Modelling of robotic manipulators

This thesis explores the different aspects of robotic manipulator modelling and covers both the dynamic and the kinematic issues for the purpose of improving the overall manipulator accuracy. It is shown that the modelling should not stop at producing the model, but rather the model should be validated. The thesis presents a description of the modelling process and examines the three most important formulations for dynamic modelling. A comparison of their performance and ease of use is made, both for manual and computer assisted implementation. Three commercial computer modelling packages are also described and compared with regard to their performance and ease of use for robotic manipulator modelling. It is shown that some software development is required to make the packages easy to use for manipulator specific modelling. As part of this work, one such development was a programme written as a back end to AUTOLEV. This combination provides a powerful tool for dynamic modelling and simulation of manipulators. A more integrated computer aided engineering approach is also discussed through modelling a large industrial manipulator using a geometric modelling package along with another dynamic modelling and simulation program. This approach is very efficient in providing useful information which is difficult to otherwise obtain from direct measurements. The thesis emphasises validation as part of the modelling process. A model does not have to be an exact mathematical description of the manipulator, inclusive of all characteristics, but rather a valid description for the intended use. It is shown that a manipulator model can be split into several joint models and validation performed on each using a parameter estimation technique. It is also shown that friction parameter tuning produces acceptable parameter values for a valid model of a Puma 560 manipulator