Accuracy of Kinematic and Dynamic Models of a Gantry-Tau Parallel Kinematic Robot

In this article, a new kinematic and a dynamic model for a 3-degree-of-freedom Gantry-Tau parallel kinematic robot are presented. Similar to an earlier proposed kinematic model, the dynamic model is based on the assumption of parallel actuator axes and constant end-effector orientation. The new kinematic model takes into account rotations of actuator axes which do not affect the end-effector orientation. Results from a calibration experiment show an improved positioning accuracy of the new kinematic model. A more general model of the robot including possible geometric inaccuracies causing deviations from the model assumptions has been developed in the modeling language Modelica. In a simulation, the proposed dynamic model is tested as a feedforward term in a control application and is found to improve the tracking performance considerably.