A new compliance control approach for traveling-wave ultrasonic motors

This paper presents a new approach for compliance control using a traveling-wave ultrasonic motor. Its objective is to demonstrate the effectiveness of using duty ratios and frequencies as control variables for both preload and stiffness control. At the home position, the motor is engaged in a standing-wave mode operation and provides self-locking torque. When the motor is deflected, it is engaged in a traveling-wave mode operation to provide a reacting torque. The torque is varied according to the deflection to provide the desired stiffness. Experiments have confirmed the effectiveness of this method. This approach can also be readily deployed into many force-feedback and haptic applications such as robotic locomotion. © 2008 IEEE.published_or_final_versio

Neuro-fuzzy speed tracking control of traveling-wave ultrasonic motor drives using direct pulse width modulation

The traveling-wave ultrasonic motor (TUSM) drive offers many distinct advantages but suffers from severe system nonlinearities and parameter variations especially during speed control. This paper presents a new speed tracking control system for the TUSM drive, which newly incorporates neuro-fuzzy control and direct pulse width modulation to solve the problem of nonlinearities and variations. Increasingly, the proposed control system is digitally implemented by a low-cost digital signal processor (DSP) based microcontroller, hence reducing the system hardware size and cost. Experimental results confirm that the proposed speed tracking controller can offer good steady-state and transient performances.published_or_final_versio

Neuro-Fuzzy Speed Tracking Control of Traveling-Wave Ultrasonic Motor Drives Using Direct Pulsewidth Modulation

The traveling-wave ultrasonic motor (TWUM) drive offers many distinct advantages but suffers from severe system nonlinearities and parameter variations, especially during speed control. This paper presents a new speed tracking control system for the TWUM drive, which newly incorporates neuro-fuzzy control and direct pulsewidth 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. Experimental results confirm that the proposed speed tracking controller can offer good steady-state and transient performance.published_or_final_versio

Neuro-fuzzy dual-mode control of travelling-wave ultrasonic motors

With their significant advantages over traditional electromagnetic motors, ultrasonic motors (USMs) are becoming attractive. This paper presents a neuro-fuzzy dual-mode controller, combining the knowledge-based fuzzy logic and the learning-incorporated neural network as well as using dual control inputs, for servo control of travelling-wave USMs. According to the proposed neuro-fuzzy control, both the driving frequency and phase difference of the USM system are simultaneously adjusted on-line. Experimental results have verified its superior steady-state and dynamic performances under various reference inputspublished_or_final_versio

Modeling of electric vehicle chargers

The chargers of electric vehicles (EV) are highly non-linear devices. They are characterized by high harmonic current distortion and poor power factor. Different models of chargers and converters had been studied and a number of papers were published. In order to study the impacts of a large number of electric vehicles to the power system, an appropriate charger model for a population of EVs should be developed. To illustrate the process in using Monte Carlo method to describe the interaction of EV chargers, the mean value of the total harmonic distortion (THD) is estimated as it is one of the most important parameters should be studied. Different charging algorithms will have different performance and harmonic distortion. Since current-voltage control charging method is widely adopted for various types of batteries, a model based on this algorithm is presented.published_or_final_versio

Design and control of a new ultrasonic stepping motor

In this paper, a systematic approach to design ultrasonic stepping motors (USMs) using spatially shifted standing vibrations is presented, with emphasis on the combination of the order of vibration mode, the number of spatial phase shifts, the number of electrode divisions and the number of sections to excite a mode. Based on the operating principle, the design equations and constraints are mathematically derived, hence proposing the design procedure. The finite element method is also employed to investigate the vibration of the stator. Moreover, by borrowing the idea of electromagnetic stepping motors, the half-step-operation control is newly applied to this USM so that the step size can be further halved. A 80-step USM is prototyped. The proposed design approach and control scheme are well supported by experimentation.published_or_final_versio

Establishment of HKU lung cancer lines in Hong Kong - an ongoing conjoint effort and progress report

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Promotor hypermethylation of the CpG Islands of human Ras Association Domain Family 1A gene (RASSF1A) in adenocarcinoma of lung in Hong Kong Chinese - a comparison between smokers and non-smokers

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Differential-phase-shift quantum key distribution using heralded narrow-band single photons

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De novo large rare copy-number variations contribute to conotruncal heart disease in Chinese patients

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