The Design Of A New Structure For Pointing Mechanism With Electrical Propulsion

Pointing mechanism is an important component in electrical propulsion system.It is not only a support structure to fix electrical propulsion thruster,but also an adjustment mechanism to change the attitude of thrusters.This adjustable function is good for increase the flexibility of station keeping of spacecraft.In this thesis,firstly,research work of pointing mechanism used in international spacecraft has been performed to find the disadvantages of present products by means of comparison analysis.Then,a new type of scheme of pointing mechanism is raised to overcome the present product disadvantages.The dimension and mass of this pointing mechanism should be smaller than 300 mm and 10 kg,respectively,and the control precision of rotational angle should be no less than 0.01° and the stiffness of entire structure should be bigger than 1k N/mm.By considering the main requirements,key technologies emerged recently in high precision mechanical engineering and disadvantages analyzed from present pointing mechanism products,a new scheme of pointing mechanism by using parallel mechanism and flex hinge is figured out.Throughout the deeper research work on aspect of flex hinge,the basic design parameters are finally determined,and further,an amplified frame,as PZT actuator's motion transfer mechanism,is designed as well to overcome the shorter distance movement of PZT actuator.Meanwhile,a high precision,continuously motion is realized by material deformation.On other aspect,throughout the deeper analysis of parallel mechanism,a triangle configuration which is 3-PSP parallel mechanism is finally determined by multi-scheme comparison.A simple and effective motion transfer function is built based on geometrical analysis and simulation work.Statics and kinematics analyses are performed to figure out the static and kinematic capabilities of this mechanism using FEM in Solidworks software.The basic principle of novel mechanism design is proved finally,and precise control of electrical thruster is basically realized by using the advantages of flex hinge and parallel mechanism respectively in this research work.The new developed mechanism has novel structure which is totally different from present products used in international spacecraft.This conceptual design is a good attempt for further development of pointing mechanism.It would be leading a new research direction of pointing mechanism using in electrical thruster of spacecraft in near future.