Reduction of the dynamic coupling between a manipulator and ROV using variable structure control

The paper has demonstrated the effect of dynamic coupling between a manipulator and ROV and has proposed a scheme to reduce it. The ROV dynamic equations and the modelling process for the manipulator, with basic hydrodynamic effects included, have been presented together, with the technique for combining the two dynamic models. Results have shown the dynamic interaction present when the ROV´s state vector is not controlled causing unacceptable errors in the end-effector position when following a trajectory. The sliding mode control scheme was applied to the ROV´s yaw angle and reduced the variation compared to the open-loop case. Significantly better results were achieved when the manipulator disturbance expression was included in the control law, and performance depended on the quality of the manipulator kinematic and inertial parameters. The method proposed forms part of an overall manipulator/ROV coordinated control scheme, which is envisaged as exploiting the increased kinematic envelope of the manipulator due to the extra degrees of freedom provided by the ROV.