Browsing by Author "Yu, Tai-Ho"

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A modal sensor integrated circular cylindrical wedge wave ultrasonic motor
(2012-02-01)
Yu, Tai-Ho
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This study investigates a new circular cylindrical wedge wave ultrasonic motor (WW-USM) integrated with modal sensors. The presented motor is driven by continuous wedge waves of the fundamental modes with an integer circumferential number. In this design, the constructive interference of two equal-intensity standing waves actuated by two comb transducers generates a traveling wedge wave. Dual-phase electrodes were parallel to the axis placed on a piezoelectric (PZT) tube at a distance of 1/4 wavelength. Two orthogonal sinusoidal signals at the resonant frequency of designated flexural mode exerting on the electrodes have the WW-USM operate in bidirectional rotation. The base height of the stator was appropriately tuned to achieve an excellent modal separation from other vibration modes. A modal sensor on the border of the PZT tube was designed to detect the dynamic characteristics of the WW-USM and to improve the performance. The wedge wave motor has a flexible mechanical performance between the angular speed and output torque. Varying the contact position of the rotor on the inclined surface of the stator may exchange the angular speed for torque output. No further modification of the entire motor structure is needed. The prototype WW-USM driven by the flexural mode F(1, 4) under 1 N static preload was operated by an AC voltage of 400 V-pp at the frequency of 36.605 kHz. The maximum values of angular speed, output torque, and electromechanical transduction efficiency are 225 rpm, 15.736 mN m, and 16.22%, respectively. (C) 2011 Elsevier B.V. All rights reserved.
A Self-sensing Wedge-wave Ultrasonic Motor Using Modal Sensors
(2009)
Yu, Tai-Ho
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This paper experimentally and computationally examines the modal sensors integrated with a recently developed rotary ultrasonic motor (USM) driven by continuous wedge waves of the fundamental modes with the integer circumferential modal number. The traveling wave is formed from constructive interference of two equal-intensity standing waves induced by two comb transducers using dual sinusoidal excitations in 90 degree phase difference. The transducers and modal sensors are segmented in strips around the circumference of piezoelectric tube in the circular wedge-like motor stator. The latter are used to monitor the dynamic response of the stator during operation. The response of USM acquired by the proposed modal sensors has distinct vital characteristics in different frequency bands. The high-pass signals are used not only to note the variation in phase difference between excitations but to detect the resonant frequency, which is altered by payload, wear situation, etc. The low-pass signal reveals the revolution speed and dynamic reaction of the motor stator exerted by frictions and contact forces because of the rotor. The time-frequency response of stator is further characterized during the period in which the revolving direction of rotor is switched over.
An Ultrasonic Motor Driven by Traveling Cylindrical Wedge Waves
(2006)
Yin, Ching-Chung
;
Yu, Tai-Ho
;
機械工程學系
;
Department of Mechanical Engineering
A novel ultrasonic motor driven by flexural waves traveling circumferentially along a circular cylindrical wedgelike acoustic waveguide is presented. A rotary motion can be induced via friction forces if a rotor normally contacts the internal inclined surface of the cylindrical wedge near the tips. The rotary motor stator has a simple structure constructed by a metal cylindrical wedge adhered on a piezoelectric tube whose polarization is in the radial direction. The wedge acoustic waves are excited by two sets of comb electrodes painted on the outer surface of the piezoelectric tube. Both comb transducers with an angular space apart are excited by AC signal in +/-90 degrees phase difference to achieve bidirectional operation for the motor. There exist a number of axial modes and circumferential modes in the stator in a broad frequency range below 100 kHz. Only the fundamental modes of the latter are considered to drive this rotary motor. Along with commercial codes of finite element method (FEM), a bi-dimensional FEM has been developed to determine the resonance frequencies of circumferential modes and their corresponding modal displacements. The angular speed and direction are controllable by altering the driving voltage and the phase difference between two comb transducers.
Bi-dimensional finite element analysis for modal separation of a circular cylindrical WW-USM
(2011-07-01)
Yu, Tai-Ho
;
Yang, Shin-Yueh
;
Lee, Chen-Liang
;
Yin, Ching-Chung
;
機械工程學系
This paper describes a modal separation model that improves the performance of wedge wave ultrasonic motors (WW-USMs) using the bi-dimensional finite element analysis (Bi-d FEA) method. Most USMs operate near the resonant frequency of a specific vibration mode, which must be well separated from the resonant frequencies of other modes. In the current prototype, unexpected disturbance induced at the instant of switching on/off or changing direction of the motor appeared in simulations and actual measurements. These fluctuations are due to vibration modes other than the driving mode occurring around the operating frequency. Bi-d FEA numerical simulation results indicate that selecting an appropriate height for the upper base under the piezoelectric tube achieves excellent modal separation. Measurements of the traveling wave taken by modal sensors show that the proposed motor performs better than traditional motors, offering a faster transient response in revolution speed and a more stable design. Suppressing the unexpected modes in excitation of the WW-USM increased the maximum output torque by 50% and the efficiency of mechanical/electrical transformation by 50%. (C) 2011 Elsevier B.V. All rights reserved.
Transient Response of Wedge-Wave Rotary Ultrasonic Motors
(2010)
Yu, Tai-Ho
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This paper presents an effort to improve performance of the wedge-wave ultrasonic motors (WW-USM) driven by circumferentially traveling flexural waves. In general, USM is operated in the vicinity of the resonant frequency of a specific vibration mode, which needs to be well separated away from the resonant frequencies of other modes. In the current prototype, transient response to the designed flexural mode is accompanied by longitudinal modes because of poling of the PZT tube and electrode layout around the tube. Uncertain disturbance induced at the instant of switching on/off or changing direction of the motor were found through both simulation and measurement. The fluctuations are attributed to unexpected vibration modes occurring around the operating frequency. Simulated results indicate that the performance has been improved if the electrodes are placed over the entire wavelength around the hoop of PZT tube and/or the tube is periodically poled through the thickness in alternate directions. Transient response becomes smooth and has twice the amplitude of displacement when the longitudinal modes are suppressed from excitation of WW-USM.