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Parallel kinematic mechanisms (PKMs) offer advantages of high stiffness to mass ratios, greater potential for accuracy and repeatability, and lower cost when compared to traditional assembly machines. Because of this, there is a strong interest in using PKMs for aerospace assembly and joining operations. This paper looks at the calibration of a prototype Gantry TAU robot by extending the higher-order implicit loop calibration techniques developed for serial link mechanisms to parallel link mechanisms. The kinematic model is based on the geometric model proposed by Dressler et al., augmented with a cubic spline error model of the motion errors for each of the three translation actuators resulting in 185 parameters. Measurements are taken with a 6-DOF laser tracker, and the kinematic parameters are solved as the maximum likelihood parameter estimate.

A consortium of interested parties has conducted an experimental characterization of two Tau parallel kinematic machines which were built as a part of the EU-funded project, SMErobot1. Characteristics such as machine stiffness, work envelope, repeatability and accuracy were considered. This paper will present a brief history of the Tau parallel machine, the results of this testing and some comment on prospective application to the aerospace industry.

Hawker de Havilland has undertaken research & development initiatives to utilise off-the-shelf automation technology to improve the functionality and efficiency of aerospace assembly processes. Several applications have been demonstrated, including the assembly of composite ribs and skins prior to consolidation, the drilling and trimming of composite components in preparation for assembly operations and the drilling of assemblies. Through all of these demonstrations, the same technology base has been applied – that of industrial robotics. This paper will present the technical aspects of two, individual problems and the solutions implemented. The problem and solution for the application of the assembly of dry, reinforced composite ribs to skins in a unitised box prior to consolidation of the composite assembly will be presented. The study will include detailed requirements and the control solution via force-torque sensor integration and manipulation.