of the drive operation: In order to obtain the rotation of the disk-shaped rotors (2), the piezoelectric elements (9) are affected by harmonic or non-harmonic electrical signals through the signal generator (15) and the signal switching device (16) using different excitation schemes. In the first case, the rotational movements of the disk-shaped rotors (2) are obtained by affecting the first group of piezoelectric elements (18) with a harmonic electrical signal, the frequency of which coincides with the resonant frequency of the longitudinal vibrations of the elastic ring (6), while the second group of piezoelectric elements (19) remains passive, as a result of which longitudinal vibrations are excited in the elastic ring (6) due to the Poisson's ratio of the material, and at the same time asymmetric bending vibrations of the double-sided trapezoidal teeth (7). Due to the asymmetric excitation scheme and the bending vibrations of the double-sided trapezoidal teeth (7) coordinated with the longitudinal vibrations of the elastic ring (6), the rigid friction elements (10) form elliptical motion trajectories, thanks to which, through the friction force, the friction elements (10) in contact with the disk-shaped rotors (2) rotate them. In the second case, the groups of piezoelectric elements (18, 19) are affected by two harmonic signals, the phase difference of which is π/2, and the frequency coincides with the resonant frequency of the longitudinal vibrations of the elastic ring (6). As a result, longitudinal traveling wave vibrations are excited in the elastic ring (6), as a result of which the double-sided trapezoidal teeth (7) bend synchronously, forming elliptical motion trajectories of the friction elements (10) and, in contact with the rotors (2), creating rotational movements. In the third case, the groups of piezoelectric elements (18, 19) are generally connected and affected by a sawtooth or rectangular electrical signal, as a result of which non-harmonic longitudinal vibrations are excited in the elastic ring (6). Such an excitation method ensures non-harmonic asymmetric bending vibrations of the double-sided trapezoidal teeth (7). The motion trajectories of the rigid friction elements (10) in this case are curvilinear and the friction elements move at different speeds forward and backward, as a result of which a friction force of different magnitude is created between the friction elements (10) and the rotor (2) and an inertial principle of operation of the gears is obtained, which ensures the rotational movement of the rotor (2).

Claims (6)

DEFINITION OF THE INVENTION 1. A piezoelectric actuator comprising an elastic ring (6) on which trapezoidal teeth (7) are permanently mounted, piezoelectric elements excited by electrical signals (9) and two rotors (2) pressed against the trapezoidal teeth, characterized in that the piezoelectric elements (9) are plate-shaped and permanently mounted on the upper and lower flat surfaces of the elastic ring (6) between the trapezoidal teeth so that the polarization directions of adjacent piezoelectric elements (9) are opposite and directed along the thickness of the elements. 2. The drive according to claim 1, characterized in that the average diameter of the elastic ring (6) is selected so that the length of the ring is divided by an integer number of the wavelength of longitudinal vibrations, and the distance between the vertical axes of symmetry of the trapezoidal teeth (7) is equal to one or more wavelengths of longitudinal vibrations excited in the elastic ring (6). 3. The drive according to claim 1, characterized in that the position of the trapezoidal teeth (7) on the elastic ring (6) is selected so that it coincides with the longitudinal oscillation pulses of the ring. 4. The drive according to claim 1, characterized in that the rotary motion of the rotor is created by affecting the first group of piezoelectric elements (18) with a harmonic electrical signal, the frequency of which coincides with the resonant frequency of the longitudinal vibrations of the elastic ring (6), and the second group of piezoelectric elements (19) remains passive. 5. The drive according to claim 1, characterized in that the rotary motion of the rotor is created when the groups of piezoelectric elements (18, 19) are simultaneously affected by two harmonic electrical signals, the phase difference of which is π/2, and the frequency of the excitation signals is matched to the resonant frequency of the longitudinal vibrations of the elastic ring. 6. The drive according to claim 1, characterized in that the rotary motion of the rotor is created when the groups of piezoelectric elements (18, 19) are collectively connected and affected by a sawtooth or rectangular electrical signal, and the frequency of the excitation signals is matched to the resonant frequency of the longitudinal vibrations of the elastic ring.