A Sophisticated Concept for Supreme AMB Reliability

Active magnetic bearings (AMBs) offer a couple of advantages compared to conventional bearings such as contact-free suspension without wear and the variation of suspension parameters such as stiffness and damping during operation. A lower reliability caused by a number of fairly complex sub-assemblies (controller, sensors, amplifiers, magnetic actuator, etc.), however, is one major reason that AMB-technology is not sufficiently accepted so far in many practical industrial applications. While many concepts for increasing the reliability of AMBs have been presented in literature so far, all of them show some weak points, which to some extent even reduce the overall reliability, such as the requirement for additional sub-assemblies within the signal flow path, coupling and communication between redundant sub- assemblies or the lack of a reliable and automatic decoupling of defective sub-assemblies. Within the scope of this proposed project a comprehensive concept for AMBs reliability shall be developed, which offers supreme reliability of the whole AMB-system, not only an improvement within single areas. Thus, supreme reliability shall be guarantied over the whole operating time and the bearing capacity shall be maintained even in case of a defect within any sub-assembly. After detailed development and modelling of this AMB-system in MATLAB-Simulink and PSpice, simulation results shall point out the effects of defective sub-assemblies on the bearing functionality. Furthermore, the achievable quality of support will be investigated. Based on these results, the electronic circuitry of the controller circuitry will be designed, a reliability analysis of the AMB-system will be carried out and a HCA prototype will be built and tested. To investigate the total AMB-system behaviour under real working conditions during induced component errors and the replacement of electronic sub-assemblies a simple AMB test stand using the AMB technology of supreme reliability will be built.

Active magnetic bearings (AMBs) offer a couple of advantages compared to conventional bearings such as contact-free suspension without wear and the variation of suspension parameters such as stiffness and damping during operation. A lower reliability caused by a number of fairly complex sub-assemblies (controller, sensors, amplifiers, magnetic actuator, etc.), however, is one major reason that AMB-technology is not sufficiently accepted so far in many practical industrial applications. While many concepts for increasing the reliability of AMBs have been presented in literature so far, all of them show some weak points, which to some extent even reduce the overall reliability, such as the requirement for additional sub-assemblies within the signal flow path, coupling and communication between redundant sub- assemblies or the lack of a reliable and automatic decoupling of defective sub-assemblies. Within the scope of this proposed project a comprehensive concept for AMBs reliability shall be developed, which offers supreme reliability of the whole AMB-system, not only an improvement within single areas. Thus, supreme reliability shall be guarantied over the whole operating time and the bearing capacity shall be maintained even in case of a defect within any sub-assembly. The main measures for achieving these goals are: A simple and completely decentralized AMB structure, comprising decoupled and redundantly assembled horseshoe magnet (HM)-channels. Exchangeability of all sub-assemblies, cabling, etc. during operation (hot-swap), without degrading system performance. Control and driving of each HM by an independent hot-swap controller amplifier module (HCA), comprising a digital controller, a switching amplifier, power supplies and a local error detection. Automatic shut down of a defective HM-channel by the local error detection within a few microseconds on occurrence of a malfunction. Generation of bearing force by adjacent HMs on occurrence of a HM-channel malfunction. Highest reliability of the HCAs, assured by a high degree of integration and a robust electronic circuitry design. Use of a direct and all-digital self sensing method, which allows air gap determination with high accuracy. After detailed development and modeling of this AMB-system in MATLAB-Simulink and PSpice, simulation results shall point out the effects of defects within HM-channels on the bearing functionality. Furthermore, the achievable accuracy of the air gap estimation using self-sensing, will be investigated. Based on these results, the electronic circuitry of the HCAs will be designed, a reliability analysis of the AMB-system will be carried out and a HCA prototype will be built and tested. To investigate the total AMB-system behavior under real working conditions during induced component errors and the hot-swap of electronic sub-assemblies a simple AMB test stand using the AMB technology of supreme reliability will be built.