Active Safety Constraint Based Adaptive Tracking Control And Application

An actual engineering system often has physical security boundary,such as assembly line industrial system,wind power generation system,power system,high-speed rail system,etc.Its own state is strictly constrained by the physical boundary to ensure longterm stable and reliable operation.Once such physical restraint device is ignored or fails,the system will suffer from the risk of over boundary and even more serious safety accidents.With increasing complexity of industrial production,nonlinearities and parameter uncertainties of the corresponding production devices or systems become more evident,which make it quite difficult to design a proper controller for these systems.Therefore,this study aimed to state constrained control of nonlinear systems with parameter uncertainties has great significance in both theory research and engineering application.We notice that the process of traction / braking control of high-speed train and its wheel rail active adhesion control is a typical tracking control problem under state constraints,which is also one of the key and difficult problems in the active safety control of high-speed train.In view of this,the main work of this paper includes the following two aspects:(1)For a general nonlinear system,its safety limits are directly introduced into a user-defined Lyapunov function,and then a feasible controller is deduced by following the procedure of a nonlinear system control design,in which state-constrained control and state tracking control are achieved within a uniform control framework.Based on this idea,two different structures of Lyapunov functions are proposed,from which two stateconstrained nonlinear adaptive controllers are derived.To deal with derivative observation of the constrained state arising from the Lyapunov function,a lowpass-filter like adaptive observer is presented to online estimate the derivative of constrained state.Theoretical analysis shows that the proposed observer based state constrained adaptive tracking controller is globally stable,by which precise state tracking is achieved and at the same time the constrained state never exceeds its given boundary.(2)The proposed state-constrained control method is applied to anti-skid traction/braking control of high-speed trains,in which both precise speed tracking and active antiskid constrained control are ensured during entire traction/braking process.The basic idea of this method is that the anti-skid condition is directly used for traction/braking controller design,such that an active anti-skid tracking controller is obtained,by which the wheelrail slip ratio is strictly limited with a practical anti-skid region.Furthermore,to deal with the problem of parameter uncertainties of high-speed train,an anti-skid constraint based adaptive traction/braking controller is developed,and its state constrained performance and global stability are analyzed and verified explicitly.Finally,numerical simulations in Matlab are implemented for the proposed control methods.It is shown that the proposed methods are effective for a general nonlinear system,by which both state-constrained control and state tracking control are truly achieved;and for the traction/braking control system of high-speed trains,both anti-skid constrain control and adaptive parameter estimation are achieved,such that compatible control between anti-skid operation and traction/braking control is realized,which improves the operation safety of high-speed trains.