LT7113B - PIEZOELECTRIC TRANSDUCER FOR HIGH POWER SLIDING MOVEMENT ACTUATORS - Google Patents

Abstract

Invention is focused on a high-power piezoelectric transducer, allowing for large linear motion force, speed, and operational stability under high loads. The piezoelectric transducer consists of a rectangular plate (4), in the center of which a double-sided trapezoidal tooth (6) is mounted, and cut (8) is formed on its vertical axis of symmetry. Piezoelectric plates (3) are mounted on the upper and lower surfaces of the rectangular plate (4). At the ends of the double-sided trapezoidal tooth (6), firmly mounted friction elements (7), rigid sliders (2) are pressed, whose linear motion is induced by applying a non-harmonic electrical signal to the piezoelectric plates (3), the frequency of which is equal to or close to the resonant frequency of the second longitudinal vibration mode of the rectangular plate (4). To obtain the linear motion of the sliders (2) in the opposite direction, the phase of the electrical signal must be reversed.

Description

FIELD OF THE INVENTION

The invention is attributed to the fields of electro-mechanical, mechatronic systems and robotics. The design of the converter, its composition and operating principle can be applied in the development of high-precision and high-power sliding motion drives used in gyroscopic, spatial or planar positioning systems designed to control the position of objects in space or in a plane. Gyroscopic or other positioning systems created using this converter are applicable to the determination and control of the spatial or planar position of small Earth satellites or other objects with high accuracy.

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 positions of satellites or devices installed on them. To achieve this goal, high-reliability, precision and high-power drives and converters are used, which, depending on their scope of application, have strict requirements for mass and volume. In order to meet the requirements, piezoelectric drives and converters are increasingly used. Currently, several technical solutions and patents are known that propose and solve these technical problems.

Patent CN216290731U describes a piezoelectric sliding motion actuator consisting of two Langevin-type piezoelectric transducers connected in a V-shaped structure through a solid mounting plate. The mounting plate is mounted so as to coincide with the nodal zones of the longitudinal vibration mode of the Langevin transducers and separate the groups of piezoelectric elements, and the free ends of the plate are fixedly fixed to the actuator body. The tops of the Langevin transducers are connected and form a contact zone. The slider is pressed against the contact zone by a spring, and its linear displacement is obtained when the groups of piezoelectric elements are excited by four independent electrical signals. In this way, elliptical trajectories of the contact zone are excited, which ensure the possibility of controlling the tangential displacement of the contact zone, as a result of which the sliding motion force created by the actuator can be increased or decreased.

Patent KR100965433B1 describes a piezoelectric bidirectional sliding motion actuator, which consists of a Langevin-type transducer consisting of two ring-shaped piezoelectric elements, a conical displacement concentrator, a counterweight and a fixing ring, interconnected by a fixing screw. Notches are formed in the conical displacement concentrator, thanks to which the amplitudes of the displacements of the contact zone are increased. The electrodes of the piezoelectric ring-shaped elements are divided into four equal parts so that by exciting the resonant bending vibrations of the transducer, it is possible to create multidirectional vibrations of the contact zone, necessary for obtaining the bidirectional movement of the slider. The transducer is pressed against the slider in a spring-loaded manner through the fixing ring, and thus a bidirectional sliding motion actuator is formed. In order to obtain a sliding motion, in one of the directions, pairs of electrodes of the Langevin transducer, located one against the other, are affected by two harmonic electrical signals, the frequency of which is equal to the resonant frequency of the second bending vibration mode of the transducer, and the phase difference is π/2. This creates an elliptical vibration trajectory of the contact zone, which ensures the possibility of exciting the linear motion of the slider. The direction of the slider movement is controlled by commutating electrical signals between the electrodes of the piezoelectric elements.

Patent CN102025286B describes a piezoelectric sliding motion actuator consisting of two square-shaped Langevin transducers, a rod and an actively controlled contact zone. The Langevin transducers consist of square-shaped counterweights, two piezoelectric plates and a fastening system element placed between the piezoelectric plates. The counterweights, piezoelectric elements and the fastening system element are fastened to the ends of the square-shaped rod by means of screws, thereby pressing the package to the rod and forming the actuator stator. In the center of the square-shaped rod, on one of the planes, a piezoelectric element is placed, on which a contact zone is placed, which is rigidly pressed against the slider, and the free ends of the fastening system are rigidly fixed. Thus, a sliding motion actuator is formed. In order to obtain the sliding motion of the slider, the transducers located at the ends of the square rod are affected by harmonic electrical signals with a phase difference of -π/2 and π/2, thus creating a longitudinal harmonic displacement of the entire structure, and the electrical harmonic signal with a phase of π is fed to the active contact zone. This ensures longitudinal displacements of the contact zone, the direction of which is perpendicular to the displacements of the entire statohaus. By synchronizing the vibrations of the contact zone and the entire drive structure, an elliptical trajectory of the contact zone movement is obtained, which ensures the sliding motion of the slider.

ESSENCE OF THE INVENTION

The essence and purpose of this invention is to increase the force, speed, operational stability and reliability of a piezoelectric transducer designed to create a sliding motion.

The object of the invention is achieved by the fact that in a piezoelectric transducer consisting of a flexible rectangular rod and piezoceramic plates mounted on its upper and lower surfaces, trapezoidal teeth are permanently placed in the center of the rod symmetrically on both sides of the rod, thus forming a double-sided trapezoidal tooth. The polarization directions of the piezoelectric plates are directed in the thickness direction and are opposite compared to neighboring plates located in the same plane or below it. The piezoelectric transducer is fixed cantilevered in places coinciding with the nodal zones of the second longitudinal vibration mode of the flexible rectangular rod.

The mechanical force generated by a piezoelectric transducer is increased when the frequency of longitudinal resonant vibrations excited in an elastic rectangular rod coincides with the frequency of the first bending mode of the trapezoidal tooth, and contact zones are formed at the tips of the teeth, in which friction elements made of a friction-resistant, high-stiffness material, such as AI2O3, are permanently placed.

The speed of displacement of the contact zone is increased due to the notch, which is formed in the double-sided trapezoidal tooth. The length of the notch is selected so that it is not more than 2/3 of the width of the elastic rectangular bar, which increases the amplitude of oscillations of the peaks of the double-sided trapezoidal tooth and reduces the total height of the double-sided tooth. The stability and reliability of the converter operation is increased by using a double-sided trapezoidal tooth, the wider base of which is permanently placed on the elastic rectangular bar, which reduces the tooth tripping under high transverse loads of the converter.

DESCRIPTION OF DRAWINGS

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

Fig. 1 Schematic diagram of a piezoelectric transducer with sliders;

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

(a) - isometric view of a piezoelectric transducer;

(b) - exploded view of the piezoelectric transducer;

Fig. 3 a, b Piezoelectric transducer excitation scheme;

(a) - top view;

(b) - bottom view;

Fig. 4 Vibration mode of a piezoelectric transducer.

DRAWINGS - description of marked objects

- piezoelectric transducer;

- rigid sliders;

- piezoelectric plates;

- elastic rectangular rod;

- anchoring brackets;

- double-sided trapezoidal tooth;

- rigid friction element;

- notch;

- signal generator;

- polarization directions;

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the piezoelectric transducer is described with reference to the drawings, but the technical implementation of the transducer is not limited to the methods presented. Various modifications and improvements of the implementation methods are possible.

Detailed description. The piezoelectric transducer (1) consists of an elastic rectangular rod (4), in the central vibration cavity of which the second longitudinal vibration mode has a non-removable double-sided trapezoidal tooth (6), the height of which is selected so as to be equal to the wavelength of the first bending vibration mode of the double-sided trapezoidal tooth (6), and rigid friction elements (7) are non-removable placed at the tops of the double-sided trapezoidal tooth (6). The transducer mounting brackets (5) are non-removable placed so that their longitudinal axial symmetry lines coincide with the nodal zones of the second longitudinal vibration mode of the elastic rectangular rod (4). The other end of the bracket is rigidly fixed in the transducer housing. By applying such a fastening, the vibration damping of the piezoelectric transducer (1) is reduced and the transducer power is increased. A notch (8) is formed in the transducer, the length of which is not more than 2/3 of the width of the elastic rectangular rod (4), formed so that its longitudinal axis of symmetry coincides with the zone of the second longitudinal vibration mode of the elastic rectangular rod (4), thus ensuring the lowest possible stiffness. Piezoelectric plates (3) are permanently placed on the upper and lower surfaces of the elastic rectangular rod (4), and the polarization directions (10) of these plates are directed in the thickness direction and aligned so that the polarization directions of the plates are opposite to each other. The piezoelectric transducer (1) is pressed against the rigid friction elements (7) in a spring-loaded manner, and due to the friction force that arises between the rigid sliders (2) and the rigid friction elements (7), the slider is driven forward or backward.

Description of the drive operation: In order to obtain the sliding movement of the rigid sliders (2), the piezoelectric plates (3) are affected by a non-harmonic sawtooth or asymmetric rectangular electrical signal through a signal generator (9), the frequency of which is equal to or close to the frequency of the second longitudinal vibration mode of the elastic rectangular rod (4), as a result of which asymmetric longitudinal vibrations of the second longitudinal mode are excited in the elastic rectangular rod (4). When excited in this way, asymmetric bending vibrations of the double-sided trapezoidal tooth (6) are generated and curvilinear motion trajectories of the rigid friction elements (7) are created, as a result of which the rigid friction elements (7) move back and forth at different speeds, thus creating friction forces of different magnitudes between the rigid friction elements (7) and the rigid sliders (2). This results in a system operating on the inertial principle, which ensures the sliding movement of the rigid sliders (2). In order to obtain the opposite direction of movement of the rigid sliders (2), the phase of the excitation signal is changed by 180 degrees.

Claims (6)

DEFINITION OF THE INVENTION 1. A piezoelectric transducer comprising a flexible rectangular rod (4) on which a double-sided trapezoidal tooth (6) is permanently mounted, at the tops of which rigid friction elements (7), piezoelectric plates (3) and rigid sliders (2) are mounted, characterized in that the piezoelectric plates (3) are permanently mounted on the upper and lower surfaces of the flexible rod, and their polarization directions (10) are selected so as to be opposite and directed in the thickness direction. 2. A transducer according to claim 1, characterized in that the position of the double-sided trapezoidal tooth (6) on the elastic rectangular rod (4) is selected so that it coincides with the central lobe of the longitudinal vibration mode. 3. The transducer according to claim 1, characterized in that the length of the elastic rectangular rod (4) is selected so that the natural frequency of the second longitudinal vibration mode of the rod (4) and the frequency of the first bending mode of the double-sided trapezoidal tooth coincide. 4. The transducer according to claim 1, characterized in that the elastic rectangular rod (4) has a notch (8) whose longitudinal axis of symmetry coincides with the center of the central lobe of the second longitudinal vibration mode of the elastic rectangular rod (4). 5. The transducer according to claim 1, characterized in that the transducer is secured by means of mounting brackets (5), which are permanently connected to the elastic rectangular rod (4) in the nodal zones of the second longitudinal vibration mode. 6. The transducer according to claim 1, characterized in that the sliding movement of the slider is created by exciting the piezoelectric plates (3) with a single non-harmonic electrical signal, the frequency of which is close to or equal to the resonant frequency of the second longitudinal vibration mode of the elastic rectangular rod (4).