Mathematics Modeling And Control Strategy Of Supercavitating Vehicle

It is proved that supercavitating can reduce the drag force of underwatervehicle observably and make vehicle achieve high speeds,which is researchedwidely by navy great power recently.This paper takes the national defense basisresearch project as background,analyzes peculiar character of supercavitatingvehicle,according to the references published in domestic and overseas andcombine with the knowledge which has been mastered.Mathematics modelingand control problems of supercavitating vehicle are researched in this paper.Themainly works as follows:Firstly,it investigates the configuration of supercavitating vehicle,becausethe fins of supercavitating vehicle can cause cavitation itself,it proposes aconfiguration without fins of supercavitating vehicle,and use cavitator as controldevice for motion control of supercavitating vehicle.Owing to the peculiarnavigating environment of supercavitating vehicle,which is almost enveloped bycavitation,acted by special hydrokinetic forces,based on navigating speeds ofsupercavitating vehicle,it gives four stable modes.Under navigating stable mode,it calculates the planning force.Associating the analysis of forces and momentsacting on vehicle,it establishes nonlinear mathematics model for supercavitatingvehicle according to Newton law and correlative kinetics theory.And it linearizesthe nonlinear mathematics model at last.Secondly,because the peculiar characters of supercavitating vehicle,itcarries out robust H_∞control for supercavitating vehicle,and applies robust H_∞control mixed sensitivity theory to design certain depth controller forsupercavitating vehicle.It analyses disturbance and the uncertainties of model,chooses weigh functions reasonable,and establishes the generalized mathematicsmodel,obtains lower rank controller,and checks out the performance of controller.It simulates the robust H_∞controller when the hydrodynamic parameters with uncertainty,the simulation results show that the controller has good dynamicperformance when system with uncertainty of hydrodynamic parameters,thecontroller resolves the relationship between performance and robustnesssuccessfully.Finally,due to certain depth robust H_∞controller of supercavitating vehiclecan not deal with large range depth change,it investigates the nonlinear H_∞control for nonlinear system.It proves the equivalence between having not minusfunction V(x) suffice for HJI inequation,γdissipative character and L₂ gainless thanγfor nonlinear system which satisfies some certain conditions.Fornonlinear systems whose control input and disturbance input satisfy matchingcondition,it apply conformation method to design nonlinear H_∞controller,andgives a sufficient condition,consequently avoids calculating HJI inequation.Baseon the character of supercavitating vehicle,it applies backstepping method tochoose deposit function directly,designs pitch nonlinear H_∞controller forsupercavitating vehicle.It simulates the nonlinear H_∞controller,the simulationresults show that the controller has good control effect for pitch.Combined withcertain depth robust H_∞controller and nonlinear pitch H_∞controller,it propose aswitch control law for depth changing of supercavitating vehicle,control pitchand depth in subsection,simulation results show that the control law canguarantee depth changing in large range.