Abstract: A novel approach, based on the concept of spatial mechanism with redundant elastic constraints is presented to set up a comprehensive precision-characterization model of an actual revolute joint. When considering component flexibility and manufacturing errors, the shaft in an actual revolute joint can move in a much more complex manner in comparison with an ideal revolute joint with only one rotational degree of freedom. In the proposed model, the rigid cams with special profiles are used to represent the geometrical error, springs are used to describe the deformations of joint components and surfaces in actual machine parts. The spatial cams, suspended by multiple straight-followers with springs, called an RE mechanism, is proposed to simulate the kinematics of the shaft in the revolute joint. The basic model equations, such as kinematic equations, equations of equilibrium, and equations of physical properties are concisely derived. With the proposed model, the precision of an actual revolute joint and its load-dependent properties can be seen as the solutions of the basic equations of a corresponding RE mechanism. An example is presented to illustrate the solution process of the precision model of a revolute joint, and numerical results were compared with the experimental results obtained from the corresponding test setup. The proposed model provides for the first time a theoretical basis for joint precision analysis and synthesis. This opens up a new application of the theory of mechanism in design of machine components.

Key words: Elastic constraint, Error, Mechanism, Redundant constraint, Revolute joint