In skilful tasks and sports, not only movement but also joint stiffness and the force are important. It is easy to watch and replicate the movement, but not to replicate the stiffness and the force. Muscle tensions cause our movement, which can be measured by EMG. Using the signals from EMG, we develop the technique to estimate the joint torque, joint stiffness, and equilibrium posture. So, while watching the hand movement, we can also feel the force and the joint torque are used. In this paper, we propose a motion assist system (MAS) that uses the pieces of internal information that are joint stiffness and joint torque based on muscle tensions. The experimental results show that the joint torque and hand stiffness were transmitted precisely using functional electrical stimulation (FES). This system will be useful not only for learning a skill, but also for supporting elder persons.

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