Abstract: The large one-dimensional extendable arm is a crucial actuation component within aerospace agencies, playing a significant role in the support frameworks of large unfolding antennas, solar sails, telescope skeletons, space manipulators, and the construction of space platforms. A space single-degree-of-freedom expansion and contraction unit combining scissor mechanisms and Sarrus linkages is designed, from which a single-degree-of-freedom large truss-type space extendable arm is achieved by connecting these units in series. It presents the folding and unfolding ratio equations for the expansion unit and the extendable arm, establishes the kinematic and dynamic models of the extendable arm mechanism, and simulates its unfolding process. The analysis of the unfolding process and the statics of the extendable arm when fully deployed shows that the inclusion of the Sarrus mechanism significantly enhances the load-bearing capacity upon deployment. A prototype of the truss-type extendable arm consisting of two serially connected units was constructed, and related experiments were conducted to verify the feasibility of the design.

Key words: space extendable arm, kinematics, static stiffness, dynamic analysis