Jeng-Sheng Huang

Parametric control of an axially moving string via fuzzy sliding-mode and fuzzy neural network methods

Abstract This study is dedicated to design effective control schemes to suppress transverse vibration of an axially moving string system by adjusting the axial tension of the string. To this end, a continuous model in the form of partial differential equations is first established to describe the system dynamics. Using an energy-like system functional as a Lyapunov function, a sliding-mode controller (SMC) is designed to be applied when the level of vibration is not small. Due to non-analyticity of the SMC control effort generated as vibration level becoming small, two intelligent control schemes are proposed to complete the task — fuzzy sliding-mode control (FSMC) and fuzzy neural network control (FNNC). Both control approaches are based on a common structure of fuzzy control, taking switching function and its derivative as inputs and tension variation as output to reduce the transverse vibration of the string. In the framework of FSMC, genetic algorithm (GA) is utilized to search for the optimal scalings for the inputs; in addition, the technique of regionwise linear fuzzy logic control (RLFLC) is employed to simplify the computation procedure of the fuzzy reasoning. On the other hand, FNNC is proposed for conducting on-line tuning of control parameters to overcome model uncertainty. Numerical simulations are conducted to verify the effectiveness of controllers. Satisfactory stability and vibration suppression are attained for all controllers with the findings that the FSMC assisted by GA holds the advantage of fast convergence with a precise model while the FNNC is robust to model uncertainty and environmental disturbance although a relatively slower convergence could be present.

Nonlinear dynamic analysis and actuation strategy for a three-DOF four-wire type optical pickup

This study presents a scheme of sliding-mode control (SMC) for precisely positioning a newly designed three degree-of-freedom (DOF) four-wire type lens actuator which is installed in optical pickups of CD/DVD drives to perform data-reading. The SMC design aims to perform precision positioning of the objective lens in the directions of focusing/tracking and simultaneously to annihilate tilting motions for a faster data-reading and better accuracy. The design of the SMC controller is started with establishing a nonlinear dynamic model to capture the motions of the actuator with considerations of dimension/assembling errors as parametric uncertainty and unbalanced radial vibrations as disturbance. A robust SMC is then synthesized to accomplish fast tracking, focusing and zero tilting at steady state. Simulations are conducted for verifying the effectiveness of the controller designed, which show that the designed controller is capable of achieving fast zero tilting with favorable tracking/focusing performances and also robust to plant uncertainty and unbalanced radial vibrations.

The Influence of Nanoimprinting Surface Structures on the Optical Efficiency of GaN-Based LEDs

Spin-on glass structures are built directly on an indium tin oxide surface by imprinting lithography to improve the optical efficiency of GaN-based blue LEDs. Two different mold materials, sapphire and silicon, are fabricated via conventional UV lithography and a wet etching process. In the UV lithography, the 750-nm linewidth mask directly contacts the thin photoresist to make a good resolution pattern. Our study shows that the periodic surface structures made via imprinting enhance the light-extraction efficiency-surface texturing reduces the total internal reflection and Fresnel reflection when light is generated by active layers of the LEDs. The light output power values of the conventional LED and imprinting nanohole-array LEDs are 21.7 and 27.3 mW, respectively, under 150-mA current injections.

Precision repositioning of the balancing ball in an auto-balancer system via a fuzzy speed regulator equipped with a sliding-mode observer

An intelligent fuzzy rotor speed-regulator is developed to reposition the balancing ball inside an automatic balancer system (ABS) to its desired location. This repositioning is designed and activated to remedy the commonly-seen mis-positionings of the rolling ball inside ABS, which is caused by an inevitable rolling friction moment of the rolling ball in contact with its race, leading to large, undesired radial vibrations. The repositioning is accomplished by essentially generating required circumferential inertial force on the ball to suppress the rolling friction. For preliminary feasibility, the case of a single ball is considered. The first step is to establish the dynamic model of the system, which is followed by the analysis to ensure stability of the desired ball equilibrium position. The second step is to forge a sliding-mode observer for estimating online position and velocity of the ball, which are offered to the fuzzy speed-regulator as inputs. The fuzzy speed regulator is then synthesized by three parts: fuzzification of inputs/output, the rule table, and a reference engine accompanied by defuzzification. Finally, an incremental speed-adjustment scheme is designed in order for the spindle to reach target operating speed, while retaining the ball at the desired position. Simulations and experiments are conducted to demonstrate the effectiveness of the proposed fuzzy ball-repositioning scheme.

57.3: Achieving Color Balance of a Large Sized BLU Directly—Lit by LEDs Capped with Customized Optical Lenses

The objective of this study is to develop a high color balance thin RGB LED backlight unit (BLU) for large-Sized LCD-TVs. Genetic Algorithm is employed to search the optimal angular placement of each RGB LED and gain the condition of better color mixing for achieving high color balance of BLU.

Design and experimental study of an observer-based controller for a three-DOF four-wire type optical pickup head

This study presents a servo scheme synthesized via methods of sliding-mode control and high-gain observer for a newly-designed three degree-of-freedom four-wire-type lens actuator which is installed in the pickups of optical disc derives to perform data-reading. The optical pickup considered herein is a particular one that owns three degrees of freedoms, focusing, tracking and tilting. The virtual work and Lagranges equation are used to derive the equations of motion. The sliding-mode control design is performed to conduct precision positioning of the objective lens in directions of focusing, tracking and simultaneously annihilate possible tilting for faster data-reading and better accuracy. The full-order high-gain observer is next designed to estimate the velocities of the lens to provide low-noised feedback signals for sliding-mode control. Simulations are carried out to verify the theoretical model and the predicted performance of designed controller and observer. Finally, experiments are conducted to validate effectiveness of the proposed controller/observer scheme.

Dynamic Modeling and Experiment Verification of a Piezoelectric Part Feeder

The study is aimed to perform dynamic modeling of the part-feeder powered by piezoelectric actuation. This part-feeder consists mainly of a horizontal platform vibrated by a pair of parallel piezoelectric beams. The parts to be transported on the platform march forward owing to their intermittent impacts on the platform. The dynamic modeling technique used herein is essentially the Rayleigh-Ritz method, which first incorporates material properties and constitutive equations of the piezoelectric materials, and then captures the complex dynamics of the parallel-beam piezo-feeder by three lower-order assumed modes in the transverse direction of the vibrating beams. With the three approximated assumed modes in hand, the system dynamics is then represented by three coupled discrete equations of motion. Based on these equations, displacement and velocity of the platform can be approximately obtained. Based on the approximated motions of the platform, the marching speed of the parts with intermittent impacts on the platform can be predicted. Numerical computations are conducted to acquire the estimated marching speed of the parts, along with the experimental study. The comparison between the theoretical predicted transporting speed of the part and the experiment counterparts.© 2005 ASME

Optimal Profile Design for the Resonator Beam of an Ultrasonic Motor via Finite Element Modeling and Taguchi Methodology

This study presents the optimal design for the resonator beam profile of a bimodal ultrasonic motor via finite element modeling and Taguchi experimental design method. General design goals of an ultrasonic motor are to maximize the output power while restraining the contact force in order to extend component lives. To achieve the aforementioned goals, based on recent studies, beam profile design could play an important role because geometric variants of profile lead to substantial changes in the output power of the motor and simultaneously affect the contact force significantly. To investigate the effect of various profiles on the performance of the ultrasonic motor, the dynamic equations of motion are first formulated by utilizing an extended Hamiltonps principle and the method of the Lagrange multiplier. The method of finite element modeling is meanwhile used to approximate the governing partial differential equations by a discrete, finite degree-of-freedom system. With the beam outer profile parametrized by cubic splines in terms of locations of two intercepts, the Taguchi experimental design method is finally applied based on the simulated dynamics of the derived finite system to distill generic design guidelines for beam profile of the ultrasonic motor It is found that a general paraboliclike profile for beam outer shape is best suited for maximizing output power, while a vaselike profile leads to the worst performance.