US 8,527,247 B1Granted

Nonlinear power flow feedback control for improved stability and performance of airfoil sections

AssigneeSandia Corporation

InventorsDavid G. Wilson, Rush D. Robinett, III

Life of this patent

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Abstract

A computer-implemented method of determining the pitch stability of an airfoil system, comprising using a computer to numerically integrate a differential equation of motion that includes terms describing PID controller action. In one model, the differential equation characterizes the time-dependent response of the airfoil's pitch angle, α. The computer model calculates limit-cycles of the model, which represent the stability boundaries of the airfoil system. Once the stability boundary is known, feedback control can be implemented, by using, for example, a PID controller to control a feedback actuator. The method allows the PID controller gain constants, KI, Kp, and Kd, to be optimized. This permits operation closer to the stability boundaries, while preventing the physical apparatus from unintentionally crossing the stability boundaries. Operating closer to the stability boundaries permits greater power efficiencies to be extracted from the airfoil system.

Claims17

Dependent claims

A method of determining pitch stability characteristics of an airfoil, comprising using a computer to numerically integrate a differential equation of motion characterizing a time-dependent response of an airfoil's pitch angle, α, measured relative to direction of an incoming fluid flowing towards the airfoil;

wherein the method comprises steps of:
a) inputting airfoil design parameters and system initial conditions to a memory unit of a computer;
b) programming into the memory unit a differential equation of motion that models a response of the airfoil's pitch angle as a function of time;
c) the computer calculating the time-dependent response of the airfoil's pitch angle, energy generation (Egen), and energy dissipation (Ediss), by using a microprocessor in the computer to numerically integrate the differential equation of motion over a specified period of time;
d) storing results of the numerical integration step in the computer's memory, wherein the results comprise:
α, Egen, and Ediss as a function of time;
e) inspecting the results, and then categorizing an airfoil's transient response as being:
(1) Passive if the response is damped and dissipative, (2) Neutral Limit-Cycle if the response is balanced and stable, or (3) Unstable if the response is generative and divergent.

5 more elements

A method of determining pitch stability of an airfoil, comprising using a computer to numerically integrate a differential equation of motion that includes terms describing PID controller action;

wherein the differential equation characterizes a time-dependent response of an airfoil's pitch angle, α, measured relative to direction of an incoming fluid flowing towards the airfoil;
wherein the method comprises steps of
a) inputting airfoil design parameters, system initial conditions, and feedback control reference values to a memory unit of a computer;
b) programming into the memory unit a differential equation of motion that has terms describing PID controller action, which models a response of the airfoil's pitch angle as a function of time;
c) the computer calculating the time-dependent response of the airfoil's pitch angle, energy generation (Egen), and energy dissipation (Ediss), by using a microprocessor in the computer to numerically integrate the differential equation of motion over a specified period of time;
d) storing results of the numerical integration step in the computer's memory, wherein the results comprise:
α, Egen, and Ediss as a function of time;
e) inspecting the results, and then categorizing an airfoil's transient response as being:
(1) Passive if the response is damped and dissipative, (2) Neutral Limit-Cycle if the response is balanced and stable, or (3) Unstable if the response is generative and divergent.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/633,045Filed 8 Dec 2009 · continuation in part
Priority: 20 Mar 2008
Granted: 3 Sep 2013
Term ends: Not estimatedThe source records don’t support an estimate.

Classification3 codes

G05B 11/06
Electric: in which the output signal represents a continuous function of the deviation from the desired value, i.e. continuous controllers
G05B 13/04
Electric: involving the use of models or simulators
G05B
Control or regulating systems in general