Singularity-free regulation of underwater vehicle-manipulator systems

A sliding mode approach for the regulation problem of underwater vehicle-manipulator systems (UVMS) is developed. Based on the body-fixed and joint-space coordinates dynamic model a control law is derived, which avoids the inversion of the system Jacobian, thus overcoming the occurrence of kinematic singularities. Further, to avoid representation singularities of the orientation, attitude control of the vehicle is achieved through a quaternion based error. A Lyapunov-like analysis is used to prove the error convergence. Finally, numerical simulation shows the performance of the control scheme in a practical case study involving a full-dimensional task