In order to meet the ride comfort of the heavy truck cab, the 1/2 heavy truck cab active suspension model established. Based on this model the LQG optimization control was selected for the active control of a 1/2 heavy truck cab suspension system. The road disturbance is integral white noise stochastic signal. By the example simulation in Matlab/Simulink, the results show that the cab active suspension with LQG control strategy can decrease the vertical accelerations, the roll angle and roll angle acceleration of the truck cab, the active suspension can improve both the ride comfort and driving safety.

The stability conditions of 1/4 vehicle active suspension with time-delay were deduced by the theory of Routh-Hurwitz stability criterion and the critical instability time-delay was discussed and calculated. Compared with PID control method of without time-delay the simulation results show that when the critical time-delay is 0.153s, the amplitude range and its root mean square value of spring load quality vertical acceleration were increased 1.2 times or so and the system was being on the critical stability. The calculation and simulation results proved that the theory of Routh-Hurwitz stability criterion laid a foundation for the design and instability mechanism of active suspension.

To ensure vehicle stability in critical and dangerous working conditions, a vehicle stability control strategy is proposed, which is to generate compensating yaw moment by using the combined action of active rear-wheel steering and differential braking. A corresponding fuzzy controller for the proposed control strategy is designed. To verify the control effect of fuzzy controller, the numerical simulation by using vehicle dynamic model is performed in critical condition. The simulation results show that the designed fuzzy control system can efficiently prevent the vehicle to lose driving stability during critical turning.

For improving the vehicle handling at high speed, an optimal controller was introduced for the four-wheel-active-steering vehicle. A closed-loop system was set up by combining vehicle model with driver model. The simulation test in the closed-loop system was carried out to verify control effect of such a optimum controller. Simulation results show that the four-wheel-active-steering vehicle under the optimal control can gain expected control effect such as wiping out sideslip angle and tracking desired yaw rate and so on. In addition, the four-wheel-active-steering vehicle with the optimal control can also track desired trajectory and its following accuracy is better than the traditional front-wheel steering vehicle. So, the steering response characteristic for the four-wheel-active-steering vehicle at high speed is improved.

Six early-warnning subsystems are build, the control parameters of tension value and time for seat belt are determined, based on the analysis of function and components for intelligent seat belt pretension system. The hardware and software are designed, the software for seat belt retractor motor is integrated to set the ralative time distance, vehicle yaw rate, steering wheel angle, vehicle deceleration, this four signals which are used as input for simulation, the output show that the tension value and tension force are directly proportional to input signal, which can be early warn for intelligent seat belt successfully and provide passengers active safety effectively.