Triple Scissor Extender : A 6-DOF lifting and positioning robot for autonomous aircraft manufacturing

Abstract

This thesis presents the Triple Scissor Extender (TSE), a novel 6-DOF robotic mechanism for reaching high ceilings and positioning an end-effector. The end-effector is supported with three scissor mechanisms that extend towards the ceiling with 6 independent linear actuators moving the base ends of the individual scissors. The top point of each scissor is connected to one of three ball joints located at the three vertices of the top triangular plate holding the end-effector. Coordinated motion of the 6 linear actuators at the base allows the end-effector to reach an arbitrary position with an arbitrary orientation. The design concept of the Triple Scissor Extender is presented, followed by kinematic modeling and analysis of the the Inverse Jacobian relating actuator velocities to the end-effector velocities. The Inverse Jacobian eigenvalues are determined for diverse configurations in order to characterize the kinematic properties. The sensitivity of the Inverse Jacobian Eigenvalues to the various non-dimensionalized design parameters is discussed. A proof-of-concept prototype has been designed and built. The detailed mechanical and electrical design, manufacture, and assembly is described, and the control software is discussed. The Inverse Jacobian for use in differential control is evaluated through experiments. A method for extending the functionality of the TSE by using multiple interchangeable end effectors is presented. The detailed design, manufacture, assembly, and testing of one such end effector, the Fastener Robot (FASBot), is described, and its performance characterized.