| More and more consumers and automobile manufactures have been paying more attention to automotive active safety system. TCS(traction control system), get the optimum vertical danymics performance by controling wheel verticle sliding rates. The driving wheel will excessive slip easily when the automobile begins to start,accelerate,or climb on the road with weak attachment coefficient ,which will deteriorate the attached conditions between tyre and road surface and also will have bad impact on driving performance maneuvering performance and stability of vehicles. When the vehcles steering or driving in the seperation road, the excessive slip driving wheel not only reduce driving performance,but also produce additional yaw torque,and that have big influence in manevering perfofmance,at the same time increase the difficult of control.The dynamic characteristics of hydraulic brake system is the essential step in the studying-process of hydraulic system design and developing hydraulic brake products.It also had directly affects on braking process,so control logic design must be based on the dynamic characteristics of hydraulic brake system. However,it is difficult to establish mathematical modeling and inaccurate. All these facts showed that experimental study is the directly method in hydraulic brake system design and analysis.There are five parts in this paper:1. Automobile driving-steering dynamic model It established automobile driving-steering dynamic model,this model sets mathematical model for engine,transmission,tire and brakes etc.A seven dof whole car model is builted by Matlab/Simulink software will satisfy the simulation of different road input, vehicles start, accelerate, drive straight,steer etc.,and simulate control effects of traction control system logic.2. Traction control strategy and control algorithm studyIdentify control target of driving steer conditions: By balancing the dynamic performance of the vehicles,it will assure the vehicles with good control stability. It proposes strategy of throttle control based on yaw angular velocity and driving wheel brake control based on slip rate.And also proposes speed eatimation based on steering wheel;nominal yaw angular velocity calculation;throttle control judge and driving wheel brake judge methods and so on;it designs PI incremental throttle control and PID,fuzzyPID driving wheel brake control strategy.3. Offline simulation study of traction control algorithmIt conducted offline simulation agaist steer contditions traction control in low attachment homogeneous road;comparative analysis agaist the results of throttle control, driving wheel brake control and joint control in this paper,which are based on determined test model parameters.The results show that:by using control strategy and control algorithm can effective inhibit driving wheel excessive slip and improve vehcles dynamic performance and stability of manipulation.It verificates correctness and reliability of algorithm for straight driving simulation in separation road, the questions yaw and driving wheel excessive slip have been contrlled effectively,dynamic performance and stability of manipulation of vehcles have been improved significantly.4. TCS hardware-in-the-loop testTCS hardware-in-the-loop test was builted basing on MATLAB/xPC Target platform,including sensor, actuator,experimental platform and signal rocessing site.It conducted TCS hardware-in-the-loop test against different driving conditions in TCS hardware-in-the-loop test-bed.the results show that TCS have effective inhibition with driving wheel excessive slip,improving vehcles dynamic performance and stability of manipulation.5. Hydraulic brake system programme and hydraulic test-bed programmeIt propses hydraulic brake system programme that have TCS function on the basis of test models,it determines hydraulic parts selection. It proposes hydraulic tast-bed overrall structureof the programme, at the same time,it selects test-bed parts model. Hydraulic brake system is in the process of being built.This paper established vehcle driving-steering dynamic model and offline simulation platform in MATLAB/SIMULINK for a linght vehcle.It praposes traction control strategy;it designs control system with different control method;traction control strategy study and traction control strategy offline simulation study is finished. On this basis,it proposes hydraulic brake system programme and hydraulic test-bed programme. |
PDF Full Text Request