Residual mode filters
AssigneeUnited Stated of America as Represented by the Administrator of the NASA
InventorsSusan A. Frost, Mark J. Balas
Life of this patent
Estimating the term…
Abstract
Methods and systems for controlling a physical system (plant) are disclosed. The plant is modeled as a linear, finite-dimensional system having a state vector, a control input vector, a plant output vector, and a disturbance vector comprising disturbances having known basis functions and unknown amplitudes. An adaptive control law is used with separate adaptive gains for an error vector associated with the plant output vector, and the disturbance vector, plus a fixed gain for a disturbance estimator. The adaptive control law is operable to adjust the control input vector so as to minimize the error vector. The plant includes modes which are not Almost Strictly Positive Real (ASPR).
Claims4
A physical system having an adaptive controller system for controlling the physical system, the physical system further comprising sensors and actuators;
- the physical system being nonlinear with unmodeled dynamics, and
- the adaptive controller system being configured
- to receive one or more output from the physical system, including indications of one or more nonlinear disturbances to the physical system,
- to analyze the output, and
- to cancel the one or more nonlinear disturbances without needing knowledge of their amplitude,
- wherein the physical system is modeled as a linear, finite dimensional system having at least one mode which is not Almost Strictly Positive Real (ASPR), wherein said at least one not ASPR mode includes one or modes associated with:
- a wind turbine train,
- a blade flap, or
- periodic interactions between turbine blades and the wind turbine drive train;
- and
- the model of the physical system further comprises:
- a state vector, a control input vector and a plant output vector;
- a disturbance vector comprising disturbances having known basis functions and unknown amplitudes and not dependent upon parameters that define the plant system, wherein the disturbance vector affects said at least one mode which is not ASPR;
- a disturbance estimator, associated with the disturbance vector, for estimating at least one of a present value and a future value of the disturbance vector;
- and
- wherein the adaptive controller system being configured to analyze the output and to cancel the one or more nonlinear disturbances includes configuring the adaptive controller system to execute an adaptive control law comprising:
- (i) a first adaptive gain for an error vector associated with the plant output vector;
- (ii) a second adaptive gain for the disturbance vector;
- and
- (iii) a fixed gain for the disturbance estimator,
- wherein the adaptive control law adjusts the control input vector, to cause the error vector to asymptotically approach a 0 value as time increases;
- (iv) a residual mode filter that causes an amplitude associated with the at least one mode that is not Almost Strictly Positive Real to asymptotically approach a zero value as time increases;
- (v) a first frequency-locked loop, operable to lock a first filter output to at least one frequency manifested by the disturbance vector;
- and (vi) a second frequency-locked loop and phase-locked loop, operable to lock a second filter output onto at least one frequency and at least one phase manifested by the residual mode filter.
Dependencies are inferred from the claim text.