Study On Algorithm Of Anti-lock Braking System For HEV Bus

The current development of ABS applications has been very wide and mature, as animportant part of passenger train braking system and also has been widely applied in the busbraking systems specifically for the hybrid electric buses. Depth Study of ABS controlalgorithm of ABS braking system in the hybrid electric bus and develop practical ABScontrol algorithm with its verification.1. Introduction and analysis of ABS system in hybrid busAccording to the ABS control theory, vehicle braking slip rate is15%~20%, when theadhesion coefficient utilization rate reached a maximum value ABS control of slip rate inthis range so it can avoid locking, but also can improve the handling and stability of vehicleand shorten braking distance.ABS is composed of three parts controller, pressure regulator and wheel speed sensor.The wheel speed sensor output is the wheel speed signal input to the controller through afilter. The controller based on the wheel speed signal and road recognition judgment whetherthe wheel is locked to the trend, then the pressure regulator issued a directive forpressurization, decompression or holding pressure control, the purpose is to adjust thebraking pressure to prevent wheel locking.The control channel hybrid electric bus ABS with various kind control modes, such as:high selection control, low selection control, independent control, and correctionindependent control. This paper adopts the method of independent control of hybrid electricvehicle’s front and rear axle using the modified independent control mode.A detailed analysis of hybrid electric bus ABS in the three key problems respectively:control logic design, the reference speed estimation and identification method.2. Research on control algorithm of ABS system of hybrid busABS control algorithm are: PID control algorithm, fuzzy control algorithm, logicthreshold control algorithm. This paper select logic threshold control algorithm, the logicthreshold control algorithm has been very mature in China; ABS products are almost always in logic threshold control. This paper will deeply study of logic threshold estimation method,the reference vehicle speed control of several algorithms such as: maximum wheel speed,slope method and comprehensive method, analyzes their advantages and disadvantages aswell as application during development. The estimation of parameters based on slip ratio,this paper analyzes its important role in the control logic in the process, and puts forward theslip correction constant (C). In this paper, analysis of the acceleration threshold effect onABS control logic, thus emphasizing the causes of failure lies in the choice of controlacceleration threshold unreasonable (too small or too large). In addition, the controlalgorithm of ABS, road recognition technology is an important factor to influence the effectof ABS control; different pavements need different control logics. Finally, this strategy isdeveloped, including the various road anti-skid control: high friction road control, the lowadhesion road control, separate road control and docking road control.Between the motor braking torque and brake torque for both interfere with each other, iscaused by the characteristics of two sets of brake system is not the same, so in this paper,two kinds of braking system dynamic response characteristics are studied, the conclusion,features faster motor braking system than dynamic air brake system response, thecoordinated control algorithm regenerative braking and ABS is presented in this paper.3. Modeling and Simulation of vehicleAimed at the vehicle system were studied in detail, such as the tire model, brake modeland vehicle model. Two kinds of analysis commonly used tire model and comparing theadvantages and disadvantages between them. Use Matlab/Simulink to build the systemmodel of a vehicle, is established by using the Stateflow control logic. Then the off-linesimulation under various conditions. The simulation results verify the validity of thedeveloped control algorithm of ABS.4. Real vehicle testsThe real test in various roads, including the open surface test, road test, docking highadhesion test and the low adhesion road. Through the real car test, ABS control algorithm isdeveloped in this paper can adapt to different road, various braking conditions.This article has use a real vehicle to verify that the ABS control algorithm, developedon the results of the analysis prove the validity and enforceability of the algorithm but there is a certain distance away from the product.