Research On The Characteristics Of Spatial Linkage Based On Bennett Mechanism

Because of the special motion characteristics of spatial linkage mechanism,its research value and application prospect are very considerable.Based on a kind of space4 R mechanism—Bennett mechanism,this paper constructs various space connecting rod mechanism through a variety of assembly methods to meet its special requirements in aerospace,medical engineering,civil engineering and other related fields.At present,the classification of mechanism types of Bennett mechanism and the relationship between mechanism types and bar parameters are not enough.Therefore,this paper classifies Bennett mechanism by selecting staggered angles of struts in different quadrants,and deduces the closed displacement equation of internal and external angles of different mechanism by establishing spherical indexes,so as to obtain the relation and difference of motion characteristics among different types of Bennett mechanism.Secondly,various spatial 5R mechanisms,spatial 6R mechanisms and other single degree of freedom spatial multi bar mechanisms are obtained by combining various types of Bennett mechanisms.The parameters and displacement equations of each spatial multi bar mechanism are derived.Then,based on a spatial double u-pair 6R mechanism obtained by Bennett mechanism combination,its motion posture is studied to verify that the 6R mechanism can become the basic unit of space foldable mechanism.Then the spatial double u-pair 6R mechanism is taken as the basic unit,the basic space folding mechanism is established by means of umbrella assembly method and cutting fork assembly method.Finally,through the establishment of institutions of D-H parameters,using homogeneous coordinate transformation and institutional closing displacement equation,the method of combining the basic unit build space folding exhibition organization and4-6R mechanism kinematics model,calculate the institutions of each connecting rod displacement,velocity and acceleration,and combined with Adams simulation by an example on the organization’s kinematics model is verified.