Thong-Shing Hwang

Stability of Networked Control Systems with Time-Varying Delays

A robust Smith predictor is proposed to compensate for the round trip delay of networked control systems (NCSs); An analytical TCP model is adopted. We show that stability of the closed-loop system is guaranteed up to some maximum upper bound of the round trip delay

An image-based LCD positioning system utilizing the modified FHT method

Summary In this paper, a LCD positioning system based on an image processing method is described. This method is effective in finding the angle of the geometric features in the cross registration mask. However, when two marks appear in the same frame, the problem of situation verification becomes more complex. We use an algorithm that assists with calculating the location and rotation angle for two marks precisely and quickly using the Fast Hough Transform (FHT). This method determines the locations of two masks and calculates the rotation angle from a blurred edge to adjust the LCD position and orientation.

Self-organized PID control design using DNA computing approach

Abstract A new design and realization method solving for the constrained multi‐objective problem via a self‐organizing PID control design using the DNA computing algorithm is proposed. Requirements of stability robustness and optimality related to the H ∞ and H 2 performance specifications are imposed as the objectives. The algorithm uses a coding method originating from the structure of biological DNA molecules to map parameters as well as the structure of PID controllers into DNA strings. Structured mutation operators are proposed to modify the control structure during the computation process. Simulations and experiments are performed to verify the performance and applicability of our design.

A new image processing method for evaluating the pupillary responses in a HMD-type eye-tracking device

In this paper, a new image processing method for evaluating the pupillary responses is described. This system is based on an eye-tracking system, using eye tracking and pattern recognition techniques with appropriate hardware and software. This pupillary response evaluation system includes a head-mounted display and a pinhole CCD camera. When the subject uses the head-mounted display to browse the screen of a computer, the CCD camera catches images of the subjects eye and transmits it to the computer. The program in the computer calculates the location and size of the pupil in the images. The pupil area calculation weighting function, visual fatigue detection, concentration detection, and eye/HMD slide compensation are included in the system. This allows the system to detect the pupil under different conditions. This system will know if anyone is using the system, then it evaluates the operating conditions of the subject, if the adjustment is correct, and guides the operator in using the system. The experimental results verified that this image system provides an economical and effective method for evaluating pupillary responses.

Twin-VCM Controller Design for the Nutator System with Evolutionary Algorithms

Abstract We present an evolutionary algorithm to optimize controller parameters for a nonlinear nutator system which is implemented in twin voice coil motors (VCMs). In this paper, genetics-based algorithm is applied to tune the proportional-integral-derivative (PID) controller for the multi-input multi-output (MIMO) coupling system. The result has been validated that this algorithm can find out all six PID control parameters in optimal and robust senses. The controller architecture of the nutator system is constructed to meet the specifications of the coupled mirror and rocker parallel loops, both adopting PID control. Two main linear VCMs operating in a push-pull organization drive the nutator subreflector. The mandatory operation mode for the nutator system is two-position switching. The required technical specifications for the nutator control system are extremely precise requirements, system tracking control with a disturbance force more challenging than that in ordinary systems. Simulation results have demonstrated the superiority of the evolutionary algorithm, satisfying the Atacama large millimeter/submillimeter array (ALMA) severe conditions and requirements.

ZPETC Path-Tracking gain-scheduling design and real-time multi-task flight simulation for the automatic transition of tilt-rotor aircraft

The purpose of this research is to accomplish the ZPETC (Zero Phase Error Tracking Control) Path-Tracking gain-scheduling control design and real-time multi-task flight simulation for the automatic transition of tilt-rotor aircraft.

Singularity Characterization and Path Planning of a New 3 Links 6-DOFs Parallel Manipulator

This paper presents singularity characterization and optimal path planning for a new three links six degreesof- freedom (DOFs) parallel manipulator. To achieve high speed handling and machining, the base platform is equipped with three linear slideways each one actuated by a linear DC motor, and each extensible vertical link connecting the upper and base platforms is actuated by an inductive AC servo motor. Characterization of workspace, singularity, and development of an optimal path planner are presented. Our special emphases are on characterization of the platform singularity using genetic algorithms (GAs) and singularity avoidance of the path planning based on a DNA evolutionary computing algorithm. We propose a path planning scheme whose coding technique speeds up the execution of search for fast path generation within the feasible workspace.

Failure detection and adaptive compensation for fault tolerant flight control systems

This paper presents an advanced aircraft flight control system with the capabilities of failure detection, identification and adaptive compensation in the event of the damage of control surface happening. For the proposed scheme, a fault tolerant mechanism is activated Io regain the control of the damaged aircraft. The approach is based on the detection of abrupt changes of the correlation functions between pitching, yawing and rolling rates and the failure compensation mechanism is realized by using a wavelet neural net-based PID controller.

MEMS technology on wafer-lever LED packaging

This study demonstrated a newly type technology of a wafer level packaging method for light emitting diode (LED) with aspheric lens and microlens array using microelectromechanical systems (MEMS) technology and transfer molding process. The novel packaging structure includes two components: the silicon-based packaging substrate which is formed with arrayed reflector depression and through-hole interconnects by bulk micromachining and the optical encapsulation with lens configuration that formed by transfer molding in wafer level. By this pattern transfer process, the precise alignment between lens configuration and the reflector of silicon substrate can be achieved and batch process can be realized to reduce the costs. Beside, the packaging element can be used more applications. In the study, the pattern transfer of various lens profiles was also accomplished successfully by using silicone gel as lens mold. The brightness of the packaging elements with single aspheric lens profile and high fill factor microlens array can be increased by 26% and 16%, respectively, in comparison to the case of optical encapsulation with smooth curved surface. Furthermore, the light radiation uniformity was improved effectively through 100% fill factor microlens array. Therefore, the structure can satisfy the requirements of wafer level LED packaging and improve the heat dissipation and light extraction efficiency.

Structure variable PID control design based on DNA coding method

A novel structure variable PID control design based on the DNA algorithm is proposed. The algorithm uses a coding method originated from the structure of biological DNA molecules to map parameters as well as the structure of PID controllers. A frameshift mutation operator is presented to modify the controllers structure while performing the molecular evolution process. Extensive computer simulations and experiments are presented to support the proposed design.