Method for confirming motion mode of corresponding free node at singular configuration part of hinge bar system mechanism

The invention discloses a method for confirming the motion mode of a corresponding free node at a singular configuration part of a hinge bar system mechanism. The method comprises the following steps of: carrying out second-order derivation on a coordination function which is dependent from a mechanism to describe the corresponding free node variable quantity, to judge whether the second-order derivative is equal to zero or not at the singular configuration place, if the second-order derivative is equal to zero, the corresponding free node at the singular configuration part can move like a limiting mechanism; and if the second-order derivative is not equal to zero, the corresponding free node can move like a first-order infinite small mechanism. According to the method, the motion mode of the corresponding free node at the singular configuration place of the hinge bar system mechanism can be confirmed, the motion mode of the mechanism at the singular configuration place can be basically confirmed, the method is high in operability, the basis is provided for the singularity avoidance and the structure design of the novel space structure, and the research of the mechanism singularity and the motion bifurcation has an important impelling action, so that the method is wide in application prospect.