Internal Force Tuning of Cooperative Object Manipulation Tasks

To manipulate an object with several cooperating manipulators, the Multiple Impedance Control (MIC) is a model-based algorithm that enforces designated impedance on all cooperating manipulators and the manipulated object. For tuning the inner object forces, it is needed to model the inner forces/torques and include them in the MIC law. In this paper, a virtual linkage model is introduced to determine the inner forces in the MIC law. Also, open loop and a closed loop controllers are designed for inner forces tuning. The MIC law will be compared to the relevant algorithms, i.e., Object Impedance Control (OIC) and Augmented Object Control (AOC). Next, the MIC is used to manipulate an object on a planned path with desired inner forces. The grasp condition is considered either solidly (with all cooperating end-effectors), or, as flexible. Finally, the effects of gain tuning on the variations of inner forces will be discussed. The obtained results reveal the merits of the proposed scheme, in terms of system flexibility and good tracking errors, as well as inner forces tuning, even in the presence of impacts caused by contact with the environment.