A Low-Cost Stewart Platform for a Radio Telescope

Most hexapods that are currently available on the market are expensive and have extremely high positional and orientation accuracies. Although the positional accuracy is high the viewing angle is limited to 60 degrees. These hexapods are designed with a small viewing angle, as they are not optimised for radio telescopes. The aim of this work is to highlight the various factors that should be considered during the design of a 6-3 Stewart platform for pointing applications. These factors are illustrated by presenting the case study of a small custom hexapod that is designed, built and tested. Modelling of the Platform is performed through the implementation of existing kinematic and dynamic models that could be verified through comparison to simulation results in literature. Components designed for the hexapod include the linear drives, base joints, platform joints, electronic controller and graphical user interface. The design process is documented and design decisions clearly motivated. Performance of the Stewart platform is measured with an inclinometer and the ability of the platform to track a sun simulation path is presented. Specifications which the hexapod is able to achieve include a viewing angle of 120 degrees +/- 0.3 degrees and the ability to carry a payload of 1kg.