Control of Redundant Submarine Robot Arms under Holonomic Constraints

AUV has undergone a major leap as technology allows higher integration, while faster sensors and actuators and new modelling techniques and its corresponding control algorithms are available. One of the new improvements of AUV technology is the capability to produce dexterous motion using robot manipulators as its end effector. This robot manipulator behaves as a multi-degrees of freedom active tool, such that the AUV stands as the free-floating base of the robot manipulator. In this case, the AUV navigates to drive the RA to its working environment, with two independent controllers, one for the AUV and another one for the RA. However, when the RA is working out its task, it is convenient to automatically control the whole AUV+RA, coined in this paper as Submarine Robot Arm or SRA for short, as a whole and unique system so as to take advantage of its redundancy and achieve better accomplishment in comparison to control the AUV and the RA independently. When the RA is in contact to a rigid object, a constrained SRA appears and the control system now must control additionally the contact forces. This sort of systems have become a new area in AUV technologies, however there is no available and proved control system for constrained SRA, which posse a complex problem because there appears a tightly coupled hyper-redundant nonlinear system subject to holonomic constraint, which produces all together a set of nonlinear algebraic differential equations of index 2. Constrained SRA deals simultaneously with navigation of its non-inertial base while controlling the pose and contact force of its RA. For the general case, we would have a freefloating hyper-redundant constrained RA. Additionally, the holonomic constraint must be satisfied all the time to maintain stable contact to a rigid underwater object, thus an efficient force controller is required to achieve stable contact while exerting a given desired contact force on this object. This rather new problem deserves a separate attention in AUV technologies, due to the subtle complexities of constrained SRA in its own right.