Design And Implement Of A Hardware Platform For Active Magnetic Bearings

An Active Magnetic Bearing (AMB) is a mechatronics product combiningtraditional mechanics with electronics and computer engineering. Based on essentialmechanical systems, an AMB employs sensors and microprocessors to acquire, processand feedback data to achieve a better performance. As AMBs require no lubrication andhave little friction loss, they are mainly used in fields of vacuum and clean roomtechnology, machine tools, turbomachineries and centrifuges.A controller is the core of an AMB system. Design methods and principles ofvarious AMB controllers, including a single-core DSP-based controller which wascurrently in use were discussed in this paper. It was found that a single-core DSPcontroller could manage real-time control data operation; however, due to DSP’s limitedcapability of peripherals management, it performed weak on real-time data transmission,on-line adjustment of parameters. Parameters in the control algorithm couldn’t beadjusted on line and the only way to modify them was to re-compile the programs.On account of these disadvantages of single-core DSP based controllers, a newtype AMB controller was conceived and implemented based on a dual-core chipOMAP-L137including a DSP and an ARM core. DSP/BIOS LINK module wasemployed to achieve efficient data transmission between the DSP and ARM core.5-channel sensor signals were acquired through two AD7865chips. Data was processedwith specific control algorithms (such as PID algorithm) by the DSP core and10-channel amplifier signals were output through three AD5344chips. ARM core wasresponsible for data transmission, accepting on-line parameter adjustment commands oruploading data to a host computer.Controllers of different hardware architectures were designed, and a final versioncontroller was completed through comparement and online test. The new controller hadrich interfaces compared to the old one. On the software side, by analyzing andcomparing a varity of data transmission models, appropriate models and related APIswere selected. Through optimization of software architecture and programs, the overallperformance of the dual-core controller was enhanced.Through tests on an AMB levitation platform, the new controller completed astable suspension of five-degree-of-freedom of the magnetic bearing employing PID control algorithm. In the experiment, through adjusting the rotor suspension position,the function of on-line control parameters adjustment was verified. In addition, withtests of acquiring data on-line without affecting the real-time control capability, the highperformance of data processing and transferring of the new controller was certified.