| After many system optimization and structural improvement,the braking performance of the braking system has been greatly improved.But most of the brakes system are still based on friction braking,and the negative effects of friction braking,such as noise,dust and thermal decay remain unresolved.Now,automobile intelligent has entered the early stage of industrialization.With the increasing demand for automobile intelligent,traditional brakes are difficult to interface with intelligent systems.Domestic and foreign researchers put forward the idea of integrated design of electromagnetic brake and friction brake.Non-contact electromagnetic brake to share part of the working load of friction brake,and reduce the negative effect of friction brake.combine friction brake and electromagnetic brake to make up for each other’s weaknesses,and then improve the environmental protection and safety of vehicles.However,most of the current studies mainly focus on the design of electromagnetic,friction integrated brake structure,the selection of parameters,the magnetic field analysis of electromagnetic brake,the test of braking performance,the body stability during braking,the anti-lock brake control strategy of electromagnetic brake and the finite element analysis of integrated brake.There are still some shortcomings in the electromagnetic and friction integrated braking switching mode hierarchical coordinated control strategy,electromagnetic brake energy consumption characteristics,integrated brake anti-lock coordination control strategy,and front and rear axle braking torque distribution.Therefore,this paper chooses brake switching mode and anti-lock brake coordinated control as the research objective to conduct in-depth research on integrated brake.This paper aiming at the problem of hierarchical coordinated control of electromagnetic and friction integrated braking system and anti-lock coordinated control of integrated system.First,established a corresponding mathematical model of the electromagnetic brake and friction brake,and analyzed the feasibility of applying hybrid theory to vehicle braking switching mode.Then,proposed a braking switchingmod based on hybrid Extended automata with related control switching strategies,and designed a non-linear ABS control law and an anti-lock braking control algorithm.Finally,relevant bench and hardware-in-the-loop experiments are carried out to prove the rationality of the proposed theory.The main research contents are as follows:(1)Establishment of electromagnetic and friction integrated braking system model.The mathematic models of electromagnetic brake,friction brake and 8-DOF vehicle are established.The model is simulated and tested by MATLAB/Simulink,and the simulation results are compared with the reference objects.The results show that the established mathematical model meets the needs of research and can be used for follow-up research.At the same time,according to the characteristic curve of the electromagnetic braking moment in the simulation results,the minimum working speed of the electromagnetic brake is preliminarily determined to be 150r/min,which is lower than the speed of stopping using the electromagnetic brake.(2)Determination of braking mode switching control strategy for electromagnetic and friction integrated braking system.According to the working characteristics of friction brake and electromagnetic brake in integrated system,the feasibility of hybrid theory applied to brake mode switching is explored.Based on Hybrid Theory and generalized automata principle,a brake mode switching model based on generalized automata is built.The working characteristics of electromagnetic brake and friction brake are analyzed,and the brake mode switching control strategy is determined.A switching model is established by using MATLAB/Stateflow.To solve the problem that the boundary of hybrid system is discontinuous and the traditional continuous system optimization method can not be used,a piecewise gradient descent method is used to optimize the braking mode switching of integrated braking system.Finally,the braking mode switching model is simulated on the experimental platform.The results show that the braking mode switching strategy and model can ensure the braking mode switching smoothly.At the same time,the optimization control algorithm can solve the problem of response delay in the braking mode switching process and improve the reliability of the integrated braking system.(3)The determination of coordinated control strategy for anti-lock braking ofelectromagnetic and friction integrated braking system.The braking moment distribution of front and rear axles and the ratio of electromagnetic and friction braking moment are determined.According to the respective characteristics of electromagnetic brake and friction brake,the anti-lock control strategy of integrated brake system under combined braking mode is determined.A design method of anti-lock brake controller based on time-varying sliding mode variable structure is proposed.The longitudinal velocity is estimated by using sliding mode differentiator instead of generalized Kalman filter to ensure that the system can track the optimal slip rate in real time and improve the system.Braking performance.Finally,the proposed coordinated anti-lock control method of integrated system is verified by simulation software.The results show that the system can effectively reduce the generation of system errors and improve the control effect of slip rate.(4)The braking switching model,anti-lock coordination control of integrated braking system and braking performance of integrated braking system were tested by rapid control prototype platform and hardware-in-the-loop simulation platform.The results show that the integrated system control method proposed in this paper can effectively reduce the corresponding braking time and shorten the braking distance. |
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