A Nonlinear Amb Model and Identification Methods

This paper presents a single axis nonlinear model of the Active Magnetic Bearing (AMB). In the AMB technology properly designed control algorithm is the most important element. The basic knowledge in the controller design process is the model of the system. It is well known that the AMB cannot operate without control due to structural instability and strong nonlinearities. Thus the modeling studies and controller performance are important stages in the AMB development. The laboratory test rig containing the AMB is presented. The system is controlled from a standard PC computer, where the integrated real-time control and rapid prototyping environment is used. The dedicated I/O board with custom logic applied in the FPGA chip is used for measurements and control signals formulation. Rotor position is measured by proximity sensors. To obtain the full information about the actuator unit operating mode the coil current is measured too. A number of identification procedures is used to obtain parameters of the AMB model. The open and closed loop identifications are used. The physical fundamentals of the behavior of the electromagnet are used in the modeling process. They are extended by nonlinear functions due to results obtained from the identification.