Kinematic constraints for assisted single-arm manipulation

Of several possible forms of human-robot collaborative manipulation, we focus on the case where the human and the robot jointly manipulate a common load. In our formulation, the robot's role is to provide a constraint surface to guide the motion of the load. The value of this form of interaction, in terms of ergonomics, accuracy, or speed, depends on how humans make use of such constraints. We are studying natural single-arm manipulation of a load constrained to move along a guide rail. In this paper we present results of experiments showing that subjects apply significant forces against the rail, depending on the configuration of the arm and the orientation of the rail. These forces are unnecessary for the manipulation task, and we hypothesize that humans apply forces against the constraint to simplify the manipulation task.