Joint configuration strategy for serial-chain safe manipulators

Multi-DoFs (Degrees of Freedom) manipulators with more than 6-DoF can perform complex and diverse tasks. To make these serial-chain manipulators safer, a variety of safety components were researched. If there is a crash at the end-effector of the serial-chain manipulators, components mounted on joints of the upper and lower arm can absorb the impact. Unfortunately, physical human-robot interaction does not occur only at the end-effector, a collision can happen anywhere from the base to the end-effector. If a collision occurs in the upper arm of relatively low DoFs, safety components attached to each joint may not work properly. Therefore, a study for joint configurations of serial manipulators is necessary with respect to the placement of safety components at the shoulder joint. Through various case studies, this paper verifies the appropriate joint configurations that place safety components at each revolute joint for physical human-robot safety.