Research On Bus Nonlinear Handling Stability And Control Strategy

Currently, as the development of economy and society, vehicle has changed from a way of transportation to generally consumable, and become indispensable part of our life. The concept of vehicle for people is developing and spreading as life space not only as a driving tool. As a main transportation tool for most people collective traveling, large bus carries our precious and happy life, whose handling stability and safety is very important. Because of the late beginning and weak foundation of our country’s vehicle industry, compared with foreign, there are still large gap in theoretical research and advanced technology. Considering the characteristic of large bus, such as high quality and high gravity, the quality and safety of the vehicle should be improving continually. Therefore, deeply researching large bus’s system dynamics mechanism, mastering handling stability characteristic, analyzing the influence factors and improving control strategy and evaluation method are still widespread concern and important subjects to be researched at present.In view to large bus dynamics model derivation and motion analysis, handling stability evaluation and influence factor, system stability, drive stability regions and control strategy evaluation, the aim of this paper is to tamp the theoretical basis. So it could guide the engineering application accurately. Specific contents are as following:5DOF large bus dynamic model is derived. Using advanced technology of GPS and inertial measurement, a kind of detecting device for large bus handling stability is integrated and developed. Vehicle dynamics in stable and transient conditions are tested with the detecting equipment and the test results are analyzed quantitatively and qualitatively. With the verified model, vehicle’s stable and transient dynamic characteristics are simulated. And vehicle instable form and characteristic in critical steering are theoretical analyzed so that vehicle handling stability characteristic and instable mechanism could be mastered. All of that are the foundations for subsequence researches of vehicle handling stability.Arranging and summarizing current vehicle handling stability theoretical and testing evaluation methods. According to the model of driver-vehicle-road closed-loop system, parameters of driver, road and large bus, such as predict time, adhesion coefficient, mass, gravity position, suspension stiffhess, absorber damp, pneumatic trail, kingpin are analyzed for vehicle stability. The import influence factors are mastered. Thus the conclusion could be valuable reference for vehicle performance matching and optimization.Based on Lyapunov stability theorem and vehicle energy conversion characteristic, quadratic Lyapunov energy function of large bus with Pacejka model is derived, as well as boundary conditions of energy function is defined. Stable and transient driving regions of large bus are estimated by the proposed method. And the rules of vehicle’s stable regions in different conditions are analyzed and mastered. The estimated driving regions are verified by the test results of vehicle’s stable circle and transient snake motion. So the stable regions could be reliable basis for judging vehicle state and evaluating handling stability.A new method for evaluating control strategy by large bus driving region is proposed. Based on typical4WS and DYC methods, Control models of large bus are established. Applying the stable and transient regions, vehicle handling stability in different control conditions are obtained and evaluated comprehensively. It could conclude that the driving region is a reliable method for evaluating vehicle control strategy.