Research On The Anti-lock Braking System Chamber Pressure And Wheel Brake Torque Identification Of Commercial Vehicle

In recent years,the driving safety of commercial vehicles has received more and more attention.Among the vehicles' active safety systems that ensure the safe driving,anti-lock braking system(ABS)plays an important role.During the vehicle braking,anti-lock braking system prevents wheels from locking,so as to ensure that the vehicle has steering capability.At present,most of the commercial vehicles are equipped with pneumatic anti-lock braking system.Compared to hydraulic system,pneumatic braking system is very different in various aspects,and its working process is more complex.From the actual situation,we should consider the dynamic characteristics of pneumatic anti-lock braking system.The purpose of this paper is to study the anti-lock braking system chamber pressure characteristics and identify wheel brake torque of commercial vehicles,at the same time,study the related characteristics.The research of this paper lays foundation for the theoretical research and practical application of the pneumatic ABS.First of all,this paper reads lots of literature to understand the composition and the basic working principle of pneumatic anti-lock braking system.And the principle of the pneumatic brake test bench is introduced,and the performance test about the ABS solenoid valve is carried out on the test bench.By applying different control signals to the solenoid valve to control the brake chamber to increase pressure,hold pressure and decrease pressure,the corresponding curves and data are obtained,which lay the foundation for further research.Then,the theoretical basis of pneumatic transmission is introduced to lay foundation for the follow-up brake chamber pressure modeling.The brake chamber pressure estimation mathematical model is built.The brake valve is simplified to the nozzle,the displacement of the primary piston of brake valve is input,and the pressure estimation model is obtained through the air mass flow in the brake chamber.At the same time,the PV characteristic curve of the pneumatic braking system is proposed by comparing the PV characteristic curve of the hydraulic braking system,and this is the other method used to estimate the air pressure.Then,the temperature model of the brake is established,which is used to simulate the temperature change process of the brake,and to prevent the phenomenon of thermal degradation during braking.And then the identification method of wheel brake torque is put forward,this method can obtain the brake torque according to the brake chamber pressure and does not depend on the brake structure.Because the ABS control strategy needs to know the road adhesion coefficient to adjust the threshold value of the control strategy in real time,the method of estimation the road adhesion coefficient is proposed.Next,the simulation model of the mathematical model is built in Simulink.We set up the vehicle model and the simulation conditions in Truck Sim and verify the accuracy of the built model through the joint simulation of Simulink and Truck Sim.Simulation results show that the model is in line with the actual situation,and they can accurately represent the change of the required characteristics.Finally,the Hardware-in-the-loop Simulation(HILS)experiment is conducted based on the semi physical situation to further verify the feasibility of the model.We connect the pneumatic ABS test bench and Simulator and Micro Auto Box which are both produced by the d SPACE Company,and build the HILS test bench.The model we build is downloaded into Micro Auto Box,and the vehicle model is downloaded into Simulator.We could control the brake chamber pressure of the pneumatic ABS test bench through Micro Auto Box.The simulation results show that the model also has good accuracy.