A classic problem in mechanism design is the dimensional synthesis of mechanisms, and established here is a relatively systematic, transpare
A classic problem in mechanism design is the dimensional synthesis of mechanisms, and established here is a relatively systematic, transparent, and simple geometric process for the dimensional synthesis of spatial linkages. Starting with the rules governing the kinematic geometry of a spatial linkage, the research object is the floating link in the linkage, simplified as a fixed line on the link. This straight line is a guiding component, and its kinematic geometric characteristics are studied under the condition of finite separation positions. On this basis, the spatial kinematic geometry model of a line in the case of finite separation positions is established, which transforms the problem of space kinematics into that of spatial geometry. Next, based on the different number of spatial positions occupied by the straight line, its multi-position problem is decomposed into several combinations of multiple few-position problems. Furthermore, the geometric correlation between the extracted geometric characteristics is studied. By combining the two-plane projection system and clarifying the main projection direction of the projection transformation, the corresponding line guidance model is constructed in the plane system, which transforms geometric problems from space to plane. Finally, according to the motion task of the mechanism, the function generation task of the spatial mechanism is transformed into the problem of finding a solution for the line guidance model by using the principles of kinematic inversion, and an effective method is proposed for the dimensional synthesis of spatial linkages. Finally, the function generation synthesis problem involving a five-position RSSR mechanism is taken as an example, and by using the geometric synthesis process for spatial linkage mechanisms, a solution is obtained whereby the RSSR mechanism can realize five sets of precise function relations. Numerical results confirm the effectiveness and practicality of the synthesis method, and not limited to the dimensional synthesis of mechanisms with rotation input and rotation output, this method is also applicable to mechanisms with rotation input and slide output, rotation input and planar motion output, and rotation input and spatial motion output.
