Effects of the design parameters of multimodel adaptive control on the performance of a flexible transmission system

SUMMARYDesign parameters selection in the multimodel adaptive control based on switching and tuning will beinvestigated. Some design parameters like number of " xed and adaptive models, forgetting factor andminimum time delay between switchings will be considered. A recently developed parameter adaptationalgorithm based on closed-loop output error will be compared with the classical least-squares predictionerror algorithm in the multimodel adaptive control. The e! ects of these parameters on the performance intracking and in regulation of a # exible transmission system will be studied via several simulation examples.Copyright ! 2001 John Wiley & Sons, Ltd. KEY WORDS: adaptive control; multimodel; switching; closed-loop identi " cation 1. INTRODUCTIONThe plants subjected to abrupt and large parameter variations are generally very di$ cult tocontrol. A classical adaptive controller or a " xed robust controller encounter the di$ culties tosolve this problem. An adaptive controller is not fast enough to follow the parameter variationsand unacceptable transients occur. Whereas a " xed robust controller normally leads to poorperformances because of large uncertainties.A solution based on switching between di! erent controllers for this type of plants has beenprobably proposed for the " rst time in Reference [1]. The main problem of switching is to decidewhen a controller should be switched to the plant. Some authors proposed a predeterminedswitching sequence [2 }4] but the multimodel approach seems m ore interesting. This approachbased on multiple models and switching will allow the transient responses to be improved in thepresence of large and fast parametric variations [5 }7]. In this approach, we suppose that a set ofmodels for di! erent operating points is a priori known. Then at every instant a controllercorresponding to the model yielding the minimum of a performance index is used to compute the