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电动汽车再生制动若干关键问题研究

Research on Key Problems of Regenerative Braking for Electric Vehicles

【作者】 赵国柱

【导师】 魏民祥;

【作者基本信息】 南京航空航天大学 , 车辆工程, 2012, 博士

【摘要】 再生制动是电动汽车节能的重要途径之一。电动汽车再生制动的工程应用存在诸多关键问题有待解决。本文主要研究如下三个问题:1.如何提高城市工况下后驱型串联式混合动力电动公交车、纯电动公交车并联再生制动策略的制动稳定性与制动能回收能力;2.如何利用再生制动与行车制动系协同作用控制直流电动机驱动的电动客车恒速下坡;3.如何使无刷直流电机电动汽车在结冰等低附着系数路面上进行纯再生制动时驱动轮具有再生ABS功能。为增强城市工况下后驱型串联式混合动力电动公交车、纯电动公交车现有并联再生制动策略的制动稳定性与制动能回收能力,提出一种技术简单、附加成本小的新型并联再生制动策略。该策略在行车制动系中引入惯性比例阀等制动力调节装置,机电并行制动时,利用惯性比例阀适当缩小机械制动力的制动比例,相应提高了再生制动力的制动份额。同时,该策略结合典型城市工况下公交车的运行实际,以ECE R13制动法规为准则,将机电并行制动的制动强度确定在0.1与0.3之间,以确保车辆机电并行制动时的制动稳定性。为验证新型并联再生制动策略的能量回收效果,对advisor2002电动汽车仿真软件进行二次开发,建立后驱型电动汽车仿真平台,仿真结果表明该策略能显著提高城市工况下制动能回收率。为利用再生制动作为辅助制动控制直流电动机驱动的电动客车恒速下坡,根据电动汽车驱动电机控制方法具有双环控制结构的特征与直流电机PWM控制系统具有变结构的特点,提出采用双滑模面变结构控制方法来控制该车恒速下坡再生制动。分析了铅酸蓄电池长时间充电接受力对驱动电机再生制动力的影响。建立了电动客车下坡动力学模型。设计了该车恒速下坡再生制动双滑模面控制器。仿真结果表明系统具有足够的稳定性和强健的鲁棒性;受蓄电池充电接受力的限制,仅用再生制动,只能在极小的坡道上(如i2%)控制车速,而且动态特性不理想;当坡度较大(如i2%)时,在减速及恒速状态下,均需机电并行制动才能有效控制车速。为使无刷直流电机电动汽车具有再生ABS功能,提出通过调节PWM占空比的方法来实现驱动轮的再生ABS功能。建立了再生ABS的使能条件;推导了驱动轮动力学数学模型;设计出再生ABS双闭环控制模型,并搭建该系统的SIMULINK仿真模型。仿真结果表明,系统具有良好的动态特性与稳定性;与滑移率的PI控制相比,滑移率在变结构控制时,系统具有更强的鲁棒性;与单管PWM调制模式相比,双管调制时,系统的控制品质更好,制动距离更短,能量回收更多。根据单管调制模式下的无刷直流电机再生制动原理,设计并制作该电机驱动的电动汽车再生ABS半物理仿真试验平台。验证了试验台在结冰等低附着系数路面进行再生制动时具有ABS功能的工程可行性。

【Abstract】 Regenerative braking is an important way to improve energy efficiency in electric vehicles. Thereare many key unresolved problems in the application of regenerative braking in electric vehicles (EV).The following three questions are studied in the dissertation. The first is how to improve the brakingstability and increase the recovery of the braking energy of a rear-drive series hybrid or pure electricurban bus using parallel regenerative braking strategy. The second is how to maintain a constant speeddownhill using cooperative braking realized by a service-brake and regenerative brake system for aDC motor driven electric bus (DCMEB). The third is how to make the drive wheels of an EV drivenby in-wheel Brushless Direct Current Motors (BLDCM) retain the anti-skid braking function whileonly performing regenerative braking actions on low adhesion coefficient roads (such as ice-orsnow-covered road).With aims of improving the parallel regenerative braking strategy for a rear-drive series hybrid orpure electric urban bus, a novel parallel regenerative braking strategy with a simple technique and asmall additional cost is proposed. According to this new strategy, Braking force distribution ratio of amechanical braking system during electro-mechanical parallel braking is adjusted to maximum withinEuropean Regulation13(ECE R13) permissible range by inertia proportional valve, and the amountof the regenerative braking force is corresponding increased. On the other hand, with a considerationon engineering practices of an electric urban bus, the braking intensity is determined between0.1and0.3to ensure the braking stability in this condition. To verify the effect of the new strategy, taking aseries hybrid electric bus simulation model in ADVISOR2002as an example, this model isredeveloped to a rear-wheel-drive series hybrid electric bus simulation model. Simulation results withthis strategy show a significant improvement of this bus braking energy reclaiming performance underthe typical urban driving cycles conditions.To use regenerative braking to act as an auxiliary brake to maintain the constant speed of aDCMEB on downhill, based on the feature of double-loop control structure of the control method forelectric vehicle traction motor and the variable structural characteristics of PWM Control System forDC Motor, a double-manifold variable structure control method to control regenerative braking isproposed for the bus cruising downhill. The impact of lead-acid batteries charge acceptance abilityover a long charging period on the regenerative braking force of a driving motor is analysed. Dynamicmodel of the bus on long downhill is established. A double-manifold variable structure controller is designed for the DCMEB on long downhill. The simulation results show that the control systemmaintains enough stability and strong robustness. It may be achieved for the bus to maintain aconstant speed downhill only by regenerative braking on a smaller slope(such as i<2%). But thedynamic process is very slow. When deceleration or constant speed is desire on a larger slope(such asi>2%), only by electro-mechanical parallel braking can the bus track the target speed precisely andquickly.A novel method of anti-skid braking is proposed to control the duty cycle of the PWM powerconverter to retain the anti-skid braking function of an EV driven by BLDCM while only performingregenerative braking actions on ice-or snow-covered road. An enable condition is designed forregenerative and mechanical braking to coordinately active. A single wheel vehicle dynamics model isderived. A double-loop control model of regenerative ABS (anti-skid braking system) is established.On this basis, a simulation model of regenerative ABS is established in MATLAB/SIMULINKenvironment. The simulation results show that slip rate can be quickly stabilized at the target slip rateon whether ice-or snow-covered road in spite of the existence of the modeling error caused by themodel uncertainty. By comparing the VSC controller and the traditional PI controller to control thewheel slip rate, the simulation results show that the system has stronger robustness and disturbancerejection capability with the former controller. The comparative analysis of the regenerative ABS usedsingle and double switching modulation scheme, respectively, shows the advantages of a higherquality control, a shorter braking distance and more energy recovery for the latter.Finally, a semi-physical test bench of regenerative ABS of an EV driven by BLDCM is designedand produced based on the principle of BLDCM regenerative braking under single-tube modulationmode. The engineering feasibility of regenerative braking as anti-skid braking system on the lowfriction coefficient road as ice-covered road is verified for this EV.

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