Supernumerary Robotic Limbs for Human Body Support

A robot attached to a human body can support the human when performing tasks in dangerous environments or when taking postures that are fatiguing and uncomfortable. This paper presents a new type of supernumerary robotic limbs (SRL) that supports the human body against floors, walls, and surrounding structures so that the human can perform a task safely, comfortably, and stably. First, the use of wearable robots for securing and supporting a human body is discussed, followed by an SRL design concept. The SRL is worn around the waist and can brace the human body by making contact with a wall, grasping a rail, or being anchored to the floor. Quasi-static stability and compliance with which the body is supported are analyzed. Two control methods for stabilizing the body support system are considered: one is null-space stabilization using Hessian matrices, and the other is joint servo stiffness, based on the Jacobian. A prototype robot is designed and tested. Potential applications of the SRL in diverse fields are discussed.