Research On Optimal Control Method Of Combined Braking For Heavy-duty Trucks

As a high-efficiency freight vehicle,heavy-duty trucks are responsible for the main transportation tasks of our country,but their operational safety has always been a hot issue.Most heavy-duty truck traffic accidents occur on long downhill sections or wet and slippery sections.The main causes of accidents are thermal degradation of service brakes and lateral brake instability.In response to the above problems,the thesis relies on the key industrial innovation chain(group)project of Shaanxi Province(2020ZDLGY16-02)"Key Technologies of Electro-hydraulic Integrated Braking for Hybrid Heavy Commercial Vehicles" and the General Project of Shaanxi Province Key R&D Program(2020GY-110)" Research on Truck Long Downhill Braking Assist Control System Based on In-transit Network Technology" to research on the optimal control method for combined braking of heavy trucks to achieve safe,stable and efficient downhill driving of heavy trucks.Firstly,the longitudinal dynamics model of a heavy-duty truck is established based on the theory of vehicle dynamics,and a mathematical model of the temperature change of the brake drum is established through the thermodynamic analysis of the heat absorption process and the heat dissipation process of the brake drum of the heavy-duty truck.In order to study the mechanical characteristics of the continuous braking system and verify the accuracy of the brake drum temperature change model,the service brake test,the engine brake flat road test and the eddy current retarder brake flat road test were carried out respectively.Through experiments,the mechanical characteristics of the continuous braking system are obtained,the mathematical model of the mechanical characteristics of the continuous braking system is established,and the validity of the mathematical model of the temperature change of the brake drum is verified.Then,based on the vehicle longitudinal dynamics model,a method for estimating the longitudinal gradient of the road using the adaptive extended Kalman filter algorithm is proposed.Taking a heavy tractor as the research object,establish a mathematical model and use Trucksim and Simulink to conduct joint simulations.The accuracy and reliability of the longitudinal slope estimation method are verified on the segmented road model with fixed longitudinal gradient value,the cosine curve longitudinal gradient value road model and the real longitudinal gradient value road model.Finally,a six-degree-of-freedom single-track model of a heavy-duty truck considering the brake drum temperature and tire model is established,and a joint total braking force adaptive MPC controller based on tracking the target reference trajectory is designed,a joint braking optimization control strategy to prevent thermal degradation of the service brake and the lateral instability of articulated vehicles is proposed.Taking a heavy commercial vehicle as the research object,establish a mathematical model and use Trucksim and Simulink to conduct joint simulations.Th effectiveness of the joint braking optimization control method is verified on the downhill turning low adhesion coefficient road model and the long downhill straight line low adhesion coefficient road model.