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

CBD Drive Cycle3530Speed (Km/h)252015105004.89.614.419.22428.833.638.443.24852.857.662.467.27276.8Time (sec)Figure 7-6 City Bus Drive cycle (CBD)The driving cycles are modeled using look-up tables and are considered as inputs for thesimulation instead of manual pushing of brake and throttle pedal.7.6 Automatic DriverTo simulate the behavior of a driver following up a certain drive cycle, a model isrequired to calculate the required wheel torque. This model is called automatic driver. Itconsists of a PI controller having the reference driving cycle, actual speed of the vehicleand grade as inputs. Its output is the reference wheel torque to trace the drive cycle. Inorder to increase the functionality of the PI controller a feed forward loop is used. Thisloop based on the reference speed and grade, calculates the traction torque needed fortracing the reference drive cycle. The error between the reference speed and the actualspeed is compensated by adding another torque calculated by the PI controller. In order toprevent integrator windup, the integrator is reset each time the speed falls down to zero.The block diagram is shown in figure 7-7.46