Dynamic modeling and analysis of junction surfaces of robotic modules

Junction surface plays an important role in the performance of a modular robot in terms of positioning error and system stiffness. In this paper, junction surfaces of robotic modules are modeled and analyzed based on virtual medium. The asperity of a junction surface is first made equivalent to an isotropic virtual medium layer, and the thick surface contact fractal theory is combined with the contact mechanics theory. The analytical dynamic model is thus established, by which the coupling relationship between the asperities of junction surface is successfully simulated. The fractal dimension and the scale coefficient of the equivalent junction surfaces are obtained by surface profilometer and power spectrum analysis, and the dynamic characteristic parameters of the virtual medium are calculated. Comparison result shows that the theoretical and measured modal shapes basically match, and the relative errors between the theory natural frequency and the test natural frequency of every order are less than 7.3%, which verifies the effectiveness of the dynamic model of the module junction surface.