Sequentially Assembled Reconfigurable Extended Joints: Self-Lockable Deployable Structure

摘要

As focal length significantly affects the performance of a telescope, the performance of spatial telescopes in astrophysical missions is mainly limited by the launchers' capabilities. An appealing solution is a deployable structure that expands after launch and thus acquires increased focal lengths. Many published articles have focused on the design and analysis of novel deployable mechanisms with a high packing ratio. However, few studies have focused on enhancing the performances of existing designs that have been flight proven. This paper highlights the idea of a unidimensional deployable structure by sequentially assembling reconfigurable extended joints, to strengthen the able deployable articulated mast (ADAM). This design inherits advantages of the ADAM mast, changes the ADAM mast from a trusslike structure (tensegrity structure) to a rigid frame once deployed, and meanwhile retains the diagonal cables. The reconfigurable extended joint is proved to be a reconfigurable parallel mechanism with many motion types, which is a special variant of the Wren platform. The stowed and deployed states can be converted with Bricard motion. Once fully deployed, the moving platform can be self-locked, utilizing the limbs' self-motions. Several advantages emerge by adopting the sequential assembling of the reconfigurable extended joints: Firstly, the whole structure can easily be deployed synchronously, because it transforms from a stowed state to a deployed state (and vice versa) with only one degree of freedom. Secondly, in the deployed state, the whole structure can be firmly self-locked by folding an arbitrary unit; thus, complicated latch mechanisms are avoided. Moreover, the tip of the structure does not rotate during the deployment due to the reciprocating deployment of adjacent units. Analysis results show that stiffness of the ADAM mast can be greatly enhanced, and the corresponding influence factors (such as the material property, element size, etc.) can be obtained analytically. Several prototypes have been developed and verified.