Detent force analysis and suppression of electrical shock absorber

Kinetic energy of a vibrating object in vehicles is normally absorbed in a form of thermal energy by mechanical dampers and other facilities. So the energy of the vibration is consumed wastefully. Using electrical shock absorber, energy of the vibration is converted into electrical energy. The electrical shock absorber consists of a permanent magnet tubular linear synchronous motor (PMTLSM), a spring and an electric energy accumulator. And PMTLSM which works as both damper and converter is the key part of the electrical shock absorber. The major goal of this paper is to analyze and reduce the detent force of short primary, long secondary PMTLSM. Finite element method (FEM) is adopted to analyze the magnetic field and detent force of PMTLSM. The result shows that the end effect is the main reason of thrust ripple and the end effect force varies in periodicity of a pole distance as the length of the primary armature increasing. The periodicity of interior PMTLSM (IPM-TLSM) and surface-mounted PMTLSM (SPM-TLSM) are uniform but SPM-TLSM lags behind IPM-TLSM. For IPM-TLSM, when the side teeth-width/pole distance is between 0.33 and 0.5, the detent force is about the minimum. While in SPM-TLSM, the minimum point is around 0.5. The periodicity has nothing to with the external diameter of TLSM. The external diameter can only influence the magnitude but not the cycle. Accordingly, optimizing the side teeth-width is very effective to reduce detent force and improve the thrust characteristic of electrical shock absorber.