Research On Integrated Control Of Brake-by-wire System And Semi-active Suspension On Braking Conditions For The Vehicle

As an important part of the chassis of the vehicle,the brake system and the suspension system are directly related to the safety and comfort of the vehicle driving process.With the development of modern vehicles in the direction of intelligence,integration and electrification,brake-by-wire system and semi-active suspensions have gradually become the trend of electronic chassis control in the future.On the braking condition,the longitudinal deceleration of the vehicle will cause changes in the attitude of the vehicle body,which in turn affects the ride comfort.At the same time,the change of the dynamic load of the wheel caused by the semi-active suspension control will affect the tire adhesion ability,which also in turn affects the safety of braking.However,the simple superposition of the independent control of brake-by-wire system and semi-active suspension,it is difficult to give full play to the advantages of their respective systems to improve the overall performance of the vehicle.Therefore,in order to further improve the comprehensive performance of the vehicle during driving,how to integrated control brake-by-wire system and semi-active suspension becomes a problem to be solved.This paper is aimed at the car with active braking function,and studies the following problems for the integrated control of brake-by-wire system and semi-active suspension on braking conditions:(1)Parameter identification of the brake-by-wire system and design the wheel cylinder pressure controller.Explain how brake-by-wire system works and establish the math model of brake-by-wire system,including high pressure accumulator model,motor pump model,solenoid valve model and brake wheel cylinder model.Based on the hardware-in-the-loop test platform of brake-by-wire system,get the wheel cylinder pressure response characteristics to the parameters of the wheel control cylinder of brake-by-wire system are identified to complete the simulation model.In addition,considering the actual hardware characteristics of the brake-by-wire system,design the anti-integral saturation PID wheel cylinder pressure controller and verify the wheel cylinder pressure controller by simulation and rapid control prototype test.The results show that the anti-integral saturation PID wheel cylinder pressure controller can meet the requirements of wheel cylinder pressure controlling for the brake-by-wire system which are building up pressure quickly and controlling pressure accurately.(2)Establish the vehicle dynamics models and design the semi-active suspension model predictive controller.Firstly,a five-degree-of-freedom half-car model considering longitudinal and vertical coupling relationship and a seven-degree-of-freedom half-vehicle model including wheel rolling model are established.Also establish the tire model,road input model and MR damper model.Among them,the five-degree-of-freedom half-car model is used to design the semi-active suspension predictive controller.MR damper model is established by parameter identification based on hyperbolic tangent model using the damper characteristic test data by genetic algorithm.According to the identified positive model of MR damper,the inverse model is derived for subsequent semi-active suspension control.Finally,design the state observer for vehicle state observation and road input estimation and design the semi-active suspension model predictive controller,which lays a foundation for integrated control of brake-by-wire system and semi-active suspension.(3)Research on integrated control of brake-by-wire system and semi-active suspension.Propose the overall architecture of integrated control of brake-by-wire system and semi-active suspension.Design the target deceleration following controller for brake-by-wire system and divide the braking conditions into non-emergency braking conditions,emergency braking conditions and ABS conditions based on the planning of longitudinal braking deceleration and vehicle status.Analyze the performance requirements of semi-active suspension on each above braking condition.In addition,this paper studies on integrated control of ABS and semi-active suspension.A compensated ABS sliding mode variable structure control based on semi-active suspension model predictive controller tire vertical force prediction is proposed.Based on integrated control architecture,use improved PSO algorithm to optimize semi-active suspension controller’s parameters offline according to the suspension performance requirements under different braking conditions which transforms the multi-objective optimization problem into a single comprehensive target problem.(4)Simulation and analysis of integrated control of brake-by-wire system and semi-active suspension.To verify the effectiveness of brake-by-wire system and semi-active suspension sub controllers and the strategy of integrated control,establish the simulation platform of integrated control of brake-by-wire system and semi-active suspension based on MATLAB/Simulink for four typical braking conditions including non-emergency braking conditions,emergency braking conditions,adaptive cruise and brake conditions and ABS conditions.The result shows that the strategy of integrated control of brake-by-wire system and semi-active suspension in this paper can improve the overall performance of the vehicle driving process.