Permanent Magnet Linear Motors Used as Variable Mechanical Dampers for Vehicle Suspensions

Linear electrodynamic motors consisting of coils of copper wire interacting with magnetic fields produced by permanent magnets can be used to construct mechanical dampers with a damping coefficient which can be rapidly varied by changing the external resistance connected to the coil. Limitations to the use of these variable dampers arise due to the coil's own resistance and mass and the practically achievable magnetic field. A moving coil system is first analyzed and then modifications to the basic results when a moving magnet design is used are given. The results indicate that for the oscillation freauencies tvoicallv encountered in road vehicle suspensions, electrodynamic variable shock absorbers are feasible. A novel coreless design appropriate for use with high energy permanent magnets is proposed which would significantly reduce the weight of the units.