Jixie chuandong (May 2022)
Analysis and Calculation of DOF of Multi-loop Coupling Mechanism based on Constraint Normal Line
Abstract
Since spatial multi-loop coupling mechanisms are more complicated than spatial parallel mechanisms， and the coupling members are more restrained by the side effects of motion between kinematic chains， a new method for calculating degrees of freedom （DOF） suitable for multi-loop coupling mechanisms is proposed. The idea is to firstly determine the coupling components in the mechanism， combine the constraint normal line distribution of the motion pairs， combine the constraints generated by the motion pairs between the various components in the mechanism， simplify into the distribution of normal lines on the constraint points， and then transform the degree of freedom analysis of the coupling mechanism into an analysis of the geometric relationship of the constraint normal lines of each coupling member. According to the established theory of determining the degrees of freedom of the constraint normal line geometric relationship， analyze and determine the nature of the degrees of freedom of the coupling member， determine the number of over-constraint of each coupling member.Finally，determine the number of virtual constraints through the continuity of the mechanism， and substitute the degrees of freedom calculation formula to obtain the degrees of freedom of the multi-loop coupling mechanism. Combined with example analysis， the method can not only obtain the degrees of freedom of each coupling member but also accurately calculate the degrees of freedom of the coupling mechanism. The new method has a sufficient theoretical basis and clear physical meaning， can be effectively applied to the analysis of the degrees of freedom of the coupling mechanism.
