Free-piston stirling machine in an opposed piston gamma configuration having improved stability, efficiency and control

An opposed piston, gamma configured, controllable, free-piston Stirling machine having an outer casing and a work space within the casing, the work space including an expansion space and a compression space, the Stirling machine comprising:

• (a) a displacer mounted for reciprocation in a displacer cylinder along a displacer axis of reciprocation for cyclically varying the proportional distribution of a working gas between the expansion space and the compression space;
• (b) at least two power pistons, the power pistons being mounted within piston cylinders positioned symmetrically around the displacer axis of reciprocation and adapted for reciprocation along piston axes of reciprocation;
• (c) a displacer rod fixed to and extending from the displacer between the pistons and beyond the piston axes of reciprocation;
• (d) an electromagnetic linear transducer operatively disposed between the displacer rod and the casing so as to drive or be driven by the displacer, the linear transducer being drivingly connected to the displacer rod at a position that is on the opposite side of the piston axes of reciprocation from the displacer and positioned outside all work space that is occupied by the pistons during their reciprocation;
• and
• (e) an electronic control having an output connected to the linear transducer and controlling the displacer amplitude of reciprocation as a function of sensed parameters of machine operation, the electronic control adapted to apply electrical power to the transducer for driving the displacer in reciprocation or absorb electrical power from the transducer for reducing the amplitude of reciprocation of the displacer by controllably adjusting one or more of the amplitude, phase and frequency of the voltage applied to the linear transducer.