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Journals

2009 Applied Physics Letters

Ultrahigh Contrast Light Valve Driven by Electrocapillarity of Liquid Gallium

 

Jeff T. H. Tsai, Chih-Ming Ho, Fu-Cheng Wang and Chi-Te Liang

 

 

Abstract
This letter describes an ultrahigh contrast valve driven by the electrocapillarity of liquid gallium. We demonstrate that a micrometer-sized gallium droplet can be used to fabricate a prototype backlight transmissive pixel cell by transforming the droplet into a flat thin film. This light valve exhibits significantly high backlight utility 96%, an exceptional contrast ratio 10^6: 1, and fast response time (0.49 ms). The high contrast ratio originated from the exceptional reflectivity of gallium, which can block backlight to prevent any transmission in the off state of our device. Without using any polarizer, the backlight utility can be improved dramatically compared to a conventional liquid crystal display. The backlight utility and switching time obtained from this prototype light valve is higher than that of commercial liquid crystal displays. This concept is also applicable to a wide variety of electro-optical devices.

2009 Vehicle System Dynamics

The Performance Improvements of Train Suspension Systems with Mechanical Networks Employing Inerters

 

Fu-Cheng Wang, Min-Kai Liao, Bo-Huai Liao, Wei-Jiun Su and Hsiang-An Chan

 

 

Abstract
This paper investigates the performance benefits of train suspension systems employing a new mechanical network element called an inerter. An inerter is a true mechanical two-terminal element with the applied force proportional to the relative acceleration across the terminals. Until now, ideal inerters have been applied to car and motorcycle suspension systems, for which a significant performance improvement was reported. In this paper, we discuss the performance benefits of train suspension systems employing inerters. The study was carried out in three phases. First, fixed suspension structures were applied to train suspension systems, and optimised for two performance measures. Secondly, this optimization was further carried out using linear matrix inequality approaches to discuss the achievable performance of passive networks. The resulting networks can then be realised by synthesis methods, such as the Brune and Bott–Duffin realisation. Finally, the nonlinear properties of inerter models and their impact on system performance were discussed. From the results, the inerter was deemed effective in improving the performance of train suspension systems.

2009 Japanese Journal of Applied Physics

The Application of Disturbance Response Decoupling to the Vibration Control of an Electron Beam Lithography System

 

Fu-Cheng Wang, Yu-Chia Tsao and Jia-Yush Yen

 

 

Abstract
This paper demonstrates a method to control an electron beam lithography (EBL) system’s vibrations with a newly developed technique called disturbance response decoupling (DRD). Resolution requirements make the vibration control of EBL systems increasingly important. Satisfying performance criteria requires considering two kinds of disturbances, load disturbances from the machine and ground disturbances from the environment, in EBL systems. Controlling lithography tools’ vibrations has been studied for many years; however, designing controllers by traditional approaches can be very complicated because of these two types of disturbances’ conflicting requirements. Therefore, DRD techniques were applied for this paper to deal independently with these performance requirements. The DRD control method was initially proposed in 2001 to address vehicle suspension control problems. This paper proposes a generalized and experimentally realized DRD control structure to suppress an EBL system’s vibrations. The work was carried out in three parts. First, passive isolators were used to isolate ground disturbances. Second, active components were applied to improve the system’s responses to load disturbances. Finally, the system was integrated to verify its overall performance. Simulations and experiments verify the proposed control strategies’ effectiveness.

2009 Proceedings of the Institution of Mechanical Engineers, Part H, Journal of Engineering in Medicine

Design and Implementation of Robust Controllers for a Gait Trainer

 

Fu-Cheng Wang, Chung-Huang Yu and Tai-Yu Chou

 

 

Abstract
This paper applies robust algorithms to control an active gait trainer for children with walking disabilities. Compared with traditional rehabilitation procedures, in which two or three trainers are required to assist the patient, a motor-driven mechanism was constructed to improve the efficiency of the procedures. First, a six-bar mechanism was designed and constructed to mimic the trajectory of children’s ankles in walking. Second, system identification techniques were applied to obtain system transfer functions at different operating points by experiments. Third, robust control algorithms were used to design H-infinity robust controllers for the system. Finally, the designed controllers were implemented to verify experimentally the system performance. From the results, the proposed robust control strategies are shown to be effective.

2009 International Journal of Hydrogen Energy

Design and Implementation of Fixed-Order Robust Controllers for a Proton Exchange Membrane Fuel Cell System

 

Fu-Cheng Wang and Hsuan-Tsung Chen

 

 

Abstract
This paper applies fixed-order multivariable robust control strategies to a proton exchange membrane fuel cell (PEMFC) system, and implements the designed controllers on a microchip for system miniaturization. In previous studies, robust control was applied to guarantee system stability and to reduce hydrogen consumption for a PEMFC system. It was noted that for standard robust control design, the order of resulting H-infinity controllers is dictated by the plants and weighting functions. However, for hardware implementation, controllers with lower orders are preferable in terms of computing efforts and cost. Therefore, in this paper the PEMFC is modeled as multivariable transfer matrices, then three fixed-order robust control algorithms are applied to design controllers with specified orders for a PEMFC. Finally, the designed controllers are implemented on a microchip to regulate the air and hydrogen flow rates. From the experimental results, fixed-order robust control is deemed effective in supplying steady power and reducing fuel consumption.

2009 IEEE Circuits and Systems Magazine

The Missing Mechanical Circuit Element

 

Michael Z. Q. Chen, Christos Papageorgiou, Frank Scheibe, Fu-Cheng Wang and Malcolm C. Smith

 

 

Abstract
In 2008, two articles in Autosport revealed details of a new mechanical suspension component with the name “J-damper” which had entered Formula One Racing and which was delivering significant performance gains in handling and grip. From its first mention in the 2007 Formula One “spy scandal” there was much speculation about what the J-damper actually was. The Autosport articles revealed that the J-damper was in fact an “inerter” and that its origin lay in academic work on mechanical and electrical circuits at Cambridge University. This article aims to provide an overview of the background and origin of the inerter, its application, and its intimate connection with the classical theory of network synthesis.

Conference

2009 Proceedings of the 3rd International Conference on Mathematical Aspects of Computer and Information Sciences

Optimization and Synthesis for a Mechatronic Network

 

Fu-Cheng Wang, Hsiang-An Chan, Jason Zheng Jiang and Malcolm C. Smith

 

 

Abstract
This paper applies a novel mechatronic system to vehicle suspensions. The proposed mechatronic system consists of a ball-screw inerter and permanent magnet electric machinery (PMEM), such that the system impedance is a combination of mechanical and electrical networks. Then we apply linear matrix inequalities (LMI) to optimize system performance, and discuss network synthesis of the obtained optimal impedances. The results demonstrate the effectiveness of the mechatronic system and newly introduced network synthesis methods.

2009 Proceedings of the 22nd International Microprocesses and Nanotechnology Conference

Vibration Isolation of a Full Electron Beam Projection Lithography System

 

Fu-Cheng Wang, Min-Feng Hong and Jia-Yush Yen

 

 

Abstract
This paper applies disturbance response decoupling (DRD) techniques [1] to the vibration control of a full electron beam lithography (EBL) system. In the previous studies [2], we demonstrated the effectiveness of DRD structures in suppressing system vibrations of a quarter EBL system. From the simulation and experimental results, the designed active robust controllers [3] can successfully reduce system responses to machine vibrations while the ground vibrations were controlled by passive elements. This paper extends these ideas to a full EBL system with seven degree of freedom (DOF). The work was carried out in four phases. First, passive isolators were used to reduce the floor disturbance, and active actuators were implemented to reduce machine vibration through DRD design.. Second, the full EBL system was decoupled into corresponding half- and quarter- sub-systems, using symmetric transformation. Third, independent controller design was conducted in the bound, pitch, roll and warp modes, using the techniques developed in [2]. Finally, the system was integrated to verify the overall performance.

2009 Proceedings of the 7th Asian Control Conference

Robust PID Controller Design Using Particle Swarm Optimization

 

Liu-Hus Lin, Fu-Cheng Wang and Jia-Yush Yen

 

 

Abstract
This paper proposes a novel method to synthesize robust proportional-integral-derivative (PID) controllers using particle swarm optimization (PSO). Robust control is well known for its ability in dealing with system uncertainties and disturbances. Standard robust control design, however, can result in controllers that are high-order and complicated and can be difficult to implement in practical applications. PID controllers are advantageous because of their simple structures and wide acceptance in engineering practice, but they lack profound theorems in dealing with system uncertainties and disturbances. Therefore, combining the advantages of these two control algorithms, robust PID-structure controllers are proposed to optimize system performance using PSO. Finally, an example is used to illustrate the design procedures. Simulation results show the proposed method to be effective.

2009 Proceedings of the European Control Conference

Multivariable Fixed-Order Robust Control for a PEMFC System

 

Fu-Cheng Wang, Hsuan-Tsung Chen, Ming-Cheng Chou and Jia-Yush Yen

 

 

Abstract
This paper applies fixed- order multivariable robust control strategies to a proton exchange membrane fuel cell (PEMFC) system. In previous studies, robust control was applied to guarantee system stability and to reduce hydrogen consumption for a PEMFC system. We noted that for standard robust control design, the order of resulting H-infinity controllers is constrained by the plants and weighting functions. However, for hardware implementation, controllers with lower orders are preferable in terms of computing efforts and cost. Therefore, in this paper we model the PEMFC as multivariable transfer matrices, and then apply three fixed- order robust control algorithms to design controllers with specified orders for a PEMFC. Finally, the designed controllers are implemented to regulate the air and hydrogen flow rates. From the experimental results, fixed- order robust control is deemed effective in supplying steady power and reducing fuel consumption.

2009 Proceedings of the 21th International Symposium: Dynamics of Vehicles on Roads and Tracks

The Use of Inerters Improves the Stability and Performance of a Full-Train Model

Fu-Cheng Wang and Min-Ruei Hsieh

 

 

Abstract
We investigated the lateral stability of a full-train suspension system by using inerters. Herein, inerters are proposed as an ideal mechanical two-port element to substitute for the mass element in the mechanical/electrical analogy. In the previous study, we used a 16 degrees-of-freedom (DOF) half-train model to demonstrate the potential improvement on critical speed brought about by the use of inerters. In this paper, we apply the ideas presented in the previous work to a 28 DOF full-train model and discuss the benefits related to stability and system performance. The results show the effectiveness of inerters with regard to improving the lateral stability and dynamic responses of train systems.

2009 Proceedings of the IEEE International Symposium on Industrial Electronics

Design and Control of an Active Gait Trainer

 

Fu-Cheng Wang, Chung-Huang Yu, Tai-Yu Chou and Nai-Chung Chang

 

 

Abstract
This paper demonstrates the design and control of an active gait trainer for children with walking disabilities. Compared to the traditional rehabilitation procedures in which two or three trainers are required to assist the patient, a motor-driven mechanism was constructed to improve the efficiency of the procedures. The work was carried out in four steps. First, a six-bar mechanism was designed to mimic the preferred trace of ankle joints. Second, system identification techniques were applied to obtain the system transfer functions. Third, robust control algorithms were used to design H-infinity robust controllers to follow the traces. Finally, the designed controllers were implemented for performance verification. Based on the simulations and experimental results, the proposed mechanism and control are deemed effective.

Domestic Conference

2009 Proceedings of 2009 CACS International Automatic Control Conference

Multivariable Robust Control for a 500W Self-Humidified PEMFC System

 

Fu-Cheng Wang, Ming-Cheng Chou and Chih-Chun Ko

 

 

Abstract
This paper illustrates the integration and control of a 500W self-humidified proton exchange membrane fuel cell (PEMFC) system. From the system point of view, a PEMFC can be regarded as a two-input-two-output system with voltage and current. By identification techniques, we find transfer functions of the PEMFC system at different operating points, and treat the un-modeled dynamics as system uncertainties. Thus, robust control strategies can be applied to stabilize the system and increase the system performance. In this paper, we design a standard H-infinity robust controller to stabilize the PEMFC system, and further apply fixed-order robust control. Finally, the system performance and efficiency are experimentally verified. The results show the effectiveness of these controllers.

2009 Proceedings of 2009 CACS International Automatic Control Conference

Robust Controller Design for an Electron Beam Projection Lithography System

 

Fu-Cheng Wang, Min-Feng Hong and Chin-Hui Hsieh

 

 

Abstract
This paper discusses the vibration control of an electron beam projection lithography (EBL) system. Two main disturbances, namely load disturbances from the machine and ground disturbances from the environment, should be considered for EPL system. Since the suspension settings to suppress these two disturbances are conflicting, we construct a double-layer optical table and apply disturbance response decomposing (DRD) techniques to insulate the disturbances independently. That is, a passive control structure is used to isolate the vibration from ground disturbances, while an active control structure is applied to reduce the vibration from load disturbances.
Because the full optical table has seven degree of freedom, symmetric transformation is applied to decouple it into the bounce/pitch and roll/warp half-table models. These two half-table models can be further decoupled into the bounce, pitch, roll and warp quarter-table models, based on the assumptions of kl-simplicity, for  H-infinity robust controller design. From both simulation and experimental results, the designed controllers are shown to effectively reduce vibrations of the EPL system.