Cavitation number and speed are capable of variation during the motion of supercavitating vehicle underwater,for example,under the condition of accelerated motion stage and external disturbance.The dynamic model and control challenge associated with the longitudinal motion of supercavitating vehicle with variable cavitation number and speed have been explored.Based on the principle of cavity expansion independence the properties of cavity and the influence on planning force of body were researched.Calculation formula of efficiency of the fin was presented.Nonlinear dynamics model of variable cavitation number and speed supercavitating vehicle was established.Stabilities of the open-loop systems of different situations were analyzed.The simulations results of open-loop systems show that it is necessary to design a control method to control a supercavitating vehicle.A gain schedule controller with guaranteed H∞ performance was designed to stabilize the dive-plane dynamics of supercavitating vehicle under changing conditions.
Regarding to the problems that supercavitating vehicles have special characteristics from traditional underwater vehicles,robust control problem was studied in this paper for the supercavitating vehicles with mismatched uncertainties.The nonlinear dynamic model was improved.For mismatched uncertainties,the robust sliding mode function was proposed based on guaranteed cost theory,and sufficient condition for the existence was given in terms of linear matrix inequality (LMI).Continuous sliding mode controller was designed,with an adaptive technology which was used to estimate the unknown upper bound of mismatched uncertainties.Meanwhile,upper bound of parameter uncertainties was not required.Simulation results demonstrated that the system responds rapidly and has good robust stability.Due to application of guaranteed cost theory,the controlled plant is not only stable but also guarantees an adequate level of performance.Therefore,it provides theoretical references for further study on control problems of supercavitating vehicles.
