Abstract: An apparatus and method for controlling the offset and dynamics of a moving assembly in a reciprocating linear machine such as a linear compressor, heat pump or engine, comprises a gas spring connected to the moving assembly of the reciprocating linear machine and a pressure adjuster for adjusting the gas pressure in the gas spring. A position detector is provided for detecting the position of the moving assembly, either directly using a sensor, or from the drive to the moving assembly, and a controller controls the pressure adjuster in response to the detected position of the moving assembly. By adjusting the gas pressure the offset of the moving assembly can be controlled, and also the spring constant provided by the gas spring, and thus the resonant frequency of the assembly, can be adjusted.

Abstract: An electromagnetic transducer which may be driven as a linear electric motor (which may be a permanent magnet motor or a variable reluctance motor) in which coils disposed around first and second cores are positioned on opposite sides of a longitudinal plane in which the longitudinal axis of the armature lies. The transducer may be arranged to work as a generator.