Efficiency analysis of two degrees of freedom epicyclic gear transmission and experimental validation

•Close match between the theoretical efficiency curves and experimental data•The proposed method and model are capable of accurately predicting efficiency of a given epicyclic gear train.•Two local loss factors are always coupled together in this device under test.•The same speed ratio may yield different efficiencies depending on the directions of the input angular velocities.•Bearing power losses and other forms of power losses will be taken into account for a better predication.

A complete method based on constraint analysis and virtual power is developed in this work. The method is applied to a two-dof epicyclic gear transmission for efficiency modelling and prediction. The power flow diagrams are constructed to obtain possible power flow patterns and to verify the balance of normal power flow and virtual power flow within the system. The theoretical efficiency formulas were derived for the full working range, and further verified by experimental data. It was found that two local loss factors are always coupled together in this device under test, and the same speed ratio may yield different efficiencies depending on the directions of the input angular velocities.