Abstract: Chassis assembly is a key part of vehicle assembly, and the form and position tolerance of the assembled parts determines the success rate and cost of assembly. This paper first describes the physical model of assembly error probability, then abstracts it into a suitably simplified assembly mathematical model by using dimension chain theory, and deduces the formula and calculates the probability of assembly success rate. Finally, the theoretical 99.986% probability of success is obtained under the conditions of tolerance and precision requirements of related tooling equipment, which is larger than the actual value. After analysis, the model is moderately simplified and the difference meets the expectation with assumed conditions. The model has been widely used in a number of standardized multi-platform vehicle hybrid assembly lines.

Key words: Integrated chassis assembly; Success probability of assembly; Dimension chain; Tolerance of form and position; Normal distribution; Bayes' theorem

摘要： 底盘盒装是整车装配关键环节，合装部件的形位公差决定合装成功率和成本。文章首 先描述了合装误差概率的物理模型，然后运用尺寸链理论将其抽象为一个适当简化的合装数 学模型，对合装成功率进行了公式推导和概率计算。最终在相关工装设备的公差、精度要求 条件下得出理论上 99.986%的成功概率，相比于实际值较大，经分析考虑到模型经适度简化 且有假设条件此差异符合预期。该模型已广泛运用于多条标准化多平台汽车混合装配线。

关键词: 底盘整体合装；合装成功率；尺寸链；形位公差；正态分布；贝叶斯定理