Efficiency measurement strategy for a planetary gearbox with 2 degrees of freedom

This paper discusses a method to calculate the efficiency of a planetary gearbox with 2 degrees of freedom. Standard measurement procedures in which the efficiency is measured as function of the load torque and input speed become infeasible due to the many possible input output configurations. To solve this, a method is proposed that combines the theory of virtual power and a limited set of measurements. The theory of virtual power is used to link the considered power flow in the device with an expression to calculate the efficiency of the planetary gear in terms of the efficiency of the power path between sun & carrier and carrier & ring. The efficiency of the aforementioned power paths is shown to depend only on the torque applied to these paths which means that speed dependent losses such as churning losses are negligible. Measurements of the efficiency as function of the torque applied to the sun for a varying speed ratio between ring and carrier are added to validate the approach