Study On Cooperative Control Algorithm Of Regenerative Braking And ABS For Electric Vehicle

As electric vehicles become development trends in auto industry, its related systemsresearch is becoming more and more attention. As the inherent advantages of the electric careconomy, Regenerative braking system has become one of the essential system of electricvehicles. In vehicle security aspect, antilock braking system received widely praised for itssignificant role to reduce the braking distance and to protect the safety of person. Due to theoutstanding performance of the two systems in their respective fields, the integration of thetow systems in electric vehicle will become an inevitable trend.However, due to the power source, the control method and the target of the two systemsare different, they will appear incongruous if integrated into one control system. In this studydirection, domestic and foreign scholars have carried out some research. But most of themmake the motor torque exit or limit the motor braking torque based on vehicle safety. Fewscholars consider the problem with the restriction and the dynamic response of the twosystems. This article is aimed at this problem, based on the research projects of cooperationwith FAW Group and takes a certain type electric vehicle of FAW Group for example tostudy on cooperative control algorithm of regenerative braking and anti-lock braking system.This study mainly composed by the following aspects:(1) Study on how to estimate tire-road friction before the trigger point of antilockbraking system. Firstly in this paper the force analysis of vehicle has been studied. The studyfound that the vehicle braking intensity can replace tire-road friction coefficientapproximately before the trigger point of antilock braking system.(2) Study on the restrictive conditions of regenerative braking system, antilock brakingsystem and software structure for coordinated control algorithm. In the antilock brakingsystem restrictive conditions research, phase plane method is used to analyzing the relationof braking torque and slip rate. According to the analysis result, the concept that torque range which will not affect the antilock braking system to dynamically adjust is raised. In theresearch of software, two software structures have been raised. One is the structure in whichthe antilock braking system algorithm can be modified. The other is the structure in whichthe antilock braking system algorithm can’t be modified.(3) Design three cooperative control algorithms of Regenerative Braking and antilockbraking system. Three control algorithms are designed based on the restrictive conditions ofthe two systems and software structure. Algorithm one is motor braking torque completelyexiting after the trigger point of antilock braking system. The original brake antilockalgorithm threshold and control status are used in this algorithm. Reduce the motor brakingtorque in the process of decompression and the motor braking torque unchanged in otherstates. With this method, motor braking torque can exit completely. This algorithm is simpleand easy to implement, but the control effect is not good. Algorithm two is motor brakingtorque exiting to stability range after the trigger point of antilock braking system. With theconcept that torque range which will not affect the antilock braking system to dynamicallyadjust, the goal of algorithm is make the motor braking torque in the range. Firstly thisalgorithm will calculate a tire-road adhesion coefficient which doesn’t affect the antilockbraking system to dynamically adjust. Then Compare this coefficient of the estimated roadfriction coefficient. If this coefficient is big, the motor braking torque will reduce in the firstcontrol loop. If this coefficient is small, the motor braking torque will be hold on. Both thetwo control process can avoid the frequency conversion of the two systems. Algorithm threeis motor braking torque completely exiting before the trigger point of antilock brakingsystem. This algorithm is put forward based on antilock braking system’s algorithm fixed.Before the trigger point of antilock braking system, motor braking torque will completelyexit by using he product of a coordinated coefficient and the motor braking torque. Thiscoordinate coefficient is calculated by wheel slip rate, road condition and wheel brakingintensity using fuzzy controller.(4) In the Matlab/Simulink algorithm models and system models have been structured,and Off-line simulation is carried out on the three control algorithms. The simulation conditions are developed according to GB/T13594-2003. And considering the evaluationindex of each of the two systems, in this paper braking distance, SOC and whether the wheelwill lock are chosen to evaluate the algorithms. At last the three algorithms are proved valid.And the different of the three algorithms will be discussed.(5) Use hardware in loop simulation platform to simulating control algorithm two. Fromthe simulation results, algorithms’ validity and operability are proved.