Method and apparatus for adaptive control

Claim 1

A method of generating a control signal for controlling a process, during each of a plurality of sampling instants, said process having at least one input variable and one output variable, the application of said control signal to said process constituting a control action causing a variation of said input variable, said method comprising: a) providing an adaptive controller adapted to store a model of said process comprising a state vector and a model parameter vector and to generate said control action; b) providing means for measuring said output variable of said process, generating a signal representing said measurement and communicating said measurement to said adaptive controller; c) selecting a number n of orthonormal series functions to model said process; d) providing a signal to define an initial state vector l(t) t=O = ##EQU12## where d i is a constant, and storing said initial state vector in said adaptive controller; e) providing a signal to define an initial predicted model parameter vector= ##EQU13## where h i is a constant, and storing said initial predicted model parameter vector in said adaptive controller; f) performing an update of said state vector in said controller using said orthonormal series functions to provide a history of said control actions and any feedforward input variables up to that sampling instant; g) measuring said process output variable and calculating a model error in the predicted model parameter vector by comparing said predicted model parameter vector to said measured process output variable; h) updating the model parameter vector with said model error by a Kalman filter recursive least squares method; i) calculating the change in controller output required to bring said process output variables to a desired value based on a predicted process output variable obtained from said updated model parameter vector and said updated state vector; j) generating a control action based on said calculated required change in controller output; k) repeating steps f) through j) at each sampling instant; l) storing a reference model parameter vector in said controller during a period of satisfactory controller operation; and m) periodically replacing said model parameter vector in said controller with said reference vector if a steadily decreasing prediction parameter gain is detected.

Claim 2

A method of generating a control signal for controlling a process, during each of a plurality of sampling instants, said process having at least one input variable and one output variable, the application of said control signal to said process constituting a control action causing a variation of said input variable, said method comprising: a) providing an adaptive controller adapted to store a model of said process comprising a state vector and a model parameter vector and to generate said control action; b) providing means for measuring said output variable of said process, generating a signal representing said measurement and communicating said measurement to said adaptive controller; c) selecting a number n of orthonormal series functions to model said process; d) providing a signal to define an initial state vector l(t) t=O = ##EQU12## where d i is a constant, and storing said initial state vector in said adaptive controller; e) providing a signal to define an initial predicted model parameter vector= ##EQU13## where h i is a constant, and storing said initial predicted model parameter vector in said adaptive controller; f) performing an update of said state vector in said controller using said orthonormal series functions to provide a history of said control actions and any feedforward input variables up to that sampling instant; g) measuring said process output variable and calculating a model error in the predicted model parameter vector by comparing said predicted model parameter vector to said measured process output variable; h) updating the model parameter vector with said model error by a Kalman filter recursive least squares method; i) calculating the change in controller output required to bring said process output variables to a desired value based on a predicted process output variable obtained from said updated model parameter vector and said updated state vector; j) generating a control action based on said calculated required change in controller output; k) repeating steps f) through j) at each sampling instant; l) storing a reference model parameter vector in said controller during a period of satisfactory controller operation; and m) periodically replacing said model parameter vector in said controller with said reference vector if a steadily decreasing prediction parameter gain is detected.