Enabling extended tool manipulation through redundancy-driven contact exploitation

Extended tool manipulation poses significant challenges for torque-limited robotic manipulators, as interaction forces acting at a distance amplify joint torques through the lever-arm effect and can compromise dynamic feasibility even when tasks are kinematically admissible. This paper presents a control methodology that enables extended-tool tasks by systematically inducing environmental support contact through redundancy resolution. The proposed framework integrates motion and force control in task space with secondary objectives in the null space that promote support contact without explicitly modeling the environment. Rather than predefining contact, the manipulator adapts its configuration under force feedback to establish and maintain support that counteracts lever-arm-induced loading. The methodological contribution lies in formalizing redundancy-driven support contact as a mechanism for extending torque feasibility in extended-tool manipulation. The approach is validated through a comparative experimental study of three null-space formulations on a seven-degree-of-freedom robotic manipulator performing a moderate-force wall-painting task with a 1.4 m tool. The results show how different null-space strategies influence contact consistency, load redistribution, and coupled motion-force interaction during sustained support. These findings demonstrate the feasibility of redundancy-driven support exploitation in moderate-force extended-tool manipulation and motivate future extensions toward higher operational loads and more complex contact conditions.