Abstract: According to the characteristic that pentahedral deployable truss units can be combined into various types of truss structures, a pentahedral deployable truss unit was designed to solve the space onorbit assembly of large space truss structures. The pentahedral deployable truss units were used for truss structure assembly after launching into space. In order to analyze the kinematic characteristics of pentahedral deployable truss unit, the degree of freedom of pentahedral structure was analyzed based on the constrained screw theory. Kinematics analysis on the pentahedral structure was carried out by using D-H coordinate transformation method, and the kinematics equation for the deployment process was acquired. The Lagrange method was used to analyze the structure dynamics and the dynamics equation for the deployment process was obtained. Analysis results show that the degree of freedom of the pentahedral deployable unit is 1. The deduced kinematics equation result is highly consistent with the simulation results of Adams simulation software, which can fully describe the structure deployment movement process. Increasing the torsion spring stiffness has less effect on the changing trend of the parameters. The joint acceleration is related not only to the driving force of the torsion spring, but also to the joint position and the joint speed. In the late stages of deployment, the influence of position and velocity on acceleration is obvious. 

Key words: pentahedral deployable truss unit, degree of freedom, kinematics, screw theory, dynamics