Abstract: Based on a study of the structural composition of planar closed kinematic chains, the basic links structure-tree method is presented to complete the type synthesis of kinematic chains. For kinamatic chains with given number of links and degrees of freedom, the constant sequences, such as link sequence, contracted link sequence, link degree sequence and basic links connective sequence, are first of all achieved by synthesis on the basis of the contracted link adjacency matrix. And then, the approaches and steps are induced to complete type synthesis for kinematic chains based on the contracted link adjacency matrix, and also the basic links structure-tree is defined. The basic links structrue matrix of the kinamatic chains is achieved by synthesizing. And a further study of approaches to matching contracted links is also made for synthsizing the connetive matrix of the kinematic chains. As a result of using the basic links structure-tree method in the process of synthesizing, the kinematic chains are classified in accordance with the structural invariants such as the degrees of links, the numbers of kinematic pairs and connective relation between links. So the type synthesis is charaterized by strong regular pattern and high efficiency, and its results are advantegeous to reducing the operation during the follow-up rigid sub-chains eliminating and isomorphinsim identifying. And the method is especially suitable for the computer to achieve automatic type synthesis for the planar closed kinematic chains with multiple links and multiple degrees of freedom. And also it is successfully used in the type synthesis for the planar closed kinematic chains with 12 links and 12-below-links. As an example, the type synthesis method is demonstrated with the aid of kinematic chains with 10 links and single degree of freedom.

Key words: Basic links structure-tree method, Contracted link adjacency matrix, Kinematic chain, Planar mechanisms, Type synthesis