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Optimal compensators for nonlinear analytic discrete time processes

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Dynamics and Control

Abstract

Construction methodology is presented, by which optimal Controllers, Estimators and Compensators can be synthesized for nonlinear discrete time processes. The nonlinearities in both the process and the measurement equations are expanded into Taylor series in the state vector, holding an arbitrary, but consistent level of truncation. Then, both the state conditional probability evolution, and the associated Dynamic Programming Equation can be solved for off line, ahead of time, retaining the same truncation level as that of the process model. This yield non-anticipative control laws that are consistently optimal, i.e., are as close to the optimum as the state models are to the exact ones. In the perfect information case the present controllers are nonlinear feedback-feedforward laws. The feedback part consists of polynomials of the state. The feedforward part includes moments of the process dynamic noise and possible forcing functions. All the gains are known ahead of time. In the fully stochastic situation, algorithms are obtained for on line update of the state conditional probability distribution, as the compensator feeds back various moments of that distribution in real time with all the gains known ahead of time.

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Shefer, M., Breakwell, J.V. Optimal compensators for nonlinear analytic discrete time processes. Dynamics and Control 5, 37–54 (1995). https://doi.org/10.1007/BF01968534

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