航天器常在其任务中出现功能失效，造成巨大的损失，而在轨模块更换技术则是利用空间机械臂自主对可接受在轨服务航天器进行故障模块更换﹑升级﹑补充消耗品等。通过对在轨可更换模块的更换方式以及设计准则等的了解，从而对在轨可更换模块进行了机构设计和结构设计，利用SolidWorks软件建立该结构的三维模型和仿真实验，实物模型验证了其可行性。

Because the spacecrafts appear functional failures very often in their missions，This will cause a great loss to us. However, on-orbit unit replacement technology makes use of the space manipulator’s own fault on the serviceable spacecraft to replace the failure units, upgrade the spacecrafts and add the consumables and so on. On the basis of the background above and some understanding of the replacing way of orbital replacement unit and its designing criteria, the mechanism designing scheme and the structure has been designed about Orbital Replacement Unit. It established 3D model of the structure and simulation experiment by using SolidWorks software. Its feasibility is verified by actual model.