Research On Double-layer Folding Mechanism Based On Overconstrained Mechanism

Deployable mechanisms refer to the mechanisms that can be folded into a bundle and be deployed into a predetermined shape.With the development of aerospace technology,the large-scale,sophisticated and complex space equipment is an inevitable development trend.The networking structure based on single closed-loop spatial overconstraint mechanism has the advantages of high stiffness,high profile accuracy and simple drive,so it has important research significance.Compared with the single-layer folding mechanism,the double-layer folding mechanism greatly improves the shortcomings of the reduced stiffness performance of the single-layer folding mechanism under large size,and ensures the characteristics of large folding ratio and high precision.In this paper,the design and analysis of large-scale double-layer folding mechanism is carried out based on the spatial overconstrained mechanism.In the study of the basic unit of networking,this paper synthesizes the extended 6R mechanism based on the equilateral Bennett mechanism by deletion method,derives the member parameters and closing equation of the extended 6R mechanism,and studies the motion characteristics and folding characteristics of the mechanism.In terms of the design of single-layer folding mechanism,this paper designs two single-layer folding mechanisms.The first is a large-scale single-layer folding mechanism built with the expansion 6R mechanism as the basic networking unit and the unit over-method as the networking method;The second is the"hexagonal"networking unit constructed based on the threefold-symmetric Bricard mechanism and the extended 6R mechanism,and the single-layer folding mechanism constructed by the 6~3-type networking method.In this paper,the structural characteristics,motion attitude and singular shape of the single-layer folding mechanism are studied.In the research of the double-layer folding mechanism,the design of the connecting unit is introduced.First,the connecting unit is designed based on the 7R mechanism derived from the extended 6R mechanism,and the double-layer folding mechanism is constructed by composite with the single-layer folding mechanism based on the expansion6R mechanism.The connecting unit is designed based on the extended 7R mechanism,the derived Sarrus mechanism and the threefold-symmetric Bricard mechanism,and the double-layer folding mechanism is constructed by composite with the single-layer folding mechanism based on the extended 6R mechanism and the threefold-symmetric Bricard mechanism.The motion characteristics and folding performance of the two double-layer folding mechanisms are analyzed finally.Based on the above research results,a variety of three-dimensional models of the overconstrained mechanism and connecting mechanism are established,the motion characteristics of the improved combined mechanism are analyzed,and the single-layer folding mechanism is further improved,and finally the folding motion at the physical level of the folding mechanism is realized.