Abstract:

Small displacement torsor(SDT) was introduced in tolerance modeling. The constraint conditions of linear symmetry tolerance were developed systematically under IP(independence principle) and MMR(maximum material requirement). The corresponding mathematical models of linear symmetry of surface feature and central feature were deduced. By using this model, the semantics of tolerance was exactly represented and can be used by the following processing. An example was proposed to show the effectiveness of the tolerance model.

Key words: tolerancing principle, symmetry, small displacement torsor, tolerance modeling

摘要：

在公差数学定义的基础上引入SDT（small displacement torsor），以孔中心轴线为对象，研究了基于公差原则的直线对称度公差数学模型。根据独立原则和最大实体要求应用于中心要素和表面要素的不同情况，详细研究了直线对称度公差的不同约束模式，系统地推导了直线对称度公差的数学模型。由此所建立的数学模型完整、准确地表示出了直线对称度公差的语义，便于公差的计算机处理。最后用实例验证了该公差数学模型的有效性。

关键词: 公差原则, 对称度, SDT, 公差建模