Multiple-layer variable structure controller with parameter adaptation.

This paper deals with the design procedure of aMultiple Layer Variable Structure Controller (ML-VSC) with on-lineparameter adaptation.The ML-VSC is obtained by non-linear interpolation of the control lawsof a set of VSC with sliding mode dynamics, each of them designed onthe basis of progressively pessimistic estimates of the parametricuncertainty and disturbance input of the plant.This new structure improves both the robustness and controlperformance of the single VS controller when poor knowledge on plantparameters and disturbance bounds is available.The control algorithm is completed by an on-line adaptation mechanismaiming to achieve fine tuning of the parameters. This mechanism isbased on the trade-off between the ``chattering'' effect and thetracking error. This heuristics, formulated in terms of ``if--then''linguistic rules, is implemented by a Fuzzy Logic (FL) algorithm.The paper also addresses the stability issue of the closed loopsystem, giving sufficient conditions for global stability in thepresence of bounded disturbance and modeling uncertainties. Finally, asimple simulation example illustrates the main design steps of thecontrol approach propose