Material Depositing Mobile Robots for Application to Cementitious Additive Manufacturing

Productivity within the construction sector is stagnating, as the current techniques are time-consuming, labour intensive, and hence costly. A step-change in the processes used for construction is urgently needed. Robotics systems have the potential to revolutionise the current construction practices to allow far superior fabrication at a fraction of the cost and time. To address this, the work reported in this thesis was set out to investigate the applications of material depositing mobile robots for construction, resulting in the following developments. Firstly, a novel low-cost localisation system based on ultrasonic sensing and time of flight measurements was developed for the tracking of a mobile robot. The system was validated against a state-of-the-art Optitrack motion capture system. It was shown that the localisation system can cover a 4.3×3.1m arena with a mean localisation error of 1.57cm and an average standard deviation of 1.39cm throughout the arena. The second major contribution of this thesis was the development of two mobile cementitious deposition systems. The first was a 330ml syringe-based actuation system, coupled with a visual-servoing system that allowed controlled multi-layer depositions. An off-shoot of this system was that it could be re-tuned to detect contrast for crack and damage identification in the ground, allowing the robotic platform to remediate simulated damage. The second mobile deposition system was a 10L Archimedes screw-style pump system, which allowed high volume output (>5L/min), for much more substantial cementitious deposits. The third contribution was a proposed support material mechanism to allow a mobile system to increase its height, ensuring flexibility not currently available in mobile Additive Manufacturing (AM) systems. The novel Polyurethane (PU) Foam depositing system allowed expansion ratios of over 33× its constituent parts and final compressive strengths exceeding 2MPa, thus allowing a mobile platform to significantly increase its height. The system resulted in an optimised mix solution that, combined with the anti-blockage procedure, meant that the system could be used as an independent module to allow terrestrial systems to overcome significant obstacles reliably. The final contribution considered the fully integrated platform, which demonstrated capabilities I path following, accurate material deposition, altitude increase and finally ability to produce multi-layer cementitious deposits, thus proving the concept and the original research aim and laying the foundation for system scaling.