Abstract: Automatic sketching of mechanism kinematic chains affects directly the efficiency and reliability of mechanism design. On the basis of a study of the topologic characteristics of planar closed kinematic chains, the maximal loop method is presented, based on contracted link adjacency matrix, to complete automatic sketching of planar closed kinematic chains. Independent loops of kinematic chains are derived by using the breadth-first spanning tree algorithm, based on which the maximal feasible loop is achieved by means of independent loops add-subtract operation. The maximal feasible loop is step by step modified in accordance with the loop relationships so that all independent loops become its normalized non-crossing inner loops. In the process of automatic sketching of kinematic chains, the joints of kinematic chain are located, from outer lane to inner lane, on the vertices of inscribed regular polygon of the concentric circles on the basis of the outer and inner loops’ relationships. As a result, the sketches of the kinematic chains appear to be normal and beautiful. The development process of this algorithm based on the outer loop and the inner loops relationships is demonstrated with the aid of several mechanism examples. The study and the application of the maximal loop method show that it is simple and comprehensive. And it is applicable for the automatic sketching of planar closed kinematic chains with multiple links and multiple degrees of freedom. It can greatly raise the efficiency in mechanism design.

Key words: Contracted link adjacency matrix, Independent loops, Link crossings, Mechanism sketch, Planar closed kinematic chains