Optimal Design of a Compound Planetary Reducer Using a Nonlinear Optimization Method

The growth of the robotics industry has led to rising demand for reducers that increase torque efficiently while reducing motor speed. Among them, compound planetary reducers can be effectively used in robots because they can achieve high gear ratios with smaller volume. The design of conventional reducers comprises the method of setting a gear ratio to design the gear dimensions and calculating efficiency through dynamic analysis. However, this method suffers from repeated designing and analysis, which makes it very time-consuming. Therefore, this study defines the problem of reducer design as the problem of optimization by setting an objective function, constraints, and boundary conditions, and proposes to obtain the results in a short period of time using the Sequential Least Squares Programming(SLSQP) method. Using the SLSQP method, optimization results can be obtained as real numbers, making it suitable for use in compound planetary friction reducers with no constraints on the selection of gear dimension. For the design problem of the conventional compound planetary gear reducer in which the module value exists, an additional optimal design method considering the module is proposed. To compare the optimal results, we have made a 30:1 compound planetary friction reducer and a 50:1 compound planetary gear reducer using 3D printing. A gear ratio evaluation experiment was conducted to evaluate the performance of the actual manufactured prototype reducers.