汽车的智能化和无人化发展增加了对汽车总线网络的依赖,如汽车的实时动力控制、操纵控制等均需要借助车载CAN网络作为信息传递的媒介。然而不像工业互联网等具有完善的信息鉴别和身份认证机制,车载CAN网络缺乏足够的安全防护措施,容易...汽车的智能化和无人化发展增加了对汽车总线网络的依赖,如汽车的实时动力控制、操纵控制等均需要借助车载CAN网络作为信息传递的媒介。然而不像工业互联网等具有完善的信息鉴别和身份认证机制,车载CAN网络缺乏足够的安全防护措施,容易被不法分子入侵。因此,为提高车载CAN网络的安全通信保障,本文提出一种基于样本熵的入侵检测系统(sample entropy-intrusion detection system,SE-IDS)。具体地,通过实时采样汽车的总线数据构建样本熵测试集,利用样本熵的计算方法统计样本熵值,通过观察熵值的突变情况确定该时刻是否有攻击发生。此外,利用实际汽车ECU(electronic control unit)进行了硬件在环测试,分别验证了提出的方法对DOS(denial of service)攻击、模糊攻击、bus-off攻击的检测能力。测试结果表明,DOS攻击、模糊攻击、bus-off攻击均会使稳定的样本熵值出现不可导点,可以据此作为通信异常的标志,从而确定CAN网络遭受的入侵行为。此外,嵌入式设备的在线检测同样验证了该方法在实际ECU上的实时执行能力。展开更多
定子无磁轭模块化(yokeless and segmented armature,YASA)轴向磁通永磁电机具有功率密度和转矩密度高、效率高、轴向结构紧凑、易于维修的优点,在电动汽车、风力发电等领域有广阔的应用前景,已有大量文献对YASA电机进行分析研究。该文...定子无磁轭模块化(yokeless and segmented armature,YASA)轴向磁通永磁电机具有功率密度和转矩密度高、效率高、轴向结构紧凑、易于维修的优点,在电动汽车、风力发电等领域有广阔的应用前景,已有大量文献对YASA电机进行分析研究。该文基于国内外对YASA电机已开展的研究工作,介绍该类电机的典型拓扑结构,并从电机电磁特性计算方法与性能优化、损耗分析与抑制技术、温升与散热研究、齿槽转矩削弱技术、结构强度校核与制造偏差分析,以及定子铁心材料选取等方面进行综述,并对该类电机当前的应用情况进行整理。最后,基于YASA电机的研究现状,对未来研究的发展趋势进行展望。展开更多
The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type...The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system(HPCRS)including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.展开更多
Selective Catalyst Reduction(SCR)Urea Dosing System(UDS)directly affects the system accuracy and the dynamic response performance of a vehicle.However,the UDS dynamic response is hard to keep up with the changes o...Selective Catalyst Reduction(SCR)Urea Dosing System(UDS)directly affects the system accuracy and the dynamic response performance of a vehicle.However,the UDS dynamic response is hard to keep up with the changes of the engine's operating conditions.That will lead to low NO_χconversion efficiency or NH_3 slip.In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions,an advanced control strategy based on an air-assisted volumetric UDS is presented.It covers the methods of flow compensation and switching working conditions.The strategy is authenticated on an UDS and tested in different dynamic conditions.The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS.The inject deviation range is improved from being between-8%and 10%to-4%and 2%and became more stable than before,and the dynamic response time was shortened from 200 ms to 150 ms.The ETC cycle result shows that after using the new strategy the NH_3 emission is reduced by 60%,and the NO_χemission remains almost unchanged.The trade-off between NO_χconversion efficiency and NH_3 slip is mitigated.The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine's operating conditions quickly.展开更多
文摘汽车的智能化和无人化发展增加了对汽车总线网络的依赖,如汽车的实时动力控制、操纵控制等均需要借助车载CAN网络作为信息传递的媒介。然而不像工业互联网等具有完善的信息鉴别和身份认证机制,车载CAN网络缺乏足够的安全防护措施,容易被不法分子入侵。因此,为提高车载CAN网络的安全通信保障,本文提出一种基于样本熵的入侵检测系统(sample entropy-intrusion detection system,SE-IDS)。具体地,通过实时采样汽车的总线数据构建样本熵测试集,利用样本熵的计算方法统计样本熵值,通过观察熵值的突变情况确定该时刻是否有攻击发生。此外,利用实际汽车ECU(electronic control unit)进行了硬件在环测试,分别验证了提出的方法对DOS(denial of service)攻击、模糊攻击、bus-off攻击的检测能力。测试结果表明,DOS攻击、模糊攻击、bus-off攻击均会使稳定的样本熵值出现不可导点,可以据此作为通信异常的标志,从而确定CAN网络遭受的入侵行为。此外,嵌入式设备的在线检测同样验证了该方法在实际ECU上的实时执行能力。
文摘定子无磁轭模块化(yokeless and segmented armature,YASA)轴向磁通永磁电机具有功率密度和转矩密度高、效率高、轴向结构紧凑、易于维修的优点,在电动汽车、风力发电等领域有广阔的应用前景,已有大量文献对YASA电机进行分析研究。该文基于国内外对YASA电机已开展的研究工作,介绍该类电机的典型拓扑结构,并从电机电磁特性计算方法与性能优化、损耗分析与抑制技术、温升与散热研究、齿槽转矩削弱技术、结构强度校核与制造偏差分析,以及定子铁心材料选取等方面进行综述,并对该类电机当前的应用情况进行整理。最后,基于YASA电机的研究现状,对未来研究的发展趋势进行展望。
基金Supported by National Natural Science Foundation of China(Grant No.51076014)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20101101110011)
文摘The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system(HPCRS)including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.
基金Supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2012AA111708)
文摘Selective Catalyst Reduction(SCR)Urea Dosing System(UDS)directly affects the system accuracy and the dynamic response performance of a vehicle.However,the UDS dynamic response is hard to keep up with the changes of the engine's operating conditions.That will lead to low NO_χconversion efficiency or NH_3 slip.In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions,an advanced control strategy based on an air-assisted volumetric UDS is presented.It covers the methods of flow compensation and switching working conditions.The strategy is authenticated on an UDS and tested in different dynamic conditions.The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS.The inject deviation range is improved from being between-8%and 10%to-4%and 2%and became more stable than before,and the dynamic response time was shortened from 200 ms to 150 ms.The ETC cycle result shows that after using the new strategy the NH_3 emission is reduced by 60%,and the NO_χemission remains almost unchanged.The trade-off between NO_χconversion efficiency and NH_3 slip is mitigated.The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine's operating conditions quickly.