Research On Lateral Stability Control Strategy For Hybrid Commercial Vehicle

Hybrid commercial vehicles are gradually popularized and applied because of the good economy and low emissions.With the development of intelligent driving assistance systems,improving the driving safety of hybrid commercial vehicles has become a research hotspot in the industry.As an active safety technology,vehicle lateral stability control can timely control a vehicle in lateral instability or critical instability state to a stable state and improve the handling stability of the vehicle.Therefore,the development of commercial vehicle lateral stability control system based on the characteristics of the hybrid system has become a major development trend.However,for different hybrid system configurations,how to realize the coordinated control between hybrid system and vehicle lateral stability control system and meet the control requirements between power source and braking system under various working modes of hybrid system are the key to ensuring driving safety.Based on this,this paper takes the three-axis commercial vehicle with P4 hybrid configuration as the research object,considers the response characteristics of different power sources of the hybrid system,and studies the coordinated control strategy of hybrid system and lateral stability of the vehicle.The main research contents of this paper include:（1）The phase plane method is used to analyze the stability of vehicle driving state.Firstly,based on the configuration of the hybrid system,determine the working mode switching rules of the hybrid system when the vehicle lateral stability control system is involved.Secondly,the two-degree-of-freedom vehicle model and tire model are built,and the phase plane method is used to analyze the lateral motion law of the vehicle under different road adhesion coefficient and driving speeds.Then,based on the differential equation of vehicle motion,the reference values of the sideslip angle and yaw rate are determined as the lateral stability evaluation indicators.Finally,taking the deviation between actual and reference values of yaw rate and sideslip angle,and the position relationship between the vehicle driving state point and the stable region of the phase plan as the instability criterion,the logical judgment rules of vehicle lateral instability,the selection formula of instability threshold and stability boundary coefficient are determined to improve the accuracy of vehicle lateral instability judgment.（2）The estimation algorithms of key control parameters of vehicle lateral stability are designed.Firstly,the vehicle yaw rate and front wheel angle are used as the judgment conditions of vehicle steady-state response to determine the driving direction and steering state of the vehicle.Secondly,considering the strong nonlinearity in the actual driving process,a model-based vehicle sideslip estimation algorithm is designed based on the unscented kalman filter theory.Then,aiming at the diversity of working condition types,based on fuzzy control and recursive least squares theory,a vehicle mass estimation algorithm considering working condition information is proposed.Finally,the algorithm is verified under different adhesion coefficient roads and the estimated error can be kept within 5%.（3）The coordinated control algorithm of hybrid system and vehicle lateral stability is developed.Firstly,based on the two-degree-of-freedom vehicle reference model and model predictive control algorithm,the additional yaw moment required for vehicle instability is calculated.Then,in the combined driving mode,the target braking wheel under oversteer and understeer conditions is determined,and the additional yaw moment distribution control strategy is formulated.Finally,in order to ensure the dynamic performance of the vehicle,the optimal control problem with multiple constraints is considered.Combined with the rapid response characteristics of the motor,the lateral instability coefficient of the vehicle is introduced,and the optimization algorithm based on quadratic programming is designed.Based on this,the joint simulation test platform and hardware-in-the-loop test are built to analyze the vehicle lateral stability of different control algorithms under typical operating conditions,and to verify the control effect and real-time performance of the proposed algorithm.