Shahram Azadi - Assistant Professor, K.N.Toosi University of Tech. / Mechanical engineering faculty;
Majid Shabani - M.S. graduated, K.N.Toosi University of Tech. / Mechanical engineering faculty
Reza Kazemi - Associate Professor, K.N.Toosi University of Tech. / Mechanical engineering faculty

One of the most important parameters are discussed in relation with a vehicle is its handling that means the vehicle obedience of the driver’s steer. This can be investigated in three modes: over steering, under steering and neutral steering. Excessive increasing of over steering or under steering can be a serious threat to the car’s safety. In order to maintain the car's handling in the acceptable range, the vehicle dynamic control system is used. By determining a desired yaw rate, this system, keeps the vehicle’s yaw rate close to desirable value. To design the vehicle dynamic control system (VDC), in this paper, optimal control strategy based on bicycle model is used. In this model, side slip angle multiplied by the cornering stiffness gives the lateral force. Considering the definition of cornering stiffness, its value changes constantly, depending on theconditions, this range of changes can be extended. Therefore, controller design based on fixed amount of cornering stiffness is wrong. So, by using an online estimator the amount of the lateral stiffness is determined and used to design the controller. The required torque to stabilize the vehicle, supplies by braking and so an anti-lock braking system is designed based on a simple strategy. The outputs of the controller apply to a model with fourteen degrees of freedom with a Fiala tire model. The results represent the improvement of vehicle stability.

vehicle dynamic control, optimal control, self-tuning, recursive least square