Stepper motor-driven cable-suspended system for automatic probe positioning

Abstract

In this thesis, the use of cable-suspended systems in automated measurement systems is assessed by building a vertical cable-suspended robot. In particular, the positioning of a measurement probe with a cable-suspended system is researched. Cable-suspended devices have grown in popularity in entertainment, sports, and industrial applications, due to their light weight and modularity. They allow moving payloads on large workspaces, with high speed and precision.

Cable-suspended systems consist of cables attached to an end-effector. By tensioning the cables and adjusting their lengths with motors and pulleys, the end-effector can be moved on a workspace. The end-effector is positioned by calculating the cable lengths corresponding to each point on the workspace and rotating the motors until these cable lengths are reached.

As part of this work, several factors contributing to the speed and precision of the built system are researched. These include mechanical tension, pathing, and non-linearities of the system. Special consideration is given to different algorithms in calculating the next positions of the probe.

The built robot mostly achieved its design goals. The probe can be moved swiftly with speed and precision in the center of the workspace. However, in the border regions of the workspace, the precision of the device degrades significantly. Still, the design demonstrates that cable-suspended devices have potential use in difficult measurement scenarios involving moving probes.