Evaluation of a 7-DoFs Robotic Manipulator as Haptic Interface During Planar Reaching Tasks

Abstract

In this work, we evaluated the suitability of using a 7 degrees of freedom robotic manipulator as a planar haptic interface for studies in motor neuroscience. In particular, we assessed to what extent it can measure human movement and forces without applying undesired perturbations. To this aim, we evaluated the amount of perturbation exerted by the robot during planar reaching movements when controlled to be as transparent as possible in the 2D task space, through an impedance control. Two planar specular configurations of the robot were tested, namely G1 and G2, which differ in the position of the “elbow joint” in the workspace. For both configurations, we estimated the inertial ellipsoids and simulated the forces for human-like forward movements. Performance was then experimentally assessed on 8 healthy participants, in 15 different positions in the workspace. The average handpath perturbation decreased and settled to 6 mm after 2 minutes of interaction. Interaction forces resulted specular for G1 and G2, with mean values below 5 N. Overall, the robotic manipulator resulted suitable for studies on planar reaching movements in both configurations, with a preference for the G1 configuration due to its symmetrical distribution of trajectory deviations, which anyway remain well below 1 cm for movements of 15 cm.