Multiple Impedance Control for object manipulation by a dual arm underwater vehicle-manipulator system

In this paper, control of an object manipulation task by a dual arm underwater vehicle-manipulator system (UVMS) is studied. The object is a heavy cylinder which should be moved and pegged precisely in an underwater structure while impacts due to contact are inevitable. The Multiple Impedance Control (MIC) is customized for this system, and the obtained results are compared with those of the augmented object model (AOM) approach. To this end, first an explicit dynamics model of the UVMS is developed. Hydrodynamic effects, i.e. added mass, drag and buoyancy are considered as external forces/moments in the task space, which are incorporated into the model by corresponding Jacobian matrices of their application points. Then, this derived model is used for preparing a MATLAB code by which the manipulation task in the 3D space is simulated. Extensive computer simulations show that in the presence of flexibility in the system that is modeled by remote center compliance the AOM does not have a stable performance, while the MIC yields a reliable performance. It is shown that even in case of appearing an impact due to contact with the environment, also severe model uncertainties, the system exhibits a smooth and nondestructive reaction.