CN102355159A - Resonance-type linear ultrasonic motor and control method - Google Patents

Abstract

The invention discloses a resonant linear ultrasonic motor and a control method, belonging to the technical field of ultrasonic motors. The stator base of the motor can be regarded as a combination of two counterweights, two rectangular beams (or rods) and two arc structures. The two rectangular beams are collinear in space, the outer ends are respectively connected with counterweights, and the inner ends are connected through two symmetrically arranged arc structures, and piezoelectric ceramics are pasted on the sides of the two rectangular beams. The arc structure acts as the driving foot of the stator, and contacts with the mover at the apex. The stator utilizes two vibration modes, and after superposition, the apex of the arc-shaped structure generates an elliptical trajectory movement, thereby pushing the mover to move through friction. The invention has the characteristics of simple structure, compactness, large thrust and the like.

Description

A resonant linear ultrasonic motor and its control method

Technical field:

The invention relates to a resonant linear ultrasonic motor and a control method, belonging to the technical field of ultrasonic motors. the

Background technique:

Ultrasonic motor is a new concept of special motor developed rapidly in the 1980s. Its general driving mechanism is: using the inverse piezoelectric effect of piezoelectric materials to excite elastic bodies to generate micro-amplitude vibrations in the ultrasonic frequency band, forcing the contact surface The mass point produces an elliptical trajectory motion, which is converted into the rotation or linear motion of the mover through the friction between the stator and the mover. Compared with electromagnetic motors, it has the advantages of variable structure, low speed and high torque, low noise operation, fast response, self-locking when power is off, good position and speed control, no magnetic field and no electromagnetic interference. Due to the above advantages, ultrasonic motors have been widely used in industrial automation, aerospace, medical, bioengineering and other fields, and have played a huge role. the

Linear ultrasonic motor is one of the more common ones. According to the working method, linear ultrasonic motor can be divided into resonant linear motor and non-resonant linear motor. The non-resonant linear ultrasonic motor is different from the traditional ultrasonic motor. Generally, the piezoelectric stack is used as the actuating unit. By controlling the static deformation of the piezoelectric stack, the motion trajectory of the contact surface particles is indirectly controlled. Its working mode is not related to the vibration mode, so it can work at a lower frequency. Since the movement trajectory of the contact surface particles comes from the static deformation of the elastic body, the thrust is relatively large and the displacement accuracy is high. But the disadvantages are: the maximum output speed is low, and the machining accuracy is very high; the resonant linear ultrasonic motor adopts the general working principle of the traditional ultrasonic motor, works in the natural vibration mode, the working frequency is generally high, and the thrust-to-weight ratio is relatively non-vibrational. The motor of the type is lower, but the maximum output speed is higher, and the manufacturing cost is lower. the

Invention content:

The invention proposes a resonant linear ultrasonic motor and its control method. The motor has the characteristics of simple structure, compactness, easy processing, miniaturization, large thrust and the like. the

The technical principle and scheme adopted in this patent are:

The resonant linear ultrasonic motor proposed by the present invention is composed of a stator, a mover, a base and accessories, including: a stator base, a piezoelectric ceramic, a base, a slider, a track, an alumina ceramic strip, a leaf spring, and a leaf spring tight Set screws, transverse set screws, longitudinal set screws, rail fastening screws, transverse springs and longitudinal springs. Among them, the slider and the alumina ceramic strip are bonded together to form the mover of the motor, which is installed on the track and can move linearly along the track, and the track is installed on the base through fastening screws. The stator base and the piezoelectric unit constitute the stator of the motor, which is placed in the base. An arc-shaped structure on the stator base acts as a driving foot, which is in contact with the mover (alumina ceramic strip) at its apex. The pre-set between the stator and the rotor The pressure is adjusted by the transverse set screw and the transverse spring, and the longitudinal set screw and the longitudinal spring are used to eliminate the longitudinal gap between the stator and the base, and to adjust the longitudinal pre-tightening force at the same time. Leaf springs are mounted on the upper side of the base to limit excess degrees of freedom of the stator.

The stator is the core of the entire motor, consisting of a stator base and piezoelectric ceramics. The stator base is a combination of two counterweights, two rectangular beams (or rods) and two arc structures. The two rectangular beams are collinear in space, the outer ends are respectively connected with counterweights, and the inner ends are connected through two symmetrically arranged arc structures, forming an integrated symmetrical structure. Piezoelectric ceramics are glued to the sides of the rectangular beams with epoxy. the

The stator has two specific modes of vibration. One vibration mode of the stator presents a symmetrical first-order longitudinal vibration mode in the left and right rectangular beam parts, and simultaneously squeezes or stretches the arc-shaped structure, forcing the apex of the arc-shaped structure to reciprocate in the vertical direction; the other of the stator The vibration mode presents an antisymmetric first-order longitudinal vibration mode in the two rectangular beam parts, which makes the apex of the arc-shaped structure reciprocate in the horizontal direction. In the above two vibration modes, the vibration amplitude at the counterweight is much smaller than that of the rectangular beam and the arc structure. After the above two vibration modes are superimposed, the reciprocating motion in the vertical and horizontal directions of the apex of the arc-shaped structure can be synthesized into an elliptical motion. the

The resonant linear ultrasonic motor proposed by the present invention works under the excitation of two sinusoidal voltage signals of the same frequency with a phase difference of 90°, and is characterized in that one of the sinusoidal voltage signals is applied to piezoelectric ceramics on both sides of a rectangular beam, and One working mode of the stator; another sinusoidal signal of the same frequency with a phase difference of 90° is applied to the piezoelectric ceramics on both sides of the other rectangular beam to excite another working mode of the stator. Under the excitation of the above two voltage signals, the two vibration modes of the stator will be excited at the same time, and the apex of the arc structure will synthesize an elliptical motion. When it is in contact with the mover, it can intermittently push the mover to output linear motion. When the excitation signal is exchanged, the direction of the elliptical motion will be reversed, and the direction of the output linear motion will also change accordingly. the

The resonant linear ultrasonic motor proposed by the present invention adopts the first-order symmetric and antisymmetric vibration modes of the two beams as the basic working mode of the stator. Through the transformation of the arc structure, an ellipse is finally superimposed on the apex of the arc structure. sports. The main functions of the two counterweights: (1) Make the two beams produce symmetrical and antisymmetrical vibration shapes; (2) Expand the amplitude of the connection between the rectangular beam and the structure, thereby expanding the displacement of the apex of the arc structure and improving the motor’s vibration. Maximum output speed and output force. The structure of the motor is simple and compact, easy to micro and miniaturized, and has a certain promotion value. the

Description of drawings:

Fig. 1 is a schematic diagram of the external structure of the resonant linear ultrasonic motor proposed by the present invention. Labels and symbol names in the figure: 1-stator base, 2-piezoelectric unit, 3-base, 4-slider, 5-track, 6-alumina ceramic strip, 7-leaf spring, 8-leaf spring fastening Screws, 9-horizontal set screws, 10-longitudinal set screws, 11-rail fastening screws. the

Fig. 2 is a schematic diagram of the internal structure of the resonant linear ultrasonic motor proposed by the present invention. Label and symbol name among the figure: 12-horizontal spring, 13-vertical and horizontal spring. the

Fig. 3 is the stator structure of the resonant linear ultrasonic motor proposed by the present invention. Labels and symbol names in the figure: 14-15-counterweight, 16-17-rectangular beam, 18-19-arc structure, 20-23-piezoelectric ceramics. the

Fig. 4 shows two vibration modes of the stator of the resonant linear ultrasonic motor proposed by the present invention. the

Fig. 5 is the steady-state response of the stator of the resonant linear ultrasonic motor proposed by the present invention. Labels and symbolic names in the figure: 1-ellipse motion track. the

Working principle and implementation method:

The specific implementation of the resonant linear ultrasonic motor will be described in detail below with reference to the accompanying drawings. the

The resonant linear ultrasonic motor proposed by the present invention is composed of a base, a stator, a mover and accessories. The structure is shown in Figure 1 and Figure 2, mainly including: 1-stator base, 2-piezoelectric ceramics, 3-base , 4-slider, 5-track, 6-alumina ceramic strip, 7-leaf spring, 8-leaf spring fastening screw, 9-transverse set screw, 10-set screw, 11-rail fastening screw, 12-transverse spring and 13-longitudinal spring. Among them, the 4-slider and the 6-alumina ceramic strip are bonded together to form the mover of the motor, which is installed on the 5-track and can move linearly along the 5-track. The 5-rail mounts to the 3-base with 11-rail fastening screws. 1-Stator base and 2-Piezoelectric ceramics constitute the stator of the motor, which is placed in the 3-base, and an arc-shaped structure on the 1-stator base acts as a driving foot, and at its apex it is connected with the mover (6-alumina ceramics Article) contact, the pre-pressure between the stator and the rotor is adjusted by two 9-horizontal set screws and 12-transverse springs, 10-longitudinal set screws and 13-longitudinal springs are used to eliminate the longitudinal gap between the stator and the base The gap is also used to adjust the longitudinal preload. 7-leaf springs are installed on the upper side of the base to limit the excess degrees of freedom of the stator. 3- There are 2 installation holes on the edge of the base for the installation of the motor. the

The stator of the above-mentioned resonant linear ultrasonic motor is the core of the whole motor, which is composed of a stator base and piezoelectric ceramics. The overall structure is shown in Figure 3. It is characterized in that the stator base body is a combination of two counterweights 14-15, two rectangular beams 16-17 (or rods) and two arc structures 18-19. The two rectangular beams are collinear in space, the outer ends are respectively connected with counterweights, and the inner ends are connected through two symmetrically arranged arc structures, forming an integrated symmetrical structure. The four pieces of piezoelectric ceramics 20-23 are respectively pasted on the four sides of the two rectangular beams through epoxy resin. the

The stator of the ultrasonic motor described above has two specific modes of vibration. It is characterized in that: a vibration mode of the stator presents a symmetrical first-order longitudinal vibration mode in the left and right rectangular beam parts (as shown in Figure 4 (1)), and at the same time squeezes or stretches the arc-shaped structure, forcing the arc-shaped structure The vertex part of the stator produces reciprocating motion in the vertical direction (in the coordinate system in the figure, along the Z-axis direction); the other vibration mode of the stator presents an antisymmetric first-order longitudinal vibration mode in the two rectangular beam parts (as shown in Figure 4 ( As shown in 2), when one beam shrinks, the other beam elongates, causing the apex of the arc-shaped structure to reciprocate in the horizontal direction (in the coordinate system in the figure, along the Y-axis direction). In the above two vibration modes, the vibration amplitude at the counterweight is much smaller than that of the beam and the arc structure. After the above two vibration modes are superimposed, the reciprocating motion in the vertical and horizontal directions of the apex of the arc-shaped structure can be synthesized into an elliptical motion. the

According to the design principles of ultrasonic motors, the frequencies of the above two vibration modes of the stator should be as consistent as possible, and at the same time, they should be as far away from the nearby interference modes as possible. These requirements can be achieved by adjusting the size of the structure. In addition, the counterweight at both ends needs to be reasonably selected in the design. The greater the quality of the counterweight, the smaller the vibration amplitude of the counterweight and the connection end between the counterweight and the rectangular beam, and the larger the vibration amplitude of the connection end between the rectangular beam and the arc-shaped structure, thereby enlarging the vibration amplitude at the apex of the structure and helping to increase the maximum motor Output speed and output force; at the same time, the smaller the amplitude of the counterweight, the smaller the impact of the pretightening force generated by the 13-longitudinal spring on the vibration mode of the stator. However, the greater the mass of the counterweight, the larger the volume of the stator. Therefore, in the actual design process, it is necessary to balance the size of the counterweight and the amplitude of the counterweight. the

The above-mentioned resonant linear ultrasonic motor works under the excitation of two sinusoidal voltage signals of the same frequency with a phase difference of 90°. It is characterized in that: one of the sinusoidal voltage signals is applied to piezoelectric ceramics on both sides of a rectangular beam to excite one Working mode: Another sinusoidal signal with the same frequency and a phase difference of 90° is applied to the piezoelectric ceramics on both sides of another rectangular beam to excite another working mode of the stator. In Fig. 3, the specific supply method of the driving signal is as follows: the ground electrode of the stator base, 7~8-the outer electrode of the piezoelectric ceramic is connected to the voltage signal: Usinωt; 9~10-the outer electrode of the piezoelectric ceramic is connected to the voltage signal: Ucosωt, where : U is the voltage value, ω is the modal frequency, and t is the time. the

Under the excitation of the above two voltage signals, the steady-state response of the stator of the above-mentioned resonant linear ultrasonic motor in one excitation cycle is shown in Figure 5 (obtained by ANSYS harmonic response analysis). In one excitation cycle, the stator undergoes four change steps from (1) to (4) in turn, and the motion trajectory of the apex of the arc structure (see point A in the figure) is: a→b→c→d→a, An ellipse in the YZ plane is formed. When the stator is installed in the 3-motor frame, and under the action of the 9-horizontal set screw and the 12-horizontal spring, the apex of the arc structure of the stator is in contact with the 6-alumina ceramic strip and maintains a certain preload , the elliptical motion at the apex of the structure can intermittently push the 6-alumina ceramic strip (mover), and output linear motion. When the excitation signals are exchanged, the motion direction of the apex of the structure will be reversed, and the direction of the output linear motion will also change accordingly. the

Claims (2)

1. A resonant linear ultrasonic motor is composed of a stator, a mover, a base and accessories, and the accessories include: a stator base, a piezoelectric ceramic, a base, a slider, a track, an alumina ceramic strip, a leaf spring, Leaf spring fastening screws, transverse set screws, longitudinal set screws, rail fastening screws, transverse springs and longitudinal springs, characterized in that: the stator of the motor is composed of a stator base and piezoelectric ceramics, and the stator base is two A combination of counterweight, two rectangular beams and two arc-shaped structures, the two rectangular beams are collinear in space, the outer ends of the rectangular beams are respectively connected to the counterweight, and the inner ends of the rectangular beams pass through two symmetrically arranged arc-shaped structures To connect, piezoelectric ceramics are pasted on the sides of two rectangular beams. 2. A control method based on a resonant linear ultrasonic motor according to claim 1, characterized in that: the ultrasonic motor works under the excitation of the same frequency sinusoidal voltage signals with a phase difference of 90° in two paths, wherein one path The voltage signal is applied to the piezoelectric ceramics on both sides of a rectangular beam; the other voltage signal with a phase difference of 90° is applied to the piezoelectric ceramics on both sides of the other rectangular beam; the stator of the motor has two specific vibrations Mode: In one vibration mode, the left and right rectangular beam parts present a symmetrical first-order longitudinal vibration mode, forcing the top of the arc-shaped structure to reciprocate in the vertical direction; in the other vibration mode, the two rectangular beam parts present antisymmetric The first-order longitudinal vibration mode makes the top of the arc-shaped structure reciprocate in the horizontal direction. After the two vibration modes are superimposed, the reciprocating motion in the vertical and horizontal directions at the apex of the arc-shaped structure synthesizes an elliptical motion.

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