A study on the path of an upper-body support arm used for assisting standing-up and sitting-down motion

We are developing basic technology for a walking-support system. As part of this technology, we have determined the best support-arm path for assisted standing-up and sitting-down motion of an elderly person who can sit but cannot stand up. We developed a program for analyzing the load acting on lower-limb joints during the motion. Experimentally measured joint positions and floor-reaction force enabled us to calculate joint torque during motion along several paths by using the Newton-Euler formulation. And we evaluated the supporting performance of the paths of a machine arm. These calculations indicate that a linear interpolating path minimizes the necessary joint torque for assisting standing-up or sitting-down motion. A sensory evaluation test showed that users tend to feel comfortable when the path shape is similar to that of unassisted motion and when hip trajectory is smooth.