Large-scale 3D printing with multiple mobile robots for building and construction

• Main Author: Zhang, Xu
• Other Authors: Pham Quang Cuong
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering::Robots
• Online Access: https://hdl.handle.net/10356/151333
• Institution: Nanyang Technological University

With its ever-increasing applications in various industrial fields, additive manufacturing, also known as 3D printing, has been gaining ground in building and construction (B&C) industry in recent years. Compared to traditional construction techniques, 3D printing carries the promise of faster, safer, more customizable, and less labor-intensive operations in multiple segments of the B&C industry. However, scalability is a problem common to existing 3D printing processes, such as the mainstream gantry-based techniques, where the size of the design is strictly constrained by the chamber volume of the 3D printer. This issue is more pronounced in the B&C industry, where it is impractical to have printers that are larger than actual buildings. There is thus a need to develop a novel robotic framework that is practical and is adaptive to large-scale printing applications in B&C industry. In this thesis, a 3D printing system based on a team of mobile robots is first proposed. Such a system can potentially print single-piece structures of arbitrary sizes, depending on the number of deployed robots. The system is then extended from a stationary-based printing to a printing-while-moving paradigm, which further extends its scalability. Next, two problems related to the practical deployment of multi-robot 3D printing are addressed. First, as hoses are indispensable for the 3D printing system to deliver fresh concrete from the mixer to the print nozzle, a method is developed to make sure that they are not entangled when robot printers move around. Second, in many settings, the structures (which possibly have been previously 3D-printed) need to be transported and assembled into other structures (also possibly 3D-printed). Since the structures to be transported and assembled are usually large and heavy, it is important to automate those tasks as well to achieve improved productivity. Thus, an admittance-based control framework is developed for multiple mobile manipulators to work in cooperation with humans. The robotic framework and algorithms presented in this thesis have been successfully demonstrated on the hardware system. Compared to other 3D concrete printing techniques, experimental results suggest that the proposed multi-robot printing system offers greater practical scalability, higher time efficiency and better on-site printing capability. On top of these superior characteristics, the system is versatile and highly adaptive to various B&C applications thanks to its modular mobile robotic manipulator configuration.