Constraint Design of a Leveling Mechanism via a Screw Theory Approach for Constraint Pattern Analysis

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-SPS1-SP leveling mechanism is pointed out,and a 1-PSV1-PSE1-S leveling mechanism is proposed in order to introduce the application of the approach in the constraint design of mechanisms.