Modeling and Simulation of Vehicular Power Systems - webfiles its ...

The gear box consists of different gears which transmit speed and torque of the tractionsystem (ICE or electric motor) to the wheels. The clutch is used to connect different gearsto the shaft of the traction system. The final drive is also contains different gears thatfurther increases the speed limitation of the traction system. It means that by applyinglow ratio gears the demand for higher vehicle speeds is met.For the modeling of the transmission system two factors must be considered:• Gear ratio• Transmission efficiencyHaving the transmission efficiency and gear ratio the equivalent load torque on the shaftof the traction system is calculated. The torque which is applied by the traction source(electric motor or ICE) on the wheels is:T = N × N × η × T( 4-18)wheelgdtransmissiontWhere N g and N d are ratio of gear box and drive line system respectively and ή is thetransmission total efficiency of the transmission line including clutch, gear box and driveline. T t is the torque of the traction system.The tractive force on the wheels is:FtT=rwheeld=Ng× Nd× ηrtransmissi ond× Tt( 4-19)The longitudinal speed of the vehicle also can be found by the following equation interms of vehicle speed:VWt× rd= ( m / s)( 4-20)N × NgdHaving modeled the dynamics of the vehicle the torque coming from the engine orelectric motor can easily be connected to the vehicle dynamics model as an input.23