Structural Design and Control of Variable Camber Wing Driven by Ultrasonic Motors

A novel variable camber wing driven by ultrasonic motors is proposed.Key techniques of distributed layout of drive mechanisms,coordination control of distributed ultrasonic motors as well as novel flexible skin undergoing one-dimensional morphing are studied.The system integration of small variable camber wing is achieved.Distributed layout of parallelogram linkages driven by geared ultrasonic motors is adopted for morphing,aimed at reducing the load for each motor and producing various aerodynamic configurations suitable for different flying states.Programmable system-on-chip(PSoC)is used to realize the coordination control of the distributed ultrasonic motors.All the morphing driving systems are assembled in the interior of the wing.The wing surface is covered with a novel smooth flexible skin in order to maintain wing shape and decrease the aerodynamic drag during morphing.Wind tunnel test shows that the variable camber wing can realize morphing under low speed flight condition.Lift and drag characteristics and aerodynamic efficiency of the wing are improved.Appropriate configurations can be selected to satisfy aerodynamic requirements of different flight conditions.The study provides a practical application of piezoelectric precision driving technology in flow control.

Tribological properties of textured stator and PTFE-based material in travelling wave ultrasonic motors

This study fabricated textures on the stator surface of a traveling wave ultrasonic motor(USM)using laser and investigated the tribological behavior of a polytetrafluoroethylene(PTFE)composite friction material and stator.Initially,the effect of textures with different densities was tested.As the results suggested,the generation of large transfer films of PTFE composite was prevented by laser surface texturing,and adhesive wear reduced notably despite the insignificant decrease in load capacity and efficiency.Next,the 100-h test was performed to further study the effects of texture.Worn surface and wear debris were observed to discuss wear mechanisms.After 100 h,the form of wear debris changed into particles.The wear mechanisms of friction material sliding against the textured stator were small size fatigue and slight abrasive wear.The wear height of friction material decreased from 3.8μm to 1.1μm.This research provides a method to reduce the wear of friction materials used in travelling wave USMs.

A Wire-Driven Series Elastic Mechanism Based on Ultrasonic Motor for Walking Assistive System

In order to improve the elderly people's quality of life,supporting their walking behaviors is a promising technology.Therefore,based on one ultrasonic motor,a wire-driven series elastic mechanism for walking assistive system is proposed and investigated in this research.In contrast to tradition,it innovatively utilizes an ultrasonic motor and a wire-driven series elastic mechanism to achieve superior system performances in aspects of simple structure,high torque/weight ratio,quiet operation,quick response,favorable electromagnetic compatibility,strong shock resistance,better safety,and accurately stable force control.The proposed device is mainly composed of an ultrasonic motor,a linear spring,a steel wire,four pulleys and one rotating part.To overcome the ultrasonic motor's insufficient output torque,a steel wire and pulleys are smartly combined to directly magnify the torque instead of using a conventional gear reducer.Among the pulleys,there is one tailored pulley playing an important role to keep the reduction ratio as 4.5 constantly.Meanwhile,the prototype is manufactured and its actual performance is verified by experimental results.In a one-second operating cycle,it only takes 86 ms for this mechanism to output an assistive torque of 1.6 N·m.At this torque,the ultrasonic motor's speed is around 4.1 rad/s.Moreover,experiments with different operation periods have been conducted for different application scenarios.This study provides a useful idea for the application of ultrasonic motor in walking assistance system.

Contact Analysis and Modeling of Standing Wave Linear Ultrasonic Motor

A contact model for describing the contact mechanics between the stator and slider of the standing wave linear ultrasonic motor was presented. The proposed model starts from the assumption that the vibration characteristics of the stator is not affected by the contact process. A modified friction models was used to analyze the contact problems. Firstly, the dynamic normal contact force, interface friction force, and steady-state characteristics were analyzed. Secondly, the influences of the contact layer material, the dynamic characteristics of the stator, and the pre-load on motor performance were simulated. Finally, to validate the contact model, a linear ultrasonic motor based on in-plane modes was used as an example. The corresponding results show that a set of simulation of motor performances based on the proposed contact mechanism is in good agreement with experimental results. This model is helpful to understanding the operation principle of the standing wave linear motor and thus contributes to the design of these types of motor.

Principle and Experimental Verification of Novel Dual Driving Face Rotary Ultrasonic Motor

Existing rotary ultrasonic motors operating in extreme environments cannot meet the requirements of good environmental adaptability and compact structure at same time,and existing ultrasonic motors with Langevin transducers show better environmental adaptability,but size of these motors are usually big due to the radial arrangement of the Langevin transducers.A novel dual driving face rotary ultrasonic motor is proposed,and its working principle is experimentally verified.The working principle of the novel ultrasonic motor is firstly proposed.The 5th in-plane flexural vibration travelling wave,excited by the Langevin transducers around the stator ring,is used to drive the rotors.Then the finite element method is used in the determination of dimensions of the prototype motor,and the confirmation of its working principle.After that,a laser Doppler vibrometer system is used for measuring the resonance frequency and vibration amplitude of the stator.At last,output characteristics of the prototype motor are measured,environmental adaptability is tested and performance for driving a metal ball is also investigated.At room temperature and 200 V(zero to peak) driving voltage,the motor’s no-load speed is 80 r/min,the stalling torque is 0.35 N·m and the maximum output power is 0.85 W.The response time of this motor is 0.96 ms at the room temperature,and it decreases or increases little in cold environment.A metal ball driven by the motor can rotate at 210 r/min with the driving voltage 300 V(zero to peak).Results indicate that the prototype motor has a large output torque and good environmental adaptability.A rotary ultrasonic motor owning compact structure and good environmental adaptability is proposed,and lays the foundations of ultrasonic motors’ applications in extreme environments.

A Novel Traveling Wave Ultrasonic Motor Using a Bar Shaped Transducer

A novel traveling wave ultrasonic motor was proposed. The structure of the motor is rather simple and different from the conventional traveling wave ultrasonic motors. Its production processes are very convenient. It is composed of a stator constituted with a ring and a bar shaped transducer and two cone shaped rotors. The rotors were pressed on inner surface of the ring by means of a pre-pressure system. The bar shaped transducer has a sand- wich-like configuration,where two sets of piezoelectric element are bolted. One set excites a longitudinal vibration of the bar, and the other set excites a flexural vibration of the bar. The ring＇s traveling wave excited with the longitudinal vibration and the bending vibration of the bar transducer was simulated with FEM （finite element method）. The prototype of the motor was made and investigated experimentally for its performance. Its maximum torque and rotating speed are 0.25 N · m and 50 r/min, respectively.

Working principle and design of a double cylinders type traveling wave ultrasonic motor using composite transducer

A double cylinders type traveling wave ultrasonic motor using composite transducer was proposed.The proposed stator contained two cylinders and one composite transducer,and the transducer located on the outer surfaces of cylinders.The composite transducer included two exponential horns located on leading ends,and the horns insected with the cylinders at tip ends.Two degenerated flexural vibration modes spatially and temporally orthogonal to each other were excited in each cylinder by the composite transducer.In this new design,a single transducer could excite two flexural traveling waves in the cylinders.Thus,elliptical motions were achieved at the particles on the teeth.The working principle of the proposed motor was analyzed.The cylinder and transducer were designed with FEM.The resonant frequencies of two vibration modals of the stator were tuned to be the same,and the motion trajectories of nodes on the teeth were analyzed.Transient analysis results show that the motion trajectories of teeth are ellipses.The results of this paper can guide the development of this new type of ultrasonic motor.

Transient Response Model of Standing Wave Piezoelectric Linear Ultrasonic Motor

A transient response model for describing the starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor was presented. Based on the contact dynamic model, the kinetic equation of the motor was derived. The starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor according to different loads, contact stiffness and inertia mass were described and analyzed, respectively. To validate the transient response model, a standing wave piezoelectric linear ultrasonic motor based on in-plane modes was used to carry out the simulation and experimental study. The corresponding results showed that the simulation of the motor performances based on the proposed model agreed well with the experimental results. This model will helpful to improve the stepping characteristics and the control flexibility of the standing wave piezoelectric linear ultrasonic motor.

Frequency-Speed Control Model Identification of Ultrasonic Motor Using Step Response

Control model of ultrasonic motor is the foundation for high control performance.The frequency of driving voltage is commonly used as control variable in the speed control system of ultrasonic motor.Speed control model with the input frequency can significantly improve speed control performance.Step response of rotating speed is tested.Then,the transfer function model is identified through characteristic point method.Considering time-varying characteristics of the model parameters,the variables are fitted with frequency and speed as the independent variables,and the variable model of ultrasonic motor system is obtained,with consideration of the nonlinearity of ultrasonic motor system.The proposed model can be used in the design and analysis of the speed control system in ultrasonic motor.

Effects of Transverse Temperature Gradient on the Rotor Velocity in an Ultrasonic Motor

As a result of the nonlinear effect, acoustic streaming has been widely used for increasing the transport coefficient or driving a rotor, for example, in resonant cavities and non-contact ultrasonic motors. It has been demonstrated by experiments that a temperature gradient transverse to the wave propagating direction can significantly increase the velocity of the streaming flows in resonant cavities. To check whether the transverse temperature gradient can also increase the working velocity of acoustic streaming-driven motors, we investigate this issue by numerically solving the hydrodynamic equations. It is found that the velocity of the rotor only weakly depends on the transverse temperature gradient, e.g., even with a temperature difference of 40℃ between the rotor and the stator, the velocity increases only -8.8%.

Experimental study of noncontact ultrasonic motor with non-symmetrical electrode

We have proposed a novel noncontact ultrasonic motor based on non-syinmetrical electrode driving. The configuration of this electrode and the fabrication process of rotors are presented. Its vibration characteristics are computed and analysed by using the finite element method and studied experimentally. Good agreement between them is obtained. Moreover, it is also shown that this noncontact ultrasonic motor is operated in antisymmetric radial vibration mode of B21 mode. The maximum revolution speed for three-blade and six-blade rotors are 5100 and 3700r/min at an input voltage of 20V, respectively. Also, the noncontact high-speed revolution of the rotors can be realized by the parts of Ⅰ, Ⅲ of the electrode or Ⅱ, Ⅳ of the electrode. The levitation distance between the s tator and rotor is about 140μm according to the theoretical calculation and the experimental measurement.

Intelligent Control Algorithm of PTZ System Driven by Two-DOF Ultrasonic Motor

It is difficult for the traditional pan-tilt-zoom(PTZ)system driven by electromagnetic motor to meet the growing demand for video surveillance system.The key challenge is high positioning accuracy,high dynamic performance and miniaturization of the PTZ system.Here a PTZ system driven by two degree-of-freedom obeliskshaped ultrasonic motor with single stator is presented,and its intelligent control algorithm is studied.The structure and driving mechanism of the presented PTZ system are analyzed by both simulation and experiment.To solve the complex nonlinear factors,e.g.time-variation,dead zone,the fuzzy PID control algorithm and the variable gain cross-coupled control strategy are combined to improve the control performance.The results show that the proposed algorithm has faster response,higher precision than traditional control algorithm,and it also has a good robustness to prevent the effect of interference.

Influence of Friction Interface Contact on Ultrasonic Motor Efficiency Under Static Conditions

The friction interface matching plays a deterministic role in the motor efficiency,and the microcosmic contact status of friction interface should be investigated to improve the ultrasonic motor performance.The main purpose is to improve the effective output power of ultrasonic motor.Hence,one studies the contact condition of the friction interface of the ultrasonic motor,analyzes the micro condition of contact interface through finite element analysis,optimizes unreasonable structures,and compares the two different-structure ultrasonic motors through experiments.The results reflect the necessity of optimization.After optimization,the stator and rotor deform after pre-pressure and the contact interface of them full contact theoretically.When reaching heat balance the effective output of the motor is 37%,and the average effective output efficiency is 2.384 times higher than that of the unoptimized.It can be seen that the total consumption of the ultrasonic motor system decreases significantly.Therefore,when using in certain system the consumption taken from the system will decreases largely,especially in the system with a strict consumption control.

Actuating mechanism and design of a T-type linear ultrasonic motor

To take advantage of merits of higher output-power and efficiency of bolt-clamped transducer,a T-type linear ultrasonic motor was proposed in this paper.The proposed motor contained a horizontal transducer and a vertical transducer.The horizontal transducer included two exponential shape horns,and the vertical transducer contained one exponential shape horn.And the horns intersected at tip ends where a driving foot was located.The longitudinal vibrations of transducers were excited by the stretching vibration of PZT ceramics.Longitudinal vibrations were superimposed in the motor and generated elliptical trajectory at the driving foot.The actuating mechanism of the proposed motor was analyzed.The two working modals of the motor were gained with FEM.The resonant frequencies of two working modals were degenerated by adjusting the structural parameters.The motion trajectory of nodes on the driving foot was gained by transient analysis.The vibration amplitude of node on the driving foot indicates that the proposed motor has potential good output characteristics.The results verify the feasibility of the proposed design and provide instructions for the development of the new ultrasonic motor.

A ring type standing wave ultrasonic motor using cantilever type longitudinal transducers

The disadvantages of classic ring type ultrasonic motor were analyzed.To obtain large mechanical output power,a ring type standing wave ultrasonic motor using cantilever type longitudinal transducers was proposed.There are four pairs of cantilevers on one side of the ring,and four PZT ceramics are set between each pair of cantilevers.A screw fastened the PZT ceramics and cantilevers together to form a longitudinal transducer.The bending vibration mode of the ring is excited by the stretching vibration of the PZT ceramics.Thus,linear simple harmonic motions are achieved at the particle on the teeth.And the driving force is the frictional force between rotor and stator.The working principle of the proposed motor was analyzed.The ring and the longitudinal transducer were designed with FEM.The sensitive parameters of resonant frequency of the transducer and ring could be gained with modal analysis.The longitudinal vibration modal of transducer and bending vibration modal of ring were degenerated,and the motion trajectories of nodes on the teeth were analyzed.The results of this paper could guide the development of this new type of motor.

Fabricated and friction test anisotropy material of ultrasonic motor

The twisters for composed of anisotropic material were designed and manufactured.And two kinds of directional-composites were made:one was fiber direction vertical with frictional interface and another was parallel with frictional interface and moving direction.By varying the proportions of epoxy resin and fiber and arranging the orientations of fiber,the composites anisotropy along longitudinal and circumferential were got.Using density measurement,the mass fraction of resin and fiber were calculated.According to composite meso-scopic mechanics,the elasticity constants of composite were analyzed and calculated.The composite different thicknesses were sliced,and attach to the rotor,then the load characteristics,no-load speed,stop load of ultrasonic motor(USM)were test.The output properties of USM with 0.6 mm thickness composite were superior.The effect of friction material on ultrasonic motor was analyzed.Elastic modulus,thickness and micro-morphology of material are main factors which affect characteristics of ultrasonic motor.

Effect of thickness of friction material on contact state of ultrasonic motor

Performances of ultrasonic motor (USM) considerably depend on contact state between stator and rotor.Based on an electric contact method,the effects of thickness of single homogeneous friction material and gradient friction material on contact state between stator and rotor were studied.The relative contact length was employed to describe the contact characteristics of stator and rotor.With the decrease of thickness of friction material,the contact characteristic of stator and rotor were analyzed and compared when single homogeneous friction material and gradient friction material were used.The experimental results showed that the effect of gradient friction material on contact characteristic is smaller than that of single homogeneous friction material when the thickness of friction material decreases.The result can provide experimental guidance for design and choosing of friction material for USM.

Dynamic Model Identification for Ultrasonic Motor Frequency-Speed Control

The mathematical model of ultrasonic motor(USM)is the foundation of the motor high performance control.Considering the motor speed control requirements,the USM control model identification is established with frequency as the independent variable.The frequency-speed control model of USM system is developed,thus laying foundation for the motor high performance control.The least square method and the extended least square method are used to identify the model.By comparing the results of the identification and measurement,and fitting the time-varying parameters of the model,one can show that the model obtained by using the extended least square method is reasonable and possesses high accuracy.Finally,the frequency-speed control model of USM contains the nonlinear information.

Design and experimental study of active balancing actuator driven by ultrasonic motor

The on-line active balancing system can suppress the vibration caused by unbalance of rotating equipment in real time,and is of great strategic significance for high-end equipment in machining,aviation and other fields.As the core equipment of the on-line active balancing system,the performance parameters of the active balancing actuator determine the overall performance of the balancing system.The balancing method of the existing mechanical balancing actuator is improved,and a new active balancing actuator structure based on ultrasonic motor is proposed.The stress distribution of the actuator is analyzed by establishing a three-dimensional model of the actuator.The feasibility and effectiveness of the above structure are verified by the experimental research on the grinder.The results show that the active balancing actuator based on ultrasonic motor can drive the counterweight to complete the required self-locking and stepping actions in the whole cycle.The structural design scheme is feasible.At the same time,it also shows that the actuator can suppress the unbalance vibration of the grinder.The active balancing actuator based on ultrasonic motor drive studied in this paper lays a foundation for the industrial application of this kind of actuator in the future.

Development of an Ultrasonic Motor That Uses an Inchworm Shaped Deformation of a Metallic Plate

At the present time, ultrasonic motors have been developed for a variety of purposes such as linear motion drives and rotational drives. The elaboration of an ultrasonic motor is time-consuming, because it is developed adapting on its application. In this study, a new ultrasonic motor structure that combines a piezoelectric element and a metallic plate is elaborated. The driving principle of this motor is that the metal plate is bent to an inchworm shape and rotates the rotor when the piezoelectric element is stretched. The objective of this study is to verify the functioning of the new motor experimentally.