Control of piston trajectory in a linear generator
Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a method and system are provided for displacing a free-piston assembly to achieve a desired engine performance by repeatedly determining position-force trajectories over the course of a propagation path and effecting the displacement of the free-piston assembly based, at least in part, on the position-force trajectory. In a dual-piston assembly free-piston engine, synchronization of the two piston assemblies is provided.
1. A method performed by a programmed computer system for controlling displacement of a free-piston assembly, the method comprising:
a) determining, using a control system, a force to apply to the free-piston assembly based on a current position of the free-piston assembly and a target position without regard to a deviation from a previously determined trajectory;
b) cause the force to be applied to the free-piston assembly for a time interval; and
c) repeating a) and b) until the free-piston assembly reaches at least one of the target position or an apex position.
2. The method of claim 1 , wherein the target position comprises a desired apex position.
3. The method of claim 1 , wherein a) comprises determining the force based at least in part on an estimated pressure in a compression section in contact with the free-piston assembly.
4. The method of claim 1 , further comprising:
d) determining a new target position of the free-piston assembly;
e) determining a new force to apply to the free-piston assembly based on a new current position of the free-piston assembly and the new target position; and
f) causing the new force to be applied to the free-piston assembly for a new time interval.
5. The method of claim 1 , further comprising:
d) determining a new force to apply to the free-piston assembly based on a new current position of the free-piston assembly and the target position; and
e) determining not to apply the new force to the free-piston assembly for a second time interval if the current position is outside of a cut-off position threshold.
6. The method of claim 1 , further comprising determining the target position.
7. The method of claim 1 , wherein determining the force to apply to the free-piston assembly is based on a difference between the current position of the free-piston assembly and the target position.
8. The method of claim 1 , wherein the time interval is a prescribed time interval comprising a fixed frequency.
9. A method performed by a programmed computer system for controlling displacement of a free-piston assembly, the method comprising:
determining, using a control system, a force to apply to the free-piston assembly based on a current position of the free-piston assembly and a target position without regard to a deviation from a previously determined trajectory;
b) cause the force to be applied to the free-piston assembly for a position interval; and
c) repeating a) and b) until the free-piston assembly reaches at least one of the target position or an apex position.
10. The method of claim 9 , wherein the position interval is a particular discrete position interval comprising a fixed distance.
11. A system comprising:
a free-piston assembly configured to traverse a positional path; and
a control system configured to:
a) determine a force to apply to the free-piston assembly based on a current position of the free-piston assembly and a target position without regard to a deviation from a previously determined trajectory;
b) cause the force to be applied to the free-piston assembly for a time interval; and
c) repeat a) and b) until the free-piston assembly reaches at least one of the target position or an apex position.
12. The system of claim 11 , wherein the target position comprises a desired apex position.
13. The system of claim 11 , wherein the control system is further configured to repeat a) and b) by:
repeatedly determining a new force to apply to the free-piston assembly based on a new current position of the free-piston assembly and the target position; and
repeatedly causing the new force to be applied to the free-piston assembly for each respective time interval.
14. The system of claim 11 , wherein the control system is further configured to:
d) determine a new target position of the free-piston assembly;
e) determine a new force to apply to the free-piston assembly based on a new current position of the free-piston assembly and the new target position; and
f) cause the new force to be applied to the free-piston assembly for a second time interval.
15. The system of claim 11 , wherein the control system is further configured to:
d) determine new a force to apply to the free-piston assembly based on a new current position of the free-piston assembly and the target position; and
e) determine not to apply the new force to the free-piston assembly for a second time interval if the current position is outside of a cut-off position threshold.
16. The system of claim 11 , wherein the control system is further configured to determine the target position.
17. The system of claim 11 , wherein the control system is further configured to determine the force to apply to the free-piston assembly based on a difference between the current position of the free-piston assembly and the target position.
18. The system of claim 11 , wherein the time interval is a prescribed time interval comprising a fixed frequency.
19. The system of claim 11 , further comprising a sensor configured to:
sense the current position of the free-piston assembly; and
communicate with the control system.
20. The system of claim 11 , wherein the control system is further configured to determine the force to apply to the free-piston assembly without regard to a time in which the free-piston assembly reaches the target position.