Control of piston trajectory in a free-piston combustion engine

Patent metadata

Field	Value
Publication number	US-10731586-B2
Application number	US-201916553052-A
Country	US
Kind code	B2
Filing date	Aug 27, 2019
Priority date	Mar 31, 2016
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

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.

First claim

What is claimed is:

1. A method performed by a programmed computer system for controlling displacement of a free-piston assembly, the method comprising:
a) determining a current position of the free-piston assembly and a current pressure in a combustion section in contact with the free-piston assembly;
b) determining a position-force trajectory for displacing the free-piston assembly based at least in part on the current position, the current pressure, and a desired engine performance;
c) effecting displacement of the free-piston assembly based on the position-force trajectory; and
repeating a), b), and c) during a stroke of the free-piston assembly.

2. The method of claim 1 , wherein determining the position-force trajectory for displacing the free-piston assembly is without regard to a previously determined trajectory.

3. The method of claim 1 , wherein the current pressure comprises a measured pressure.

4. The method of claim 1 , wherein the current pressure comprises an estimated pressure.

5. The method of claim 1 , wherein the current pressure corresponds to the current position, the method further comprising determining the current pressure based on a pressure at a previous position, a volume of gas at the previous position, and a volume of gas at the current position.

6. The method of claim 1 , further comprising determining the current pressure based on a force balance model applied to the free-piston assembly.

7. The method of claim 1 , further comprising determining the current pressure based on an energy balance model.

8. The method of claim 1 , wherein the current pressure is indicative of a combustion section pressure, the method further comprising determining the current pressure based on a current pressure of a gas spring, a previously calculated force, a current acceleration of the free-piston assembly and a mass of the free-piston assembly.

9. The method of claim 1 , wherein determining the position-force trajectory is further based on an estimated amount of work associated with moving the free-piston assembly from the current position to a target position.

10. The method of claim 9 , wherein the estimated amount of work is determined based on the current position and the current pressure.

11. The method of claim 1 , wherein the desired engine performance comprises a desired apex position.

12. The method of claim 1 , wherein the desired engine performance comprises a desired synchronization between the free-piston assembly and another free-piston assembly.

13. A control system for controlling displacement of a free-piston assembly, the system comprising:
control circuitry to:
a) determine a current position of the free-piston assembly and a current pressure in a combustion section in contact with the free-piston assembly;
b) determine a position-force trajectory for displacing the free-piston assembly based at least in part on the current position, the current pressure, and a desired engine performance;
c) control displacement of the free-piston assembly based on the position-force trajectory; and
repeat a), b), and c) during a stroke of the free-piston assembly.

14. The control system of claim 13 , wherein the current pressure comprises an estimated pressure.

15. The control system of claim 13 , wherein the current pressure corresponds to the current position, and wherein the control circuitry further determines the current pressure based on a pressure at a previous position, a volume of gas at the previous position, and a volume of gas at the current position.

16. The control system of claim 13 , wherein the current pressure is indicative of a combustion section pressure, and wherein the control circuitry further determines the current pressure based on a current pressure of a gas spring, a previously calculated force, a current acceleration of the free-piston assembly and a mass of the free-piston assembly.

17. The control system of claim 13 , wherein the control circuitry further determines the position-force trajectory based on an estimated amount of work associated with moving the free-piston assembly from the current position to a target position.

18. The control system of claim 13 , wherein the desired engine performance comprises a desired apex position.

19. The control system of claim 13 , wherein the desired engine performance comprises a desired synchronization between the free-piston assembly and another free-piston assembly.

20. A control system for controlling displacement of a free-piston assembly, the system comprising:
control circuitry to:
a) determine a current position of the free-piston assembly and a current pressure in a combustion section in contact with the free-piston assembly;
b) determine a position-force trajectory for displacing the free-piston assembly based at least in part on the current position, the current pressure, and a desired engine performance, wherein the control circuitry determines the position-force trajectory for displacing the free-piston assembly without regard to a previously determined trajectory;
c) control displacement of the free-piston assembly based on the position-force trajectory; and
repeat a), b), and c) during a stroke of the free-piston assembly.

Assignees

• Etagen Inc
• Mainspring Energy Inc

Inventors

• Roelle Matthew
• Gadda Christopher

Classifications

• F02D41/1402

  Adaptive control · CPC title

• F02D29/06

  peculiar to engines driving electric generators · CPC title

• F02B71/00

  Free-piston engines; Engines without rotary main shaft · CPC title

• F02B71/04

  Adaptations of such engines for special use; Combinations of such engines with apparatus driven thereby · CPC title

• F02D35/023

  by determining the cylinder pressure · CPC title