【作者】 李明；

【导师】 赵国柱；

【作者基本信息】 南京农业大学 ， 机械工程硕士（专业学位）， 2015， 硕士

【摘要】 汽车在山区行驶时,经常遇到下长坡的工况,为保证行驶安全,需要对车速进行必要的控制,因此车辆行车制动系统长时间处于持续制动状态,对于传统内燃机汽车来说,往往采取安装辅助制动系统来缓解制动器的热负荷。而电动汽车可采用再生制动作为辅助制动来减轻行车制动系统的制动负荷,减少制动器升温,提高制动安全性;并且通过再生制动可实现将惯性能量部分转化为电能储存于蓄能器中,从而有效延长电动汽车行驶里程。本文对利用模糊控制实现电动汽车匀速下坡进行了研究。首先对电动汽车再生制动原理、影响因素等进行了简要介绍。在此基础上着重分析了铅酸蓄电池充电能力对再生制动系统的影响,以ADVISOR中的中型电动轿车为例,蓄电池可持续充电能力只能满足该车在坡度小于4.5%的道路上实现匀速下坡,从而提出了利用再生制动系统与机械制动系统协同制动的方法来实现电动汽车匀速下坡车速控制。然后在分析两轴式汽车理想制动力分配曲线以及ECE制动法规对前后轴制动力分配限制的基础上,以制动稳定性和提高再生制动能量回收效率为前提,研究了长下坡时再生制动力与机械制动力的协调分配,提出了满足ECE制动法规要求的电动汽车匀速下坡制动力分配控制策略,该策略根据制动强度的不同确定了前后轴制动力份额以及机械制动力与再生制动力的份额。而后通过对电动汽车匀速下坡制动过程进行动力学分析,建立了基于模糊控制的电动汽车匀速下坡制动力控制策略。该策略可根据道路坡度变化以及目标车速与实际车速速度差实时调节制动力,以实现并维持车辆以目标车速匀速下坡。最后,本文采用Matlab/Simulink建立了电动汽车关键部件仿真模型,包括车辆下坡纵向动力学模型、电机模型、蓄电池模型、制动力分配模型以及制动模式转换模型等。通过仿真分析得出如下结论:设计的模糊控制器控制效果理想,在坡度突变的路面上适应性高,鲁棒性强,取得了理想的制动效果;同时也表明,仅利用再生制动只能控制车辆在小坡道上(如i ≤4.5%)的稳态车速,而且动态特性不理想;当在较大坡道(如i>4.5%)上,若要实现减速制动及维持稳态车速,需要机电复合制动才能完成。更多还原

【Abstract】 In order to ensure the driving safety,the travel speed needs necessary control when the car traveling in the mountain area is in downhill condition.In this period,the vehicle brake system is under continuous braking condition.In case of large heat load of brakes,the load in the brake of the conventional vehicle can be released with the auxiliary braking.Electric vehicle can reduce the mechanical braking load by using the regenerative braking as the auxiliary braking.Consequently,the brake generate less heat and the braking safety can be improved.In the meantime,inertia energy is transformed to electric energy storing to the energy accumulator through the regenerative braking,thus the driving range of electric vehicle can be prolonged.Firstly,this paper gives a brief introduction to the principle and influencing factors for the regenerative braking of cars.On this basis,this paper emphatically analyzes the influence of the charging capacity of lead-acid battery on the regenerative braking system.Taking the medium electric cars from ADVISOR for example,the constant charging capacity of batteries could only ensure that the cars go down in uniform velocity a slope with a slope gradient less than 4.5%.Therefore,this paper proposes a method combining regenerative braking system and the mechanic braking system to realize uniform-velocity of electric cars when going down slopes.Afterwards,on the basis of analyzing the ideal braking force distribution curve of two-axle cars and the restriction on the braking force distribution to the front and rear axles by the ECE braking regulation,aiming at the braking stability and increasing the braking energy recycling efficiency,this paper studies the coordinated distribution of regenerative braking force and mechanic braking force while going down a long slope and proposes the braking force distribution control strategy that meets the ECE braking regulation’s requirement while ensuring uniform velocity of electric cars going down slopes.According to different braking strength,this strategy determines the percentage of the braking force on the front axle and rear axle and the percentage of the mechanic braking force and regenerative braking force.Then,through dynamic analysis on the braking process of electric cars in uniform velocity,this paper establishes the fuzzy control-based braking force control strategy for electric cars in uniform velocity.This strategy could adjust the braking force on a real-time basis according to the changes of slope gradient of roads and the difference between the target speed and actual speed of the car to realize and maintain the cars going down slopes in uniform velocity.Finally,this paper uses Matlab/Simulink to establish a simulating model of critical components of electric cars,including the longitudinal dynamic model for a car going down slopes,the motor model,the storage battery model,the braking force distribution model and the braking mode transformation model,etc.Through simulating analysis,following conclusions are drawn out:using the fuzzy control-based braking force control strategy proposed in this paper could realize reliable control on cars going down slopes in uniform velocity;meanwhile,t also shows that using regenerative braking could only control the stable speed of cars on small slopes(such as i 4.5%)with poor dynamic characteristics;on a large slope(such as i>4.5%),to realize retarding brake and maintain stable speed,the complex mechanic and electric braking is also needed.更多还原