Study On Control Strategy Of Regenerative Braking For Electric Bus Based On Braking Comfort

As the governments pays more and more attention to the environmental pollution and the shortage of energy, the electric vehicle development also entered a new stage along with it. The electric vehicle development is a rare historicl opportunity in fierce competition of the international automobile industry competition for our country, Also one of the important strategic measure for enhance automobile industry international competitiveeness. However, since the limited driving range of electric vehicle has been restrict popularity and development of the electric vehicle, Therefore improve the electrical energy utilization and the driving rang is the problem to be solved in the electric vehicle development process. Compared with the traditional automobile the electric vehicle can undertake regenerative braking, the partly braking will be kinetic energy into electricity recycled to the battery for reuse, Thus improve driving range of electric vehicle, regenerative braking technology has been the development of electric vehicle as the key technology more and more attention.Electric vehicle braking system is different from the traditional internal combustion engine vehicle, The braking torque consists of both, the regenerative braking torque caused by the motor braking, and the friction braking torque by conventional brake, both constitute the sum total braking torque of electric vehicle. Electric vehicle during braking, the regenerative braking system cannot be done individually braking, Must be with the traditional mechanical braking cooperate to complete, Because of regenerative braking torque participation braking, changed the original mechanical braking system braking performance, Therefore, the electric vehicle braking system design will be faced with the following questions:(1)Reasonable allocation regenerative braking torque and mechanical friction braking torque in front and rear axle, improve comfortableness for occupant under the premise of meeting braking safety requirements, Avoid joining regenerative braking function later automobile actual braking deceleration greater than traditional automobile in the same target braking strength, or is stepping on time gradually the brake pedal, the automobile deceleration has the obvious change to cause the occupant feeling unwell. (2)Distributing the share of regenerative braking in the total braking demand reasonably within the regulation requirements, to recapture as much braking energy as possible under the premise of the crew comfortableness. (3)The automobile has regenerative braking in the braking, to ensure the braking safety requirements, the braking distance is not greater than Conventional vehicles under the same conditions the braking distance when braking.The regenerative braking energy recovery control strategy of electric bus is one of the important links in vehicle development, at present, at home and abroad, the research on this issue is commonly focused on making the automobile slow down through automobile raking motor brake and hydraulic brake system working together, the regenerative braking control strategy of his article is not only do not change the original hydraulic braking system but also plus the electric braking system. Based on the studied and summarized of predecessors' achievements, designed the regenerative braking control strategy of CA6700E electric high-grade business minibus, The main content of this study are as follows:(1) After considering the power generation of electric motor under different condition, battery allowed charging power and range of regulatory requirements use regenerative braking, recycling kinetic energy to improve energy utilization efficiency and the driving rang of electric vehicles.(2) Due to the add of the regenerative braking to the conventional braking, the comfortableness of the crew changed during the braking, so this paper choose different algorithm of regenerative braking considering the generating power of the motor, battery charging power, the regulation requirements etc, to guarantee the comfortableness of the personnel.In this paper, a primary discussion is sitting comfort for passengers when composite braking system of electric vehicle braking, The main research work and conclusions are as follow:(1) Doing dynamic analysis of the electric bus when braking, and have made some calculation according to the structure parameters of the bus, brake structure parameter, motor parameter, battery parameter and the requirements of ECE braking regulation, the calculation lay a foundation for the making of the regenerative braking algorithm of the electric bus.(2) The brake pedal of the original bus modified by adding a angular sensor to study the relationship of the deceleration and the brake pedal angle. Analyzed the reason for the decrease of the comfortableness, and make two regenerative braking algorithm combined the analysis above. One algorithm is based on the maximum energy recovering and the second is based on the fixed ratio of the comfortableness. Then simulation and comparing is done according the two algorithms above, which shows that the second algorithm is better than the first in comfortableness .(3) The algorithms are programmed under the engineering software CoDeSys, then it will be downloaded to the vehicle controller of the CA6700E electric graded business bus to do the test. The analysis of the experiment result shows that the algorithm based on the fixed ratio of the braking comfortableness has a increase in comfortableness than the algorithm based on the maximum energy recovering, which has reach the goal of the paper .