Direct Kinematics for a Novel Robotic System Used as External Fixator

The structure of traditional Stewart Platform systems contains six rods to connect upper and lower platforms. In this work, λ-module - a novel connection element between the platforms is proposed and its orthopaedical application along with the associated direct kinematic analysis is presented. Physical appearance of the λ-module resembles the Greek letter λ and it consists of two cylindrical parts which may be defined as long and short rods. When the λ-modules are used as the connection element, the risk of singularity decreases as well as the obstruction possibility of bone fragments in x-ray images. The direct kinematic analysis is based on converting the (3–6) and (6–3) systems into (3–3) SP configuration. Two numerical examples are given to support the proposed method.