1. When calculating the degree of freedom of the mechanism, it is assumed that the roller is consolidated with the component where the roller is installed, which is regarded as a component.
2. The local degree of freedom is the degree of freedom that has nothing to do with the movement of the output component. When calculating the degree of freedom of the mechanism, the local degree of freedom should be removed.
3. Under specific geometric or structural conditions, the constraints introduced by some kinematic pairs may have the same restrictive effect as those imposed by other kinematic pairs. Such repeated constraints that do not have an independent restrictive effect are called virtual constraints.
4. When sliding friction becomes rolling friction, rollers should be added, and there should be balls in the bearing.
5. If the degree of freedom of some components in a mechanism is only related to their own local motion and does not affect the motion of other components, then this degree of freedom is called local degree of freedom.