为提高双体船的空间利用率，使其便于存放、运输和投放作业，设计了一种基于平面连杆机构组成的可折叠收放机构。以收放过程中船体角λ移最小为优化目标，连杆机构成立条件及尺寸设计要求为约束条件，建立收放机构尺寸优化模型。利用闭环矢量法，分析优化后机构收放过程的运动学变化规律。结果表明，该机构可实现双体船的收起与展开功能;尺寸优化后,浮筒最大角λ移幅值降低了79%，收放过程更平稳，并且冲击较小。

In order to improve spatial efficiency and convenience in storage, transportation and launching of the catamaran, a planar linkages based foldable retractionextension mechanism was designed. Aiming at minimizing the hull angular displacement during the retraction process and the constraints on linkage mechanism condition and dimension design requirement, a dimension optimization model was established．By using the closed loop vector method, the optimized kinematic variation law of the mechanism was analyzed. The results show that the mechanism can realize the functions of retraction-extension of catamaran. After size optimization, the maximum angular displacement amplitude of pontoon is reduced by 79%, and the retraction-extension process is more stable with less impact.