Safe Motion Planning for Human-Robot Interaction: Design and Experiments

Abstract

Robots have been successfully employed in industrial settings to improve productivity and perform dangerous or monotonous tasks. More recently, attention has turned to the use of robots to aid humans outside the industrial environment, in places such as the home or office. For example, as the population in the developed world ages, robots that can interact with humans in a safe and friendly manner while performing necessary home-care/daily living tasks would allow more seniors to maintain their independence. Such devices could alleviate some of the non-medical workload from health-care professionals, and reduce growing healthcare costs. To achieve such objectives, robotic devices must become more safe and user friendly. Untrained users need to feel comfortable and confident when interacting with a device that, unlike most passive household appliances, is potentially active in its interaction with the user. Two key issues hampering the entry of robots into unstructured environments populated by humans are safety and dependability (Corke, 1999; Lee, Bien et al., 2001). To ensure the safety and intuitiveness of the interaction, the complete system must incorporate (i) safe mechanical design, (ii) human friendly interfaces such as natural language interaction and (iii) safe planning and control strategies. Our work focuses on this third item. The design of safe planning and control strategies can be divided into three key components: safe planning, human interaction monitoring, and safe control (Kulic and Croft, 2003). Discussion of the human monitoring and control system components can be found in Kulic and Croft (Kulic, 2005; Kulic and Croft, 2006a; Kulic and Croft, 2006b). Here, we specifically address the planning aspects related to safety in human-robot interaction (Kulic and Croft, 2005). First we discuss the development of a motion planning approach for robots that minimize a danger index based on the physical parameters of the robot and its proximity to the user. Then we present experiments where users are asked to evaluate the robot motions with regard to their perception of the safety of the robot motion. Subjects reported significantly less anxiety and surprise, and reported feeling more calm when safe planned motions were presented, as compared to a conventional motion planner.