Equivalent Vehicle Rotational Inertia Used for Electric Vehicle Test Bench Dynamic Studies

This paper provides an easy yet accurate approach for estimating vehicle inertia for the purpose of simulating the effect of vehicle inertia using a large flywheel. The method used to properly map the linear inertia of a vehicle to an equivalent rotational inertia is described in detail and an expression for equivalent rotational inertia of a vehicle is derived analytically using two different approaches considering kinetic energy of a moving mass in the linear and rotational context and vehicle dynamic equations. A MATLAB/Simulink model of a test bench consisting of a torque actuator connected to a large flywheel is used to emulate the effect of vehicle inertia. Using this model, the dynamic inertia effect of an electric vehicle on its traction motor is illustrated for two standard drive cycles. The results obtained from simulation are validated by ADVISOR to confirm the effectiveness of the proposed method in estimating vehicle inertia and it is shown that the use of a flywheel with a calculated rotational inertia using the proposed method can be sufficient in emulating vehicle inertia effect on a test bench