Study On Adaptive Switching Control Method Of UUV's Speed

Control system design as one of the difficulties of UUV research, its performance can directly affect the autonomy and working precision of the UUV. As one of the parts of UUV movement control, UUV speed control strategy is the premise condition of the UUV position and pose control. Considering the complicated of UUV's task, single speed control strategy can not reach the dual requirements of accuracy and efficiency. As UUV dynamic model is strong coupling, nonlinear, and contains uncertain inputs, an adaptive speed ANFIS controller is designed which is not depend on the accuracy mathematical model. T-S fuzzy state observer based on UUV model is introduced to estimate UUV's states information and then feedbacks this information to control UUV's speed, realizing the adaptive switching of UUV speed control strategy. The main contents of the paper are described as following:1. Different cases are designed based on the dynamical model of UUV to analyze the influence of UUV speed between system response times, steady-state error and steer effect.The simulation results show that when UUV yaws in horizon plane or dives in vertical plane,the high speed causes system overshoot; steady-state error accretion heeling and trim stability get worse.2. ANFIS attitude controller and T-S fuzzy state observer which are based on UUV model are designed. While the training of ANFIS net, to avoid the traditional BP learning algorithm's slow convergence speed and easily getting into local minimum, the parameters be trained are divided into linear parameters and nonlinear parameters. Least Squares Estimate(LSE) method is used to estimate the linear parameters, and BP learning algorithm is considered to estimate nonlinear parameters. The T-S fuzzy observer is designed based on the global fuzzy model of UUV which is constructed by singleton fuzzification and center weighted defuzzification method, and then the stability of the T-S observer is proved.3. The adaptive switching control strategies are put forward. Considering the difference requirements of speed when UUV is under different tasks and status, the speed control strategies are put forward which is driven by both task and UUV state; To realize the real-time and stable switching of the strategies designed, the adaptive switching law is designed which can be confirmed by UUV's states,the stability is analyzed further.4. On account of UUV actual application,ADCP/SSS observation case is designed to illustrate the validation of adaptive speed switching strategy. Fixed propeller thrust, speed maintenance and adaptive speed switching strategy are applied respectively to control the UUV speed in the simulation. The simulation result shows that the speed switching strategy designed can reduce the execution time of the task, so as to improve work efficiency; The lateral deviation and heeling angle is reduced, which can improve the UUV's stability while yaws in horizon plane. Overshoot and steady-state error of the control system is reduced,and then the lever crossing error or path tracking error is decreased and improves the steady-state ability of control system.