Research On Direct Yaw-Moment Control System For Light Vehicle

With the development of vehicle electronics technology, Direct yaw-moment controlsystem has become a focus of the automakers. Direct yaw-moment control system,whichcombines the advantages of anti-lock braking control system and traction control system cannot only improve the braking performance and driving performance, but can also provideactive braking to the appropriate wheels when the vehicle has over-steer or under-steer trend.Direct yaw-Moment control system can prevent vehicles from entering the non-steady state,thus improve vehicle handling stability and driving safety. Therefore, in order to reduce therisk of vehicle instability, the key of this study are optimal control allocation of directyaw-moment and design of direct yaw-moment control system.The objective of this paper is to investigate direct yaw-moment control on light vehicles.The main research contents are as follows:1. Analyzing and Modeling of Vehicle DynamicsBased on the target vehicle and according to the requirement of direct yaw-momentcontrol strategy, a fourteen freedom nonlinear vehicle dynamics model is built, whichincludes the longitudinal, lateral, vertical, roll, pitch and yaw motion of the sprung mass, thefour vertical vibration freedoms of unsprung mass, and the rotation of four wheels. Vehicledynamics model provides a basis for off-line simulation and hardware-in-the-loop tests.2. Direct Yaw-Moment Control AlgorithmAccording to the automobile systematic dynamic theory, the general scheme of thedirect yaw-moment control system which has the hierarchical structure is designed. Thecontrol system consists of the main loop, servo loop and execution layer. Classical PID algorithm is used as the control algorithm to design the main loop controller of the directyaw-moment control system. Optimal control allocation method is used to design the yawmoment allocation servo loop system. Afterwards, active brake controller is designed toachieve close loop control of the direct yaw-moment control system.3. Off-line Simulation for Direct Yaw-Moment Control SystemThe direct yaw-moment control system offline simulation platform is build withMatlab/Simulink based on vehicle dynamics model and direct yaw-moment controlalgorithm.On the condition of the driver open-loop control (sinewave turning and squarewave steering) and the driver closed-loop control steering,(single line change and doublelane change), the offline simulations were carried out on the platform and vehicleperformance curves are compared. The simulation results show that direct yaw-momentcontrol system based on optimal control allocation enables the vehicle yaw rate and sideslipangle to follow their respective nominal value well and ensures that the vehicle has goodhandling stability.4. Hardware-in-the-loop Test for Direct Yaw-Moment Control SystemThe direct yaw-moment control system hardware in the loop experimental platform,which includes three parts: software system, hardware system and real-time platform, isdesigned based on dSPACE platform. The typical driving test conditions are chosen to carryout the hardware in the loop test on the platform. The results show that the directyaw-moment control system designed in this paper has good control performance,adaptability and robustness.