Abstract: Constraint pattern analysis handles the mechanical design problem from a viewpoint of freedom and constraint, because of the generality for the concept of freedom and constraint, the method is a wide guide for machine design. From a viewpoint of a general design method for rigid mechanisms and mechanical interfaces, screw theory is applied in constraint pattern analysis. Point contact constraint and degree of freedom are denoted as a pure wrench and a twist, respectively. The geometrical concept for constraint pattern analysis is provided. The freedom hyper-plane is presented via reciprocal screw, and the analytical approach for freedom of parallel connections and constraint of serial connections are provided. The screw algebra basis for the equivalence rule for a freedom line and the rule of complementary pattern are proposed, a screw theory approach for constraint pattern analysis is formed. The application for the approach is carried out by a leveling mechanism for an optical projection exposure machine. The under-constraint and uncertain motion in the common 2-SPS&1-SP leveling mechanism is pointed out, and a 1-PSV&1-PSE&1-S leveling mechanism is proposed in order to introduce the application of the approach in the constraint design of mechanisms.

Key words: Constraint design, Constraint pattern analysis, Leveling mechanism, Point contact constraint, Screw theory