Self-calibration of a redundantly actuated parallel kinematic machine tool

Redundantly actuated Parallel Kinematic Mechanisms (PKMs) have recently attracted interest of researchers because they allow reducing some drawbacks of classical, nonredundant PKMs, as for example singularities. The main problem with the calibration of those machines is that the redundancy leads to some mechanical strains in the structure. This makes it difficult to identify the structure geometrical characteristics without taking into account its elastic deformations. The purpose of the work is to provide a self-calibration method that allows the identification of both the geometrical and stiffness parameters of a planar PKM with a 2nd-order actuation redundancy. The first part of the paper will present the applied method. The second one will present its application on the machine. At last, the identification strategy involved in the proposed elastogeometrical calibration method will be presented before concluding