Helal, M., Xi, F., and Lin, Y., "Robotic Tooling Self-Calibration," SAE Technical Paper 2013-01-2118, 2013, doi:10.4271/2013-01-2118.
Industrial robot calibration packages, such as ABB CalibWare, are merely developed only for robot calibration. As a result, the robotic tooling systems designed and fabricated by the user are often calibrated in an ad hoc fashion. In this paper, a systematic approach for robotic tooling calibration is presented in order to overcome this problem. The idea is to include the tooling system as an extended body in the robot kinematic model, from which two error models are established. The first model is associated with the robot, while the second model is associated with the tooling. Once the robot is fully calibrated, the first error will be eliminated. Thus, our method is focused on the second error model. For this calibration, a self-calibration method is developed by using a calibration plate with multiple holes. Then, the tooling calibration model is formulated against the distance between the two holes. For measurements of the distances, a camera is mounted on the tooling system. To present the error mapping, a virtual kinematic link is proposed, which directly connects the camera to the tooling system. For error identification, a linear computational method is utilized to determine the tooling calibration parameters. The linear computational method is based on the Taylor expansion of the robotic tooling model. Once the error is identified, the next step is to implement the error in the tooling kinematic model. A case study is provided to demonstrate the effectiveness of the proposed method.