Machines using rectified oscillatory motion

Since the size of an electromagnetic machine specifies the torque, any further increase in torque for a given volume is achieved conventionally by a gearbox. The paper considers the implications of attaching a mechanical system consisting of a ratchet and resiliences to an oscillating actuator with a view first to exploiting the magnetic attraction force and secondly to obtaining a torque amplification by mechanical tuning. Both variable-gap and conventional reluctance actuators are considered, and the characteristics of prototype machines are explained in terms of the equations of motion. A consideration of the `perfect ratchet¿ is included, and design criteria presented which permit imperfect ratchets to be used to the best advantage.