Safe human-robot interaction requires robots endowed with perception. This paper presents the design of a multi-modal sensory array for continuum robots, targeting operation in semi-structured confined spaces with human users. Active safety measures are enabled via sensory arrays capable of simultaneous sensing of proximity, contact, and force. Proximity sensing is achieved using time-of-flight sensors, while contact force is sensed using Hall effect sensors and embedded magnets. The paper presents the design and fabrication of these sensors, the communication protocol and multiplexing scheme used to allow an interactive rate of communication with a high-level controller, and an evaluation of these sensors for actively mapping the shape of the environment and compliance control using gestures and contact with the robot. Characterization of the proximity sensors is presented with considerations of sensitivity to lighting, color, and texture conditions. Also, characterization of the force sensing is presented. The results show that the multi-modal sensory array can enable pre and post-collision active safety measures and can also enable user interaction with the robot. We believe this new technology allows for increased safety for human-robot interaction in confined and semi-structures spaces due to its demonstrated capabilities of detecting impending collision and mapping the environment along the length of the robot. Future miniaturization of the electronics will also allow possible integration in smaller continuum and soft robots.
Keywords: Continuum robots; Human-robot interaction; Multi-modal sensing.