The automobile industry is expected to enter the era of eco-friendly autonomous multi purpose mobility beyond the era of simple electric vehicle. And these types of mobilities are reckoned to be operated and managed by cargo businesses or logistics businesses. These businesses will request a large interior space to carry more people or more cargo and more efficient mobility in terms of energy and cost because they are based on the profitability of their businesses. For that reason, in-wheel motor is attracting attention to implement a large interior space. And also energy efficiency of multi motors is considered very important because of not only their businesses but also global environmental issues such as pollusion and warming. Therefore multi in-wheel motors in a mobility must be managed efficiently for energy. This paper covers motor torque distribution algorithm with a greater emphasis on regenerative braking distribution, especially for autonomous driving mobility with multiple motors such as 4 individual in-wheel motors focusing on not only optimizing energy efficiency but also path tracking. Optimizing energy efficiency through motor torque distribution can be obtained by minimizing powertrain power loss and tire slip power loss. The energy efficient torque distribution for front to rear wheel can be obtained on the ideal braking characteristic curve and the energy efficient torque distribution for left to right side can be found on the understeer characteristic curve. These analysis are proceeded based on quasi static model. And autonomous path tracking can be implemented by compensated direct yaw moment due to motor torque distribution when it intervenes during autonomous driving. This paper shows how much energy can be saved by energy efficient motor torque distribution through the simulation results of autonomous driving skid pad test using Matlab Simulink and IPG Carmaker. The results will show how motor torques are allocated to increase energy efficiency visually.
Mr. Gwichul Kim, Senior engineer, Hyundai Motors