| During starting up or accelerating on the weak adhesive roads,such as ice or snowy road, sand etc., the driven-wheels of vehicle are tending to over-spin,which leads to the adhesive force between the tires and road decrease, hence the performance of the acceleration and stability is influenced disadvantageously. Traction control system can make use of the road adhesion effectively through controlling the slippage state of wheels, and the performances of traction and stability of vehicle are improved. The research on traction control system for a light off-road 4WD vehicle and its utilized "V-mode" rapid development method were performed. And the work was combined with the research of projects "Research on Traction Control System for Off-Road Vehicle" and "Traction Control Technology for Light Vehicle". The control strategy and algorithms based on integrated control of driven wheel brake, engine electronic throttle position and automated transmission gear state were proposed, and the algorithm was of practicality. The traction control system off-line simulation platform and hardware-in-the-loop test platform were built, and some off-line simulation and hardware-in-the-loop test of representative condition were carried out on these two platforms. Verifying and debugging to the software and hardware of the traction control system were accomplished in the stage of control algorithm prototype. The results of the thesis provide some important reference to the development of 4WD traction control system.1. 4WD Vehicle Accelerating Dynamics ModelIn order to build the traction control system off-line simulation platform and hardware-in-the-loop test platform, 4WD vehicle accelerating dynamics model was built based on the principle of modular model building. This dynamic model included: driver intention sub-model, 14 freedom degree vehicle model, powertrain and driveline sub-model composed by engine model, TC+AMT model, gearbox model, and wheels dynamics model, tire sub-models for hard road and deformable road, brake system sub-model, road vertical input sub-model. The tire model for deformable road was a semi-empirical tire model, and it was simplified for guarantee of the real-time simulation process. Finally, the 4WD vehicle acceleration model was built, it can simulate these conditions such as startup/acceleration, constant steer angel acceleration on the level or inclined road with different road vertical input and adhesion. This 4WD vehicle acceleration model provided the foundations for building of the off-line simulation platform and hardware-in-the-loop test platform.2. Research of the control Strategy and Algorithms for Traction Control SystemThe control strategy and algorithms for traction control based on the integrated control of driven wheels brake, engine throttle position and transmission gear stage were proposed:â—‹1 The control principle and the overall scheme of control algorithms for traction contrl system were designde, and the algorithms of vehicle velocity estimation was proposed;â—‹2 The influence of the road roughness to traction control system was analyzed, and the algorithms of the recognition for road roughness was designed.â—‹3 The algorithms of startup condition judgement and the judgement algorithms of traction control system start/quit;â—‹4 The algorithms of calculation of the target spin ratio was designed, and the target spin ratio was adjusted according with the running conditions of vehicle, for example the vehicle velocity, hence the acceleration and stability were harmonized reasonably;â—‹5The driven wheels brake control logics and algorithms were designed, the state of the brake pressure included fast increasing pressure, slow increasing pressure, holding pressure and decreasing pressure, and the thresholds of the wheels target velocity were adjusted according with the conditions of the states of road roughness, strarting up, deformable road state, etc.;â—‹6 The engine throttle position control algorithms was designed, which was combined with the threshold control algorithm and incremental PI control algorithm, and the parameters of these algorithms were adjusted according with the vehicle running condition;â—‹7The influence of the transmission gear stage changing to the traction control system was analyzed, the shift law of the transmission was adjusted according with the vehicle running state, and the gear state was controlled to improve the performance of the traction control system.3. Off-Line Simulation Platform and the SimulationVehicle dynamics simulation model and traction control system control algorithms prototype were built with Matlab/Simulink development tools based on 4WD vehicle accelerating dynamics model and traction control system control algorithms; the GUI interface was built by used of the Matlab/GUIDE toolbox; three dimension virtual scene was designed by used of Matlab virtual tool. The 4WD vehicle traction control system off-line simulation platform was built by combining the vehicle simulation model, GUI interface, three dimensions scene. Some off-line simulations of the traction control system control algorithms under representative conditions were carried up on this platform, and the results of off-line simulation showed that:â—‹1 The offline simulation platform was qualified to the research of traction control system;â—‹2 The control algorithms of traction control system could control the over-spin of the driven wheels effectively when the driven wheels were over-spining, and the acceleration ability and stability of vehicle were improved;â—‹3 The control algorithms could response exactly and in time when the adhesion of road step-changed;â—‹4 The control algorithms could eliminate the bad influence of the road roughness to the performance of traction control system through self-adjusting the control parameters when the vehicle was running on the rough road;â—‹5 The control algorithms could adjust control parameters reasonably, for example vehicle velocity, and could choose and harmonize the methods of engine throttle position, driven wheels brake and transmission gear stage according with the running condition of vehicle, finally the accelerating ability and stability of vehicle were improved reasonably.The building of off-line simulation platform and off-line simulation provided some foundations to the hardware-in-the-loop test platform and the following hardware-in-the-loop test.4. Hardware-in-the-Loop Test Platform and TestIn order to verify the control algorithms of traction control system, the hardware-in-the-loop test platform which some sensors and actuators hardware were embed into was built based on the overall scheme of the test platform of 4WD vehicle traction control system. So the real environment of vehicle was simulated with high accurateness indoors, and the dependence of road test during the development process of the traction control system decreased, the development time and cost were decreased; The sensors included brake pressure sensors, steer angle sensors, and the actuators included electronic throttle system, TC+AMT system, hydraulic control unit.Some hardware-in-the-loop test of representative conditions were carried out on this platform, and the test results showed that: the software and hardware could match each other reasonably, and the over-spin could be controlled effectively. The driven wheel brake control, engine throttle control and transmission gear stage control could be going along correctly. So the utilizing of the road adhesion was improved, and then the dynamic performance and stability on the weak adhesive roads were improved, and the traction control system could respond quickly when the road adhesive coefficient changed abruptly.5. Research on Evaluation System for Traction Control SystemThe influences of the traction control system to the vehicle's performance were studied, for example the influences to dynamic performance, stability, riding comfort, etc., and the evaluation parameters of traction control system performance during the traction control system was working under some representative conditions; Some evaluation parameters were choosed based on the characteristics of the target researching vehicle, and then four kinds of evaluation indicators for traction control system, i.e. dynamic performance improvement index, stability improvement index, road adaption ability index and pass ability on deformable road improvement index; The objective evaluation system of "evaluation parameter-classificatory evaluation index-general performance of traction control system " for traction control system, and the methods of how to calculate the evaluation parameters were proposed.The performance of the traction control system of this dissertation researched was evaluated on this traction control system objective evaluation system.
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