Tactile-Based Prioritized Compliance for Mobile Manipulators: A Case Study of Human Walking Support

Large-scale tactile sensors facilitate mobile manipulators to perform close and safe physical human–robot interactions with the perception of physical contact. Particularly in applications such as elderly walking support, we introduce a dual-arm mobile manipulator equipped with tactile skin, enabling a more humanlike support mechanism. To make the robot support humans, we establish a task hierarchy; and to make it follow humans walking, we aim to strike a balance between tasks and the compliance to contact forces. If maintaining tasks with compliance in the null-space, the compliant motions will get constrained. In this article, we propose a method that shapes prioritized compliant behavior from null-space compliance (NS-C) to whole-body compliance for walking support. Our approach evaluates the feasibility of NS-C, and in barely feasible cases, hierarchically propagates infeasible force components into task space, allowing the robot to generate appropriate compliant motions. Using this method, we can shape various compliant behaviors through specific task settings. We validate the approach through experiments on the dual-arm mobile manipulator.