Design & analysis of a parallel drive spherical rotation mechanism for application in high tech farming robots

Abstract

Increasing global use of pesticides has resulted in a significant amount of pollution which continues to harm the life and ecology of our planet. This thesis proposes and investigates a mechanized alternative to chemical pesticide use which employs high tech farming robots to directly identify and eliminate harmful insects and invasive plant species in agricultural settings. We focus specifically on the design and control of a parallel drive spherical rotation mechanism capable of manipulating a miniaturized steam jet ejector along the surface of a sphere. The jet ejector is capable of shooting out a lethal high-pressure steam jet towards the targeted pest while the rotation mechanism allows for fast and precise control of the jet ejector through a full hemisphere of rotation. This is well beyond the small angle range achieved by other commonly utilized parallel drive mechanisms such as the Gough-Stewart Platform. The design of the parallel spherical rotation mechanism was inspired by a similar parallel manipulator invented by Professor Ian Hunter in 1990. The mechanism design was simplified, miniaturized, and adapted to fit the design requirements of our specific use case. The forwards kinematics of the mechanism as well as the mathematical inversion problem are analytically solved for. An alpha prototype of the device is designed, constructed, and controlled using the derived equations. Through testing the device demonstrated targeted levels of precision and repeatability.