Digital control of an experimental active magnetic bearing rotor using open source software

A real time digital control system using Real Time Linux is developed and implemented on a bench-top rotor suspended on active magnetic bearings. The digital controller operates in a multiple-input, multiple-output mode at 10 kHz and is implemented on a Pentium3 personal computer. The software also enables the capability to modify the control law "on-the-fly" as the rig is operating, and a low cost tachometer and shaft angular position sensor is incorporated in the experimental setup. This combination of simple hardware and open source software provides a useful research platform for digital control methods that is unencumbered by proprietary constraints as well as one that is much more cost effective than available commercial systems.; A low order rotor model and a phase-lead controller with a parallel integrator give predictions of closed loop performance for the rotor rig which agree well with experimental data obtained at low rotational speed. In addition, the corresponding root locus plot demonstrates the ability to control the value of the rotor critical speed.; Experimental evidence of instability above the first critical speed was found, but was not investigated due to safety concerns in an open laboratory environment and the time and financial constraints imposed by a possible catastrophic failure of the apparatus.