Dynamics of Path Following and Constrained Path Synchronization Applied to Graded Concrete Element Fabrication

The technology of functionally graded concrete (FGC) is a novel approach in the construction sector, enabling mass savings of up to 50% in concrete elements. Before fabrication, mineral hollow spheres are placed inside the formwork, thus creating cavities after the concrete is applied. In order to evenly fill up the formwork, the concrete must be extruded along a path over the element. This constitutes a path synchronization and following problem for the manipulator and the pumping system mounted on its TCP. In this paper, we present a novel approach to this issue. We derive an explicit dynamic equation for the path parameter, allowing us to incorporate a feedforward path in the synchronization. Under certain conditions, the local input vector has a fixed direction, which is exploited to incorporate linear input restrictions, and allows for a synchronized path velocity maximization for multiple systems. The method is demonstrated in simulation for generating the fabrication trajectories of an FGC element.