Real Time Digital Control of an Active Magnetic Bearing using Open Source Software

A digital control system using a real time variant of Linux is developed and implemented on a bench-top rotor suspended on active magnetic bearings. The combination of simple hardware and open source software provides a useful educational and research platform for digital control methods that is unencumbered by proprietary constraints as well as one that is more cost effective than available commercial systems. A real time operating system must ensure that specific tasks are executed at a fixed rate regardless of other system level demands. This is achieved with special purpose kernels that allow Linux to run as a low priority task within the real time operating system. Digital filters are constructed and coded in C, the native language of Linux. The controller is implemented on an off-the-shelf Pentium 3 personal computer operating in a multiple channel configuration at 10 KHz.