A. Forrai

Fuel-cell parameter estimation and diagnostics

In the future, a major role of fuel cells in combined heat and power generation systems is envisaged. It is well known that a fuel cells efficiency is highly dependent on the operating conditions, such as temperature, humidity, and air flow. In the aim to assure optimal operating conditions as well as to minimize the losses, parameter identification, diagnostics, and control are going to play an important role. The paper deals with parameter identification and diagnostics of a low-power proton-exchange membrane fuel cell considering a system identification approach. This multi-input multi-output electrochemical system can be tested or monitored by identifying its parameters, which has real importance in the manufacturing, exploitation, and maintenance phase. Therefore, parameter identification represents the core of any diagnostics or online monitoring procedure. Furthermore, online parameter estimation might be used for control purposes to maintain the fuel cell in an optimal operating point with minimal losses. The proposed parameter identification method is simple, cost-effective, and can be extended easily for fuel-cell stacks too.

Fuzzy logic based vibration suppression control of flexible structures

The paper deals with vibration suppression control of flexible structures applying a fuzzy controller. Due to the complexity of the mathematical model related to the flexible structures, due to the restriction imposed by the actuator (force stroke limitation) as well as economical aspects, a fuzzy logic based approach of the control system is proposed. The experimental results using a fuzzy controller are compared with those obtained in case of conventional or traditional control. Moreover, sensitivity analysis is performed.

New estimation method of state of batteries based on system identification

This paper proposes a new approach for the assessment of battery state using a mathematical model of internal impedance. State of charge and degradation might be estimated by methods using system identification techniques. The final objective of this research is to find out a simple, time and cost effective method. In this paper, the targets of estimation are Ni-Cd, Ni-MH batteries that are widely used in portable equipment, but for which exact state estimation is difficult. In the proposed method, a new signal-processing scheme is used to detect voltage fluctuation of batteries. Using the proposed method and system identification method suitable for batteries, parameters of mathematical model are obtained from experiments. The obtained parameters have sufficient information in order to estimate the state of batteries.

Design of robust controllers with constraints on the control signal application for brushless DC drives

Controller design for systems with hard constraints is a quite vivid area of research, due to the fact that most practical control problems are dominated by constraints on the control signal. The paper presents a general theoretical framework of how robust controllers can be designed, taking into account the constraint on the control signal. The systematic design of a robust controller is illustrated in case of a vector controlled brushless DC motor drive, which is identified using advanced identification techniques. In order to enhance the dynamic performances of the designed control system, in case of limitation of the control signal, a gain-scheduled control strategy is considered. The robust stability of the gain-scheduled control system, considering the variation rate of the time-varying parameter is studied by linear matrix inequalities. The proposed robust controller design approach is verified by experimental results in case of a brushless DC motor drive, when the control algorithm is implemented on a DSP board.

Active vibration suppression control of flexible structures by scheduled H/sub /spl infin// control considering the control force saturation

This paper proposes vibration suppression control of flexible structures by taking into consideration the saturation of the control force. At first, the structure is modified by direct velocity feedback control (DVFC) as a minor feedback loop, that contains the saturation of the control force. Due to the control force saturation DVFC gains are varying. A scheduled H/sub /spl infin// controller, therefore, must be designed in the presence of control force saturation. The proposed scheduled H/sub /spl infin// controller is compared with a linear-time-invariant (LTI) controller against a scaled El Centro loading. The simulations and experimental results proved the superiority of the designed controller to LTI controllers.