Effect of number of planetary gears on fuel consumption and vehicle performance in the hybrid powertrain of a passenger car

A Planetary Gearbox (PG) is an essential component of a hybrid powertrain. Most hybrid electric vehicles (HEV) incorporate PGs to interconnect various powertrain components together. To author’s best knowledge, the effect of varying the number of PGs on emissions has not been reported by previous authors. Studies have not considered the same powertrain component sizes (i.e. engine capacity, motor torques, vehicle mass, tire radius) for comparing the effect of PGs. This study aims to bridge the gap of component sizing, emission, fuel consumption and acceleration performance to provide insight into the impact of the numbers of PGs on the performance of hybrid powertrains. A HEV model has been built using the Automotive Simulation Models (ASM) from dSPACE. Simulations were conducted to test the behaviour of various parameters such as fuel consumption, emission, acceleration performance, battery state of charge (SOC), and the efficiency of components upon increasing the number of PGs. Simulations have been run for only one mode, namely the input split mode. The latter is chosen because it consists of working of internal combustion engine, motor 1 and motor 2. The result of this work identifies the optimal number of planetary gears to be used in the gearbox of a hybrid powertrain in order to minimise fuel consumption and emissions.