Research On The Fault Tolerant Control System Of Active Magnetic Bearing

Comparing with traditional mechanical bearings,active magnetic bearings have such advantages as non-contact,frictionless and no lubrication,so they are widely used in high-speed rotating machinery.As the safety issue is one of the one of the priorities of the whole system,in this paper,two fault tolerant systems are proposed for the switching elements error and transducers error especially.First,the fundamental concept of active magnetic bearing has been reviewed and analyzed.Based on the basic concept of magnetic bearing,the linear model of active magnetic bearing is eastablished by using Taylor series,and the dynamic model of rigid rotor of magnetic bearing is eastablished,then the equivalent inductance model is deduced,the inverse relationship between the inductance and air gap is also the basic theory of the self-sensing technique of magnetic bearing.The fault-tolerant system consists two parts: fault detection and auxiliary equipment.For the switching elements fault-tolerant system,its drive circuit has two working modes,the normal mode and the auxiliary mode.The system detects the failure of switching elements by examining the windings current,if an open circuit error happens,the drive of the system will switch from the normal mode to the auxiliary mode and keep the rotor suspend steadily;if a short circuit error happens,the system will block down all the switches and shut down the system safely.For the sensor fault-tolerant control system,it takes the self-sensing technique as the auxiliary sensor.The small signal injection and nonlinear parameter eastimation are discussed in detail,then a current signal injection method is eastablished.When the transducers fails,the displacement detected by the current signal injection method will replace the sensor displacement as the feedback signal and keep the system running stably.Finally,the switching elements fault-tolerant control system is verified on the test rig.