Method for estimation of at least one engine parameter

• US 8,185,292 B2
• Filed: 12/20/2010
• Issued: 05/22/2012
• Est. Priority Date: 05/12/2006
• Status: Expired due to Fees

• Current Assignee: The United States Of America As Represented By The Secretary Of The Army
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Litt, Jonathan S.
• Primary Examiner(s): Chen, Shelley
• Application Number:
  US12/973,385
• Publication Number:
  US 20110118950A1
• Time in Patent Office: 519 Days
• Field of Search: 701/29
• US Class Current: 701/100
• CPC Class Codes: G01M 15/14 Testing gas-turbine engines or jet-propulsion engines

Abstract

A system comprising determination of tuning parameters enabling optimal estimation of unmeasured engine outputs, e.g., thrust. The level of degradation of engine performance is generally described by unmeasurable health parameters related to each major engine component. Accurate thrust reconstruction depends upon knowledge of these health parameters, but there are usually too few sensors to estimate their values. A set of tuning parameters is determined which accounts for degradation by representing the overall effect of the larger set of health parameters as closely as possible in a least squares sense. The method utilizes the singular value decomposition of a matrix to generate a tuning parameter vector of low enough dimension that it can be estimated by a Kalman filter. Generation of a tuning vector specifically takes into account the variables of interest. The tuning parameters facilitate matching of both measured and unmeasured engine outputs, as well as state variables.

Claims

1. A method of measuring the health of an engine using h number of parameters, where h is defined as a complete set of health parameters sufficient to fully define a health condition, said method comprising:

measuring a predetermined number of engine outputs using sensors, the predetermined number being less than h;

estimating unmeasured outputs of an engine using a tuning vector q in combination with a transformation matrix V* where q=V*p, where p is a vector of health parameters h, and q contains some information from each of the h number of parameters needed to compute the health condition; and

estimating the health condition of said engine based upon measured engine outputs.

2. The method of claim 1, wherein the engine is a turbofan engine and the unmeasured parameters which are estimated by the tuning vector q in conjunction with a transformation matrix are capable of detecting a stall condition during the flight of an aircraft.

3. The method of claim 1, wherein the unmeasured output that is estimated using the tuning vector is one selected from the group consisting of gross thrust and net thrust.

4. The method of claim 1, wherein the step of estimating the unmeasured outputs comprises determining degraded operation of an engine due to shifts in the health parameters, and wherein the health parameters include fan efficiency, fan flow capacity, low pressure compressor efficiency, low pressure compressor flow capacity;

high pressure compressor efficiency;

high pressure compressor flow capacity;

high pressure turbine efficiency;

high pressure turbine flow capacity;

low pressure turbine efficiency and low pressure turbine flow capacity.

5. The method of claim 1, wherein the tuning vector is represented by q and its estimate of value corresponds to the relationship expressed as:

6. The method of claim 5, wherein the measured parameters are measured by sensors y, and further selecting a k number of values, where k is equal to the number of sensors less the number of zero eigenvalues in the matrix A.

7. A method of determining faults in a turbofan engine where the fault is not in a measured parameter, by estimating the tuning vector q of claim 5 a number of times and determining abrupt shifts in the tuner as an indication of a fault.

8. The method of claim 1 wherein p is mapped into q through the transformation matrix V* such that q=V*p where V* is full rank.

9. The method of claim 1 wherein the step of estimating unmeasured engine outputs using a tuning vector comprises employing a computer to estimate the tuning vector q a number of times and determining abrupt shifts in the tuning vector as an indication of a fault.

10. The method of claim 9, where the unmeasured parameter is one selected from the group consisting of gross thrust and net thrust.

11. The method of claim 9 wherein the unmeasured parameters comprises net thrust and gross thrust the method is used to control an i-flight engine.

12. The method of claim 11, wherein the relationship between tuning vector q and the unmeasured parameters satisfies the expression

13. The method of claim 1 wherein engine component performance is estimated by health parameters in the following state-space equations

{dot over (x)}=Ax+Lh+Bu_cmd

y=Cx+Mh+Du_cmd+v

where the vector x represents the state variables, x(dot) is the derivative dx/dt, h represents health parameters, u_cmd represents control variables, y represents the sensor measurement vector which is corrupted by the noise vector v;

and the matrices A, B, C, D, L and M have appropriate dimensions.

14. The method of claim 1 wherein the health parameters define a health condition sufficient to determine deterioration manifested as a shift in operating point from a baseline engine.