Two-level Hierachical Intelligent Planning Algorithm for On-orbit Assembly

On-orbit assembly of large space truss structures requires extensive assembly planning in order to effectively carry out assembly missions.A two-level hierachical intelligent planning algorithm was presented to generate optimal assembly sequences.Firstly,the inherent hierarchical nature of truss structures allows assembly sequences to be considered from strut level and structural volume element(SVE) level.At the strut level assembly sequences were represented by the connectivity matrix.And,at the SVE level the directed graph representation was used.Then,a virtual strut concept-based serial assembly strategy was applied.Furthermore,at the first-level planning,one ant colony algorithm was improved to adopt assembly direction and time as heuristic information and didn't considered assembly missions.And,at the second-level planning,another colony algorithm was improved to adopt idle mission and path as heuristic information and considered assembly missions.Finally,a case illustrates results of two-level planning and demonstrates the validity of the approach.