3-DOF vehicle steering model and state equations based on considering air forces

In oder to decrease the influence of air forces, predigest the multiple-DOF steering dynamics equations of vehicle, air forces were considered, a 3-DOF steering dynamics model was proposed. The state equations of the model was induced, sideslip angle in mass vehicle center, yaw angle, yaw velocity, roll angle and roll velocity were state variables, steering angle in front axle and crosswind force were input variables, sideslip angle in vehicle mass center, yaw angle, yaw velocity, roll angle were output variables. The simulation credibility of the equations was validated by using a test vehicle with an active steering angle pulse. The simulation result with the 3-DOF model and equations was compared with that from 2-DOF steering dynamics model. Comparison result shows that the Absolute values of sideslip angle and yaw velocity from the 3-DOF model and equations are less, which indicates that air forces strengthen the lacking steering property of vehicle. The sideslip values gained by the tow models are larger than the test value, but the value gained by the 3-DOF model is closer to the test value. Obviously, the credibility of the 3-DOF equations is higher.