Showing papers by "Abdul Rashid Husain published in 2007"

Sliding Mode Control with Linear Quadratic Hyperplane Design: An application to an Active Magnetic Bearing System

Abstract: This paper deals with modeling and control of a nonlinear horizontal active magnetic bearing (AMB) system via current control scheme. The gyroscopic effect and mass imbalance inherited in the system are proportional to the rotor speed in which these nonlinearities cause high system instability as the rotational speed increases. In order to synthesize a robust controller that can stabilize the system under a wide range of rotational speed, the dynamic AMB model is transformed into a deterministic model to form a class of uncertain system. Then, based on Sliding Mode Control (SMC) theory and Lyapunov method, a new robust controller that stabilizes the system is proposed wherein the Linear Quadratic Regulator (LQR) is used to design the sliding surface. Under this control, the reaching condition is guaranteed and the closed loop system is stable. The performance of the controller applied to the AMB model is demonstrated through simulation works under various rotational speeds and system conditions.

Deterministic Models of an Active Magnetic Bearing System

Abstract: In this paper the development of mathematical model of voltage-input and current-input active magnetic bearing (AMB) system in deterministic form is presented. The AMB system, which is open-loop unstable and highly coupled due to nonlinearities inherited in the system such as gyroscopic effect and mass imbalance, requires a dynamic controller that can stabilize the system. In order to synthesize the controller, the nonlinear AMB model is transformed into its deterministic form by using the known upper and lower bounds of the parameters and the state variables of the system. The voltage-input AMB model shows that the system contains mismatched uncertainty and non-zero system states value which suggests that synthesizing nonlinear dynamic controller for this model is almost unfeasible. Overcoming these problems, the current input AMB model, however, is in the structure that is more suitable for the design of a stabilizing controller. A result from a computer simulation work shows that the states of the system behave nonlinearly without feedback control; however, this final system model with its numerical values can be used for the design of a class of a dynamic controller for system stabilization.

Modeling of a Horizontal Active Magnetic Bearing System with Uncertainties in Deterministic Form

Abstract: In this paper the derivation of mathematical model of a horizontal active magnetic bearing (AMB) system in deterministic form is presented. The system is open-loop unstable and highly coupled due to nonlinearities inherited in the system such as gyroscopic effect and mass imbalance. Based on the equation of motions of the rotor and dynamic equation of electromagnetic coils, the dynamic model of the system with eight inputs is derived and represented in state-space format in which the system matrix is 16times16 in size. By using the upper and lower bounds of the parameter and the state variables of the system, the model is transformed into deterministic form where it can be shown that the system contains mismatched uncertainties in the state and disturbance matrices. This final system model with its numerical values can be used for the design of a class of a dynamic controller for system stabilization

Design of a fault diagnostic engine for power transformer using data mining

Abstract: The power transformer is one of the main components in a power transmission network. Major faults in these transformers can cause extensive damage which does not only interrupt electricity supply but also results in large revenue losses. Thus, these transformers are needed to be routinely maintained. Due to the large number of transformers of different makes and capacities, routine maintenance and diagnosis of such transformers are rather difficult as different transformers exhibit different characteristics and problems. Moreover, different climatic and operating conditions may not be able to draw correct conclusion to some problems. In Malaysia, the lack of local expertise makes dependency on foreign consultants imminent which are rather expensive. To help in overcoming such problems, a Software for Intelligent Diagnostics of Power Transformers known as ADAPT, using the technique of fuzzy logic is developed in this study. The technique allows the interpretation of the Dissolved Gas Analysis (DGA) to be performed routinely on the transformers. In order to ensure that all the transformers are diagnosed and maintained properly, a new intelligent diagnostic architecture known as Total Intelligent Diagnostic Solution (TIDS) has been developed to improve the diagnosis accuracy of the conventional DGA approaches. The TIDS structure has a main interpretation module which consists of Fuzzy TDCG and Fuzzy Key Gases and a supportive interpretation module which consists of Fuzzy Rogers Ratio and Fuzzy Nomograph. The TIDS structure is incorporated into the ADAPT software which allows for multiple diagnostic methods to reach an ultimate outcome especially when verified by four methods. This new architecture leads to the diagnostic of a wider range of transformer fault types and provides a more detail information about the transformer condition, thus help to reduce maintenance costs, prevent unnecessary force outages and avoid explosion danger.

Sliding mode control of an active magnetic bearing system

Abstract: Magnetic bearing is an attractive device in precision engineering field because of its non-contacting nature and controllability of its dynamic characteristics. This paper provides a method of designing a sliding mode control for an active magnetic hearing(AMB) system which is used to support the elevation axis of a target tracking sight instead of mechanical bearings to eliminate the effect of mechanical friction. In such system, the axis should be levitated and supported within a predetermined air gap while AMB is excited by base motion. Experimental results showed that the sliding mode control is effective in disturbance rejection than conventional PID-control without any additive measurements.