| With the vigorous development of China's road transport industry,the production of trailers has increased,so the brake safety requirements for trailers are getting higher and higher.At the same time,the market for hydraulic retarders has grown and matured.With the deepening of the research on the braking performance of the hydraulic retarder,it is more and more urgent to study the coordinated control of the combined braking system composed of the traditional pneumatic brake system and retarder.At present,domestic and foreign scholars have made some research progress in the field of combined braking system,but they are mostly limited to pneumatic brakes and regenerative braking,electromagnetic braking,eddy current retarders and other forms of integrated braking systems.There is little research on the combined braking system consisting of air brake system and hydraulic retarder.Through the analysis of domestic and foreign literatures,it is found that the scholars mainly study the air brake and the hydraulic retarder brake as two independent braking systems.Therefore,for the combined braking system of pneumatic brake and hydraulic retarder,the following research is carried out:(1)The model of pneumatic brake system is established.The hysteresis characteristics of the model are verified by simulation and real vehicle test.The accuracy of the simulation model of the pneumatic brake system is verified and provides a basis for subsequent research.The influence of braking hysteresis on the braking performance of the car train's pneumatic braking system is simulated.The results show that the braking hysteresis has a negative effect on the braking efficiency and the directional stability during braking.In order to improve the brake hysteresis of the trailer's pneumatic brake system,the structural improvement scheme of the air brake system was proposed,and the simulation analysis,bench test and road test were carried out.The simulation and experimental results show that the proposed scheme can effectively improve or even eliminate the brake hysteresis,and can significantly improve the braking performance of the pneumatic brake system from the braking distance and braking time,and can significantly improve the braking directional stability.(2)The structure and working principle of the hydraulic retarder are introduced.The mathematical model of the braking torque of the hydraulic retarder is established.According to the braking torque of the various gears of the hydraulic retarder and the characteristic curve of the transmission shaft speed,a new braking torque segmentation function is established.For the hydraulic retarder placed in the gearbox,this paper analyzes the influence of the retarder on the braking force distribution of the car train,and simulates the influence of the hydraulic retarder on the braking stability of the car train.Test verification is made as well.The analysis results show that the hydraulic retarder can shorten the braking distance and braking time of the tractor-semitrailer,but at the same time,the hydraulic retarder deteriorates the hysteresis characteristics of the braking system and has a negative impact on the stability of the car train during braking.And on the low-attachment road,the high-speed retarder braking force intervention may cause the vehicle to be slightly locked and dragged.(3)A coupled nonlinear model of the combined braking system of pneumatic brake and hydraulic retarder is established.The combined braking system is simplified into a dual inertia system for analysis.The dynamic equilibrium equation of the output torque of the hydraulic retarder,the elastic axis model and the backlash nonlinear model are established respectively,and the nonlinearity in the combined braking system is analyzed.The mechanism of the generation of factors is analyzed as well.The Bode diagram is drawn by the state space equation and the transfer function.The effects of the elastic characteristics of the shafting system and the nonlinearity of the backlash on the coupling of the combined braking system are analyzed respectively.The active compensation control target is proposed according to the coupled nonlinear mechanism of the combined braking system.Based on the hybrid theory,the state of the combined braking system is estimated.The PID algorithm is used to actively compensate the shafting elasticity.Based on the sliding film control algorithm,the backlash nonlinearity is actively compensated and controlled,and the control algorithm is simulated and verified.The simulation results show that the active compensation control of the combined braking system reduces the negative impact of the coupling nonlinearity of the combined braking system,and effectively improves the control accuracy and control quality.(4)The hybrid characteristics of pneumatic brake and hydraulic retarder combined brake system are analyzed.The switching rules of pneumatic brake and hydraulic retarder combined brake hybrid system are designed.The pneumatic brake and hydraulic force are established based on Petri net model.Based on the Petri net model,a hybrid braking system model of pneumatic brake and hydraulic retarder is established.The system stability of the pneumatic brake and hydraulic retarder combined brake hybrid system in the switching process is proved.Based on BP neural network inverse system theory,the decoupling controller of pneumatic brake and hydraulic retarder combined braking system is designed.Combined with the nonlinear compensation control coupled with pneumatic brake and hydraulic retarder combined braking system,the combined brake system controller is designed.The simulation control of the air brake and hydraulic retarder combined brake system switching control is carried out.Based on the genetic fuzzy immune PID algorithm,the constant speed brake control strategy for the train downhill condition of the semi-trailer is designed.The effectiveness of the control strategy is verified by simulation.(5)The combined braking system coordinated control test platform is constructed.The test platform includes the hardware part and the software part.It realizes the detection and acquisition of the vehicle driving parameters,and realizes the charging of the pneumatic brake and the hydraulic retarder combined braking control strategy.The experimental results verify the feasibility of the coordinated control scheme of the combined braking system proposed in this paper,and verify the effectiveness of the coupled nonlinear active compensation algorithm for the combined braking system. |
PDF Full Text Request