Identification géométrique des machines outils à structure parallèle : proposition d'une méthode basée sur l'usinage d'une pièce

A main limitation of Parallel Kinematics Machine tools (PKM) in high-speed machining tasks is their low level of tool pose accuracy. In case of parallel kinematics mechanisms, the pose defect is largely due to the inverse transformations realised by the controller. These errors can be reduced by identifying the geometrical parameters of the inverse kinematics model. The aim of this paper is to present different identification methods used for PKM. In a first time, the general principle of PKM geometrical identification is described. Then, a static method using a 3D ball-bar is presented from past experiences on serial machines tools. This method is applied today on the Verne machine tool located in IRCCyN (Nantes). Finally, a new calibration method based on the measure of a machined part is described. This method is implemented in three steps: machining of a dedicated part, measurement, and identification of the geometrical parameter values.