METHODS AND SYSTEMS FOR FREE PISTON ENGINE CONTROL

• US 20130298874A1
• Filed: 04/02/2013
• Published: 11/14/2013
• Est. Priority Date: 04/02/2012
• Status: Active Grant

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Sun, Zongxuan, Li, Ke, Sadighi, Ali
• Granted Patent: US 10,132,238 B2
• Time in Patent Office: Days
• US Class Current: 123/46.A
• CPC Class Codes: F02B 63/06 for pumps
• CPC Class Codes: F02B 71/00 Free-piston engines; Engines without rotary main shaft
• CPC Class Codes: F02B 71/04 Adaptations of such engines for special use; Combinations of such engines with apparatus driven thereby
• CPC Class Codes: F02B 71/045 with hydrostatic transmission
• CPC Class Codes: F02D 35/02 on interior conditions
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: F02D 35/025 by determining temperatures inside the cylinder, e.g. combustion temperatures
• CPC Class Codes: F02D 41/1497 With detection of the mechanical response of the engine

Abstract

Motion control of a hydraulic free-piston engine is achieved in order to enable advanced combustions such as low temperature combustion. To accomplish this, an active controller acts as a virtual crankshaft, which causes a piston to follow a reference trajectory using energy from a storage element. Given the periodic nature of free-piston engine motion, an advanced controller of the present invention is preferably of robust repetitive type that is capable of tracking periodic reference signals.

Claims

1. A free piston engine comprising:

a piston movably provided within an engine cylinder for providing a combustion chamber on one side of the piston and another engine chamber on an opposite side of the piston, the piston being operatively connected with a load device; and

an active control system that is operatively connected with an energy storage device for controlling piston trajectory during a firing mode of the engine, the active control system comprising an operative connection between the active control system and at least one engine chamber that is provided adjacent to the piston for controllably moving the piston within the engine cylinder, and the active control system further comprising at least one engine sensor for determining at least one of piston position, combustion chamber pressure, engine chamber pressure, combustion chamber temperature, and engine chamber temperature.

2. The free piston engine of claim 1, wherein the active control system comprises a repetitive control provided with desired piston trajectory information, wherein the desired piston trajectory information can be varied on a stroke by stroke basis of the piston relative to the engine cylinder.

3. The free piston engine of claim 2, wherein the combustion chamber is operatively connected with an engine power control that provides a desired power output signal, as such may be programmed or dynamically electrically provided to the engine power controller, to a fuel injection controller for creating a desired combustion within the combustion chamber.

4. The free piston engine of claim 2, wherein the piston is connected with a plunger of a hydraulic pump that is operatively connected with an energy storage device.

5. The free piston engine of claim 4, wherein the energy storage device comprises a high pressure fluid source connected with the hydraulic pump on one side thereof while a low pressure fluid source is connected with another side of the hydraulic pump.

6. The free piston engine of claim 4, wherein the active control system further comprises at least one controllable valve that allows high pressure fluid as stored within the high pressure source to be selectively connected to at least one hydraulic chamber of the hydraulic pump in real-time by providing control signals to the control valve.

7. The free piston engine of claim 6, wherein control signals are provided to the control valve from the repetitive control.

8. The free piston engine of claim 7, wherein the control valve can selectively connect either of the low pressure fluid source and the high pressure fluid source to either of a plurality of chambers of the hydraulic pump under the control of the active control system for defining a desired piston trajectory.

9. The free piston engine of claim 8, wherein the active control system is also functional to cause a motoring mode of the free piston engine using energy from the energy storage device selectively to cause movement to the hydraulic pump which is thus transferred to the piston of the free piston engine.

10. The free piston engine of claim 1, wherein the piston is connected with a component of a linear alternator and the energy storage device comprises a battery.

11. A method of controlling operation of a linear free piston engine, the engine comprising a piston movably provided within an engine cylinder for providing a combustion chamber on one side of the piston and another engine chamber on an opposite side of the piston, the piston being operatively connected with a load device, the method comprising controlling a piston trajectory during a firing mode of the engine by way of an active control system that is operatively connected with an energy storage device, by sensing at least one of piston position, combustion chamber pressure, engine chamber pressure, combustion chamber temperature, and engine chamber temperature, and thereafter determining a piston trajectory for controlling the piston trajectory according to the determined piston trajectory by way of an operative connection between the active control system and at least one engine chamber that is provided adjacent to the piston.

12. The method of claim 11, wherein the active control system comprises a repetitive control provided with desired piston trajectory information, and the method further comprises a step of providing desired piston trajectory information on a stroke by stroke basis and controlling piston trajectory relative to the engine cylinder on a stroke by stroke basis.

13. The method of claim 12, wherein the combustion chamber is operatively connected with an engine power control, and the method further comprises a step of providing a desired power output signal, as such may be programmed or dynamically electrically provided to the engine power controller, to a fuel injection controller and thus creating a desired combustion within the combustion chamber.

14. The method of claim 13, further comprising moving a plunger of a hydraulic pump by the piston, wherein the plunger is operatively connected with an energy storage device.

15. The method of claim 14, wherein the energy storage device comprises a high pressure fluid source connected with the hydraulic pump on one side thereof while a low pressure fluid source is connected with another side of the hydraulic pump, and wherein during engine firing mode fluid can be transferred from the low pressure source to the high pressure source by the hydraulic pump.

16. The method of claim 14, wherein the method further comprises a step of controlling at least one controllable valve by way of the active control system and utilizing high pressure fluid as stored within the high pressure source by selectively connecting the high pressure fluid to at least one hydraulic chamber of the hydraulic pump in real-time by providing control signals to the control valve.

17. The method of claim 16, wherein control signals are provided to the control valve from the repetitive control.

18. The method of claim 17, wherein the control valve selectively connects either of the low pressure fluid source and the high pressure fluid source to either of a plurality of chambers of the hydraulic pump under the control of the active control system for defining a desired piston trajectory.

19. The method of claim 18, including a step of causing a motoring mode of the free piston engine using energy from the energy storage device selectively to cause movement to the hydraulic pump which is thus transferred to the piston of the free piston engine.

20. The method of claim 11, wherein the piston is connected with a component of a linear alternator as the load device and the energy storage device comprises a battery for providing energy to the active control system for controlling piston trajectory during a firing mode of the free piston engine.