Analysis of Lockable Passive Prismatic and Revolute Joints

This paper analyzes the stresses, positional errors, and friction in lockable passive prismatic and revolute joints. The joints’ locking mechanisms that use solenoids to trigger the locking action have a self-alignment capability. The stress analysis evaluates the strength and material deformation of the joints’ components. The positional error analysis relates the clearances and contact deformations in the joints’ assembly with the positional errors of the joints. The friction analysis investigates how the friction during the locking motion interacts with the joint load, the pushing force, and the locking acceleration. The stress analysis was performed analytically for simplified cases and by finite element analysis for cases involving complex geometries and nonlinear contact. The positional error and friction analyses were performed analytically by deriving the kinematic and dynamic equations. Discussions based on the analyses provide a deeper understanding of the behavior of lockable joints that applies not only to the specific joints discussed in this paper but also to other lockable joints working with similar principles.