Building a safe care-providing robot

A service robot especially a care-providing robot, works in the vicinity of a human body and is sometimes even in direct contact with it. Conventional safety methods and precautions in industrial robotics are not applicable to such robots. This paper presents a safety approach for designing the safe care-providing robot FRIEND. The approach is applied in each step of design iteratively to identify and assess the potential hazards during design. The steps are explained briefly in this work. The main contribution of this paper is verification of safety requirements using the Ramadge-Wonham (RW) framework. The greater complexity of the tasks the robot will perform, the more complex is the identification of safety requirements. Use of this framework led us to analyze the requirements and verify them formally, systematically and on a modular basis. In our approach human-robot interaction (HRI) is also modeled by a set of uncontrolled events that may happen any time during operation. Subsequently the safety requirements are modified to consider these interactions. As a result the safety module behaves like a controller, running in parallel with the system, which maintains the system safe and works according to the safety requirements by enabling the admissible sequences of events.