CN102237818A - Tower-like ultrasonic motor with asymmetrical structure and asymmetrical modes thereof as well as electric excitation mode of asymmetrical modes - Google Patents

Abstract

The utility model relates to an ultrasonic motor with an asymmetrical structure similar to a tower shape and an asymmetrical mode and electric excitation mode, belonging to the class of ultrasonic motors. The motor consists of a stator and a linear guideway. The guide rail is pressed against the stator drive foot by a preload. The stator as a whole is approximately tower-shaped, and includes two piezoelectric vibrators with unequal lengths and angles. Each piezoelectric vibrator includes a rear end cover, piezoelectric ceramics and electrode sheets, and a front end cover in turn; a front end cover and a rear end cover. The end cover is pressed and fixed by pressing bolts; the upper ends of the front covers of the two piezoelectric vibrators are connected together through a flexible hinge with a suddenly smaller cross-sectional area to form a driving foot. The stator is designed with two asymmetric working modes; when any one of the asymmetric working modes is excited, the motion trajectory of the surface particles driven by the stator is an oblique straight line, and the inclination direction of the oblique straight line changes with the change of the working mode , so as to promote the forward and reverse movement of the guide rail. The ultrasonic motor has large thrust, wide driving frequency and reliable operation.

Description

Asymmetric structure similar to tower-shaped ultrasonic motor and asymmetric mode and electric excitation method

Technical field:

The invention relates to an asymmetric structure similar to a tower-shaped ultrasonic motor and an asymmetric mode and electric excitation mode, belonging to the field of ultrasonic motors.

Background technique:

Ultrasonic motor is a new type of power output device that utilizes the inverse piezoelectric effect of piezoelectric ceramics and ultrasonic vibration. Among them, the linear motion ultrasonic motor is a kind of ultrasonic motor. Compared with the traditional electromagnetic motor, the ultrasonic motor has the advantages of low speed and high torque, fast transient response, high positioning accuracy, good control characteristics, no magnetic field and no magnetic field influence, etc. It has great advantages in precision drive, medical equipment, aerospace and other fields. Wide application prospects.

It is found through literature retrieval of existing approximate tower-shaped ultrasonic motors that Kurosawa et al. published "Transducer for High Speed" in "Ieee transactions on ultrasonics, ferroelectrics, and frequency control" (1998, Vol. 45, No. 5, No. 1188-1195). and Large Thrust Ultrasonic Linear Motor Using TwoSandwich-Type Vibrators", this paper analyzes the motion mechanism of a single-drive foot V-shaped large-thrust linear ultrasonic motor with a symmetrical structure in detail. Orthogonal symmetry-anti-symmetry vibration modes make elliptical motion on the mass point of the driving foot on the contact surface of the stator driving foot and the guide rail, and push the mover to move in a straight line. During the search, it was also found that "Design and Experimental Research of High-Speed and High-Thrust Linear Ultrasonic Motor" published by Li Yubao et al. The motion mechanism of a butterfly-shaped high-thrust linear ultrasonic motor with double-drive feet and a symmetrical structure is analyzed in detail. An elliptical motion is generated on the mass point of the foot, which pushes the mover to move in a straight line.

The linear ultrasonic motors proposed in the above two documents both excite two orthogonal vibration modes at the same time to generate elliptical motion on the particle of the stator on the contact surface between the stator and the guide rail to push the guide rail to move. There are following deficiencies in this:

1. To excite two orthogonal vibration modes at the same time, it is required that the two orthogonal working modes have similar resonant frequencies;

2. Due to the error of theoretical calculation and actual processing, plus the contact between the stator and the rotor when the motor is working, changes in temperature and load, there is a certain degree of difference in the resonance frequency of the two orthogonal working modes;

3. Under the excitation of a single frequency alternating signal, due to a certain degree of difference in the resonance frequency of the two orthogonal operating modes, the two orthogonal operating modes cannot be excited to the maximum at the same time, which affects the performance of the motor. The operating efficiency and performance also make the frequency domain that the motor can drive narrow.

One of the solutions to this problem is to use a single modality driven excitation method. The excitation method using a single mode drive has the following advantages: there is no frequency consistency problem of the composite mode ultrasonic motor; the frequency domain that can be driven is wide; the operating efficiency of the motor is high; the anti-interference ability is strong during operation; the drive can be simplified Power supply, easy to realize miniaturization and integration of power supply.

After searching the literature on the existing single-mode drive ultrasonic motor, it was found that "Bidirectional Standing Wave Linear Ultrasonic Motor" published by Qian Xiaohua et al. This paper proposes a rectangular plate type linear ultrasonic motor driven by a single mode, which has two working modes B3 and B4 (only one mode can participate in the work at the same time). When the B3 mode works, the mass point of the stator on the contact surface of the stator and the guide rail produces a rightward oblique linear motion, and the mover moves forward; when the B4 mode works, the mass point of the stator on the contact surface of the stator and the guide rail produces Slanted linear movement inclined to the left, the mover moves in the opposite direction. Its disadvantage is that the clamping position of the stator is not placed near the node, node line or node surface of the working mode, which will cause the impact of the clamping of the stator on the working mode and increase the energy loss; when the motor is working, only Half of the piezoelectric film is working, which is not conducive to improving the mechanical output performance of the motor; in order to take into account both forward and reverse motion, the position of the motor driving foot is not at the maximum amplitude, and the utilization rate of vibration energy is not high.

Invention content:

Aiming at the deficiencies of the prior art, the present invention proposes a single-mode drive, which can realize forward and reverse motion, simple structure, large output force, large thrust-to-weight ratio, high excitation efficiency, high vibration energy utilization rate, and fast response speed. The asymmetric structure is similar to the tower-shaped ultrasonic motor and the asymmetric mode and electric excitation method.

The asymmetric structure of the present invention approximates a tower-shaped ultrasonic motor, which is composed of a stator and a mover, wherein the mover is a linear guide rail, and the stator is composed of a first piezoelectric vibrator, a second piezoelectric vibrator and a driving foot. Under the action of pressure, it is pressed on the driving foot of the stator; it is characterized in that: the first piezoelectric vibrator and the second piezoelectric vibrator are asymmetrical, that is, the lengths of the first piezoelectric vibrator and the second piezoelectric vibrator are different, wherein The length of the first piezoelectric vibrator is L1, the length of the second piezoelectric vibrator is L2, and L1>L2.

The asymmetric structure of the present invention approximates to a tower-shaped ultrasonic motor, which is characterized in that the above-mentioned stator is V-shaped or U-shaped.

The asymmetrical structure of the present invention approximates to a tower-shaped ultrasonic motor, which is characterized in that the above-mentioned piezoelectric vibrator is a piezoelectric ceramic sheet bolt fastening type or a piezoelectric ceramic sheet pasting type.

The asymmetric structure of the present invention approximates the two asymmetric vibration modes used by the tower-shaped ultrasonic motor, and is characterized in that the two asymmetric vibration modes are respectively the first asymmetric vibration mode and the second asymmetric vibration mode, Wherein the resonance frequency of the first asymmetric vibration mode is ω ₁ , the resonance frequency of the second asymmetric vibration mode is ω ₂ , and ω ₁ <ω ₂ . The characteristics of the mode shape of the first asymmetric vibration mode are: the first piezoelectric vibrator with a length L1 is a local longitudinal-bending composite vibration, and the second piezoelectric vibrator with a length L2 is a local bending vibration. The characteristics of the mode shape of the second asymmetric vibration mode are: the first piezoelectric vibrator with a length L1 is a local bending vibration, and the second piezoelectric vibrator with a length L2 is a local longitudinal-bending composite vibration.

The asymmetrical structure of the present invention is similar to the electric excitation mode of the asymmetrical mode of the tower-shaped ultrasonic motor, which is characterized in that: the direction of movement of the guide rail to the second piezoelectric vibrator is the positive direction, and the direction of movement of the guide rail to the first piezoelectric vibrator is the opposite direction; when the first piezoelectric vibrator excitation signal and the second piezoelectric vibrator excitation signal input the same excitation signal E ₁ =Vsin(ωt), and the excitation frequency ω is located at the resonant frequency ω ₁ of the first asymmetric vibration mode Nearby, the first asymmetric vibration mode of the stator will be excited, so that the motion track of the mass point on the end surface of the driving foot is a reciprocating linear motion inclined to the positive direction, thereby pushing the guide rail to move in the positive direction; when the first piezoelectric vibrator excitation signal and the second Piezoelectric vibrator excitation signal input same excitation signal E ₂ =Vsin(ωt), and the excitation frequency ω is located near the resonant frequency ω ₂ of the second asymmetric vibration mode, which will excite the second asymmetric vibration mode of the stator, so that The trajectory of the mass point on the driving foot end surface is a reciprocating linear motion inclined in the opposite direction, thereby pushing the guide rail to move in the opposite direction.

Compared with the background technology, the innovations of the asymmetric structure similar to the tower-shaped ultrasonic motor and the asymmetric mode and electric excitation method of the present invention are:

1. Compared with the single-drive V-shaped high-thrust linear ultrasonic motor with symmetrical structure proposed by Kurosawa et al. in the article "Transducer for High Speed and Large Thrust Ultrasonic Linear Motor Using Two Sandwich-Type Vibrators", the symmetrical structure proposed by Kurosawa et al. The V-shaped high-thrust linear ultrasonic motor with a single drive foot uses two symmetric-antisymmetric vibration modes that are orthogonal and have similar resonance frequencies to generate elliptical motion on the particle of the drive foot on the contact surface between the stator drive foot and the guide rail, and push the mover linear motion. The asymmetric structure is similar to the tower-shaped ultrasonic motor, which uses two single-modes with a large difference in resonance frequency to work, so that the particle of the driving foot on the contact surface of the stator driving foot and the guide rail generates a reciprocating oblique linear motion relative to the guide rail, pushing The mover moves forward and reverse in a straight line.

2. Compared with the double-drive butterfly-shaped high-thrust linear ultrasonic motor proposed by Li Yubao et al. in the article "Design and Experimental Research of High-speed and Large-thrust Linear Ultrasonic Motor", the double-drive foot butterfly-shaped large-thrust linear ultrasonic motor proposed by Li Yubao et al. The thrust linear ultrasonic motor utilizes two symmetric-antisymmetric vibration modes that are orthogonal and have similar resonance frequencies, so that the particle of the driving foot on the contact surface of the stator driving foot and the guide rail produces an elliptical motion, and pushes the mover to move linearly. The asymmetric structure is similar to the tower-shaped ultrasonic motor, which uses two single-modes with a large difference in resonance frequency to work, so that the particle of the driving foot on the contact surface of the stator driving foot and the guide rail generates a reciprocating oblique linear motion relative to the guide rail, pushing The mover moves forward and reverse in a straight line.

3. Compared with the single-mode driven rectangular plate linear ultrasonic motor proposed by Qian Xiaohua et al. in "Bidirectional Standing Wave Linear Ultrasonic Motor", the clamping position of the stator of the single mode driven rectangular plate linear ultrasonic motor It is not placed near the node, nodal line or nodal surface of the working mode, which will cause the clamping of the stator to affect the working mode and increase the energy loss; At the maximum, the vibration energy utilization rate is not high. The clamping position of the asymmetric structure similar to the tower-shaped ultrasonic motor is placed near the node line of the working mode, which has little influence on the working mode and reduces energy loss; when the motor is working, all piezoelectric sheets participate in the work, which is beneficial to improve The mechanical output performance of the motor; at the same time, the position of its driving foot is at the maximum amplitude of the working mode, and the utilization rate of vibration energy is high.

4. The asymmetric structure of the present invention is similar to the tower-shaped ultrasonic motor and the asymmetric mode and electric excitation method. The biggest innovation points are: (1) Structural innovation. The asymmetric structure is similar to the tower-shaped ultrasonic motor stator. The lengths of the first piezoelectric vibrator and the second piezoelectric vibrator are not equal. This asymmetric structure makes the working mode of the stator symmetry-anti-symmetry with a resonant frequency close to the symmetrical structure. The vibration mode (Fig. 2) is dissimilated into two asymmetric working modes (Fig. 3) with a large difference in resonance frequency, and further makes the motor suitable for single-mode driving; (2) Innovation in the working mode. The asymmetrical structure is similar to the tower-shaped ultrasonic motor. The stator is designed with two asymmetrical working modes with different resonant frequencies, so that when the stator works in any one of the modes, the movement track of the stator-driven foot surface particles is an oblique straight line, and the oblique straight line The inclination direction of the guide rail changes with the change of the working mode, thereby pushing the guide rail to move forward and backward.

Description of drawings:

Fig. 1. Schematic diagram of the stator structure of an asymmetrical structure similar to a tower-shaped ultrasonic motor;

Figure 2. Schematic diagram of the working mode of the stator of the V-shaped linear ultrasonic motor with symmetrical structure;

Figure 3. Schematic diagram of the working mode of the stator of the asymmetrical tower-shaped ultrasonic motor;

Figure 4. Schematic diagram of the polarization arrangement and electrical excitation mode of the piezoelectric ceramics in the stator of the asymmetrical tower-shaped ultrasonic motor;

Figure 5. Figure 6. Schematic diagram of the working principle of an asymmetrical tower-shaped ultrasonic motor;

Fig. 7. The structural representation of the second embodiment (U-shaped structure and piezoelectric ceramic bolt fastening type) of an asymmetrical structure approximate tower-shaped ultrasonic motor;

Fig. 8. Schematic diagram of the polarization arrangement and electric excitation mode of piezoelectric ceramics in the second embodiment (U-shaped structure and piezoelectric ceramic bolt fastening type) of an asymmetric structure similar to a tower-shaped ultrasonic motor;

Fig. 9. The structural representation of the third embodiment (V-shaped structure and piezoceramic pasting type) of an asymmetric structure approximate tower-shaped ultrasonic motor;

Fig. 10. Schematic diagram of the polarization arrangement and electric excitation mode of piezoelectric ceramics in the third embodiment (V-shaped structure and piezoelectric ceramic paste type) of an asymmetrical structure similar to a tower-shaped ultrasonic motor;

Fig. 11. The structure schematic diagram of the fourth embodiment (U-shaped structure and piezoelectric ceramic paste type) of an asymmetric structure approximate tower-shaped ultrasonic motor;

Figure 12. Schematic diagram of the polarization arrangement and electric excitation mode of piezoelectric ceramics in the fourth embodiment (U-shaped structure and piezoelectric ceramic paste type) of an asymmetrical structure similar to a tower-shaped ultrasonic motor;

Label names in the figure: 1 first piezoelectric vibrator; 2 first rear end cover; 3 first compression bolt; 4 piezoelectric ceramic; 5 electrode sheet; 6 second piezoelectric vibrator; 7 second rear end cover; 8 Second compression bolt; 9 front end cover; 10 flexible hinge; 11 driving foot; 12 linear guide rail; 13 symmetrical vibration mode shape of symmetrical structure stator; The first asymmetric vibration mode shape of the structural stator; 16 The second asymmetric vibration mode shape of the asymmetric structure stator; 17 The polarization direction of piezoelectric ceramics; 18 Grounding; 19 The excitation signal of the first piezoelectric vibrator; 20 The second piezoelectric vibrator excitation signal; 21 The asymmetric structure stator works in the first asymmetric vibration mode to drive the movement track of the foot end surface particle; 22 The asymmetric structure stator works in the guide rail movement direction in the first asymmetric vibration mode; 23 Stator with asymmetric structure works in the second asymmetric vibration mode to drive the motion trajectory of the foot end surface particle; 24 stator with asymmetric structure works in the direction of guide rail movement in the second asymmetric vibration mode; 25 stator metal elastic body; 26 paste on the stator Piezoelectric ceramic discs on metal elastomers.

Detailed ways:

An asymmetrical tower-shaped ultrasonic motor with an asymmetrical mode and electric excitation method is shown in FIG. 1 . It is composed of a stator and a mover, wherein the mover is a linear guide rail 12 . Its characteristics are: under the action of pre-pressure, the guide rail 12 is pressed on the stator driving foot 11 . The stator includes a first piezoelectric vibrator 1 with a length of L1 and a second piezoelectric vibrator 6 with a length of L2, where L1>L2; the first piezoelectric vibrator 1 sequentially includes a first rear end cover 2, piezoelectric ceramics 4 and electrodes sheet 5, front end cover 9, front end cover 9 and first rear end cover 2 are compressed and fixed by first compression bolt 3; second piezoelectric vibrator 6 includes second rear end cover 7, piezoelectric ceramic 4 and electrode sheet in turn 5. The front end cover 9, the front end cover 9 and the second rear end cover 7 are compressed and fixed by the second compression bolt 8; wherein the piezoelectric ceramic 4 is placed on the front end cover 9 and the first rear end cover 2 or the second rear end cover 7, the electrode piece 5 is placed between every two pieces of piezoelectric ceramics 4; the upper ends of the front-end covers of the two piezoelectric vibrators are connected as a whole by a flexible hinge 10 whose cross-sectional area suddenly decreases to form a driving foot 11; the above-mentioned flexible hinge 10 is realized by processing three holes near the stator driving foot 11; the first piezoelectric vibrator 1 and the second piezoelectric vibrator 6 have an included angle, and the overall structure is a V-shaped or U-shaped structure that is approximately tower-shaped.

The two asymmetrical working modes of an asymmetrical tower-shaped ultrasonic motor stator are shown in Figure 3. When the geometric dimensions of the asymmetrical tower-shaped ultrasonic motor stator are determined, the resonant frequency and mode shape of the two asymmetrical working modes can be calculated by the finite element software ADINA. The resonant frequency of the first asymmetric vibration mode 15 of the asymmetric structure stator shown in Fig. 3 (a) is ω ₁ , the second asymmetric vibration mode 16 of the asymmetric structure stator shown in Fig. 3 (b) is The resonance frequency is ω ₂ , ω ₁ <ω ₂ . The mode shape characteristics of the first asymmetric vibration mode 15 are: the first piezoelectric vibrator (1) with a length of L1 is a local longitudinal-bending compound vibration, and the second piezoelectric vibrator (6) with a length of L2 is a local bending vibration, The trajectory of the mass point on the end surface of the driving foot 11 is a reciprocating linear motion inclined to the direction of the second piezoelectric vibrator (6); the mode shape characteristics of the second asymmetric vibration mode 16 are: the length of the first piezoelectric vibrator ( 1) is a local bending vibration, and the second piezoelectric vibrator (6) with a length of L2 is a local longitudinal-bending compound vibration, so that the motion track of the mass point on the end surface of the driving foot 11 is a reciprocating straight line inclined to the direction of the first piezoelectric vibrator (1) sports.

The polarization arrangement and electric excitation method of the stator piezoelectric ceramics of an asymmetrical tower-shaped ultrasonic motor are shown in Figure 4. The stator has four groups of eight piezoelectric ceramics in total, located between the front end cover 9 and the first rear end cover 2 or the second rear end cover 7, and each group contains a pair of piezoelectric ceramics with opposite polarization directions. The arrow direction 17 is the polarization direction of the piezoelectric ceramics, and the piezoelectric ceramics are polarized along the thickness direction, and the vibration of the stator is excited by the inverse piezoelectric d ₃₃ effect. Electrode sheets are placed in the middle of each group of piezoelectric ceramics for external connection of the first piezoelectric vibrator excitation signal 19 or second piezoelectric vibrator excitation signal 20; electrode sheets are placed on both sides of each group of piezoelectric ceramics for external connection of signal ground 18 . When the first piezoelectric vibrator excitation signal 19 and the second piezoelectric vibrator excitation signal 20 input the same excitation signal E ₁ =Vsin(ωt), and the excitation frequency ω is located near the resonant frequency ω ₁ of the first asymmetric vibration mode 15 , will excite the first asymmetric vibration mode 15 of the stator; when the first piezoelectric vibrator excitation signal 19 and the second piezoelectric vibrator excitation signal 20 input the same excitation signal E ₂ =Vsin(ωt), and the excitation frequency ω is at Near the resonant frequency _ω2 of the second asymmetric vibration mode 16, the second asymmetric vibration mode 16 of the stator will be excited.

The working principle of an approximate tower-shaped linear ultrasonic motor with asymmetric structure and asymmetric vibration mode is shown in Figure 5 and Figure 6. Let the moving direction of the guide rail to the second piezoelectric vibrator (6) be the positive direction, and the moving direction of the guide rail to the first piezoelectric vibrator (1) be the opposite direction; when the stator works in the first asymmetric vibration mode 15, the driving The mass point motion track 21 of the foot end surface is a reciprocating linear motion inclined to the positive direction, thereby pushing the guide rail to move along the forward direction 22; when the stator works in the second asymmetric vibration mode 16, the mass point motion track 23 of the driving foot end surface is in the opposite direction The tilted reciprocating linear motion pushes the guide rail in reverse direction 24 .

Structural Design Principles:

1. The first piezoelectric vibrator 1 and the first piezoelectric vibrator 6 of the stator have different lengths. The length of the first piezoelectric vibrator 1 is L1, and the length of the first piezoelectric vibrator 6 is L2, wherein L1>L2;

2. The size of the thinnest part of the flexible hinge 10 should be appropriate. The size of the thinnest part of the flexible hinge 10 directly affects the longitudinal vibration amplitude and strength of the stator. Therefore, the size of the thinnest part of the flexible hinge 10 should take into account the needs of the longitudinal vibration amplitude and strength of the stator.

3. The piezoelectric ceramic 4 is placed in front of the vibrating nodal surface, such an arrangement can make the vibration energy radiate to the driving foot 7 to the maximum extent.

Claims (5)

1. a unsymmetric structure is similar to the turriform ultrasound electric machine, constitute by stator and mover, wherein mover is a straight line guide rail (12), stator is by first piezoelectric vibrator (1) and second piezoelectric vibrator (6) and drive foot (11) and forms, and described guide rail (12) drives enough on (11) being pressed in stator under the effect of precompression; It is characterized in that: described first piezoelectric vibrator (1) and second piezoelectric vibrator (6) are asymmetric, promptly first piezoelectric vibrator (1) is different with second piezoelectric vibrator (6) length, wherein the length of first piezoelectric vibrator (1) is L1, and the length of second piezoelectric vibrator (6) is L2, L1＞L2.

2. unsymmetric structure according to claim 1 is similar to the turriform ultrasound electric machine, it is characterized in that: said stator is V-type or U type.

3. unsymmetric structure according to claim 1 is similar to the turriform ultrasound electric machine, it is characterized in that: above-mentioned piezoelectric vibrator is piezoelectric ceramic piece bolt matable or piezoelectric ceramic piece adhesive type.

4. the nonsymmetrical vibration mode of the approximate turriform ultrasound electric machine of unsymmetric structure according to claim 1, it is characterized in that: have two nonsymmetrical vibration mode to be respectively the first nonsymmetrical vibration mode (15) and the second nonsymmetrical vibration mode (16), wherein the resonance frequency of the first nonsymmetrical vibration mode (15) is ω ₁, the resonance frequency of the second nonsymmetrical vibration mode (16) is ω ₂, ω ₁＜ω ₂The vibration shape characteristics of the first nonsymmetrical vibration mode (15) are: length is that first piezoelectric vibrator (1) of L1 is the local buckling complex vibration, and length is that second piezoelectric vibrator (6) of L2 is local curved shaking; The vibration shape characteristics of the second nonsymmetrical vibration mode (16) are: length is that first piezoelectric vibrator (1) of L1 is local curved shaking, and length is that second piezoelectric vibrator (6) of L2 is the local buckling complex vibration.

5. utilize the electric excitation mode of the described nonsymmetrical vibration mode of claim 4, it is characterized in that: establishing guide rail is positive direction to the direction of motion of second piezoelectric vibrator (6), and guide rail is in the other direction to the direction of motion of first piezoelectric vibrator (1); As the first piezoelectric vibrator pumping signal (19) and the identical pumping signal E of the second piezoelectric vibrator pumping signal (20) input ₁=Vsin (ω t), and driving frequency ω is positioned at the resonance frequency ω of the first nonsymmetrical vibration mode (15) ₁Near, will excite the first nonsymmetrical vibration mode (15) of stator, make that driving sufficient end face particle motion trace is the linear reciprocating motion that tilts to positive direction, thereby promote guide rail along positive movement; As the first piezoelectric vibrator pumping signal (19) and the identical pumping signal E of the second piezoelectric vibrator pumping signal (20) input ₂=Vsin (ω t), and driving frequency ω is positioned at the resonance frequency ω of the second nonsymmetrical vibration mode (16) ₂Near, will excite the second nonsymmetrical vibration mode (16) of stator, make that driving sufficient end face particle motion trace is the linear reciprocating motion that tilts in the other direction, thereby promote guide rail along counter motion.

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