Abstract: An improved ant colony algorithm based on third-order B-spline curve fitting is proposed for the 3-D path planning and collision avoidance of underactuated AUV in complex waters，in which the underactuated motion characteristics and vehicle constraints are considered. An underwater space environment is modeled by simulating the real sea environment complexity. For the short service life issue of the underactuated AUV steering wheel，which is caused by large angle of turn and zigzagging route coming from the global path planned by original ant colony algorithm，a global path is planned by setting a vertical safety zone and redesigning the fitness function and evaluation function based on the factors of short path length and high path smoothness.TAn optimized path is fitted by using B-spline curve. And the continuous and safe path trajectory satisfies the velocity vector constraint of goal point. The simulated results show that the planned path is feasible on the precondition of guaranteeing the high convergence speed and global search capability.

Key words: underactuatedautonomousunderwatervehicle, improvedantcolonyalgorithm, B-splinecurvetheory, velocityvectorconstraint