Traveling Wave Type Ultrasonic Motor Research Articles

Structural Design and Performance Analysis of α Particle Micro-thruster

The α particle propelling is a technology under developing by the author’s research group, which uses α decay isotopes emitting high-speed particles to generate thrust. In this paper we mainly designed the thrust magnitude control and vector control structure suitable for this propelling principle and preliminarily analyzed its control performance. The proposed structure mounts the trust film composed of the decay nuclides onto a quasi-spherical frame surface that is conducive to vector synthesis. The traveling wave type ultrasonic motor drives the diaphragm to control the thrust magnitude of each thrust unit independently and efficiently. The vector control of the joint thrust is implemented by taking advantage of the diversity of combination of multiple thrust units. Theoretical calculation and analysis showed that the thruster structure could achieve the thrust magnitude control accuracy of 0.05µN, and the thrust angle control accuracy of 0.5-1.5 degrees.

ループゲイン調整型適応アルゴリズムに基づく超音波モータの位置制御

In the ultrasonic motors (USM), there are various driving principles such as a standing wave type, a traveling wave type, etc. Among them, the traveling wave type USM is applied in different devices at various situations, because its shape is like DC (direct current) motors. The control performance is reduction because of the dynamic characteristics of USM, which are greatly fluctuate, depending on the influence of nonlinearity via the friction, frictional heat caused by the driving principle, the magnitude of the load and driving conditions. Up to now, various control methods are proposed, and a lot of researches are conducted to control precision positioning, but a simple method to realize the high positioning performance is not proposed yet. In this research, it is offered a two-degrees-of-freedom control method. It introduces a simple adaptive algorithm which holds the loop gain as a constant value, assuming the steady-state gain is decreased as the reduction of the rotational speed of USM. The characteristic of this method is that the control performance can be compensated with only one gain adjustment. Its effectiveness is verified by experiment which uses USM.

Modeling of Rotary Traveling Wave Ultrasonic Motor

Comparedwith traditional electromagnetic motor, the ultrasonic motor (USM) exhibits unique performance advantages. To speed up the research and development of thedriving ASIC for a rotary travelingwave type ultrasonic motor in diameter of 45mm, it is necessaryto obtain its motor model. The modeling of USM which is composed of two parameters (resistance andcapacitance) is presentedand explained. Both the modeling and simulation are based on our real tested motor-drivercharacteristic data by PSIM software. The testeddata can be reproducedby adjusting the unknown two parameters in our model. Some preliminary simulation resultsindicate that this method used to define two parameters of 45mm motormodel is practicable. This work may establish basic foundation for nonlinear modeling of USM.

Research on the Three-Dimensional Elliptical Motion of Rotary Traveling Wave Ultrasonic Motor

The model of a particle on the stator tooth side of traveling wave type rotary ultrasonic motor is established based on the plate theory, which shows that trajectories of particles on the surface of the stator teeth are essentially three-dimensional Oblique elliptical motion. Take the RTUM60 type ultrasonic motor as an example, the three-dimensional elliptical motion of stator tooth’s endpoint is studied through numerical experiments, and the results show the energy loss caused by the radial sliding between stator and rotor is considerable. The influences of tooth height on effective elliptical motion, the velocity in the three direction under Cylindrical coordinate system and radial slip are also discussed, which conclude that the model can be used for further study on the contact model design and optimization traveling wave type ultrasonic motor.

The Contact Problem in Ultrasonic Traveling-Wave Motors

In this paper the contact mechanism between stator and rotor will be considered in detail, which plays a key role in ultrasonic motors. A planar contact model for the stator-rotor interaction in traveling-wave type ultrasonic motors is derived, including rotor flexibility and differenciating between stick and slip regions in the contact zones. The model analysis shows that depending on the motor’s operating conditions, complicated contact behavior may occur with several stick-slip subzones in each contact zone. The typical nonlinear resonance observed in ultrasonic motors can be explained with the present analysis. Both the stiffness of the contact layer and of the rotor may drastically influence the speed-torque characteristics. The results will contribute to a better understanding of the contact mechanics in ultrasonic motors.

An Analysis of the Resonance Characteristics of a Traveling Wave Type Ultrasonic Motor by Applying a Normal Force and Input Voltage

Piezoelectric ceramics, constituting an active element, make a stator vibrate generating a rotational force in ultrasonic motors. In the drive of ultrasonic motors, many factors exist that can affect the resonance characteristics of piezoelectric ceramics. For example, those factors are the bonding conditions with the elastic body, the magnitude of the electric field, the normal force for the frictional drive, the emission of heat due to vibration and friction, and so on. Therefore, it is important to properly research the inclination for variation of piezoelectric ceramics in the circumstance where complex elements are involved. In this paper, we focus on the analysis of the resonance characteristics of an ultrasonic motor due to the magnitude of the input voltage and normal force.

Neuro-fuzzy speed control of traveling-wave type ultrasonic motor drive using frequency and phase modulation

This paper presents a Fuzzy Neural Network (FNN) control system for a traveling-wave ultrasonic motor (TWUSM) driven by a dual mode modulation non-resonant driving circuit. First, the motor configuration and the proposed driving circuit of a TWUSM are introduced. To drive a TWUSM effectively, a novel driving circuit, that simultaneously employs both the driving frequency and phase modulation control scheme, is proposed to provide two-phase balance voltage for a TWUSM. Since the dynamic characteristics and motor parameters of the TWUSM are highly nonlinear and time-varying, a FNN control system is therefore investigated to achieve high-precision speed control. The proposed FNN control system incorporates neuro-fuzzy control and the driving frequency and phase modulation to solve the problem of nonlinearities and variations. The proposed control system is digitally implemented by a low-cost digital signal processor based microcontroller, hence reducing the system hardware size and cost. The effectiveness of the proposed driving circuit and control system is verified with hardware experiments under the occurrence of uncertainties. In addition, the advantages of the proposed control scheme are indicated in comparison with a conventional proportional-integral control system.

A new driver based on dual-mode frequency and phase control for traveling-wave type ultrasonic motor

A mode conversion rotary traveling-wave ultrasonic motor (TWUSM) has potential applications in miniature robotics. However, its electrical drive circuit presents unique challenges, particularly in producing a high frequency (about 40 kHz), high voltage (400 V peak-to-peak) signal input to a low impedance capacitive motor, while achieving high efficiency. A novel driving circuit is proposed to provide two-phase balance voltage for a TWUSM. This paper describes the design of TWUSM drive circuit, intended for simultaneously employs both the driving frequency and phase modulation control scheme. The operating principles and a detailed analysis of the proposed driving circuit, consisting of voltage-controlled oscillator (VCO), voltage-controlled phase-shifter circuit and power amplifier circuit, are introduced. To drive the USM effectively a two-phase power amplifier converter using non-resonant technique was designed to provide a balanced two-phase voltage source, and the two-phase output driving voltages could be maintained at the same peak voltage value at the driving frequency under varying phase-modulation processes. Detailed experimental results are provided to demonstrate the effectiveness of the proposed driving circuit.

Analytical model of traveling-wave type ultrasonic motor based on the energy equivalent method

The analytical model was proposed to analyse the steady-state characteristics of the traveling-wave type ultrasonic motor (TWUSM) based on the energy equivalent method. Firstly, the simplified equivalent composite beam model of the piezoelectric stator was presented with the energy equivalent principle. By involving the rotary inertia and the shearing deformation of the piezoelectric stator, the equation describing the frequency and the amplitude of transverse vibration of the stator were obtained according to the Timoshinko beam theory. Then the force transfer model and the efficiency of the contact surface between the stator and the rotor were derived with the elastic contact theory. And the mechanical performance expression and the output power of the TWUSM were defined by regarding the friction loss of the contact surface and the output power of the rotor as one of parts of the equivalent damp loss of the stator vibration. Finally, all factors, such as the physical demension, the material parameters, the preload, the driving frequency and the friction layer characteristics, influence the vibration characteristics and the mechanical characteristics were analyzed, and the accuracy of the analytical model was verified by comparison with the experimental results.

Effect of flexible rotor on performance of traveling wave type ultrasonic motor

First the definition of flexible rotor of traveling wave type rotary ultrasonic motor (TRUM) is given.It is pointed out that the flexible rotor can be classified in the range of elastic annular plate with large overall motion.And the kinematical equation of flexible rotor is derived.Then the rigid-flexible coupling dynamic model of flexible rotor is obtained by Lagrange equation.So the complete model of TRUM is derived by the integration of the contact model based on flexible rotor,stator's semi-analytical model and flexible rotor model.The analysis examples show that the complicated contact mechanism with asymmetry occurs at the inter- face between the stator and flexible rotor.The analyses explain how the appropriate damp of rotor can lead to the good performance of motor.Moreover the proper flexible rotor is proved to improve the motor's output efficiency by decrease of the friction in the ra- dial direction at the interface.Finally the results of simulation are found to be in good agreement with those of experiments,so the proposed model provides the theoretical foundation for the design of the flexible rotor.

Modelling of ultrasonic motor with dead-zone based on Hammerstein model structure

The ultrasonic motor (USM) possesses heavy nonlinearities which vary with driving conditions and load-dependent characteristics such as the dead-zone. In this paper, an identification method for the rotary travelling-wave type ultrasonic motor (RTWUSM) with dead-zone is proposed based on a modified Hammerstein model structure. The driving voltage contributing effect on the nonlinearities of the RTWUSM was transformed to the change of dynamic parameters against the driving voltage. The dead-zone of the RTWUSM is identified based upon the above transformation. Experiment results showed good agreement between the output of the proposed model and actual measured output.

ADHENSIVE TECHNOLOGY AND ITS EFFECTS ON PERFORMANCES OF STATOR OF ULTRASONIC MOTOR

Focused on the bonding of the piezoelectric ceramic of traveling wave type ultrasonic motors (TWUSM), the effects of the material characteristics and the thickness of the adhesive layer on the vibrating performances of the stator are studied based on the electromechanical coupling finite element model of the stator, and the resisting-shear and vibrating performances of the adhesive layer under different excitating conditions are detailedly analyzed. The methods of improving the bonding quality of the piezoelectric ceramic are presented, and the bonding process and the optimum design of the TWUSM stator are determined at last. It is shown that the thickness of the adhesive layer has little effect on the stator frequency, but great effect on the stator vibration characteristics, and on the premise of enough bond strength, reducing the thickness of the adhesive layer can improve the performance of the TWUSM. Based on the bonding process and optimum design, the 80 mm TWUSM prototype has a good performance that the maximum torque is 1.2 N·2 m and the no-load rotational speed is 80 r/min.The researching results contribute to the industrialization of USM.

A micro ultrasonic motor using a micro-machined cylindrical bulk PZT transducer

In this paper, a micro ultrasonic motor using a micro-machined bulk piezoelectric transducer is introduced. The cylindrical shaped bulk piezoelectric transducer, a diameter of 0.8mm and a height of 2.2mm, was developed as stator transducer for traveling wave type ultrasonic motor. The transducer was made of lead zirconate titanate (PZT) bulk ceramics, and formed by micro machining, Ni plating and laser beam cutting process. Using this stator transducer, we have fabricated a cylindrical micro ultrasonic motor, a diameter of 2.0mm and a height of 5.9mm. We have also evaluated some characteristics and succeeded in driving the micro ultrasonic motor.

611 マイクロ超音波モータ用振動子の小型化と評価

In this paper, an evaluation of transducer for a micro ultrasonic motor is introduced. The motor is a traveling wave type ultrasonic motor driven by the cylindrical shaped bulk piezoelectric vibrator, a diameter of 0.8 mm and 2.2 mm. The dimensions of the motor were 1.8 mm of diameter and 5.8 mm of height. We have fabricated the transducer, the vibrator for the driving of motor, and evaluated its characteristics.

An electric contact method to measure contact state between stator and rotor in a traveling wave ultrasonic motor

Performances of ultrasonic motor (USM) depend considerably on contact state between stator and rotor. To measure the contact state in a traveling wave ultrasonic motor (TWUSM), a special test method is necessary. This paper develops a new method named electric contact method to measure contact state of stator and rotor in traveling wave type USM. The effects of pre-load and exciting voltage (amplitude) of stator on contact state between stator and rotor are studied with this method. By a simulating tester of friction properties of TWUSM, the variations of stalling torque and no-load speed against the pre-load and the exciting voltage have been measured. The relative contact length that describes the contact characteristic of stator and rotor is proposed. The relation between the properties of TWUSM and the contact state of stator and rotor are presented. Additionally, according to a theoretical contact model of stator and rotor in TWUSM, the contact lengths at given conditions are calculated and compared with the experimental results.

Identification and control of rotary traveling-wave type ultrasonic motor using neural networks

Neural networks (NNs) with varied learning rates are proposed to identify and control a nonlinear time-varying plant. First, the network structure and the online learning algorithm of an NN are described. To guarantee the convergence of error states, analytical methods based on a discrete-type Lyapunov function are proposed to determine the varied learning rates of a three-layer NN with one hidden layer. A rotary traveling-wave type ultrasonic motor (USM), which is driven by a newly designed high-frequency two-phase voltage source inverter using double inductances double capacitances resonant technique, is studied as an example of nonlinear time-varying plant to demonstrate the effectiveness of the proposed control system. Then, a robust control system is designed using two NNs to control the rotor position of the USM. In the proposed control system, the Jacobian of the USM drive system is identified by a neural-network identifier to provide the sensitivity information to a neural-network controller.

Neural-network controller for parallel-resonant ultrasonic motor drive

A newly designed driving circuit for the traveling-wave type ultrasonic motor (USM), which is composed of a push-pull DC-DC power converter using PWM direct duty-cycle control and a current-source two-phase parallel-resonant capacitor-parallel load inverter, is described in this study. Moreover, since the dynamic characteristics of the USM are difficult to obtain and the motor parameters are time varying, an online trained neural-network (NN) controller is proposed to control the rotor speed and position of the USM. Accurate tracking response can be obtained due to the powerful online learning capability of the NN controller. Furthermore, the influence of parameter variations and external disturbances on the USM drive also can be reduced effectively. The effectiveness of the NN controlled USM drive system is demonstrated by experimental results.

An ultrasonic motor with an integrated position sensor

This paper presents a method of measurement of the angular position of a traveling wave type ultrasonic motor (TWUM). This method uses the mechanical vibrations on the rotor to estimate its position. The working principle and the mathematical modeling of this kind of motors are reviewed and the position measurement system is described. Then the results of basic expenments are discussed. The obtained position and the measured one proved to be in good agreement.

A piezomotor using longitudinal actuators

A new travelling wave type ultrasonic motor has been developed which uses longitudinal piezoelectric actuators to generate a progressive wave on the surface of a metallic ring. The rotor, which moves through frictional force, is pressed on this elastic plate. This paper deals with the motor construction and its characteristics. Theoretical modelling and experimental performances obtained with the motor prototypes are reported. A maximum of 0.8 Nm and a no-load rotation speed of 120 rpm have been obtained with a double rotor prototype. The results indicate that this piezomotor is proved to operate successfully at a mechanical output power of 4 W.

Micromachined Traveling Wave Motors: Three Dimensional Mechanical Optimization and Miniaturization Limits Evaluation

This paper concerns a physical limits evaluation with respect to the miniaturization of traveling wave type ultrasonic motors (TWUM) down to the millimeter scale. According to present knowledge in research dedicated to centimeter scale TWUM, two different prototypes, whose external diameters are φ 5 mm and φ 2 mm, have previously been designed through numerical calculations, and fabricated using watch making technologies. An experimental characterization has been carried out in order to identify the main physical and technological limitations specific to millimeter scale traveling wave motors. The very first numerical results presented in this paper show important outcomes related to the miniaturization of TWUM. In particular, the limits of current mechanical assumptions such as those related to the two-dimensional mechanical behavior of the stator/rotor interface and also to the rotor's rigidity are clearly shown by a three dimensional finite element calculation. New design rules are thus given in order to allow the mechanical architecture of TWUM to be optimized. The corresponding results indicate that powerful torque/speed characteristics can be expected, and therefore show the adequacy of traveling wave ultrasonic motors for direct-drive actuation down to the millimeter scale.