中文摘要：

通过对汽车自动变速器驱动挡自由度的计算与研究发现：用公式（A）和K氏公式计算是正确的;用传统的契氏公式和派生公式计算有时就会出现错误,正确率为60%和90%,其关键是没有考虑机架,缺少公共约束数。根据机构自由度计算新方法,通过在结构原理图中标注各个运动副的自由度数,划分传动的封闭环,用移动壳体支座（机架）作为各挡机构的临时支座解各挡机构自由度,为汽车自动变速器的理论研究与设计,提供可靠的理论依据。

英文摘要：

According to calculation and research on DOFs of automatic transmission D（Drive）：It is correct to calculate with the formula A and K-formula,while some mistakes may appear if we do it with traditional Chebyshev-formulation and the derived formula,are at the percentage of 60% and 90% respectively.This situation happened mainly because we didn＇t consider the rack and lack of some common constraints.Based on the new method to calculate the agency＇s DOFs,we can use the number of DOFs on each kinematic pair in the principal and structure diagram,dividing closed loop of transmission and using mobile frame（rack）as a temporary frame of all gear mechanisms to calculate DOFs of gears.This theory provided automatic transmission a reliable basis.