VEHICLE MODELING AND PERFORMANCE EVALUATION USING

Abstract

During sharp maneuvers, to control the yaw stability of a vehicle, the available solutions may be either brake based or lifting of gas pedal. These systems helps in controlling the braking and driving forces that operate on the left and right wheels in such a way that a driver has a direct control over these cornering forces. As a result, they facilitate an appreciably safer and more enjoyable driving, however the vehicle systems based on brakes, on sharp maneuvers, have been exposed to decline the longitudinal performance, and impose an understeer or oversteer behavior, as their system conforms to more stability and less performance. An alternate to the system described above is Active Torque Distribution system using either electronically controlled differential or electronically controlled central transfer case. Until now much work was done on torque distribution between right and left wheels using electronic control differentials. A limited amount of work on torque distribution between front and rear axles was done using electronically control transfer case. This research uses the second approach due to following reasons:- a. Use of active differential is costly as compared to a electronically controlled central transfer case (as proposed in this research) b. Loss of energy/power as in the case of differential braking will be solved by using this strategy. In conducting this research, a non-linear ten degree-of-freedom vehicle model incorporating a non-linear tire model was adopted and simulated in the MATLAB environment. Using this model, various VDC torque management architectures as well as choices of feedback controllers were studied. For the purposes of yaw stability control design, the desired or reference performance of the vehicle was obtained from a neutrally steered vehicle model. Standard test maneuvers such as J-turn test and Double Lane Change (DLC) were simulated to evaluate the effectiveness of the proposed torque distribution strategies. The simulation results indicated that all VDC torque management strategies were generally very effective in tracking the reference yaw rate of the vehicle on both dry and slippery surface conditions