如何根据作业任务需求设计约束变胞机构的构型，特别是包含变胞运动副的类型与约束方式的变胞机构，是变胞机构在实际应用中有待解决的关键问题之一。将作业任务分解为子任务，获取对应的变胞构态及其输出运动形式，进而获得对应的变胞运动副的类型及约束周期，构成了基于任务的变胞机构的输出运动与约束组合循环图。根据变胞运动副的类型和邻接关系，归纳出扩展Assur杆组可以提供的输出运动形式，建立了扩展Assur杆组与变胞机构的运动形式与约束组合的关联，因而可以便捷设计出变胞源机构。通过研究变胞机构的组合变胞循环图与变胞机构的等效阻力梯度变化的对应关系，求得约束变胞运动副的约束形式和结构，代入变胞源机构即可得到对应带有变胞运动副约束形式的全部变胞机构；同时进一步考虑工艺条件及运动的可靠性等因素，从中选取适合作业要求的变胞机构。以设计实例演示和验证了提出的设计理论和设计方法的可行性和实用性。
How to design constraint metamorphic mechanisms according to the requirements of tasks, especially involved with the types of metamorphic kinematic pairs and the ways of constraints, is one of the key issues to be urgently solved during the practical application of metamorphic mechanisms. With the decomposition of the tasks, the corresponding configurations and movement output forms of metamorphic mechanisms are mapped, and as well as the types and constraint period of metamorphic kinematic pairs are achieved. Based on it, a task-based metamorphic mechanisms diagram concerned with the output motions and the constraints is presented. Subsequently, according to the types of metamorphic kinematic pairs as well as their adjacent relations, the movement output forms generated by the augmented Assur groups are summarized. Further, the relationships between the movement forms and constraint combinations of metamorphic mechanisms and the augmented Assur groups are established, which results in a convenient design of source metamorphic mechanisms. Followed by it, the constraint forms and structures of metamorphic kinematic pairs in the constraint metamorphic mechanisms is solved by studying the relationship between the task-based metamorphic mechanisms diagram and the gradien variation of equivalent resistance in the metamorphic mechanisms, which is further applied to the source metamorphic mechanisms so as to achieve whole metamorphic mechanisms with constraint forms of metamorphic kinematic pairs. Then, considering the influences such as process conditions and movement reliability, the metamorphic mechanisms meeting the requirments of the tasks is choosed from them. In the end, the feasibility and effectiveness of the proposed theory and method are demonstrated and verified.
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