Abstract: In a free piston machine, initial collisions of the piston with structures at the end of the cylinder are detected and generate a change in the magnitude of a perturbation signal, which is applied to the summing junction of a closed loop feedback control system controlling a piston force. The change is applied in a direction to reduce piston amplitude. In embodiments in which maximization of piston amplitude is desirable, the magnitude of the perturbation signal is also varied in the opposite direction in the absence of collisions to increase piston amplitude of oscillation so that operation then hunts between initial nondestructive collisions and a non-colliding maximum amplitude of piston oscillation.

Abstract: In a free piston machine, initial collisions of the piston with structures at the end of the cylinder are detected and generate a change in the magnitude of a perturbation signal, which is applied to the summing junction of a closed loop feedback control system controlling a piston force. The change is applied in a direction to reduce piston amplitude. In embodiments in which maximization of piston amplitude is desirable, the magnitude of the perturbation signal is also varied in the opposite direction in the absence of collisions to increase piston amplitude of oscillation so that operation then hunts between initial nondestructive collisions and a non-colliding maximum amplitude of piston oscillation.

Abstract: A refrigeration system having a modulatable compressor and a Rankine cycle refrigeration circuit having at least two evaporators. The flow rate of the compressor is modulated in response to the sensed temperature of the masses being cooled, and the control circuit switches valves to control the refrigerant flow path and modulates the flow rate of the compressor to optimize the efficiency of the refrigeration system.

Abstract: A refrigeration system having a modulatable compressor and a Rankine cycle refrigeration circuit having at least two evaporators. The flow rate of the compressor is modulated in response to the sensed temperature of the masses being cooled, and the control circuit switches valves to control the refrigerant flow path and modulates the flow rate of the compressor to optimize the efficiency of the refrigeration system.

Abstract: A piston end position limiter for a free piston machine of the type having a piston sealingly reciprocating in a cylinder and separating a work space bounded at one end of the piston from a second space bounded at the opposite end of the piston. The work space and the second space contain a working fluid having an average pressure. A first valve is connected in communication between a fluid reservoir and the work space and is adapted to open only when the working fluid pressure varies sufficiently in one direction from its average pressure. A second position responsive valve is connected between the reservoir and the second space and is operatively linked to the piston for opening in response to the piston reaching a selected end limit of its reciprocation.

Abstract: An improved mechanical transducer of the type having a body reciprocating in a chamber, the body being linked to a housing by a linkage including an axially compliant spring. An anti-friction fluid bearing applies a lateral centering force upon the body and a linkage component of the linkage has a lateral compliance sufficient for the centering forces exerted by the fluid bearing to at least equal the sum of lateral force exerted by the linkage and other lateral forces exerted upon the body. That lateral compliance allows the centering forces of the fluid bearing to be effective in moving the body away from the chamber wall and thereby minimize contact and consequent wear of the interfacing surfaces between the body and the chamber wall.