Kinematic calibration of a hexapod robot based on monocular vision

Robot kinematic calibration is an effective way to reduce the errors of kinematic parameters and improve the positioning accuracy of a robot. This paper presents a cost-effective kinematic calibration method for a hexapod robot that only needs a monocular camera and two planar markers. The markers are attached to the body and the foot-tip of the robot separately, and the robot's six legs are calibrated one by one. The kinematic model and error model of the robot are established based on the local product of exponential (POE) model, and the calibration task is formulated as a nonlinear least squares problem where 24 unknown parameters are estimated for each leg. The proposed calibration procedure is successfully evaluated on a real hexapod robot, and the experimental results show that the robot can have a better walking performance after calibration.