Proposal of a Fault-Tolerance Technique for 1-ph Open Circuit Fault in Resolvers

Due to their cost-effective manufacturing and robust structure, an electromagnetic sensor called resolver is being applied in a wide range of applications, especially in those which high reliability is particularly essential. Since resolvers are usually chosen as position detector units in harsh environments, their chronic exposure to high temperature and mechanical shocks is unpreventable and accordingly, performance failure as a result of output signal winding open circuit fault (OCF) is inevitable. In this paper, a new technique is proposed to keep the performance of the resolver within an acceptable range of position error while one of the output signals (SIN/COS) is inaccessible. To this end, normalized cross-correlation (NCC) was utilized to detect the OC faulted signal winding. Since Resolver-to-Digital Converter (RDC) needs two separate input signals to measure the position of the rotary part, the faulted output signal is reconstructed by means of a healthy signal envelope and quadrant of the resolver's signal. The mentioned technique was implemented on a toroidally-wound variable reluctance 5-X resolver. Time-stepping finite element analysis (TSFEA) is used for all the simulations to justify the proper functioning of the proposed technique. Eventually, close agreement between the results of experimental and TSFEA outputs indicate the satisfactory precision of the simulations and the method.