State Based Adaptive Feedback Feedforward PID Controller

• US 20070021850A1
• Filed: 09/25/2006
• Published: 01/25/2007
• Est. Priority Date: 06/20/2000
• Status: Active Grant

• Current Assignee: Fisher-Rosemount Systems Incorporated (Emerson Electric Company)
• Original Assignee: Fisher-Rosemount Systems Incorporated (Emerson Electric Company)
• Inventors: Blevins, Terrence, Wojsznis, Wilhelm
• Granted Patent: US 7,551,969 B2
• Time in Patent Office: Days
• US Class Current: 700/42
• CPC Class Codes: G05B 11/42 for obtaining a characteristic which is both proportional and time-dependent, e.g. P. I., P. I. D.
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 17/02 electric

Abstract

A state based adaptive feedback/feedforward PID controller includes a model set component, communicatively coupled to a process input, having a state variable defining a number of process regions, and a number of models grouped into the process regions. Each of the grouped models includes a plurality of parameters having a value selected from a set of predetermined initial values assigned to the respective parameter. The adaptive controller further includes an error generator communicatively coupled to the model set component and a process output. The error generator configured to generate a model error signal representative of the difference between a model output signal and a process output signal. The error generator, communicatively coupled to a model evaluation component, is configured to compute a model squared error corresponding to a model and correlating the model squared error to parameter values represented in the model. The adaptive controller further includes a parameter interpolator communicatively coupled to the model evaluation component for calculating a respective adaptive parameter value for parameters represented in the model and a controller update component, communicatively coupled to the parameter interpolator, for updating the controller in response to adaptive parameter values upon conclusion of an adaptation cycle.

Claims

1. A method of automatically switching an adaptive PID controller comprising:

defining a model set having a plurality of individual models representative of the controlled process, wherein each of the models includes a plurality of parameter values;

defining a plurality of model subsets within the model set;

wherein each of the model subsets includes a state parameter representative of a process variable input and a plurality of initial parameter values representative of the model subset;

determining the state parameter and updating the PID controller with the plurality of initial parameter values associated with the state parameter;

evaluating each of the models in the model subset corresponding to the state parameter and calculating a model squared error for each model;

determining an adaptive parameter value as a function of the model squared error; and

updating the PID controller in response to the adaptive parameter value.