Dissertation
Dissertation > Aviation, aerospace > Aerospace ( Astronauts ) > Space instrument,spacecraft devices,spacecraft guidance and control > Electronic equipment > Spacecraft antenna

Dynamic Pointing Accuracy Analysis of the Two-axes-position Mechanism with Clearance for Satellite Antenna

Author ChengDongQi
Tutor WangXingGui
School Harbin Institute of Technology
Course Mechanical Engineering
Keywords two-axis-position mechanism dynamic pointing accuracy jointclearance dynamic characteristics dynamics model
CLC V443.4
Type Master's thesis
Year 2012
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With the rapid development of Satellite Technology,the requirements of thesatellite’s orbital lifetime and operation reliability are also rising. Pointing accuracyand degree of stability are the important part of the two-axis-position mechanism’swork life and reliability, so in system design process the driving mechanismpositioning accuracy must be ensured, the impacts of each factors on the dynamicproperty of the system also should be considered. This paper, taking thetwo-axes-position mechanism for satellite antenna for object, The influences ofseveral factors such as the gaps,redundant constraints and structure properties havebeen thoroughly analyzed.First of all, this thesis describes the driver clearance joint model whichcontains three sub-models. One is the clearance joint dynamics model based on theforce interaction including joints with clearance, second is contact normal forcemodel according to the nonlinear equivalent spring model, third is tangentialfriction force model considering the coulomb friction model. At the same time, thisthesis sets up the virtual prototype model of satellite dish double-shaft drive, inwhich inset the clearance joint dynamics model, and verifies its rationality which isthe base of following research and analysis of positioning accuracy and dynamicalproperty.Secondly, the trend of the system dynamic pointing error with the size of thekinematic pair clearance is analysis. The influence of azimuth axis clearance andpitch axis clearance and two-axis clearance coupling with the dynamic pointingaccuracy is researched. The sensitivity of dynamic pointing accuracy with thedifferent positions of the gap size is analysis. The presence of the kinematic pairclearance on the stability of institutions running is further analysis. The law of thedynamic characteristics such as velocity and acceleration changing was summarized.Through the analysis of the influence law, finally give the influence trend ofclearance on the point of accuracy and dynamic characteristics and providereference data for life prediction and reliability analysis of the drive mechanism atthe same time.For another thing, considered the effect of the different gap size, that betweenredundant constraints, concentricity error, the change of the spacing between theconstraint location and other factors on the drive mechanism of pointing accuracyand dynamic characteristics. The presence of redundant constraints resulted in theincrease of the influencing factors on the drive mechanism. Especially when thesize of this gap is inconsistent, the influence on the dynamic characteristics such as precision and speed is considered. Due to the limitation of the assembly condition,the impact of the concentricity error cannot be ignored in Satellite antennamechanism which requires a high precision. In the design process of its drivemechanism, the distances between the deputy campaigns also have some impact onpositioning accuracy.Finally, this thesis analysis the influence on the satellite antenna pointingaccuracy and dynamic features from the structural property considering the factorsof clearance friction, stiffness, damp and so on. Then this thesis refines the frictioninteraction description of joints with clearance which accurately expresses thestiffness and damping behavior of joints with clearance. The existence of friction,stiffness and damp will affect the dynamic positioning accuracy of the dishdouble-shaft drive and bring unpredictable external excitation and vibration to themechanism. Therefore, the study of the influence on the mechanism dynamicperformance from the above factors can provide a reference for feedback control.

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