Multi-functional safety sensor coupling capacitive and inductive measurement for physical Human–Robot Interaction

Safety devices are essential for humans and robots to work alongside each other or together. This paper introduces a multi-functional safety sensor for physical Human–Robot Interaction (pHRI). We adapted dual-type capacitive and inductive measurements for the proposed sensor. It enables the sensor to detect the human body and the metal sensitively and distinguish whether an object is a human body. The tendency of the capacitance and the inductance depending on the thing is significant to recognize the objects. We introduce three practical techniques to enhance sensor performance. The conversion time control allows the sensor to adopt the dual-type measurement. The carbon micro-coils (CMC) and the active shield improve the sensitivity and the signal integrity. Three typical pHRI functions have been verified, from proximity range to contact interaction. Emergency stop, collision avoidance, and direct teaching are the representative functions. The sensor allows the robot to interact with the operator’s body for emergency stop, collision avoidance, and even interact with conductive objects. However, only the operator’s hand is allowed in the direct teaching function for safe human–robot collaborative work. Experimental results have shown that the sensor enables a robot to perform the various safety functions with a maximum of 300 mm of proximity and 11 N of force sensing capability.