INFORMATION FUSING THROUGH PAN-TILT ASSEMBLY UNIT-LASER RANGER FINDER UNIT SELF-CALIBRATION: A NEW METHOD

This study proposes a new method for the information fusing through calibrating a pan-tilt assembly unit (PTU) and a laser ranger finder unit (PTULaser). To this end, a self-calibration algorithm is proposed for computing the 3D measured coordinates with different-dimensional data measured by the sensors. The PTU-Laser is regarded as a "3DoF robot", comprising two rotation joints and one translation joint, with measurements related to the joint's angels. Next, the process of computing the 3D measured coordinates is converted into a forward kinematics problem of the "robot". Hence, an accurate kinematic model is crucial for calculating the end-effector (i.e., laser spot) position. Using mathematical tools of the group theory and differential geometry, considering the adjoint transformation relationship between the theoretical and actual values of joint twists in the product-of-exponential (POE) formula, the differential of the kinematics equation is converted into an equivalent linear form, including the joint's constraints. Finally, a least-squares algorithm is used to iteratively derive the kinematics parameters. The test results prove the feasibility and effectiveness of the proposed method, which significantly improved the accuracy of 3D measurements compared to other methods.