Research On Coordination Control Strategy Of Central Transfer Case Controller And ESC For All-wheel-drive Vehicle

In recent years,the vehicle active safety technology is becoming more mature.Andpeople’s awareness of safety has been constantly improved,therefore,the four-wheel-drive vehicles that used to emphasize the dynamic performance and trafficability cannot meet the needs of people any more.The four-wheel-drive technology with the combination of the various performance such as trafficability,handling ability,and security has been gradually accepted by people.Electronic Stability Control System(ESC)is the research focus of the vehicle handing stability,which has been widely used in various vehicle types.It can not only keep the riding stability of the vehicle,but also assist an unsteady vehicle to return to a steady state.Comparing with the two-wheel-drive vehicle,the all-wheel-drive one equipped with the Central Transfer Case Control System(CCC)have their own unique features.Meanwhile,with this function,the vehicle handing stability can be improved properly.Thus,the system which can distribute the shaft torque intelligently according to the vehicle running situation has become a vital research subject in recent years.This paper,mainly based on the characteristics of the ESC system and CCC system,designs the two systems and their coordination control algorithm to realize the integrated control.In the first place,within the limitations of the tire mechanical friction circle theory and the restrictions of maximum tire adhesion,the different torque distribution coefficients between the front and rear can influence the vehicle handling stability.And then the results of the joint simulation between Carsim and Simulink show that the proposed algorithm is feasible.In the second place,the Central Transfer Case with the electromagnetic multi-plate clutch is the object of study in this paper.And then the CCC system is totally designed based on the Piecewise Affine(PWA)Controller,the Anti-windup PI Feedback Controller,and theTemperature Compensated Feedforward Controller.This system can achieve a more accurate and effective control by approximating to the nonlinear system through the method of linear system,at the same time,allowing for the change of the CCC working station because of the fluctuations of outside and plates temperature.What’s more,the modified yaw moment calculation model is designed based on fuzzy control strategy in this paper.In addition,the starting flag of ESC system is set based on the side-slip angle phase and a series of threshold values mentioned in this paper,and then the ESC system will begin to brake the optimal wheel if the flag reaches the starting condition.At last,the overall coordination control algorithm of these two systems is proposed for keeping the vehicle handling stability.And the results of the joint simulation between Carsim and Simulink also verify the feasibility and effectiveness of algorithm under some special simulation conditions.