Whole-Body Control Based Strategy Simulation of Exo-Suit considering Singularity

Abstract

Many human movements can be aided by exo-suit. One of them is that humans put a lot of strain on their knee and waist joints while lifting large objects, but using an exo-suit can lessen the risk. However, since the weight of the exo-suit itself acts as an additional burden on body, an appropriate torque distribution strategy considering the entire system is necessary. To solve this problem, this paper proposed an assistive technique based on whole-body control. Meanwhile, when the legs are fully extended during torque control, the system has a singularity problem and the required torque will be highly increased. Singularity is serious problem because it is essential to fully straighten the legs during the lifting operation. In this paper, this problem was solved by adding a straight-leg term to the whole-body control cost function. The feasibility of the proposed method was verified through simulation, and it was shown that the exo-suit could stably perform lifting motions due to the method.