Shengjun Shi

A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot

A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot was proposed in this paper. The stator of proposed motor contains a horizontal transducer and a vertical transducer. Longitudinal vibrations are superimposed in the stator and generate an elliptical trajectory at the driving foot. The sensitivity analysis of structural parameters to the resonance frequencies of two working modes of the stator was performed using the finite element method. The resonance frequencies of two working modes were degenerated by adjusting the structural parameters. The vibration characteristics of stator were studied and discussed. A prototype motor was fabricated and measured. Typical output of the prototype is a no-load speed of 1160 mm/s and maximum thrust force of 20 N at a voltage of 200 Vrms.

A u-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 Vrms.

A new traveling wave ultrasonic motor using thick ring stator with nested PZT excitation

To avoid the disadvantages of conventional traveling wave ultrasonic motors?lower efficiency PZT working mode of d31, fragility of the PZT element under strong excitation, fatigue of the adhesive layer under harsh environmental conditions, and low volume of the PZT material in the stator- a new type of traveling wave ultrasonic motor is presented in this paper. Here we implement the stator by nesting 64 PZT stacks in 64 slots specifically cut in a thick metal ring and 64 block springs nested within another 64 slots to produce preloading on the PZT stacks. In this new design, the d33 mode of the PZT is used to excite the flexural vibrations of the stator, and fragility of the PZT ceramics and fatigue of the adhesive layer are no longer an issue. The working principle, FEM simulation, fabrication, and performance measurements of a prototype motor were demonstrated to validate the proposed ideas. Typical output of the prototype motor is no-load speed of 15 rpm and maximum torque of 7.96 N?m. Further improvement will potentially enhance its features by increasing the accuracy in fabrication and adopting appropriate frictional material into the interface between the stator and the rotor.

A cylindrical standing wave ultrasonic motor using bending vibration transducer.

A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200V(rms).

A Linear Ultrasonic Motor Using Bending Vibration Transducer with Double Driving Feet

A linear ultrasonic motor using bending vibration transducer with double driving feet was proposed. The motor consists of two exponential shape horns located on the two leading ends. Two orthogonal bending vibrations are superimposed in the motor and generate elliptical trajectories at the driving feet. The motion trajectories of the driving feet were deduced. Transient analysis was developed to gain the vibration characteristics of motor. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 990 mm/s and maximum thrust force of 12 N at a voltage of 150 Vrms.

A Cylindrical Traveling Wave Ultrasonic Motor Using Longitudinal Vibration Transducers

A cylindrical type traveling wave ultrasonic motor using longitudinal vibration transducers is proposed in this paper. A flexural traveling wave is excited in the cylinder by the longitudinal vibrations of transducers. The working principle of proposed motor is analyzed. The function of flexural traveling wave and motion trajectory of particle on the tooth are developed. The longitudinal resonant frequency of transducer and bending resonant frequency of cylinder are degenerated. A prototype motor is fabricated and measured. Typical output of the prototype is no-load speed of 290r/min and maximum torque of 1.95N·m at a voltage of 200Vrms.

An electromechanical coupling model of a bending vibration type piezoelectric ultrasonic transducer

An electromechanical coupling model of a bending vibration type piezoelectric ultrasonic transducer is proposed. The transducer is a Langevin type transducer which is composed of an exponential horn, four groups of PZT ceramics and a back beam. The exponential horn can focus the vibration energy, and can enlarge vibration amplitude and velocity efficiently. A bending vibration model of the transducer is first constructed, and subsequently an electromechanical coupling model is constructed based on the vibration model. In order to obtain the most suitable excitation position of the PZT ceramics, the effective electromechanical coupling coefficient is optimized by means of the quadratic interpolation method. When the effective electromechanical coupling coefficient reaches the peak value of 42.59%, the optimal excitation position (L1=22.52 mm) is found. The FEM method and the experimental method are used to validate the developed analytical model. Two groups of the FEM model (the Group A center bolt is not considered, and but the Group B center bolt is considered) are constructed and separately compared with the analytical model and the experimental model. Four prototype transducers around the peak value are fabricated and tested to validate the analytical model. A scanning laser Doppler vibrometer is employed to test the bending vibration shape and resonance frequency. Finally, the electromechanical coupling coefficient is tested indirectly through an impedance analyzer. Comparisons of the analytical results, FEM results and experiment results are presented, and the results show good agreement.

Design and fabrication of a linear ultrasonic motor using push-pull type L-B hybrid Langevin transducer with single foot

A linear ultrasonic motor using longitudinal and bending (L-B) vibration hybrid Langevin transducer was developed to achieve high output power. The motor consist two exponential shape horns intersected at tip ends where located a single driving foot. L-B vibrations were superimposed in the elastic body of the motor and generated elliptical trajectory at driving foot which can actuate linearly. The sensitivity analysis of structure parameters to the L-B resonant frequencies were performed using finite difference method based on the classical horn theory and flexural horn transfer matrix analysis method, and then degenerated frequencies to 27.476 kHz by choosing the most sensitive parameter. FEM simulation and impedance characteristic test agreed well with the calculated results. The coupling effect between two vibrations was studied and discussed through one phase driving phenomenon. Typical output performances of the prototype were no-load velocity of 1280mm/s and maximum driving force of 45N.

NUMERICAL SIMULATION OF BATOID LOCOMOTION

The hydrodynamics of batoid swimming motions is investigated using the three-dimensional simulation of a self-propelled body in still water. The kinematics of batoid swimming is characterized by large amplitude undulations of the pectoral fins while the middle part of the body remains straight. The majority of the thrust is generated by pectoral fins. Linear and quadratic amplitude variations are used for the pectoral fins in analyzing the locomotion of the batoid. Navier-Stokes equations are used to solve the unsteady fluid flow. A user defined function and a dynamic mesh method are applied to track the batoid locomotion. The mean swimming velocities of 1.6 BL/s and 1.3 BL/s are achieved, respectively, with thrust coefficients of 0.13 in and 0.095 in the dynamical simulation, where BL/s is the body length per second. The maximum propulsive efficiency 19% is achieved when the frequency of the undulation is 2.2 Hz in both amplitude variations.

A rotary ultrasonic motor using bending vibration transducers

A rotary ultrasonic motor using bending vibration transducers is proposed. In each transducer, two orthogonal bending vibrations are superimposed and an elliptical trajectory is generated at the driving foot. Typical output of the prototype is a no-load speed of 58 rpm and maximum torque of 9·5 N·m under an exciting voltage of 200 Vrms.