Motion Control Of Supercavitating Vehicles For Fixed Depth State With Limited Rudder Surface Adjustment

The supercavitation technology can reduce the fluid resistance of a high-speed supercavitating vehicle(HSSV),thereby greatly improving the speed of the HSSV.However,the supercavitation technology makes a supercavitating vehicle more difficult to control than a ordinary underwater vehicle.In the existing research on the control theory of the supercavitating vehicle,in order to simplify the design or reduce the design difficulty,the saturation characteristic of the actuator itself is often removed from the motion model of the supercavitating vehicle.Combined with previously published experimental data,this paper analyzes the saturation characteristics of the actuators such as cavitators and rudders that cause the instability of the HSSV.Based on analysis conclusions,The linear active disturbance rejection controller(LADRC)is designed.And Two saturation compensation scheme,based on the linear expansion state observer(LESO)or error,are used to compensate for actuator saturation.The simulation results prove that the schemes proposed in this paper can compensate for actuator saturation,and ensure the stable motion of the HSSV.The main research contents of this paper are as follows:First of all,different three-dimensional coordinate systems are established for the supercavitating vehicle,and its motion and force are analyzed in the vertical plane.The nonlinear longitudinal motion model of the supercavitating vehicle is tried to be linearized by using the "small disturbance theory",and then the linear longitudinal motion model of the supercavitating vehicle is established.Secondly,the pole placement method is used to design the state feedback controller for the supercavitating vehicle.As a classic design scheme that does not consider the saturation of the actuator,it is likely to cause the instability of the movement of the supercavitating vehicle,only relying on the pole placement method;At the same time,from the perspective of fluid mechanics,this paper also elaborates the mechanism of the actuator-induced cavity instability.This paper will set an upper limit for the rotation angle of the actuator,and also add the rotation frequency of the actuator and the motor thrust as constraints to the model.In this way,the mathematical model of the longitudinal motion of the supercavitating vehicle is more realistic.Thirdly,linear active disturbance rejection controller(LADRC)is introduced,and it is the outer loop controller for the HSSV,which has been designed by the pole place.The analysis is done for state boundaries performance of the control system.Two saturation compensate schemes,based on the linear expansion state observer(LESO)or error,are used to compensate for actuator saturation.Finally,a lot of simulation tasks is carried out to verify that the saturation compensate schemes in this paper can effectively compensate saturation of actuators in angular amplitudes.