Real Time Control of a Magnetic Bearing Suspension System for Flexible Rotors

Suspension of a magnetic bearing system involves significant computational effort. Control systems based upon embedded Digital Signal Processors (DSP) boards often require specialized programming and development tools, may lack flexibility when computational requirements change, and are often relatively expensive. Magnetic bearing systems need 1) real time monitoring of the plant states, inputs, and outputs 2) real time plotting functions such as rotor position vs. time, Fast Fourier Transform (FFT) functions and user specified filters, 3) controller parameter updates, and 4) access to reference signals. It is desired to employ a hardware/software system which is low cost, easy to use, is extensible as more advanced versions of hardware/software become available, and distributable over local networks of DSPs. A system with all of the above desired characteristics has been implemented for control of a magnetic bearing supported flexible rotor using RT-Linux, a free modification of Linux, intended to support hard real-time computation. Experiences designing the software architecture, defining timing requirements of the control tasks, implementing the control tasks in RT-Linux, and measuring the predictability of RT-LimL, c for this application are discussed.