Two-step scheduling optimization method for multi-robot parallel machining of large spacecraft cabin brackets

The multi-robot parallel machining (MRPM) system provides an efficient, precise, and safe solution for the composite manufacturing of multiple brackets on large spacecraft cabins. The multi-operation requirements of the brackets necessitate that some brackets require multiple robots with different functions to sequentially complete multiple operations. Additionally, the cabin's rotatability results in different distribution postures of the brackets at different rotation angles. Therefore, the scheduling and planning problem for MRPM of large cabin brackets (LCBs) is a complex optimization problem with multiple constraints. To address this, the paper first comprehensively considers various constraints from the machining and process planning layers. Starting from system production efficiency and robot task load balancing, optimization models are constructed respectively. Then, a two-step scheduling optimization method is proposed, which divides the overall planning problem into two steps: balanced task allocation under multiple rotating workstations and multi-robot task sequencing. Finally, simulation experiments validate the effectiveness of this method under different scales. Moreover, for task allocation under multiple rotating workstations, the proposed method reduces task load differences among similar robots while increasing system productivity under the constraint of minimizing rotation counts.