Singularity Avoidance for a Deployable Mechanism Using Elastic Joints

This paper aims at dealing with the deployment vibration problem of the rigid-links deployable mechanism caused by mobility bifurcation. A triangular prismoid deployable mechanism with mobility bifurcation is employed as an example to demonstrate the design and analysis process. First, the mobility of the triangular prismoid deployable mechanism is analyzed, which shows that there exists mobility bifurcation and the possibility of deployment vibration. Second, the revolute joints that introduce mobility bifurcation are analyzed, which shows that they can be replaced by the elastic joints without changing its mobility. Third, a detailed design procedure for this type of elastic joints is discussed; the main parameters of the elastic joints can then be determined based on the mobility and motion range of the deployable mechanism. Physical prototypes of both the rigid-links prismoid deployable mechanism and the corresponding improved mechanism with elastic joints are fabricated, and the deployment experiments of both mechanisms are conducted to show improvement in the latter mechanism.