Dry Stacking for Automated Construction with Irregular Objects

We describe a method for automatically building structures from stacked, irregularly shaped objects. This is a simplified model for the problem of building dry stacked structures (i.e. no mortar) from found stones. Although automating such construction methods would be ideally suited for disaster areas or remote environments, currently such structures need to be built by skilled masons. No practical methods for automating the assembly planning process are known. The problem is challenging since each assembly action can be drawn from a continuous space poses for an object and several local geometric and physical considerations strongly affect the overall stability. We show that structures that are built following a stacking order for perfect bricks can accommodate a limited amount of irregularity, however, their performance degrades quickly when objects deviate from their ideal shape. We present a strategy for stacking irregular shapes that first considers geometric and physical constraints to find a small set of feasible actions and then further refines this set by using heuristics gathered from instructional literature for masons. The proposed method of choosing assembly actions allows construction with objects that contain a significant amount of variation.