Dynamics of integrated planetary geared bearings

Abstract

The gear bearing drive is a new robotic transmission that was developed by NASA for compact and lightweight robotic applications. Compared to conventional simple and compounded planetary gear trains, the mechanical assembly of the gear bearing drive does not require a planetary carrier and individual planet needle bearings to maintain the gearset alignment. Instead, the design integrates the gearing and bearing functions together such that a constant pressure angle is maintained throughout the mesh cycle by the use of cylindrical rollers that are mounted parallel to the gear mesh. This paper examines the vibration characteristics of this planetary architecture and extracts its natural frequencies and mode shapes using both analytic and finite element methods. The design is compared against a conventional system with a floating carrier for comparative analysis. A simple and systematic approach to analytically and numerically solve the dynamics of complex, multi degree of freedom gear train systems using MATLAB is presented that can be easily applied to study other complex non-linear dynamic systems.