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Journals

2007 Journal of Power Sources

System Identification and Robust Control of a Portable Proton Exchange Membrane Fuel-Cell System

 

Fu-Cheng Wang, Yee-Pien Yang, Chi-Wei Huang, Hsin-Ping Chang and Hsuan-Tsung Chen

 

 

Abstract
This paper will discuss the application of system identification techniques and robust control strategies to a proton exchange membrane fuel-cell system. The fuel-cell system’s dynamic behaviour is influenced by many factors, such as the reaction mechanism, pressure, flow-rate, composition and temperature change, and is inherently non-linear and time varying. From a system point of view, however, the system can be modelled as a two-input, two-output linear time-invariant system whose inputs are hydrogen and air flow rates, and whose outputs are cell voltage and current. On the other hand, the system’s non-linearities and time-varying characteristics can be regarded as system uncertainties and disturbances that are treated by the designed robust controllers. This paper is comprised of three parts. First, system identification techniques were adopted to model the system’s transfer functions. Second, the H-infinity robust control strategies were applied to stabilise the system. Finally, the system’s stability and performance were compromised by introducing weighting functions to the controller’s design. From the experimental results, the designed H-infinity robust controllers were deemed effective.

2007 Journal of Power Sources

Low Power Proton Exchange Membrane Fuel Cell System Identification and Adaptive Control

 

Yee-Pien Yang, Fu-Cheng Wang, Hsin-Ping Chang, Ying-Wei Ma and Biing-Jyh Weng

 

 

Abstract
This paper proposes a systematic method of system identification and control of a proton exchange membrane (PEM) fuel cell. This fuel cell can be used for low-power communication devices involving complex electrochemical reactions of nonlinear and time-varying dynamic properties. From a system point of view, the dynamic model of PEM fuel cell is reduced to a configuration of two inputs, hydrogen and air flow rates, and two outputs, cell voltage and current. The corresponding transfer functions describe linearized subsystem dynamics with finite orders and time-varying parameters, which are expressed as discrete-time auto-regression moving-average with auxiliary input models for system identification by the recursive least square algorithm. In the experiments, a pseudo-random binary sequence of hydrogen or air flow rate is fed to a single fuel cell device to excite its dynamics. By measuring the corresponding output signals, each subsystem transfer function of reduced order is identified, while the unmodeled, higher-order dynamics and disturbances are described by the auxiliary input term. This provides a basis of adaptive control strategy to improve the fuel cell performance in terms of efficiency, as well as transient and steady state specifications. Simulation shows that adaptive controller is robust to the variation of fuel cell system dynamics, and it has proved promising from the experimental results.

Conference

2007 Proceedings of the 46th IEEE Conference on Decision and Control

Performance Analyses of Building Suspension Control with Inerters

 

Fu-Cheng Wang and Cheng-Wei Chen

 

 

Abstract
This paper discusses the application of a new mechanical element, called Inerter, to building suspension control. The inerter was proposed as a real two-terminal mechanical element, which is a substitute for the mass element, with the applied force proportional to the relative acceleration across two terminals. To investigate the performance benefits of building suspension with inerters, three building models were utilized to analyze the performance using two proposed performance indices. From the simulation results, inerters were deemed effective in reducing vibrations from earthquakes and traffic.

2007 Proceedings of the 46th IEEE Conference on Decision and Control

Multivariable System Identification and Robust Control of a Proton Exchange Membrane Fuel Cell System

 

Fu-Cheng Wang, Hsuan-Tsung Chen, Yee-Pien Yang and Hsin-Ping Chang

 

 

Abstract
This paper develops a multivariable robust controller for a proton exchange membrane fuel cell (PEMFC) system. To give a perspective of the system, a PEMFC can be simplified as a two-input-two-output model, where the inputs are air and hydrogen flow rates, while the outputs are cell voltage and current. By fixing the output resistance, we aim to control the cell voltage output by regulating the air and hydrogen flow rates. Due to the nonlinear characteristics of this system, a multivariable robust controller is designed to provide robust performance and to reduce hydrogen consumption. The study is carried out in three parts. First, the system transfer functions are experimentally identified. Secondly, robust control algorithms are adopted to design a 2-by-1 H-infinity controller to deal with the system uncertainty and performance requirements. Finally, the designed H-infinity controller is implemented to control the air and hydrogen flow rates. From the experimental results, the multivariable robust control is deemed effective.

2007 Proceedings of the 46th IEEE Conference on Decision and Control

Model Reference Adaptive Control of a Low Power Proton Exchange Membrane Fuel Cell

 

Yee-Pien Yang, Zhao-Wei Liu and Fu-Cheng Wang

 

 

Abstract
Nonlinearity and time-varying dynamics of fuel cell (FC) systems make it complex to design a controller for improving the output performance. This paper introduces an application of model reference adaptive control to a low power proton exchange membrane (PEM) FC system, which consists of three main components: a FC stack, an air pump to supply air, and a solenoid valve to adjust hydrogen flow. From the system perspective, the dynamic model of PEMFC can be expressed as a multivariable configuration of two inputs, hydrogen and air flow rates, and two outputs, cell voltage and current. The corresponding transfer function can be identified off-line to describe the linearized dynamics with a finite order at a certain operating point, and is written in a discrete-time auto-regression moving-average model for on-line estimation of parameters. This provides a basis of adaptive control strategy to improve the FC performance in terms of efficiency, transient and steady-state specifications. Experiments show that the proposed adaptive controller is robust to the variation of FC system dynamics and power request.

2007 Proceedings of the 8th International Symposium on Measurement Technology and Intelligent Instruments

Signal Detection and Control of an Intelligent Robot

 

Fu-Cheng Wang, Hon-Min Lin, Pei-Kang Chen, Fu-Yui Chang and Kuang-Chao Fan

 

 

Abstract
This paper utilizes embedded systems to control an intelligent robot implemented with seven sensor networks. The work was carried out in two phases. The first step developed scanning circuits to feed the sensor signals back to the process systems. The second step installed seven motors and a voice circuit on the robot to respond to the sensor signals. From the results, the proposed embedded system was deemed effective.

2007 Proceedings of the 20th International Symposium: Dynamics of Vehicles on Roads and Tracks

The Impact of Inerter Nonlinearities on Vehicle Suspension Control

 

Fu-Cheng Wang and Wei-Jiun Su

 

 

Abstract
This paper discusses the nonlinear properties of Inerter and their impact on vehicle suspension control. Inerter was recently introduced as an ideal mechanical two-port element which is a substitute for the mass element with the applied force proportional to the relative acceleration across the terminals. Until now, ideal Inerter has been applied to vehicle, motorcycle and train suspension systems, in which significant performance improvement is achieved. However, due to the mechanical construction, some nonlinear properties of the existing mechanical models of Inerter are noted. This paper will investigate the Inerter nonlinearities, including friction, backlash and the elastic effect, and their influence on vehicle suspension performance. A testing platform will also be built to verify the nonlinear properties of the Inerter model.

2007 Proceedings of the European Control Conference

Robust Control Design of a Proton Exchange Membrane Fuel-Cell System

 

Fu-Cheng Wang, Yee-Pien Yang, Chi-Wei Huang, Hsin-Ping Chang and Hsuan-Tsung Chen

 

 

Abstract
This paper utilizes the system identification and robust control techniques for a Proton Exchange Membrane fuel-cell system. The dynamic behaviour of the fuel-cell system is influenced by many effects, such as the reaction mechanism, pressure, flow-rate, composition and temperature change, and is inherently non-linear and time-varying. However, from the system point of view, a fuel cell can be modeled as a two-input, two-output linear system with inputs of hydrogen and air flow rates, and outputs of cell voltage and current. And the un-modeled non-linear and time-varying characteristics of the system can be regarded as system uncertainties and disturbances that are treated by the designed robust controllers. This paper is comprised of three parts. First, system identification techniques were adopted to model the fuel-cell system. Secondly, a H-infinity robust controller was designed to stabilize the system. Finally, the system stability and performance were compromised by introducing a weighting function to the controller design. From both the simulation and experimental results, the designed H-infinity robust controllers were deemed effective.

2007 Proceedings of the 5th International Conference on Fuel Cell Science, Engineering and Technology

Multivariable Robust Control of a Proton Exchange Membrane Fuel Cell System

 

Fu-Cheng Wang, Hsuan-Tsung Chen, Yee-Pien Yang and Hsin-Ping Chang

 

 

Abstract
This paper develops a multivariable robust controller for a proton exchange membrane fuel cell (PEMFC) system. To give a perspective of the system, a PEMFC can be simplified as a two-input- two-output model, where the inputs are air and hydrogen flow rates, while the outputs are cell voltage and current. By fixing the output resistance, we aim to control the cell voltage output by tuning the air and hydrogen flow rates. Due to the nonlinear characteristics of this system, a multivariable robust controller is designed to provide robust performance and to reduce hydrogen consumption. The experiments are carried out in three parts. First, the system transfer functions are identified. Secondly, robust control algorithms are adopted to design a 2-by-1 H-infinity controller to deal with the system uncertainty and performance requirements. Finally, the designed H-infinity controller is implemented to control the air and hydrogen flow rates. From the experimental results, the multivariable robust control is deemed effective.

2007 Proceedings of the 2007 IEEE/ICME International Conference on Complex Medical Engineering

Optimization of the Sit-to-Stand Motion

 

Fu-Cheng Wang, Chung-Huang Yu, Yi-Ling Lin and Chen-En Tsai

 

 

Abstract
This paper proposes a method to evaluate the influence of moving tracks on body loadings. The sit-to-stand movement is selected and analyzed, in order to illustrate how a special form of physical therapy known as the Alexander Technique can effectively reduce the loads placed on the joints. Because force and moment sensors cannot be implemented to take direct measurements within the joints, we used a motion analysis system to analyze information about body position and then input the data into ADAMS models to estimate the reaction forces and moments on the joints. Furthermore, an optimal control algorithm is introduced to quantitatively identify the optimal contours of the movements. By analyzing the reactions of the joints, this paper demonstrates that better moving tracks are beneficial for reducing body loads.

Domestic Conference

2007 Proceedings of 2007 CACS International Automatic Control Conference

Vibration Control of EPL System by Disturbance Response Decoupling

 

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

 

 

Abstract
This paper utilizes Disturbance Response Decoupling (DRD) techniques to suppress vibrations of an Electron Beam Projection Lithography (EPL) system. Due to the resolution requirement, vibration control of EPL systems is increasingly important. Generally speaking, vibration control should cope with two kinds of disturbances, namely load disturbances from the machine and floor disturbances from the environment. In practice, anti-vibration tables are usually utilized to insulate disturbances, by either active or passive control algorithms. However, the controller design is complicated due to the conflicting requirements for the two disturbances. Therefore, we apply DRD techniques to deal with the control requirements independently. We use the passive isolators to reduce the floor disturbances, and the active isolators to cope with the load disturbances. Furthermore, a new mechanical network component, called Inerter, is considered in the design of passive isolators to further improve the system performance. From the simulation results, the proposed control strategies are deemed effective.