Research On 3-RRR Sphere Parallel Manipulator With Vectored Thruster For Underwater Vehicle

The ocean which is full of metal oil and gas are considered as the cradle for life, resources treasure. With the development of science and technology, the ocean becomes the second space for the subsistence and development of human beings gradually. In the course of marine resources exploration and exploitation, underwater vehicle(UV) could schlep a serried of detecting instruments such as camera, mechanical arm and sonar survey system, which can be used under water shoot, maintain, sample, and even make maps of the ocean floor. Moreover, in military matters, underwater vehicles are widely used as scout, monitor and minesweeping.Ocean environmental condition is complex and vile, so the UV should be favorable maneuverability and flexibility. At present, the propulsion system and guidance system are not combined in UV, which caused the unsatisfactory travelling performance. In this paper, a vectored thruster based on the spherical parallel mechanism is developed; it can change the magnitude and direction of driving force, which will bring new design ideas to the propulsion device.A sort of the spherical parallel mechanism to meet the challenge is chosen by analyzing the freedom of motion and mechanism combination rules of parallel mechanism. It will be used in UV vectored thruster, to realize the movement of multi degree of freedom, such as pitching, yawing and rolling. The structure designs of selected 3-RRR spherical parallel mechanism are improved and the model of spherical parallel mechanism is established, the mapping relation between the motion platform and the three coordinates of driving joint is obtained by analyzing the structure parameters.For the new type vectored propulsion UV, the fixed and hull coordinate systems are built up, and various freedom of motion while in the UV motion are analyzed. The UV nonlinear dynamic equation is established, and the detailed calculation is carried out in connection with items in the equation such as the additional mass, Coriolis force, centripetal force, towing force, driving force, force moment, buoyancy force and fluid acceleration.A special control system is developed for the vectored-feed mechanism, and simulation is also performed by simulink to ensure the stronger robustness and autonomy of system, which can meet the control requirements of the UV to guarantee the favorable maneuverability.The research of this paper provides a new mentality of designing and the reference for the further optimizations of vectored thruster.