Bracing the human body with supernumerary Robotic Limbs for physical assistance and load reduction

A new approach to physically assisting the human with a wearable robot is presented. Supernumerary Robotic Limbs (SRLs) attached to the human waist support the body efficiently when the human is taking fatiguing postures, e.g. hunching over, squatting, or reaching the ceiling. Unlike a leg exoskeleton, where powered joints are attached to the human joints and are constrained to move together with the human limb, the SRL can take an arbitrary posture to maximize the load bearing efficiency. Taking a near-singular configuration, the SRL can bear a large load with small power consumption. First, the “bracing” strategy for supporting the human body is described, followed by a mathematical analysis of the load bearing efficiency. The optimal SRL posture and joint torques are then obtained in order to minimize the human load. Numerical and experimental results using a prototype of the SRL demonstrate the effectiveness of the method.