2.1Basic Concepts of Mechanisms(1) Degree of Freedon(自由度) The system's DOF is equal to the number of independent parameters which are needed to uniquely define its position in space at any instant of timeDegree of Freedom（自由度） The system’s DOF is equal to the number of independent parameters which are needed to uniquely define its position in space at any instant of time. 2.1Basic Concepts of Mechanisms(1)