Camera-Projector-Robot Calibration for Human-Robot Collaboration

Abstract

Effective and safe human-robot collaboration relies on the clear communication of information relevant to the shared task. Contextual information, such as work areas, object placement locations and safety zones can be projected on the work space, observable by the human operator, in an unobtrusive way. To facilitate this, a projector-camera system needs to be installed alongside a robotic arm as perception and communication tool. As the camera, projector and robot all operate in their own work space, calibration is needed to align the workspaces and compensate for distortion effects. This paper describes the calibration processes and all required tools for such system, including calibration between projector and camera, robot end-effector and camera, and camera intrinsics. As outcome the calibration should find the relationship between projected points and the world coordinate frame. The approach is evaluated with two workcells; a collaborative robot workcell and an industrial robot workcell, each with different configurations for the projector-camera system. The results demonstrate the procedures for all three calibration methods in detail, showing that an accurate calibration can be obtained for both workcells. The software is available at https://github.com/cogrob-tuni/projector-interface.