Two-arm manipulation tasks with friction assisted grasping

This paper studies human dual arm manipulation tasks and develops a computational model that predicts the trajectories and the force distribution for the coordination of two arms moving an object between two given positions and orientations in a horizontal plane. Our ultimate goal is to understand the dynamics of dual arm coordination in order to develop better robot control algorithms. Our computational model is based on the hypothesis proposed by Uno et al. (1989) who suggest that human movements minimize the integral of the norm of the rate of change of actuator torques. We compare the experimental trajectories and force distributions with this computational model. The first important observation is that the trajectories show a significant degree of repeatability across trials and across subjects. Next, we observe that the trajectories in the sagittal and frontal plane are characterized by asymmetric features that are hard to model using such integral cost functions. Finally, we show that the internal forces play an important role in trajectory generation. While these are repeatable across trials, they vary significantly from subject to subject.