Multi-Robot Hillside Excavation Strategies for Mars Settlement Construction

Multi-robot earthmoving strategies were studied for the simulated excavation of a large hillside section. This could be the first construction phase of a permanent settlement on Mars, which would consist of masonry structures built in the dug-out area and buried under a regolith layer for protection. The robotic fleet consists of 8 compact skid-steered wheel loaders and 8 or more dump trucks. The basic strategy is to assign each loader its own workspace along the slope face, separated from neighbouring workspaces to avoid possible conflicts, and for two loaders to share the same dump truck for load transfer while extra trucks wait. The workspaces are arranged along a row which advances into the hillside after all material in the row is excavated, in an attempt to excavate the slope evenly. The strategies developed generate commands which nominally allow the robots to operate autonomously until job completion. Various parameters can be modified in the simulator, such as the workspace dimensions, dump truck location, and slope height. Several simulations were conducted in order to test the effect of these parameters on the excavation rate and amount of driving required by the machines. It was found that while the workspace dimensions could be adjusted to increase the excavation rate, larger advantages could be gained by positioning the machines favourably so as to decrease the driving needed for load transfer.