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Present implementations provide an approach that allows for a double-acting, multi-cylinder, thermodynamically resonant, alpha configuration free-piston Stirling system. The system includes overstroke preventers that control extent of piston travel to prevent undesirable consequences of piston trave

Present implementations provide an approach that allows for a double-acting, multi-cylinder, thermodynamically resonant, alpha configuration free-piston Stirling system. The system includes overstroke preventers that control extent of piston travel to prevent undesirable consequences of piston travel beyond predetermined limits. The overstroke preventers involve controlled work extraction out of the system or controlled work input into the system. Implementations can also include duplex linear alternators, and/or frequency tuning systems, and/or vibration balancing configurations.

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The invention claimed is: 1. A Stirling system comprising: a plurality of double-acting non-fluidic free-pistons; a plurality of overstroke preventers, each coupled to at least a different one of the pistons; a plurality of cylinders, each having a different one of the pistons positioned therein fo

The invention claimed is: 1. A Stirling system comprising: a plurality of double-acting non-fluidic free-pistons; a plurality of overstroke preventers, each coupled to at least a different one of the pistons; a plurality of cylinders, each having a different one of the pistons positioned therein for reciprocal motion, each of the cylinders coupled to a different corresponding pair of other ones of the cylinders to fluidly couple the cylinder to a first cylinder and a second cylinder of the corresponding pair; and a Stirling cycle working fluid, portions of the Stirling cycle working fluid positioned in the cylinders and in contact with the pistons, the reciprocal motion of the piston positioned in each of the cylinders being coupled to the reciprocal motion of the piston positioned in the first cylinder of the corresponding pair solely through the Stirling cycle working fluid and being coupled to the reciprocal motion of the piston positioned in the second cylinder of the corresponding pair solely through the Stirling cycle working fluid. 2. The system of claim 1 wherein each of the cylinders is coupled to the first cylinder of the corresponding pair to provide for transfer of a first portion of the Stirling cycle working fluid therebetween and coupled to the second cylinder of the corresponding pair to provide for transfer of a second portion of the Stirling cycle working fluid therebetween. 3. The system of claim 2 wherein each of the cylinders has a hot end and a cold end, and wherein each of the cylinders is coupled to the corresponding pair by coupling of the hot end of the cylinder with the cold end of the first cylinder of the corresponding pair and by coupling of the cold end of the cylinder with the hot end of the second cylinder of the corresponding pair. 4. The system of claim 2 wherein each of the cylinders is coupled to the corresponding pair by coupling of the cylinder with the first cylinder of the corresponding pair via a first heat exchanger circuit and by coupling of the cylinder with the second cylinder of the corresponding pair via a second heat exchanger circuit. 5. The system of claim 1 further comprising a plurality of flexure bearings, and wherein each of the pistons is coupled to the cylinder within which positioned through at least a different one of the flexure bearings. 6. The system of claim 1 wherein the cylinders are located with respect to one another in positions to cancel a substantial portion of reaction forces resulting from operation of the pistons to reduce vibration. 7. The system of claim 1 wherein each of the overstroke preventers includes a linear alternator having a mover and further includes a controller configured to control the mover to avoid undesirable travel of the piston coupled to the overstroke preventer. 8. The system of claim 2 wherein the controller controls to avoid travel of the piston past a predefined end point of reciprocal motion. 9. The system of claim 1 further comprising a tuning system having an accumulator fluidly coupled to at least one of the cylinders through a first fluid line and a second fluid line, the first fluid line having a first check valve configured to allow fluid flow from the at least one cylinder to the accumulator and to prevent fluid flow from the accumulator to the at least one cylinder, and the second fluid line having a second check valve configured to allow fluid flow from the accumulator to the at least one cylinder and to prevent fluid flow from the at least one cylinder to the accumulator. 10. A method for operating a Stirling system, comprising: positioning each of a plurality of double-acting non-fluidic free-pistons in a different one of a plurality of cylinders; allowing each of the pistons to reciprocate within its respective cylinder; controlling the reciprocal motion of each of the pistons within its respective cylinder to prevent undesirable travel of the piston within the respective cylinder; including portions of a Stirling cycle working fluid in the cylinders and contacting the pistons; and coupling the reciprocal motion of each of the pistons with the reciprocal motions of a different pair of the pistons solely through the Stirling cycle working fluid. 11. The method of claim 10 wherein allowing each of the pistons to reciprocate within its respective cylinder includes coupling each of the pistons to the respective cylinder through at least one flexure bearing. 12. The method of claim 10 further comprising adjusting the amount of the Stirling cycle working fluid to adjust frequency of the reciprocal motion of the pistons within their respective cylinders. 13. The method of claim 10 further comprising locating the cylinders with respect to one another in positions to cancel a substantial portion of reaction forces resulting from reciprocation of the pistons to reduce vibration. 14. The method of claim 10 further comprising coupling at least one linear alternator to at least one of the pistons, and wherein the controlling the reciprocal motion of each of the pistons further comprises controlling an amount of travel of a mover of the linear alternator coupled to the at least one piston. 15. The method of claim 10 wherein controlling the reciprocal motion of each of the pistons further comprises for each pair of different pistons using a controller to control a stator of a duplex linear alternator to control an amount of travel of two movers of the duplex linear alternator, each of the two movers coupled to a different one of the pistons of the pair. 16. The method of claim 10 wherein controlling the reciprocal motion of each of the pistons to prevent undesirable travel is to prevent piston travel that causes damage to at least one of the following: the piston or the cylinder within which the piston is positioned. 17. The method of claim 10 further comprising extracting work from the reciprocal motion of the pistons. 18. The method of claim 10 further comprising inputting work into the reciprocal motion of the pistons. 19. A Stirling system comprising: a Stirling cycle working fluid; a plurality of double-acting non-fluidic free-pistons, the pistons in contact with portions of the Stirling cycle working fluid; a plurality of overstroke preventers, each of the overstroke preventers coupled to at least a different one of the pistons; and a plurality of cylinders, each of the cylinders having some of the Stirling cycle working fluid therein and coupled to a different corresponding pair of other ones of the cylinders to couple the cylinder to a first cylinder of the corresponding pair to provide for transfer of a first portion of the Stirling cycle working fluid therebetween and to couple the cylinder to a second cylinder of the corresponding pair to provide for transfer of a second portion of the Stirling cycle working fluid therebetween, each of the pistons positioned in a different one of the cylinders for reciprocal motion therein, the piston positioned in the cylinder being coupled to the piston positioned in the first cylinder of the corresponding pair through the Stirling cycle working fluid and coupled to the piston positioned in the second cylinder of the corresponding pair through the Stirling cycle working fluid. 20. The system of claim 19 further comprising a plurality of flexure bearings, and wherein each of the pistons is coupled to the cylinder with which positioned through at least a different one of the flexure bearings. 21. The system of claim 19 wherein the cylinders are located with respect to one another in positions to cancel a substantial portion of reaction forces to reduce vibration. 22. The system of claim 19 wherein the overstroke preventers includes at least one duplex linear alternator having two movers, each mover coupled to a different one of the pistons, and further includes a controller configured to control at least the two movers to avoid undesirable travel of the pistons coupled to the overstroke preventer. 23. The system of claim 20 wherein the controller controls to avoid travel of each of the pistons to an extent past a predefined end point of reciprocal motion for the piston. 24. The system of claim 19 further comprising a tuning system having an accumulator fluidly coupled to at least one of the cylinders through a first fluid line and a second fluid line, the first fluid line having a first check valve configured to allow fluid flow from the at least one cylinder to the accumulator and to prevent fluid flow from the accumulator to the at least one cylinder, and the second fluid line having a second check valve configured to allow fluid flow from the accumulator to the at least one cylinder and to prevent fluid flow from the at least one cylinder to the accumulator. 25. A method for operating a Stirling system, comprising: allowing each of a plurality of double-acting non-fludic free-pistons to reciprocate within a different one of a plurality of cylinders; including a Stirling cycle working fluid within at least portions of the cylinders to contact the free pistons; controlling the reciprocal motion of each of the pistons within its respective cylinder to limit travel of the piston therein; and fluidly coupling each of the cylinders to a different corresponding pair of other ones of the cylinders to couple the cylinder to a first cylinder of the corresponding pair to provide for transfer of a first portion of the Stirling cycle working fluid therebetween and to couple the cylinder to a second cylinder of the corresponding pair to provide for transfer of a second portion of the Stirling cycle working fluid therebetween, with the piston positioned in each cylinder coupled through the Stirling cycle working fluid with the piston within the first cylinder of the corresponding pair and through the Stirling cycle working fluid with the piston within the second cylinder of the corresponding pair. 26. The method of claim 25 wherein allowing each of the pistons to reciprocate within its respective cylinder includes coupling each of the pistons to the respective cylinder through at least one flexure bearing. 27. The method of claim 25 further comprising adjusting the amount of the Stirling cycle working fluid to adjust frequency of the reciprocal motion of the pistons within their respective cylinders. 28. The method of claim 25 further comprising locating the cylinders with respect to one another in positions to cancel a substantial portion of reaction forces resulting from reciprocation of the pistons to reduce vibration. 29. The method of claim 25 further comprising coupling at least one linear alternator to at least one of the pistons, and wherein the controlling the reciprocal motion of each of the pistons further comprises controlling an amount of travel of a mover of the linear alternator coupled to the at least one piston. 30. The method of claim 25 wherein controlling the reciprocal motion of each of the pistons further comprises for each pair of different pistons using a controller to control a stator of a duplex linear alternator to control an amount of travel of two movers of the duplex linear alternator, each of the two movers coupled to a different one of the pistons of the pair. 31. The method of claim 25 wherein controlling the reciprocal motion of each of the pistons to limit travel is to limit piston travel sufficient to avoid damage to at least one of the following: the piston or the cylinder within which the piston is positioned. 32. The method of claim 25 further comprising extracting work from the reciprocal motion of the pistons. 33. The method of claim 25 further comprising inputting work into the reciprocal motion of the pistons. 34. A Stirling system comprising: a plurality of double-acting non-fluidic free-pistons mechanically disconnected from each other; a plurality of overstroke preventers, each coupled to at least a different one of the pistons; and a plurality of cylinders, each having a different one of the pistons positioned therein for reciprocal motion, each of the cylinders coupled to a different corresponding pair of other ones of the cylinders to fluidly couple the cylinder to a first cylinder and a second cylinder of the corresponding pair; a Stirling cycle working fluid, portions of the Stirling cycle working fluid positioned in the cylinders and contacting the pistons, the reciprocal motion of each piston being coupled to the reciprocal motion of at least another one of the pistons through the Stirling cycle working fluid being transferred between the respective cylinder of the piston and the respective cylinder of the at least another one of the pistons; and means for extracting work from the reciprocal motion of the pistons. 35. A Stirling system comprising: a plurality of double-acting non-fluidic free-pistons mechanically disconnected from each other; a plurality of overstroke preventers, each coupled to at least a different one of the pistons; and a plurality of cylinders, each having a different one of the pistons positioned therein for reciprocal motion, each of the cylinders coupled to a different corresponding pair of other ones of the cylinders to fluidly couple the cylinder to a first cylinder and a second cylinder of the corresponding pair; a Stirling cycle working fluid, portions of the Stirling cycle working fluid positioned in the cylinders and contacting the pistons, the reciprocal motion of each piston being coupled to the reciprocal motion of at least another one of the pistons through the Stirling cycle working fluid flowing between the respective cylinder of the piston and the respective cylinder of the least another one of the pistons; and means for supplying work to the reciprocal motion of the pistons. 36. A Stirling system comprising: a plurality of double-acting non-fluidic free-pistons mechanically disconnected from each other; a plurality of cylinders, each having a different one of the pistons positioned therein for reciprocal motion, each of the cylinders fluidly coupled to a different corresponding pair of other ones of the cylinders to fluidly couple the cylinder to a first cylinder and a second cylinder of the corresponding pair; and a Stirling cycle working fluid, portions of the Stirling cycle working fluid positioned in the cylinders and contacting the pistons, the reciprocal motion of the piston positioned in each of the cylinders being coupled to the reciprocal motion of the piston positioned in the first cylinder of the corresponding pair through the Stirling cycle working fluid via the fluid coupling of the cylinder to provide for transfer of a first portion of the Stirling cycle working fluid therebetween in which the piston is positioned to the first cylinder of the corresponding pair, and being coupled to the reciprocal motion of the piston positioned in the second cylinder of the corresponding pair through the Stirling cycle working fluid via the fluid coupling of the cylinder to provide for transfer of a second portion of the Stirling cycle working fluid therebetween in which the piston is positioned to the second cylinder of the corresponding pair. 37. The system of claim 36 wherein each of the cylinders has a hot end and a cold end, and wherein each of the cylinders is coupled to the corresponding pair by coupling of the hot end of the cylinder with the cold end of the first cylinder of the corresponding pair and by coupling of the cold end of the cylinder with the hot end of the second cylinder of the corresponding pair. 38. The system of claim 36 wherein each of the cylinders is coupled to the corresponding pair by coupling of the cylinder with the first cylinder of the corresponding pair via a first heat exchanger circuit and by coupling of the cylinder with the second cylinder of the corresponding pair via a second heat exchanger circuit. 39. The system of claim 36 further comprising a tuning system having an accumulator fluidly coupled to at least one of the cylinders through a first fluid line and a second fluid line, the first fluid line having a first check valve configured to allow fluid flow from the at least one cylinder to the accumulator and to prevent fluid flow from the accumulator to the at least one cylinder, and the second fluid line having a second check valve configured to allow fluid flow from the accumulator to the at least one cylinder and to prevent fluid flow from the at least one cylinder to the accumulator. 40. A free-piston Stirling system comprising: a plurality of double-acting non-fluidic free-pistons; a plurality of cylinders, each having a different one of the pistons positioned therein for reciprocal motion, each of the cylinders fluidly coupled to a different corresponding pair of other ones of the cylinders to fluidly couple the cylinder to a first cylinder and a second cylinder of the corresponding pair; and a Stirling cycle working fluid, portions of the Stirling cycle working fluid positioned in the cylinders, the reciprocal motion of the piston positioned in each of the cylinders being coupled to the reciprocal motion of the piston positioned in the first cylinder of the corresponding pair through the Stirling cycle working fluid via the fluid coupling of the cylinder to provide for transfer of a first portion of the Stirling cycle working fluid therebetween in which the piston is positioned to the first cylinder of the corresponding pair, and being coupled to the reciprocal motion of the piston positioned in the second cylinder of the corresponding pair through the Stirling cycle working fluid via the fluid coupling of the cylinder to provide for transfer of a first portion of the Stirling cycle working fluid therebetween in which the piston is positioned to the second cylinder of the corresponding pair, whereby the Stirling system operates without use of a separate displacer piston. 41. The system of claim 40 wherein each of the cylinders has a hot end and a cold end, and wherein each of the cylinders is coupled to the corresponding pair by coupling of the hot end of the cylinder with the cold end of the first cylinder of the corresponding pair and by coupling of the cold end of the cylinder with the hot end of the second cylinder of the corresponding pair. 42. The system of claim 40 wherein each of the cylinders is coupled to the corresponding pair by coupling of the cylinder with the first cylinder of the corresponding pair via a first heat exchanger circuit and by coupling of the cylinder with the second cylinder of the corresponding pair via a second heat exchanger circuit. 43. The system of claim 40 further comprising a tuning system having an accumulator fluidly coupled to at least one of the cylinders through a first fluid line and a second fluid line, the first fluid line having a first check valve configured to allow fluid flow from the at least one cylinder to the accumulator and to prevent fluid flow from the accumulator to the at least one cylinder, and the second fluid line having a second check valve configured to allow fluid flow from the accumulator to the at least one cylinder and to prevent fluid flow from the at least one cylinder to the accumulator. 44. A method for operating a Stirling system, comprising: positioning each of a plurality of double-acting non-fluidic free-pistons in a different one of a plurality of cylinders, the pistons being mechanically disconnected from each other; allowing each of the pistons to reciprocate within its respective cylinder; including portions of a Stirling cycle working fluid in the cylinders; and coupling the reciprocal motion of each of the pistons with the reciprocal motions of a different corresponding pair of the pistons through the Stirling cycle working fluid moving between the cylinders. 45. The method of claim 44 wherein coupling the reciprocal motion of each of the pistons with the reciprocal motions of a corresponding pair of pistons through the Stirling cycle working fluid includes fluidly coupling each of the cylinders to a different corresponding pair of the cylinders in which in the corresponding pair of pistons are positioned to fluidly couple the cylinder to a first cylinder and a second cylinder of the corresponding pair of cylinders. 46. The method of claim 44 further comprising adjusting the amount of the Stirling cycle working fluid to adjust frequency of the reciprocal motion of the pistons within their respective cylinders. 47. A Stirling system comprising: a Stirling cycle working fluid; a plurality of double-acting non-fluidic free-pistons mechanically disconnected from each other; and a plurality of cylinders, portions of the Stirling cycle working fluid located therein, each of the cylinders coupled to a different corresponding pair of other ones of the cylinders to couple the cylinder to a first cylinder of the corresponding pair to provide for transfer of a first portion of the Stirling cycle working fluid therebetween and to couple the cylinder to a second cylinder of the corresponding pair to provide for transfer of a second portion of the Stirling cycle working fluid therebetween, each of the pistons positioned in a different one of the cylinders for reciprocal motion therein, the piston positioned in the cylinder being coupled to the piston positioned in the first cylinder of the corresponding pair through the Stirling cycle working fluid and coupled to the piston positioned in the second cylinder of the corresponding pair through the Stirling cycle working fluid. 48. The system of claim 47 further comprising a tuning system having an accumulator fluidly coupled to at least one of the cylinders through a first fluid line and a second fluid line, the first fluid line having a first check valve configured to allow fluid flow from the at least one cylinder to the accumulator and to prevent fluid flow from the accumulator to the at least one cylinder, and the second fluid line having a second check valve configured to allow fluid flow from the accumulator to the at least one cylinder and to prevent fluid flow from the at least one cylinder to the accumulator. 49. A method for operating a Stirling system, comprising: allowing each of a plurality of double-acting non-fluidic free-pistons to reciprocate within a different one of a plurality of cylinders, the pistons being mechanically disconnected from each other; including a Stirling cycle working fluid within at least portions of the cylinders; and fluidly coupling each of the cylinders to a different corresponding pair of other ones of the cylinders to couple the cylinder to a first cylinder of the corresponding pair to provide for transfer of a first portion of the Stirling cycle working fluid therebetween and to couple the cylinder to a second cylinder of the corresponding pair to provide for transfer of a second portion of the Stirling cycle working fluid therebetween, with the piston positioned in each cylinder coupled through the Stirling cycle working fluid with the piston within the first cylinder of the corresponding pair and through the Stirling cycle working fluid with the piston within the second cylinder of the corresponding pair. 50. The method of claim 49 further comprising adjusting the amount of the Stirling cycle working fluid to adjust frequency of the reciprocal motion of the pistons within their respective cylinders. 51. A Stirling machine having a plurality of cylinders, each cylinder having a double-acting non-fluidic free-piston therein, a system comprising: an accumulator; a first fluid line fluidly coupled to the accumulator and at least a first one of the cylinders; a first solenoid valve positioned in the first fluid line, the first solenoid valve configured to be controlled to open and close; a first check valve positioned in the first fluid line, the first check valve configured to allow fluid flow from the at least first one cylinder to the accumulator and to prevent fluid flow from the accumulator to the at least first one cylinder when the first solenoid valve is open; a second fluid line fluidly coupled to the accumulator and at least a second one of the cylinders, the at least first one cylinder and the at least second one cylinder being the same cylinder or different cylinders; a second solenoid valve positioned in the second fluid line, the second solenoid valve configured to be controlled to open and close; and a second check valve positioned in the second fluid line, the second check valve configured to allow fluid flow from the accumulator to the at least one second cylinder and to prevent fluid flow from the at least one second cylinder to the accumulator when the second solenoid valve is open. 52. For a Stirling machine having a plurality of cylinders, each cylinders having a non-fluidic free-piston therein, a system comprising: an accumulator; a first fluid line fluidly coupled to the accumulator and at least a first one of the cylinders; a first valve positioned in the first fluid line, the first valve configured to be controlled to open and close; a first check valve positioned in the first fluid line, the first check valve configured to allow fluid flow from the at least first one cylinder to the accumulator and to prevent fluid flow from the accumulator to the at least first one cylinder when the first solenoid valve is open; a second fluid line fluidly coupled to the accumulator and at least a second one of the cylinders, the at least first one cylinder and the at least second one cylinder being the same cylinder or different cylinders; a second valve positioned in the second fluid line, the second valve configured to be controlled to open and close; a second check valve positioned in the second fluid line, the second check valve configured to allow fluid flow from the accumulator to the at least one second cylinder and to prevent fluid flow from the at least one second cylinder to the accumulator when the second solenoid valve is open; and a controller coupled with the first valve and the second valve, the controller configured to control the first valve and the second valve based at least in part on a desired operating frequency for the Stirling machine. 53. A method comprising: providing a first multicylinder double-acting non-fluidic free-piston machine having a first plurality of cylinders, the first cylinders being interconnected to share a first Stirling cycle working fluid, each first cylinder with a first piston reciprocally mounted therein, the first piston having at least one moveable component of an overstroke preventer coupled thereto; providing a second multicylinder double-acting non-fluidic free-piston machine having a second plurality of cylinders, the second cylinders being interconnected to share a second Stirling cycle working fluid, the first cylinders unconnected with the second cylinders to prevent the first cylinders from sharing the second Stirling cycle working fluid and to prevent the second cylinders from sharing the first Stirling cycle working fluid, each second cylinder with a second piston reciprocally mounted therein, the second piston having at least one moveable component of an overstroke preventer coupled thereto; and locating the first multicylinder machine and the second multicylinder machine with respect to one another and controlling movement of the first pistons and the second pistons with the overstroke preventers to cancel reaction forces resulting from reciprocation of the pistons to reduce operational vibration.