Research On Design Of Deployable Mechanisms Based On The Planar Four-bar Crank Slider Mechanism

The deployable mechanism which occupies small space and light mass is widely used in satellite antenna and space supporting structure,due to the limitations of the volume and cost of the launch vehicle.The deployable mechanism has two stable states of folding and deployment.When the rocket is in the carrier stage,the deployable mechanism reduces its size by folding to make it able to be placed in the launch vehicle.When it enters the predetermined position,the mechanism is then deployed to form a satellite antenna or a space supporting structure.With the continuous development of space technology,the accuracy and volume of communication,satellite positioning,earth observation,deep space exploration and other equipment have been put forward higher requirements.Research on deployable mechanisms has become a hot topic in the field of mechanism.Based on the planar four-bar crank slider mechanism,by analyzing the output characteristics of the mechanism,the basic unit kinematical chain suitable for constructing the deployable mechanism is synthesized.The method and process of constructing deployable mechanism are put forward,and the planar four-bar crank slider mechanism is applied to the design of deployable mechanism.The main contents include:First,the path-generating characteristics and functional output characteristics of planar four-bar crank slider mechanism are analyzed,the characteristics of the trajectory,function output and geometric shape change of the mechanism are obtained and the feasibility of constructing deployable mechanism based on planar four-bar slider kinematic chain as basic unit is discussed.A comprehensive analysis of the structural composition and configuration change characteristics of deployable mechanism is made.The method and process of constructing deployable mechanism based on planar four-bar crank mechanism are developed,and the design steps are given.Then,a new type of equal width basic deployable mechanism with a degree of freedom of 1 is proposed based on the path-generating characteristics of the planar four-bar crank mechanism,the expansion ratio and its influencing factors are analyzed.A new constant cross section prism deployable unit is constructed by combining the equal width basic deployable mechanisms with the way of circumferential array combination,and the parameter model of the unit mechanism is given.The freedom degree of the unit mechanism is 1 by the modified formula of the degree of freedom.Based on the series combination of unit mechanism,a new constant cross section prism mechanism is constructed,and the parameter model of the deployable mechanism and the motion transmission between the units are given.The freedom degree of the deployable mechanism is 1,the expansion ratio and the motion characteristics of the mechanism are analyzed.Taking the constant section prism deployable mechanism with three units as an example,the static and dynamic simulation analysis of the mechanism is carried out.Last,based on the function output characteristics of the planar four-bar crank slider mechanism,a new negative Poisson's ratio deployable unit with 1 degree of freedom is proposed,and the characteristics of the shape change of the mechanism are analyzed.The process of the space geometry of regular polygon section with straight prism expanding to be plane is analyzed,and the development principle of round deployable mechanism is obtained.The round deployable mechanism is proposed and the parameter model is given.The deployment processes of the round deployable mechanism with triangular frame and three units and three levels and mechanism with regular hexagon frame and three units and three levels prove the correctness of the parameter model.The degree of freedom of the round deployable mechanism is 1 analyzed by the modified formula of freedom.Taking the deployable mechanism with regular hexagon frame and three units and three levels as an example,the structural performance of the round deployable mechanism is simulated and analyzed.