Calibrating a pair of inertial sensors at opposite ends of an imperfect kinematic chain

This paper addresses the problem of determining the poses of a pair of inertial sensors mounted at the opposite ends of an imperfect kinematic chain. Due to constraints during design, robots may not be equipped with the required sensors to intrinsically recover the kinematic state up to the required precision. To recover the unknown state using a pair of inertial sensors their relative pose to the opposite ends must be known. We propose an approach to calibrate these unknown relationships in a straightforward and methodically sound way while considering any existing inaccuracies in the kinematic chain. To obtain the desired parameters the calibration problem is formulated as a least squares batch-optimization problem. The proposed approach is integrated on DLR's humanoid robot Agile Justin to determine the pair of inertial sensors mounted at the opposite ends of the torso/head chain and further experimentally validated.