Contribution to calibration of hexapod positioning units in industrial environment

The calibration of parallel mechanisms with hexapod design is very complex due to the kinematic transformation. In this paper a calibration algorithm is developed which allows the re-calibration of hexapod mechanisms with relatively little effort, and the applicability of the calibration in an industrial environment is discussed. All parameters associated with the replacement of a leg and corresponding joints are determined only by performing six tool center point (TCP) measurements in each six degrees of freedom (DOF) after the new leg has been separately measured. The choice of measurement poses is based on the condition of the identification Jacobian matrix, so that increased robustness can be shown compared to the evaluation of a much bigger number of measurement poses using the Householder transformation.

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► Discrete algorithm for solving direct kinematics for hexapods derived.
► Re-calibration approach for hexapods derived and simulated.
► Achievable positioning precision after calibration estimated.
► Re-calibration approach metrological validated for hexapod prototype.