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US 10,132,238 B2Granted
Methods and systems for free piston engine control
AssigneeRegents of the University of Minnesota
InventorsZongxuan Sun, Ke Li, Ali Sadighi
Life of this patent
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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.
Claims9
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 by coordinating cylinder combustion and piston load, the active control system comprising an active repetitive controller including desired piston trajectory information and a discretized dynamic model of the free piston engine, the active control system being represented as
- y
-
- (
- k
- )
- =
- B
-
- (
- q
- -
- 1
- )
- A
-
- (
- q
- -
- 1
- )
-
- u
-
- (
- k
- )
- (
- 2
- )
- u(k)=C(q−1)[r(k)−y(k)] (3)
- where k is a discrete step index, q−1 is the one step delay operator, u(k) and y(k) are an input and output of a dynamic model of a free piston engine, r(k) is a desired motion profile and C(q−1) is the active repetitive controller which can be described as:
- C
-
- (
- q
- -
- 1
- )
- =
- R
-
- (
- q
- -
- 1
- )
-
- q
- -
- N
- 1
- -
- q
- -
- N
- ,
- (
- 4
- )
- where R(q−1) is a stable filter based on the dynamic model of the free piston engine,
- the active control system also comprising an operative connection between the active repetitive controller and at least one engine chamber that is provided adjacent to the piston for transmitting a control signal for controlling a desired trajectory of the piston within the engine cylinder according to a predetermined trajectory from the desired piston trajectory information based at least partially upon actual piston trajectory information and a model dependent stroke by stroke updated calculation of the control signal, 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 for trajectory tracking by the repetitive controller so that that piston motion, including piston displacement, velocity, and acceleration will follow the predetermined trajectory and the desired piston trajectory information can be varied on a stroke by stroke basis of the piston relative to the engine cylinder.
61 more elements
Dependencies are inferred from the claim text.