Positioning uncertainty of the Tricept type parallel kinematic structure

The paper discusses theoretical aspects that arised during determination of theoretical positioning accuracy of parallel kinematic structures (PKS) with special regard to the Tricept type PKS. Apart from the conventional serial structures that employ translate or rotational movement (or their combination) of individual driving axes, parallel structures comprise a set of telescopic driving rods that are joined together via solid platform. Due to this fact, the mathematical model describing relationship between the driving actions of telescopic rods and resulting coordinates of the desired effector's endpoint is rather complex. To determine the theoretically achievable positioning accuracy of the endpoint, authors investigated theoretical influence of geometrical imperfections of the machine design and employed the law of uncertainties propagation. Their aim was to investigate theoretically achievable positioning accuracy of the machine prior to the final design solutions thus helping the designer to optimize the machine's design.