Eng Kiong Wong

Application of Active Force Control and Iterative Learning in a 5-Link Biped Robot

This paper investigates the efficacy of the implementation of the conventional Proportional-Derivative (PD) controller and different Active Force Control (AFC) strategies to a 5-link biped robot through a series of simulation studies. The performance of the biped system is evaluated by making the biped walk on a horizontal flat surface, in which the locomotion is constrained within the sagittal plane. Initially, a classical PD controller has been used to control the biped robot. Then, a disturbance elimination method called Active Force Control (AFC) schemes has been incorporated. The effectiveness and robustness of the AFC as “disturbance rejecter” has been examined when a conventional crude approximation (AFCCA), and an intelligent active force control scheme, which is known as Active Force Control and Iterative Learning (AFCAIL) are employed. It is found that for both of the AFC control schemes proposed, the system is robust and stable even under the influence of disturbances. An attractive feature of the AFCAIL scheme is that inertia matrix tuning becomes much easier and automatic without any degradation in the performance.

Supervised Locally Linear Embedding in face recognition

Locally Linear Embedding (LLE), which has recently emerged as a powerful face feature descriptor, suffers from a limitation. That is class-specific information of data is lacked of during face analysis. Thus, we propose a supervised LLE technique, known as class-label Locally Linear Embedding (cLLE), to overcome the problem. cLLE is able to discover the nonlinearity of high-dimensional face data by minimizing the global reconstruction error of the set of all local neighbors in the data set. cLLE utilizes user class-specific information in neighborhoods selection and thus preserves the local neighborhoods. Since the locality preservation is correlated to the class discrimination, the proposed cLLE is expected superior to LLE in face recognition. Experimental results on three face databases: ORL, AR and Yale databases, demonstrate that the proposed technique obtains better recognition performance than PCA and LLE.

Performance evaluation of fuzzy-based decision system for pool

An important step in any machine intelligence is to automatically and reliably decide on a solution/outcome based on the inputs given. The mapping of the inputs to an output decision often follows a set of critical rules that mimic the decision that would often be decided by a human being. In this paper, the performance of a fuzzy-based decision system for playing a game of pool is presented by comparing the results involving direct hit with two known systems. The performance is also compared to the decision that would be made by the human players. The design steps for the fuzzy-based decision system are presented using the fuzzy logic approach by employing a three-input one-output fuzzy inference system based on a set of 24 rules. The results have shown that fuzzy logic is able to accurately decide on the best move, which is as good as the human players themselves.

Development of low-loss sapphire mirrors

We report on the successful development of low-loss sapphire mirrors for use at a 1-mum wavelength. Methods for polishing and coating are described. The analysis of each process shows a roughness of better than 0.1 nm, a coating scattering of 1 ppm, and a surface scattering of 13 ppm. The mirrors have been characterized in a Fabry-Perot cavity, having a finesse of 100, 000. Mode doublets result from the birefringence of the coatings.

MOBILE ROBOT PATH PLANNING USING HYBRID GENETIC ALGORITHM AND TRAVERSABILITY VECTORS METHOD

Abstract The shortest/optimal path generation is essential for the efficient operation of a mobile robot. Recent advances in robotics and machine intelligence have led to the application of modern optimization method such as the genetic algorithm (GA), to solve the path-planning problem. However, the genetic algorithm path planning approach in the previous works requires a preprocessing step that captures the connectivity of the free-space in a concise representation. In this paper, GA path-planning approach is enhanced with feasible path detection mechanism based on traversability vectors method. This novel idea eliminates the need of free-space connectivity representation. The feasible path detection is performed concurrently while the GA performs the search for the shortest path. The performance of the proposed GA approach is tested on three different environments consisting of polygonal obstacles with increasing complexity. In all experiments, the GA has successfully detected the near-optimal feasible...

Measurement of the thermal expansion coefficient of an all-sapphire optical cavity

We present measurements of the frequency-temperature dependence of an all-sapphire Fabry-Perot optical cavity to be used as an optical frequency reference. Measurements were made by tracking the frequency of the cavity relative to a second high-stability cryogenic sapphire-spaced cavity-a technique with impressive resolution for measurements of the coefficient of thermal expansion (CTE). Measurements presented here cover the temperature range of 11 K to 26 K. We find that the CTE of the all-sapphire cavity for these temperatures is given by /spl alpha//sub cavity/=(7.7/spl plusmn/0.9)/spl times/10/sup

Intelligent Pool Decision System Using Zero-Order Sugeno Fuzzy System

/ -/sup 13/T/sup (3.23/spl plusmn/0.05/).

Explicit communication in designing efficient cooperative mobile robotic system

This paper describes the approach of using the zero-order Sugeno fuzzy system to design an intelligent decision system for a game of pool. The decision system consists of three types of playing strategies for a normal game of pool: direct, combination and bank shots. For each of the playing scenario on the pool table, the decision system comes out with one output shot (or best shot): presenting which ball should be chosen and which path should it follow. The system has been tested step-by-step on a real pool game and results are tabulated in the paper. The decision is designed as the brain for a robotic pool system.

Temperature-compensated cryogenic Fabry–Perot cavity

This paper presents the design of ant-inspired control strategies that mimic the ant colony foraging behavior. Inter-agent communication, in particular explicit communication is applied to create multiple cooperating mobile robots in order to accomplish the foraging task. Explicit communication can significantly multiply the capabilities and effectiveness of teams of robotic systems. However, the drawback is it introduces more interference among robots at the goal and home region in comparison to robotic system without the implementation of inter-agent communication. Thus, to investigate how well the explicit communication can be adopted in designing efficient cooperative mobile robotic system, experiments were carried out on the simulated robots. The efficiency of the strategies are measured in terms of three criteria: time, density of robots and interference.

Measurement of the coefficient of thermal expansion of a cryogenic, all-sapphire, Fabry-Perot optical cavity

We show that temperature compensation based on differential thermal expansion between sapphire and fused silica can be used to create a Fabry-Perot cavity with an exceptionally low coefficient of thermal expansion at low temperatures. We describe the design of such a cavity that utilizes shaped fused silica mirrors and a sapphire spacer. The geometry of the fused silica mirror was designed using a finite element model to have a small platform, giving a frequency temperature turning point of 16.6 K. The measured turning point was 16.2 K and the curvature was 6 x 10(-10) K(-2), both of which were consistent with the model.