Soft interaction between body weight support system and human using impedance control based on fractional calculus

In recent years, research and development have been conducted on robots designed to assist people with disabilities in daily activities. There is a great demand for control technology for realizing flexible contact and cooperative behavior. We here report a novel impedance control method based on a fractional calculation inspired by the viscoelastic properties of biomaterials such as muscle. This paper presents an evaluation of this concept by simulation and by experiment using a robotic system for body weight support. The experimental results demonstrated that the fractional impedance controller has superior contact force absorption performance compared with a conventional controller, especially for high-stiffness objects and high-velocity movement. This fractional impedance controller may be useful especially for the purpose of flexible contact for assistive and rehabilitation robots for people.