Over-constraint reduction method for the one-DOF deployable trusses based on the modules with boundary determinability

The large number of redundant constraints in the deployable trusses may lead to deployment failure of space equipment in orbit. For the enhancement of deployment stability, in this paper, an over-constraint reduction method is proposed for one-DOF (degree of freedom) deployable trusses based on modules with boundary determinability. Following this method, a significant constraint reduction is first achieved within the deployable modules, and then a small number of boundary constraints are introduced to realize the required one-DOF deployment of the truss mechanism, utilizing the constraint transmission among combined modules. To ensure the feasibility of constraint transmission, the required mechanism property of the modules achieved after constraint reduction is explored and defined as boundary determinability. The identification criterion of boundary determinability is achieved with the screw theory and constraint equations of the module. To verify the feasibility of the proposed method, the over-constraint reduction of a one-DOF deployable planar truss is conducted. The dynamic simulation results validate the mechanism design of the derived deployable planar truss, and demonstrate the effectiveness of the proposed over-constraint reduction method. This work may provide instruction for the construction of deployable mechanisms with fewer redundant constraints.