Automatic and self-contained calibration of a multi-sensorial humanoid´s upper body

Complex manipulation tasks require an accurate interplay of actuation and sensing. This accuracy can only be achieved by calibrating the relevant components beforehand. Typically calibration procedures are time-consuming and often include subsequent calibration steps, involve multiple people and require external tools. In this paper we alleviate these issues by auto-calibrating the different sensors of DLR´s humanoid Rollin´ Justin in a single, completely automatic and self-contained procedure, i.e. without calibration plate. By observing a single point feature on each wrist while moving the robot´s head, the stereo cameras´ intrinsic and extrinsic parameters are calibrated together with the arm joint elasticities and joint angle offsets. Additionally, we use the head motion to calibrate an Inertial Measurement Unit (IMU) extrinsically. Parameters are obtained by formulating the calibration problem as a batch-optimization problem that estimates all parameters jointly. A rough initial guess, as is, e.g., available when re-calibrating, is needed for the estimation and to facilitate marker detection. The procedure is validated on real hardware and reduces the effort considerably allowing rapid (5 min movement time), automatic, and accurate calibration by simply “pushing a button”.