Integrated control for pHRI: Collision avoidance, detection, reaction and collaboration

We present an integrated control framework for safe physical Human-Robot Interaction (pHRI) based on a hierarchy of consistent behaviors. Safe human robot coexistence is achieved with a layered approach for coping with undesired collisions and intended contacts. A collision avoidance algorithm based on depth information of the HRI scene is used in the first place. Since collision avoidance cannot be guaranteed, it is supported by a physical collision detection/reaction method based on a residual signal which needs only joint position measures. On top of this layer, safe human-robot collaboration tasks can be realized. Collaboration phases are activated and ended by human gestures or voice commands. Intentional physical interaction is enabled and exchanged forces are estimated by integrating the residual with an estimation of the contact point obtained from depth sensing. During the collaboration, only the human parts that are designated as collaborative are allowed to touch the robot while, consistently to the lower layers, all other contacts are considered undesired collisions. Preliminary experimental results with a KUKA LWR-IV and a Kinect sensor are presented.