DOF Calculation Method of Planar Mechanisms Based on Constraint Normal Line

In the analysis and calculation of degree freedom (DOF) mechanisms, it is generally a complicated problem to judge virtual constraint correctly. Under what conditions do constraints exist, how many are there? Understanding these problems can contribute effectively tackling difficulty calculating DOF. With planar mechanisms as research object, among various components simplified into point constraints, common normal at referred normal. According whether move relative frame in its direction, normals divided different categories. Based on geometric theorem for judging DOF workpiece, set theorems their nature, over-constraint, quantity established. After correlation between over-constraints clarified, total number mechanism calculated. The several typical demonstrate that new method logically rigorous, simple, intuitive, be accurately