Abstract: By taking Delta robot as an example, an error modeling technique is developed for the kinematic calibration of a class of 3-DOF translational parallel kinematic machines with parallelogram struts. The model allows the geometric errors affecting the position and orientation accuracy of the end-effector to be separated. Utilizing the properties of parallel kinematic machines, I.e. the pose of the end-effector in the Cartesian space is the non-linear mapping of all servo motions of the actuated variables in the joint space, an effective calibration method is proposed that enables the full set of geometric errors to be identified by only measuring the flatness about the xy plane, the straightness along x(y) axis and the orientation error at the initial configuration. An error compensation strategy is also developed by modifying the ideal input of the system. An example is given to demonstrate the effectiveness of this approach.

Key words: Error modeling, Kinematic calibration, Parallel kinematic machines Delta robot