Abstract
This paper discusses transmission characteristics of tendon-sheath driving system typically used to actuate robotic finger joints, and also their effects on force control system. For a simple tendonsheath model, we first formulate the transmission characteristics with the newly introduced two physical parameters apparent tendon-stiffness and equivalent backlash. An interesting aspect is that apparent tendon-stiffness changes when the tendon is pulled or loosened, while tendon-stiffness itself keeps constant. This unexpected behavior is confirmed by simulations as well as experiments. We also consider the effect of apparent tendon-stiffness on force control precisely and show that the direction-dependent behavior ofapparent tendon-stiffness eventually brings about a direction-dependent response in the force control system.
