Offline platform trajectory planning for print-while-drive additive manufacturing using mobile manipulators^*

The limited productivity growth within the construction industry in the last decades has increasingly driven the development of innovative manufacturing processes. Especially the expanding research field of robotic additive manufacturing in construction (AMC) is said to enhance the flexibility and efficiency. In particular, the usage of mobile manipulators as 3D printers enables the creation of manufacturing environments that are not constrained by the reach of the robotic arm. While initial approaches have implemented mobile manipulators that print from stationary positions before relocating, more sophisticated approaches focus on print-while-drive. Print-while-drive eliminates the risk of inducing weakening cold joints into the component during repositioning and further enhances the flexibility of the printing process. Existing approaches to print-while-drive rely exclusively on mobile manipulators with holonomic drives, such as Mecanum wheels. However, due to their design, Mecanum wheels are not suitable for use on uneven, contaminated, or loosely deposited surfaces. Such conditions, however, are common on construction sites. The application of alternative drive concepts, such as differential drive systems — commonly employed in track driven platforms — necessitates the development of novel trajectory-planning concepts for mobile manipulators. To this end, this publication proposes a trajectory planning algorithm to derive a suitable mobile platform trajectory based on a given tool center point (TCP) / printing trajectory. The functionality of the developed algorithm is demonstrated and evaluated by simulating the trajectories for large-scale components.