文章认为“以2个可能位移之差作为虚位移”更具普遍性．首先，基于这种虚位移概念，不但同样可以推出导数运算与变分运算可交换次序、积分运算与变分运算可交换次序这些基本性质，可以导出哈密顿原理，且可以研究更多类型的约束系统的虚变更，研究同一约束系统的更多类型的虚变更，从而导出系统的广义虚位移满足的方程；同时，对于一般性的一阶非完整约束系统，基于这种虚位移概念，无论令其发生1个Jourdain虚变更，还是令其发生1个高斯虚变更，都可以导出Chetaev关系式，一阶、线性约束系统在这2种虚变更下的广义虚位移关系式只是Chetaev关系式的特殊情形．

The article argues that defining virtual displacement as the difference of two possible displacements is more general. In this way, one can not only obtain the same commutative properties of derivative and variational operations and the commutative properties of integral and variational operations, but also obtain the Hamiltons principle. More importantly, one can study the virtual perturbations of more types of constrained systems and different types of virtual perturbations occurring in the same constrained system, so as to derive the equations satisfied by the generalized virtual displacements of the system. Meanwhile, for a general firstorder nonholonomic constrained system, whether it is subjected to a Jourdain virtual perturbation or a Gauss virtual perturbation, the Chetaev relation can be derived. The relation satisfied by the generalized virtual displacement of a firstorder linear constrained system is simply a special case of the Chetaev relation.