Product low carbon design plays a significant part in reducing carbon emissions during the product life cycle and achieving sustainable development. Aiming at the uncertainty of the carbon footprint caused by the unknown decision of product material solution, this paper proposes a low carbon design approach that uses the multigraph and colour marking to solve the problem of one edge assigned with multiple weights and the constraint problem of vertex combination in the decision space of product low carbon design. After a weighted edge-coloured graph (WECG) is proposed for low carbon design, the multi-stage product low carbon design model for product life cycle is discussed in detail. An algorithm of searching the alternative set of optimal design is also put forward in detail, including to create the directed WECG, to define the complete path, to find the ideal solution set using breadth-first search, to judge the ideal solution set by colouring the graph to obtain the feasible paths, and to rank paths in the ideal solution set in ascending order. The low carbon design of a robot is given as an example to demonstrate the methodology.

产品低碳设计对于减少产品生命周期中的碳排放，实现可持续发展具有重要意义。针对产品材料方案未知决策导致的碳足迹的不确定性，本文提出了一种低碳设计方法，利用多图和颜色标记来解决一个边分配多个权重的问题和顶点的约束问题。产品低碳设计决策空间的结合。在提出低碳设计的加权边彩色图（WECG）后，详细讨论了产品生命周期的多阶段产品低碳设计模型。还详细地提出了寻找最优设计备选集的算法，包括创建有向WECG，定义完整路径，使用广度优先搜索找到理想解集，通过对图着色得到可行路径来判断理想解集，并在理想解集中对路径进行升序排列。以机器人的低碳设计为例来演示该方法。