Dongchao Yang

Topology Synthesis and Classification of Low-Mobility Parallel Mechanisms

Topology synthesis of low-mobility parallel mechanisms is an important direction of mechanism research. At present, various systematic methods for topology synthesis have been proposed, and large numbers of new mechanisms that satisfy the motion requirements have been synthesized through step-by-step deducing. However, some fundamental problems are ignored. In this paper, some significant synthesis methods are compared from the aspects of the description of output character, limb structure synthesis and geometrical relationship between limbs. The commonly existent problems are analyzed, including the strict description of the output character of the moving platform and the instantaneous mechanisms in the process of topology synthesis. The limitation of existent methods is also indicated. Moreover, a classifying method for low-mobility parallel mechanisms from the viewpoint of topology synthesis is proposed. This classification has guiding effect for synthesis, analysis and application of parallel mechanisms.Copyright

Coupling Degree of Mechanism and Its Application

The kinematic and dynamic analysis of an spatial multi-loop mechanism especially parallel mechanism is significant but always complex. Based on the topological structure of mechanisms, this paper proposes the concept of coupling degree of mechanism systematically, and applies it to the criterion of basic kinematic chains(BKCs) and other problems. The relation between topology, kinematics and dynamics of parallel mechanisms is established, and then it is achieved to quantitatively describe the analysis complexity of a parallel mechanism and to obtain its simplest solving path, according to its topological structure. The preliminary method for unified modeling of the topology, kinematics and dynamics of parallel mechanisms is proposed, using BKC as the basic analysis unit. Some suggestions for optimization and selective preference of parallel mechanisms are also presented.Copyright