Regenerative Braking Control Strategy Research For Electric Bus Based On Real Load

As the public transport tool,the city electric bus start and stop frequently during the whole drive cycle,the load quality affected by the platform position and the travel time of passengers changes a lot from the passenger flow peak time to the low flow time during the day.Thus,if the relationship between motor braking force and mechanical braking force is adjusted according to different load condition of electric bus,it can improve the recovery of braking energy in premise of meeting the request of the driver’s braking.In this thesis,a regenerative braking control strategy is proposed based on the actual load of electric bus.This strategy has certain theoretical reference value to the design of the braking system of city electric bus and it has certain engineering practicability.The regenerative braking system of city electric bus is introduced firstly in this paper,and the working mechanism and control strategies of motor braking and mechanical braking are introduced in brief.Then force of the rear drive electric vehicle during braking are analyzed,the formulas of adhesion coefficients for both front axle and rear axle are acquired after adding the regeneration braking force.According to the constraints of ECE R13 regulation on utilization adhesion coefficient,the range of regenerative braking power of motor is calculated.On this basis,the optimized mathematical model of the braking system is established by using ECE R13 braking regulation as constraint conditions.The optimization goal of this model is to make sure that the square sum for the difference between adhesion coefficient and braking strength can reach to the least,and genetic algorithm is used to calculate the optimal braking force distribution coefficient under different load cases.Center of mass for the bus is calculated based on the vehicle assembly quality and its center of mass position,and then the center of mass for the bus under different load conditions case are calculated.According to the optimal braking force distribution coefficient acquired from the optimization model,mechanical brake force is allocated under the restriction of ECE R13 regulations.The electro-mechanical brake area when brake strength is in the range of 0～0.3 is gained,which can be used to calculate the front and rear axle mechanical braking force share and the motor braking force share.To carry out the simulation of braking strategy on electric vehicle software ADVISOR,the add-on functions development is made for this software.Rear drive module for the vehicle are embedded in,vehicle driving types selection buttons are added in the input interface to choose drive type conveniently.New control strategy module is added in control library.The strategy is simulated in UDDS cycle under the no-load,half-load and full load cases.The simulation results show that the braking control strategy can increase the amount of regenerative braking energy on the premise of braking stability.The proposed control strategy of this paper is verified in the semi physical simulation platform.The results show that the new control strategy can achieve the desired consequence,it can increase the share of brake motor braking force.