Abstract: A method for use in controlling a free piston Stirling machine having a cold end and a warm end and driven by a linear motor having an armature winding to which a drive voltage is applied. The method comprises (a) sensing internal mechanical collisions; (b) repeatedly sensing the temperature of the cold end, the temperature of the warm end and the drive voltage; (c) storing, as associated data, a value representing drive voltage, the temperature of the cold end and the temperature of the warm end at the time of sensed collisions; and (d) limiting the drive voltage to less than the drive voltage that was sensed at a collision and is stored in association with stored warm end and cold end temperatures that are proximate currently sensed warm end and cold end temperatures.

Abstract: An apparatus for determining position of a free piston used in such as hydraulic compressor, which has no mechanical connection with crank shaft, and an apparatus for controlling reciprocating motion of the free piston are disclosed. A free piston position determining apparatus comprises a magnetic sensor disposed in a case containing a free piston, and a magnet disposed on the free piston. The magnet sensor generates pulse train when the magnet is positioned within a pre-determined distance form the magnet sensor. Stroke of the free piston is computed based on duration of the pulse, and offset of the average piston position from designed average position is computed based on interval of the pulse.