Research On Multi-Motor Underwater Differential Speed Coordination Control System Based On Ring Cross-Coupling

With the increasing importance of marine resources,many new technologies have been applied to explore and exploit the oceans.The underwater robots have become important equipment for exploring and mining marine resources,due to their small size,high flexibility,and the ability to operate in deep-sea environment for long periods of time.However,the complexity of the deep-sea environment with its disturbing flow and undulating terrain,affects the safety of underwater robot and the quality of its trajectory tracking.It is even impossible to ensure that underwater robot completes subsequent tasks.So,high real-time multiple propellers coordinated differential speed control technology for underwater robots is of great importance to resist the flow disturbance and enable rapid course adjustment.Firstly,aiming at the problem of large computation of multiple propeller motors in resisting the flow disturbance and adjusting the hull posture,a method is designed to normalize the real multiple propeller motors to three virtual propeller motors.By transforming the real power layout of multiple propeller motors to the virtual propeller motors,the method realizes a significant reduction in computational effort by only calculating the adjustment values of the three virtual propeller motors when controlling the hull heading and attitude.Then,according to the requirements of dynamicity and coordination of multiple propeller motor systems for underwater robots,an improved multi-motor ring cross-coupling control method is designed.It determines the main tracking objects of the multi-motor system under different operating conditions,to solve the problem of parameter differences among the three virtual motors after normalization.Based on the theory of backstepping control,a multiple propeller motors differential speed coordinated controller is designed by combining the Lyapunov function.This method can improve the speed and accuracy of convergence of speed synchronization error in multi-motor differential speed running.Finally,the simulation analysis of the control method designed in this thesis and the experiment of three permanent magnet synchronous motor differential speed coordinated control are completed.Simulation and experimental results demonstrate that the improved multiple propeller motors ring cross-coupling control method designed in this thesis can effectively suppress the flow disturbance and realize high coordination,dynamicity,and control accuracy for the underwater robot propeller system.