Synthesis of Spatial mechanism CS-3SS for Multi-Phase Body Guidance

Abstract

The spatial mechanism CS-3SS with two degrees of freedom is synthesized in order to execute two-phase body guidance by means of adjusting link lengths or positions of fixed pivots. This mechanism consists of fixed base, moving platform and four supporting legs. The cylindrical joint is the input. A special feature of CS-3SS is that it is analogous to a spherical Assur kinematic chain after the C joint moves to a specified position or is fixed, and the configurations can thus be analyzed successfully. The maximum number of precision poses that can be assigned by using CS-3SS is analyzed. Techniques of synthesizing mechanisms with the aid of optimization search are illustrated. Two necessary conditions are proposed to get rid of mechanisms with branch defect. If the lengths of supporting legs remain the same and the positions of fixed pivots are adjustable, a numerical example of five precision poses for each phase is discussed. The process of synthesis, planning of objective functions, evaluation of branch defect, and performance of the mechanism are all illustrated. If only the lengths of supporting legs are adjustable, an example with five poses and three poses for both phases is shown.