On the Design of Human-Safe Robot Manipulators

Bringing robot manipulators in the same environment as humans seems a natural evolution in the path towards more advanced robotics. This upcoming co-existence will offer a tremendous potential to improve many industrial applications such as manufacturing and assembly. In this paradigm, an efficient synergy between human and robot can be obtained by combining the human’s reasoning ability and adaptability in unstructured environments with the inexhaustible strength of robots. The current generation of commercially available robot manipulators is not designed to fit the specific needs required by this novel collaboration. Indeed, control algorithms that enable an intuitive and efficient interaction between humans and robots are still missing to industrial robots. At an even more fundamental level, the way they are currently designed presents significant risks in the proximity of humans. Many studies have investigated this last aspect to demonstrate the potential danger of a robot Zinn, Khatib, Roth & Salisbury (2004a) and to understand and provide metrics to characterize to the level of this threat Haddadin, AlbuSchaffer, Frommberger & Hirzinger (2008); Haddadin, Albu-Schaffer & Hirzinger (2008); Yamada et al. (1997). The next step for robot designers should focus on increasing human safety to an acceptable level according to the conclusion of these studies. The aim of this chapter is to present how, at the conceptual level, robot manipulators should be mechanically designed to be harmless for humans. Both established and novel concepts will be reviewed to provide actual guidelines to the robot designer. Serial elastic actuators (SAE), distributed macro-mini (DM2) and variable stiffness joints will be reviewed whereas more emphasis will be placed on force limiting devices (FLD), robot soft covering and a method for efficiently coupling robot joint actuators for reducing their potential of transferring energy to the surrounding environment.