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A high-bandwith robot-workpiece interaction requires a stiff robot without resonances in the frequency range of operation. In this article, the compliance dynamics of the Gantry-Tau parallel kinematic robot were identified using subspace-based identification and physical modeling. Measurements were performed both with a camera vision system developed and with a laser tracker. Although promising simulation results for another Gantry-Tau prototype exist, both vision and laser tracker experiments identified multiple resonances around 14 Hz, which can reduce force control performance.

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Estimation-based iterative learning control (ILC) is applied to a parallel kinematic manipulator known as the GantryTau parallel robot. The system represents a control problem where measurements of the controlled variables are not available. The main idea is to use estimates of the controlled variables in the ILC algorithm, and in the paper this approach is evaluated experimentally on the Gantry-Tau robot. The experimental results show that an ILC algorithm using estimates of the tool position gives a considerable improvement of the control performance. The tool position estimate is obtained by fusing measurements of the actuator angular positions with measurements of the tool path acceleration using a complementary filter.