Characteristics Of Ultrasonic Motor Research Articles

Analysis of stator rotor of rotating traveling wave ultrasonic motor

Abstract As a new type of energy exchange device, the operation characteristics of ultrasonic motor is a hot issue in current research. In this paper, the thermo-electro-mechanical coupling model of the stator and rotor of the rotary traveling wave ultrasonic motor is constructed by finite element software. The frequency and amplitude of the working mode of the stator and rotor of the ultrasonic motor under different temperature conditions are studied, and the influence of the piezoelectric ceramic lamination on the working state of the ultrasonic motor is discussed. The following conclusions are drawn: with the increase of temperature, the resonant frequency of the working mode of the ultrasonic motor B09 decreases and the amplitude increases slightly; piezoelectric ceramic delamination can improve the amplitude-frequency characteristics of stator and rotor. Considering comprehensively, the superposition of two layers of piezoelectric ceramic plates is the most suitable structure.

MISO Nonlinear Gauss-Hammerstein Model Identification of Ultrasonic Motor

A novel two-input nonlinear Hammerstein model of ultrasonic motor is proposed to provide the basis for the design and analysis of motor’s multivariable control system. The static nonlinear part of the model is designed as Gauss function to describe the nonlinear characteristics of ultrasonic motor more accurately. Differential evolution algorithm is used to identify the model parameters, and the algorithm is improved to ensure the correctness and validity of the modeling process. The debugging method of optimization algorithm parameter value is also proposed to ensure the robustness of the algorithm. The comparison between the experimental data and the calculated results of the model indicates that the established model has higher precision and the modeling method is effective.

Analysis and control of micro-stepping characteristics of ultrasonic motor

Micro-stepping motion of ultrasonic motors satisfies biomedical applications, such as cell operation and nuclear magnetic resonance, which require a precise compact-structure non-magnetization positioning device. When the pulse number is relatively small, the stopping characteristics have a non-negligible effect on the entire stepwise process. However, few studies have been conducted to show the rule of the open-loop stepwise motion, especially the shutdown stage. In this study, the modal differences of the shutdown stage are found connected with amplitude and velocity at the turn-off instant. Changes of the length in the contact area and driving zone as well as the input currents, vibration states, output torque, and axial pressure are derived by a simulation model to further explore the rules. The speed curves and vibration results in functions of different pulse numbers are compared, and the stepwise motion can be described by a two-stage two-order transfer function. A test workbench based on the Field Programmable Gate Array is built for acquiring the speed, currents, and feedback voltages of the startup-shutdown stage accurately with the help of its excellent synchronization performances. Therefore, stator vibration, rotor velocity, and terminal displacements under different pulse numbers can be compared. Moreover, the two-stage two-order model is identified on the stepwise speed curves, and the fitness over 85% between the simulation and test verifies the model availability. Finally, with the optimization of the pulse number, the motor achieves 3.3 µrad in clockwise and counterclockwise direction.

A life test of ultrasonic motors under different torque loads and the analysis of the characteristics of wearing surfaces

Without a coil and a gearbox, an ultrasonic motor has an important application in space engineering and so forth with advantages of light weight, small volume, less electromagnetic radiation, fast dynamic response, and high energy density. However, the obvious friction and wear between the stator and the friction material (as a part of the shaft assembly) restrict the reliability and life time of the ultrasonic motor. In this paper, a life test of ultrasonic motors is designed and carried out for 3041.7 h, and the eight motors are divided into four groups with torque loads of 0.03 Nm, 0.09 Nm, 0.16 Nm, and 0.21 Nm in the test. The evolution characteristics of the displacement frequency response and the wear on the stator contact surface under different torque loads during the wear process are analyzed. Some start-up problems occur during the early time in the life test are found and explained based on a meshing effect between the stator and the friction material, and some targeted suggestions are proposed to overcome the problems. The study can help to understand the wear failure mechanism and characteristics of ultrasonic motors.

Variable Gain PID Control of Ultrasonic Motor using Novel Hybrid PSO with Improved Searching Ability

The ultrasonic motor (USM) is a type of actuator driven by frictional force. At present, because of their excellent features, USMs are used in a range of applications, such as for autofocus of cameras and in actuators for devices in MRI environments and microrobots. However, because the dynamic characteristics of USMs vary according to temperature, humidity, and load conditions, their mathematical modeling is difficult. Thus, PID control has conventionally been used for the control of USMs. However, conventional PID control with fixed gains cannot compensate for the non-linear characteristic variation of a USM. In this research, we propose a novel hybrid particle swarm optimization (PSO) system for USM control. The proposed method uses PSO to automatically tune the optimized PID gains. The experiments demonstrated that optimized gains in USM control can be obtained in real time, and high accuracy.

Nonlinear Iterative Learning Control of Travelling Wave Ultrasonic Motor

The relatively simple control strategy can decrease the complexity of the ultrasonic motor system and increase the cost performance. The nonlinear iterative learning control algorithm is simple, the control parameters can be determined according to little experimental knowledge. According to the control characteristics of ultrasonic motor, the nonlinear iterative learning control algorithm is improved and the nonlinear iterative learning control strategy of motor’s speed is designed. Experiments show that the motor system has good iterative learning capacity, the control effect is improved generally in the repeated learning process and the control strategy is simple and effective.

Self-tuning speed control of ultrasonic motor combined with efficiency optimization

Aiming at the nonlinear characteristics of ultrasonic motor (USM) control system, a self-tuning pole assignment speed control strategy is proposed in this paper. The parameters of motor system are identified online, and then the controller is modified online according to the identified parameters of motor. In view of the short-time working characteristic of USM, a method for determining initial values of parameters with online identification algorithms is presented. Using this method, efficient self-tuning control can be realized using a small quantity of testing data. The proposed strategy is robust and relatively simple. Experimental results indicate that the speed control performance is good.

Nonlinear Modeling of Electrical Equivalent Circuit of Rotary Traveling Wave Ultrasonic Motor

It has difficulty in nonlinear modeling of performance characteristic of ultrasonic motor for its complex micro-structure. Through matching three sets of Vpp-Im data measured near the resonance frequencies of five ultrasonic motors, we run PSIM 6.0 to extract a new model in which nonlinear resistance and micro capacitance are tuned till touching the minimum relative errors between model Vpp (mean)-I1 data and measured Vpp-Im data. The experimental results show that five key parameters of this model match for actual driving data of ultrasonic motors with diameter of 45mm and their waveforms show well too. This work will provide both compact ideas for future nonlinear modeling and applied simulation basis for its ASIC design.

Spherical Ultrasonic Motor for Pipe Inspection Robot

We present a pipe inspection robot using a newly developed spherical ultrasonic motor (SUSM) as a camera actuator. The novel SUSM has improved the range of movement compared to previous SUSMs, and the robot can point a camera in any direction. In this study, we determined a method for controlling the rotational direction and strategic control from the kinematics and characteristics of ultrasonic motors. The rotational directions were defined by the phase differences of the applied voltages, and the rotational speeds were changed with the frequencies. Additionally, we developed a very small position sensing system using rotary potentiometers. In the control experiment performed using the sensing system, the SUSM showed the returnability to the default position from several specified points, within an accuracy of 1°.

PID-like Wavelet Neural Networks Control for Multiple Joint Robot Driven by Ultrasonic Motors

In view of the operating characteristics of a multiple joint robot driven by ultrasonic motors, a new speed-position double closed-loop PID control mode is put forward, which has effectively curbed the dramatic change of speed caused by quick response of the ultrasonic motor, so as to enhance the smooth movement of the robot. To further improve the performance of the robot and to real-time adjust the PID control parameters according to the changes of characteristics of ultrasonic motors, a PID-like wavelet neural networks (WNN) is presented. The speed-position double closed-loop PID control, practical experience, the current trajectory error and its change are all taken into account in the frame of the proposed PID-like wavelet neural networks. A back propagation algorithm based on gradient descent is developed to train the PID-like WNN on line by using δ adaptation law. Experiment results prove that the PID-like WNN controller is superior to PID controller and PID neural networks controller, and has a good anti-interference capability.

212 ロボットハンド用超音波モータの駆動特性の最適化(ロボティクスおよび人間機械共存系,学術講演)

212 ロボットハンド用超音波モータの駆動特性の最適化(ロボティクスおよび人間機械共存系,学術講演)

208 超音波クラッチの開発

In the present paper, a newly developed ultrasonic clutch is proposed. The ultrasonic clutch can solve problems of conventional passive elements, such as time delay, instability, and large size, by using unique characteristics of ultrasonic motor, as fast response, silent motion, and non-magnetic feature. It can also be designed to be smaller than conventional elements due to its simple structure. The clutch locks or releases the rotor by use of ultrasonic levitation phenomenon. First, we have designed the structure of the ultrasonic clutch using an equation of ultrasonic levitation phenomenon, results from structural analysis and finite element (FE) analysis of piezoelectric material of the vibrator. Then we have manufactured the ultrasonic clutch and have conducted a driving experiment. Finally, we have demonstrated that the maximum levitation force is around 20 N and the static friction torque of the ultrasonic clutch is up to 0.14 Nm.

Piezoelectric ultrasonic motor and fine positioner with two freedoms

A rod-type piezoelectric ultrasonic motor using based bending vibration mode with small size of 15mm in diameter and 25mm in length, improved construction and a fine positioner with two freedoms driven directly by a couple of the piezoelectric ultrasonic motors were developed. High displacement resolution and large driving force of the positioner can be obtained utilizing the characteristics of ultrasonic motors with large torque at low speed and high angle resolution. Controlled by a microprocessor, the positioner can move in stepping mode responding to a pulse signal. A prototype with displacement resolution of 12nm and driving force of 1 kgf has been successfully applied to precision regulating mechanism for laser resonant cavity.

Characteristics of a Bidirectional Rotary Ultrasonic Motor Using Obliquely Polarized Piezoelectric Transducers

Obliquely polarized piezoelectric ceramic transducers are newly employed to an ultrasonic motor. Since the direction of polarization is neither parallel nor perpendicular to the applied electric field, the longitudinal and the torsional vibrations are excited simultaneously. In addition, the direction of rotation can be switched by changing the driving frequency. Thus, this motor rotates in both clockwise and counterclockwise directions in spite of a single-phase input signal. The principle and the characteristics of the ultrasonic motor are described.

Adaptive control-based high-performance drive system implementation of traveling-wave-type ultrasonic motor

In recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Several kinds of constructions and characteristics of USMs have been reported so far. Of these USMs, a traveling wave-type USM has many characteristics such as: high torque in the low-speed range, large holding torque based upon frictional force, flexible free forms, compactness in size and low magnetic noise. In practice, an inherent mechanical resonant frequency and a velocity amplitude of USM are changed largely according to operating temperature due to frictional drive, load disturbance torque, and applied voltage levels. Therefore, it is necessary to develop a new control system which solves these items and always supplies the required power with high efficiency and high performance in the practical applications. This paper proposes mainly a new sensorless high-performance control scheme of an inverter-fed ultrasonic motor, which is based on a control system technology with two feedbacks incorporating automatic resonant frequency tracking and constant velocity amplitude control strategies. This control system is realized in terms of a high-frequency chopper and a two-phase series/parallel resonant inverter. The experimental results are demonstrated and discussed compared with the theoretical ones.

Adaptive control-based high-performance drive system implementation of traveling-wave type ultrasonic motor.

In recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Some sorts of constructions and characteristics of USMs have been reported so far. Of these USMs, a traveling-wave type USM has many characteristics such as high torque at low speed range, large holding torque based upon frictional force, flexible free forms, compactness in size and low magnetic noise. In practice, an inherent mechanical resonant frequency and a velocity amplitude of USM are largely changed according to operating temperature due to frictional drive, load disturbance torque, and applied voltage levels. Therefore, it is necessary to develop a new control system which solves these items and always supplies the required power with high-efficiency and high-performance in the practical applications. This paper is mainly a newly-proposed sensorless high-performance control scheme of inverter-fed ultrasonic motor, which is based upon a control system technology with two feedbacks incorporating an automatic resonant frequency tracking and a constant velocity amplitude control strategies. This control system is realized in terms of high-frequency chopper and two-phase series/parallel resonant inverter. The experimental results are demonstrated and discussed as compared with the theoretical ones.

Ultrasonic motors using a piezoelectric ceramic multi-mode vibrator

Abstract This paper deals with some constructions and some experimental characteristics of ultrasonic motors using piezoelectric circular or annular plates. In the first part, the theoretical analysis of the non-axisymmetric modes of a circular plate or an annular one is shown. On the basis of this consideration, the mode that is suitable to be used for an ultrasonic motor is determined. In the next part, some constructions and characteristics of the rotary type motor using the two degenerated non-axisymmetric modes are reported. In the last part, construction of the linearly self moving motor using a non-degenerated mode ((1,1)) and a radial mode (R,l) mode is described.