Develop Human Safety Mechanism for Human-Symbiotic Mobile Manipulators: Compliant Hybrid Joints

Today, robots are expected to provide various services directly to humans in environments, this situation has led to the idea of teams consisting of humans and robots working cooperatively on the same task. Various names for this type of human–robot cooperation system have emerged including human-friendly robots, personal robots, assistant robots and symbiotic robots. These robots will continue to be employed also in the 21st century to cope with the increase in the elderly and handicapped, the decrease in the birth rate and working population and will be introduced into non-industrial areas such as homes and offices to make a rich and comfortable life. Such robots as home-use robots, assistance robots, and service robots, should deal with diverse tasks (Fujie, Tani, and Hirano 1994; Kawamura and Iskarous 1994). One of the specific situations in the non-industrial areas is that the robots coexist and help humans in their life environments. The robots, therefore, must be with the capability of human-robot coexistence. They can be called “humansymbiotic robots” (HSRs). There are various problems to be solved to develop the HSRs. Working and moving among humans requires special concerns on the safety issues, the safety of human in view of an unexpected collision should be assured. A HSR should weight not significantly more than a human, but mechanical compliance of the surface and joints is also a necessity. In the past two decades, many researchers have studied to reduce in advance the unexpected collision accidents between an industrial robot and a human operator by isolating robots in work cells that automatically shut down if a person enters; visuals (signs, flashing lights), and audio devices would indicate conditions by the operation and vision/sound alarms, and so on. Because these accident precautions approaches are difficult to assure human safety in human-robot environments in which an interaction between the person and the robot is presupposed, we have to consider other ways to deal with human-robot collisions and such contacts can take place anywhere on the body of the robot. Therefore, the HSR should be constructed on the basis of a new philosophy from that of past robots. Lim and Tanie (2000) proposed the HSR must be constructed for