Showing papers by "Chun-Hsiung Fang published in 2010"

Self-constructing recurrent fuzzy neural network for ultrasonic motor drive

Abstract: The ultrasonic motor (USM) is a popular actuator and used in industry and academic research in the last decades because it has the advantages of high holding torque, good response characteristics, high torque density, silent operation, free of electromagnetic noise and compact size However, the motor are time-varying and highly nonlinear system which the parameters varied with increasing temperature and changes in drive frequency, load torque and phase difference of two-phase voltages The investigations are focused on three parts, first we construct complex dynamic model of traveling-wave ultrasonic motor (TWUSM) by MATLAB/ SIMULINK in this paper, a hybrid model which combines the strength of the equivalent circuit method and the finite element method is derived, On the other hand, a novel controller and driving system are presented For the part of control, we present a self-constructing recurrent fuzzy neural network for the speed control of a TWUSM to track periodic reference trajectories Two types of online learning algorithms are the structure learning and the parameter learning The structure learning has the ability of identifying whether the fuzzy rules are generated or not, while the parameter learning algorithm used the supervised gradient decent method to adjust the connected weights in the consequent part When the system is in steady state, fuzzy decision-making method is used to delete unimportant fuzzy rules automatically, so that to get the simplest structure of SCRFNN while maintaining the good control performance Finally, simulation results show that the control effort is effective, as well as confirm the theoretical work

A new approach to stabilization of T-S fuzzy systems

Abstract: A more relaxed stabilization condition for continuous time T-S fuzzy systems is proposed by using the multiple Lyapunov function and the non-PDC controller. All stability conditions are represented in terms of linear matrix inequalities (LMIs). The proposed approach is simpler and more realizable in dealing the time derivatives of membership functions in comparison with existing results.

Evaluating the Dosimetric Impact of Interfraction Variations During Image-Guided Radiotherapy Using Six-degree-of-freedom Image Registration and Equivalent Uniform Dose Method

Abstract: This study proposed an off-line method to quantitively analyze the dosimetric impact of daily setup variations on Intensity-modulated radiotherapy (IMRT) when these variations are not corrected due to the lack of image guidance. Series of daily Cone-beam computed tomography (CBCT) images and treatment plan data of a patient with esophageal cancer previously treated using Image-guided radiotherapy (IGRT) were analyzed retrospectively. Daily setup shifts were applied to IMRT plans on a fraction-by-fraction basis using six-degree-of-freedom rigid image registration. The mean interfraction translation displacement was 2.3 ± 1.8, 2.1 ± 0.9, and -1.8 ± 2.6 mm in the LR, AP, and SI directions, respectively. The average interfraction rotation displacement was 2.2 ± 1.2, -0.7 ± 0.8, and -0.7 ± 0.6 degree around the three orthogonal axes. Due to variations, a loss of equivalent uniform dose (EUD) up to 6% for planning target volume (PTV) was noted. Findings confirmed that successful implementation of high precision IMRT required daily image guidance to ensure accurate delivery of sharp gradient dose distributions.

Stabilization and H-infinity control for interval descriptor systems

Abstract: This paper considers H-infinity control problem for interval descriptor systems. Necessary and sufficient LMI-based conditions are derived for quadratic-like H-infinity control analysis of interval descriptor systems. Using the analysis result, two types of feedback controllers are designed so that the closed-loop interval descriptor systems are admissible with H-infinity-norm less than a prescribed value. To the best of the authors’s knowledge, this is the first paper to deal with the H-infinity control problem of interval descriptor systems in the literature.

An improved result for stabilization and H ∞ control of T-S fuzzy systems

Abstract: A new stabilization condition for T-S fuzzy systems via the fuzzy Lyapunov function and the non-PDC controller is proposed in this paper. Unlike the existing literature, the bounds of the time derivatives of membership functions are not required and the BMIs problems do net arise, either. All stability conditions are expressed in the form of linear matrix inequalities (LMIs). We also extend the proposed idea to solve the H ∞ fuzzy control problems. At the end of each subsection, practical examples are given to illustrate the success of the proposed approach.