DEPLOYMENT SIMULATION OF A LARGE UNFURLABLE STRUCTURE

Abstract

Large unfurlable structure is used extensively as an appendage for spacecraft. This is an assembly of a large deployable antenna structure (LDAS) and a flexible reflective metallic mesh, which serves as reflector. The large unfurlable structures are used for satellite communication. These LDAS are to be compactly stowed during launch to accommodate within the launch vehicle envelope and are deployed to a very large diameter (much larger than the spacecraft). These serve as a deployable support structure which hold the mesh and undergo large geometric transformation during the deployment of the antenna. This dissertation deals with the synthesis of a deployable mechanism for such a structure. The LDAS considered here for study is a closed loop ring type spatial structure having both radial and circumferential structural elements. A state-of-the-art review of the various deployable mechanisms used for space applications is presented in this dissertation. Three different configuration models to synthesize a mechanism for the deployment of the circumferential elements called as deployable ring truss structure (DRTS) are explored and compared to obtain a final kinematic structure of the DRTS. A general kinematic model of the DRTS based on a parallelogram deployable linkage (PDL) has been established in MATLAB to carry out the position analysis of any point on the DRTS. A kinematic model is then developed in MSC ADAMS/View to validate the conceptual work, A two precision point synthesis of a function generating four-bar linkage using Freudenstein equation for the deployment of radial members called as radial deployable mechanism (RDM) is presented to arrive at a suitable configuration. This concept overcomes the hardware complexity by the removal of the gearing mechanisms which are otherwise required for the deployment of radial members. This dissertation then analyse the full kinematic simulation of the LDAS, by integrating the corresponding mechanism of the DRTS and the RDM through multi-body dynamics software tool - MSC ADAMS/View. With a single input it is shown that the proposed mechanism can drive the LDAS from a folded configuration to a deployed configuration. In addition the dissertation also presents the use of macro feature of ADAMS/View to automate the model building process of the different sizes of LDAS. Macro helps in quickly

creating several models with various configurations and with different hardware details which are required in the initial design phase. The main advantage of the proposed concept is that it can be utilised to synthesize large deployable mechanisms of different sizes involving large number of links and joints.