Reduced complexity adaptive nonlinear control of a distributed collector solar field

Abstract

An approach to the control of a distributed collector solar ®eld relying on feedback linearization, Lyapunov based adaptation and a simpli®ed plant model is presented. The control objective consists of manipulating the oil ̄ow so that the outlet oil tem- perature is regulated around a given setpoint. For dealing with plant nonlinearities and external disturbances, a nonlinear trans- formation is performed on the accessible variables such that the transformed system behaves as an integrator, to which linear control techniques are then applied. Since the transformation depends on an unknown parameter, an adaptation law is designed so as to minimize a Lyapunov function for the whole system's state. For the sake of control synthesis a simpli®ed plant model which retains the bilinear nonlinearity is employed. The resulting control law has the same control structure of the one yielding exact input-output linearization but assumes a di􏰒erent placement of a temperature sensor. In order to justify this procedure, plant internal dynamics is studied. Experimental results obtained in the actual ®eld are presented. 5 2001 Elsevier Science Ltd. All rights reserved.