Automated Robotic Assembly Planning of Space Trusses for Injection 3D Concrete Printing

Injection 3D Concrete Printing (I3DCP) is an emerging fabrication technique that enables spatial concrete extrusion within a carrier liquid, reducing gravitational effects and allowing the creation of complex space trusses. However, I3DCP introduces new challenges in toolpath planning due to material rheology and mechanical constraints. This paper introduces an automated planning method tailored for I3DCP, integrating a constraint satisfaction problem (CSP)-based sequence planner with a Cartesian motion planner. The sequence planner uses heuristic local search with forward checking and backtracking, while the motion planner addresses end-effector redundancy with kinematic and velocity constraints. The method is validated by fabricating a 3-meter-span pedestrian bridge using a stationary 6-axis robotic arm and tested on multiple prototypes of increasing geometric complexity through simulation, demonstrating its effectiveness and scalability for intricate structural designs.