TITLE: The Inverted Stewart Platform: Control in 6 Degrees of Freedom with Non-orthogonal Coord. AUTHOR: Marius Hauser
SCHOOL: Lexington High School
SCHOOL ADDRESS: Lexington, MA 02173

The basic Inverted Stewart Platform (and the surrounding octahedral control frame) is a machine that uses non-orthogonal actuators (cables) to move and position objects smoothly, coordinate systems. This machine, capable of six degrees of motion including Euclidean position (x, y, z) and angular orientation (pitch, roll, yaw), is the basis for many interesting machines and areas of research, including crane technology, underwater research, air-to-air rescue, flight simulation, satellite dish positioning, and robotic manufacturing methods. Its benefits include a sturdier triangular design, compared to conventional rectangular crane designs, and smooth control made possible by kinematically balancing the forces of the actuators, compared to orthogonal controls which are not smooth and are subject to overshoot. The Inverted Stewart Platform consists of a work platform in the shape of an equilateral triangle that is suspended by six cables from an octahedral control frame. The cables (strings in my model) are attached to the vertices of the platform, run through pulleys attached to the upper vertices of the octahedral frame, and continued down to the base where they are attached to cranks which control the lengths of the cables. By changing the cable lengths, the operator (whether human or computer-controlled) can control all six degrees of freedom (position and orientation) accurately, smoothly and without overshoot. In this project, I construct the machine from basic materials, derive the mathematics of position and orientation control, test the ability of the mathematics to approximate observed movements of the platform and test the smoothness, accuracy, and lack of overshoot.