基于Vicsek分形结构的智能航天器集群在轨组装动力学与控制

由于目前运载火箭运输能力的局限性,超大型空间结构往往无法采用折叠收拢发射入轨、在轨展开的方式完成搭建,而在轨组装是实现超大型空间结构的有效途径.本文受Vicsek分形结构启发设计了一种空间超大型结构,并基于智能航天器集群提出了相应的在轨组装控制策略.首先,针对在轨组装过程中航天器的位置和姿态运动描述问题,建立了刚性航天器的位置和姿态动力学方程并导出追踪航天器与目标航天器的相对运动参数.其次,以Vicsek分形结构为基础设计了125个航天器分阶段组装规划,将每个阶段分为预组装和完全组装两个过程.在预组装环节,控制追踪航天器使其和目标航天器达到较为接近的相对距离并且保持相对静止；在完成预组装后,控制器驱动追踪航天器缓慢逼近目标航天器,使得两航天器完全对接.针对预组装环节复合了一个避撞控制器与PD控制器,在缓慢对接环节仅采用了PD控制策略.最后通过数值仿真验证了所提出的控制策略的有效性.

In-Orbit Assembly Dynamics and Control of Intelligent Spacecraft Cluster Based on Vicsek Fractal Structure

Due to the limitation of the capacity of current rockets, the ultra-large space structures can’t be built by in-orbit deployment technique. In-orbit assembly is an effective way to construct these ultra-large space structures. In this paper, an ultra-large space structure is designed inspired by the Vicsek fractal, and the corresponding in-orbit assembly control strategy is proposed for intelligent spacecraft cluster. To describe the position and attitude motion of spacecraft during in-orbit assembly, the position and attitude dynamics equations of rigid spacecraft are built. Also, the relative motion parameters of the chaser spacecraft and target spacecraft are given. The assembly configuration of 125 spacecraft is designed based on Vicsek fractal structure which is divided into 3 stages, and each stage is further divided into two phases: pre-assembly and assembly. In the pre-assembly phase, the chaser spacecraft is expected to approach the target spacecraft with a small distance and maintain a relatively static state. After completing the pre-assembly, the controller drives the chaser spacecraft to slowly approach the target spacecraft, and the chaser spacecraft will dock with target spacecraft. For the pre-assembly phase, the compound controller with collision and PD controller is designed, and only PD control is used for the slow docking phase. Finally, the effectiveness of the control law for the assembly mission is verified by numerical simulation.