Lattice structures allow robotic systems to operate in complex and hazardous environments, e.g. construction, mining and nuclear plants, reliably and effectively. However, current navigation systems for these structures are neither realistic, as they assume simplistic motion primitives and obstacle-free workspaces, nor efficient as they rely solely on global discrete search in an attempt to leverage the modularity of lattices. This paper tackles this gap and studies how robots can navigate lattice structures efficiently. We present a realistic application environment where robots have to avoid obstacles and the structure itself to reach target locations. Our solution couples discrete optimal search, using a domain-dependent heuristic, and sampling-based motion planning to find feasible trajectories in the discrete search space and in the continuous joint space at the same time. We provide two search graph formulations and a path planning approach. Simulation experiments, based on structures and robots created for the Innovate UK Connect-R project, examine scalability to large grid spaces while maintaining performances close to optimal.

Mobile 3D Printing (M3DP), using printing-in-motion, is a powerful paradigm for automated construction. A mobile robot, equipped with its own power, materials and an arm-mounted extruder, simultaneously navigates and creates its environment. Such systems can be highly scalable, parallelizable and flexible. However, planning and controlling the motion of the arm and base at the same time is challenging and most deployments either avoid robot-base motion entirely or use human prescribed robot-base paths. In a previous paper, we developed a high-level planning algorithm to automate M3DP given a print task. The generated robot-base paths avoid collisions and maintain task reachability. In this paper, we extend this work to robot control. We develop and compare three different ways to integrate the long-duration planned path with a short horizon Model Predictive Controller. Experiments are carried out via a new M3DP system - Armstone. We evaluate and demonstrate our algorithm in a 250 m long multi-layer print which is about 5 times longer than any previous physical printing-in-motion system.

In this paper, we explore the problem of task-consistent path planning for printing-in-motion via Mobile Manipulators (MM). MM offer a potentially unlimited planar workspace and flexibility for print operations. However, most existing methods have only mobility to relocate an arm which then prints while stationary. In this paper we present a new fully autonomous path planning approach for mobile material deposition. We use a modified version of Rapidly-exploring Random Tree Star (RRT*) algorithm, which is informed by a constrained Inverse Reachability Map (IRM) to ensure task consistency. Collision avoidance and end-effector reachability are respected in our approach. Our method also detects when a print path cannot be completed in a single execution. In this case it will decompose the path into several segments and reposition the base accordingly.

Mobile multi-robot construction systems offer new ways to optimise the on-site construction process. In this paper we begin to investigate the functionality requirements for controlling a team of robots to build structures much greater than their individual workspace. To achieve these aims, we present a mobile extruder robot called YouWasp. We also begin to explore methods for collision aware printing and construction task decomposition and allocation. These are deployed via YouWasp and enable it to deposit material autonomously. In doing so, we are able to evaluate the potential for parallelization of tasks and printing autonomy in simulation as well as physical team of robots. Altogether, these results provide a foundation for future work that enable fleets of mobile construction systems to cooperate and help us shape our built environment in new ways.

In this paper, we present a Mobile Agile Printer (MAP) construction robot; a highly agile, 4-legged, omnidirectional robot capable of 3D printing large structures. To overcome dynamic challenges when operating within an outdoors construction site, MAP incorporates a high-DoF 3D printing system connected to a mobile platform with novel features designed to enable disturbance rejection and live adaption to the robot's pose. In doing so, we demonstrate the benefits of designing construction robots with a focus on agility, a compact working volume and ability to operate within a potentially unlimited workspace. Performance tests were conducted showing smooth omni-directional motion as a key requirement for maintaining low 3D printing trajectory deviations over a large volume. In doing so, we show that MAP has the ability to construct in new ways more sensitive to its environment, context and concurrent on-site operations.