Dynamic Positioning Technology For UUV Disturbed By Working Manipulators

The Ocean is a mysterious space with infinite vitality as well as abundantresources.The humans gradually realize the importance of ocean exploitation with the rapid development of science and technologyand the urgent need forresources. The humans has made a great progress in ocean exploitation, and the UUV (Unmanned Underwater Vehicle)autonomous operating system is an important research direction, where the UUV assembled with necessary devices, such as manipulators, performs specific underwater tasks autonomously. It is required that the UUV could effectively maintain expected positions and attitudes to ensure the successful fulfilment of the underwater tasks. However, the manipulators would inevitably impact on the UUV in the form of disturbing forces and torques, affecting position and attitude maintenance of the UUV and even the quality of the underwater tasks.In this paper, the dynamic positioning technology of UUV disturbed by working manipulators is studied and the main research contents are explained as follows:Firstly, the dynamic model of the UUV under the case of disturbance by working manipulators is established. The space motion equations of the UUV are established with analysis of hydrodynamic forces and disturbing forces by the ocean current. The dynamic equations of the manipulators are established in order to compute the disturbing forces and torques impacted on the UUV. The dynamic model of the UUV disturbed by working manipulators are then obtained.Secondly, the dynamic positioning capability of the UUV is analyzed. The general model describing the configuration of the thrusters is presented as well as the conditions to realize the dynamic positioning. Considering the disturbance by the current, the maximum rates of the current in different directions are computed. The ranges of the disturbing forces and torques by manipulators are analyzed based on its typical working conditions. Then the reasonability of the UUV propelling system configuration is verified.Thirdly, the controller realizing the dynamic positioning of the UUV under the case of disturbane is designed. Cconsidering the features of MIMO (Multiple Input Multiple Output), coupling effects and uncertain disturbance of the UUV dynamic model, a Fuzzy Switching Gain Based Sliding Mode Controller is proposed to achieve the dynamic positioning of the UUV. The fuzzy switching gain is introduced to eliminate the chattering effects of the sliding mode controller and maintain its robustness as well as disturbance immunity, and thus the practicability is enhanced.Finally, the proposed control method is verified by means of simuation cases. The simulation cases are designed and performed that UUV approaches the target position with current disturbance and maintain specific positions and attitudes with working manipulators disturbance. The Fuzzy Switching Gain Based Sliding Mode Controller is contrasted with the Fixed Switching Gain Based Sliding Mode Controller to demonstrate its reasonability,effectiveness and practicability.