A nonlinear control design approach based on multi-linear models

A relatively simple method which is however capable of controlling some complex nonlinear processes using multiple models is presented. The idea is based on developing local linear models for the whole operating range of the process being controlled. First different operating zones where the nonlinear process can be approximated with linear models are found. Then the nonlinear plant is approximated by a set of local models where each model is valid for a small operating region. The models are smoothly connected together to form a global continuous model using validity functions. Once the global model is developed, it is embedded within a linear control framework and a global control system for the whole operating range of the process is designed. Simulation results of the applications of this approach for the modeling and control of a typical chemical engineering process are presented. The performance of the control system is illustrated for different operating conditions which show the capability of the technique for controlling nonlinear processes