Robot tasks are becoming more complex, as they can now be coded off-line by integrating the robot mathematical model into the controller. One of the main technological barriers in the robotics industry has been the reduction of discrepancies between the robot mathematical model and the actual robot geometry, by means of a process called geometric calibration. In this work, an inexpensive, time-effective and versatile closed-loop calibration method for serial robots is introduced. Contrary to most calibration methods, the proposed method does not require any external measurement system. The main idea is to fix the end-effector of a seven-degree-of-freedom 3D kinematic chain, formed with the robot joints and, if required, additional passive joints. Then, while performing a self-motion, i.e. changing the posture of the chain without changing its last link pose, the robot joint positions are recorded. Finally, the last link pose, computed using the mathematical model of the chain for the different postures, is subtracted from all others, thereby resulting in an overdetermined non-linear system of equations, from which the robot geometric parameters can be found. Two parameter representations were first chosen and applied to the CUATRO Arm, a serial four-degree-of-freedom redundant positioning robot, and the Thermo CRS A465, a seven-degree-of-freedom industrial robot. A versatile calibration set-up was then designed and manufactured to fix the end-effector of these robots. Moreover, different numerical identification methods were proposed and tested by means of simulation. Finally, the calibration method adopted here was applied to the CUATRO Arm and the Thermo CRS A465 robot. Although the experimental results correlated with the simulation results, the proposed calibration method was found to be highly sensitive to input noise.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.98968 |
| Date | January 2006 |
| Creators | Houde, Geneviève. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Engineering (Department of Mechanical Engineering.) |
| Rights | © Geneviève Houde, 2006 |
| Relation | alephsysno: 002487889, proquestno: AAIMR24965, Theses scanned by UMI/ProQuest. |
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