Pick-and-place process sequencing for transformation of rasterized 3DÂ structures

We present an optimization method for process sequencing in automated assembly of three-dimensional physical structures comprised of uniform elements using robotic equipment. This is part of a process of large-scale construction based on a pick-and-place (PnP) assembly approach. We show that PnP process sequencing is a kind of assignment problem that can be solved by the Hungarian method. There exists a theoretical lower bound of the required work, while a feasible motion sequence may exceed the lower bound due to physical constraints. Subject to those particular constraints, we compare several process sequencing strategies against various data sets. Evaluated under a cost and a processing-time metrics, one of the strategies outperforms the rest. The approach adopted in the strategy may be generalized in different application-dependent scenarios, such as from crane operations to large scale 3D printing.