Research On Integrated Chassis Control Strategy For Vehicle Active Safety

As the major transportation in modern society, the vehicle industry promotessocio-economic development and people's living standard rapidly, but the annual death tolland economic loss caused by traffic accidents are shocking, and vehicle safety issues havebecome a worldwide social problem. With the rapid development of the electronictechnology, sensor technology and in-vehicle network technology, the chassis active safetytechnology has developed rapidly, and the applications used in vehicle have increased,,regardless of vehicle driving safety or riding comfort has been improved remarkably, butthese electronic control systems are designed and developed by various part-suppliermanufacturers independently, only focusing on improving its performance and withoutconsidering the interaction and coupling with the other electronic control systems, so thesimple superposition of electronic control systems are not only fail to fully reflect theirproper performance, but also will reduce the whole vehicle performance. Therefore,comprehensive consideration of all the electronic control systems, achieving vehicle optimalperformance by the way of integration and optimization, has become a hot research topic inthe field of automotive active safety. As the future development direction of active safetysystem, domestic research of vehicle chassis integrated control has just started, therefore,following the development trend of automotive technology closely is not only have a greatrealistic significance in shortening the gap between the technological levels of our countryand developed countries, but also greatly accelerates the progress of automotive industry and other related industry.This thesis is associated with the "Integrated Development of Electronic StabilityProgram(ESP) and Integrated Control Technology of Electronic Power Steering(EPS)"subject, supported by the project of National863Program "Integrated Development ofAdvanced Technology for X121Passenger Car". Based on the summary of the domestic andforeign research achievements, this thesis focuses on the research of integrated chassiscontrol for vehicle active safety, and a domestic passenger car is chosen as benchmark. Asequence research work of the high-quality modeling of vehicle dynamics, electronicstability control strategy and simulation, vehicle test of electronic stability control strategy,integrated chassis control strategy and simulation and HIL test of integrated chassis controlare carried out in detail. The main contents are as follows:First chapter is the introduction. It systematically introduces the development of vehiclechassis active safety systems, leads to the advantage and necessity of vehicle chassisintegrated control, analyses the the key issues of the chassis integrated control, and thensummaries the domestic and foreign research achievements of chassis integrated control, theacademic and applying background of this thesis are described, and the main content of thispaper are given.The second chapter is the high-quality modeling of vehicle dynamics research. Based onthe characteristics of integrated chassis control, the16-DOF nonlinear vehicle dynamicsmodel is established using modularization method, which has high precision and strictreal-time. It is composed of engine model, powertrain model, brake system model,hydraulic regulator model, suspension model, tire model, vehicle body model and drivermodel. And the vehicle model is validated using the handling test data of the target vehicle.The results show that the vehicle model can describe the dynamical characteristics inlinear and nonlinear area correctly and accurately.The third chapter is electronic stability control strategy and simulation research. Theoverall architecture and content of sub-modules of electronic stability control algorithm aredesigned using the hierarchic method. Based on vehicle lateral dynamics, the necessity of combined control of the yaw rate and sideslip angle is illustrated. Focusing on the yawstability control strategy, yaw moment decision algorithm is designed based on LQR methodand GPC method, and the effectiveness of these two algorithms are validated by simulation.Finally, the effectiveness of the ABS control algorithm are validated by simulation.The fourth chapter is experimental study on the electronic stability control strategy. Theelectronic stability controllers, the vehicle attitude sensors, PC monitoring system and thevehicle test platform are designed and developed. Considering the dependence of the actualenvironment and the cost of the product, the sideslip angle and wheel cylinder pressure areestimated, and validated by electronic stability control test platform. The functionality of thevehicle attitude sensor, yaw stability control algorithm and the effectiveness of the ABScontrol algorithm validated by electronic stability control test platform.The fifth chapter is simulation study on integrated chassis control strategy. The overallarchitecture of integrated chassis control strategy is designed using the hierarchic method.Studying on integrated chassis control includes two levels, and the first level is theintegration of braking and steering control, electronic stability control and active frontsteering control are integrated, and the second level is the integration of braking, steering andactive suspension control, then the integrated chassis control is achieved in strict sense.Seven degrees of freedom predictive model and model predictive control algorithm areestablished for the integrated control of braking and steering, and the accuracy andeffectiveness of prediction model and model predictive control algorithm are validated bysimulation. The total yaw moment is designed based on the sliding mode variable structurecontrol algorithm for the integrated control of braking, steering and suspension, and the tireforce estimation and optimal tire force distribution algorithm are designed.The sixth chapter is the hardware in the loop test reaserch of integrated chassis controlstrategy. In order to further verify the effectiveness of the integrated control algorithm in theenvironment by adding sensors, actuators and controller, integrated chassis controlhardware-in-the-loop test rig is designed and developed based on Matlab/xPC Targettechnology, including a driving simulator system, real-time simulation system and ESC hydraulic braking system. According to the network topology of integrated chassis controlhardware-in-the-loop test rig, the CAN communication protocol is developed independentlybased on SAE J1939protocol, and the host software is developed, which is used to protocolanalysis and control system online debugging and calibration. The effectiveness of theintegrated control algorithm for braking, steering and suspension is validated by hardware inthe loop test.The seventh chapter concludes the whole content of this thesis, and it put forward thedirection and the keystone for the future.For resolving practical issues, this thesis studies the aspects related to developing vehicleintegrated chassis control system. And it has creative works following:(1) The overall architecture of integrated chassis control strategy is developed using thehierarchic method. Focusing on the yaw stability control strategy, yaw moment decisionalgorithm is developed based on GPC method, and the effectiveness of the algorithm isvalidated by the in-vehicle test platform of electronic stability control.(2) Focusing on integration of differential braking and active front steering, theintegrated control algorithm is designed based on MPC method, and the effectiveness of thealgorithm is validated by vehicle dynamics simulation platform.(3) Focusing on integration of differential braking, active front steering and activesuspension, the total yaw moment decision algorithm based on SMVSC method, the tireforce optimal allocation algorithm are designed, and the effectiveness of algorithms arevalidated by hardware in the loop test platform of integrated chassis control.