【作者】 闫兵；

【导师】 王金诺；

【作者基本信息】 西南交通大学 ， 机械设计及理论， 2005， 博士

【摘要】 随着内燃机的广泛使用和现代科学技术的发展,传统的事后维修和定时检测已不适应目前视情维修体制的要求;而由于内燃机的复杂性,一般的机械故障诊断技术也难以直接应用于内燃机故障诊断,因此,必须发展针对内燃机特点的状态监测和故障诊断技术。内燃机曲轴角振动信号以其测量简便和信息丰富的优点,得到了国内外的广泛关注,是目前内燃机故障诊断领域的前沿和研究热点。本文针对内燃机曲轴角振动诊断系统研制中,在信号测量、信号处理及诊断方法等关键技术上存在的问题,提出了A/D采样拟合法、畸点滤波法和曲轴角振动简谐诊断法,为研制实用而有效的内燃机曲轴角振动诊断系统奠定了理论基础。 本文首先按照软件加通用硬件替代专用仪器的虚拟仪器设计思想,提出了基于通用A/D采样卡的角振动测量新方法——A/D采样拟合法。该方法具有测量精度较高、硬件成本低、通用性强、测量持续时间长的优点,并能实现角振动信号与其它信号的同步测量。利用A/D采样拟合法测量持续时间长,可以采集较大内燃机工作循环数的优点,进行了内燃机非稳定工况角振动测量分析。揭示了内燃机工况不稳定会导致曲轴角振动信号中存在趋势项这一本质特性,研究了趋势项对扭振分析的影响及消除方法。对A/D采样拟合法进行了完善,提出了消除角振动随机测量误差的循环内多点平均方法。 通过对曲轴角振动信号中干扰信号基本特性的分析,本文提出了一种只衰减周期信号中畸点处误差值而不影响非畸点处原值的畸点滤波法。对畸点滤波法的关键步骤进行了证明,推导了畸点处误差值衰减的规律,估计了畸点滤波法计算量。为适应在线测量或实时控制的运算速度要求,提出了畸点滤波快速算法。畸点滤波法及其快速算法不仅可以用于曲轴角振动信号滤波,还可广泛用于其他各种周期性信号、甚至衰减简谐信号中。为消除衰减简谐信号中的畸点,本文提出了一种先将衰减简谐信号变换为同频简谐信号,再采用畸点滤波法消除衰减简谐信号中畸点的思路。将衰减简谐信号成分变换成同频简谐信号,可用本文提出的模态参数识别新方法——负阻尼傅立叶变换实现。 论文以内燃机动力学和傅立叶变换理论为基础,深入研究了曲轴激振力矩与角振动响应间的关系,首次推导出了多缸内燃机任意测点的简谐角振动与各更多还原

【Abstract】 With extensive applications of internal combustion engine (ICE) and developments of modern science and technology, the conventional breakdown maintenance and periodic monitor methods are not adapted to the demands of present maintenance system. Because of the complexity of ICE, the general mechanical fault diagnosis techniques are difficult to be applied in the diagnosis of ICE, so the condition monitoring and fault diagnosis techniques must be developed to fit in the characteristics of ICE. The crankshaft angular vibration signal of ICE gains abroad attentions both here and abroad for its advantages of simple measurement and abundant information, which is the hotspot in fault diagnosis field of ICE presently. This paper presents the A/D sampling fitting method, the distorted point filtering method and the angular vibration simple harmonic diagnosis method respectively directing towards the key problems existing on signal measurement, signal processing, diagnosis methods, which establish the theoretical basis for studying practical and effective crankshaft angular vibration diagnosis system of ICE.Firstly, following the virtual instrument design principle of software added universal hardware instead of special hardware, it puts forward a new measuring method of angular vibration based on universal A/D sampling card—A/D sampling fitting method which reduces the hardware cost, increases commonality, extents sampling time and can realize the synchronous accurate measurement of angular vibration signal with other signals. A/D sampling fitting method, through adjusting the sampling frequency and data length, can sample smartly the operating cycle number of ICE, angular vibration of unstable operating condition of ICE was measured and analyzed. It also reveals an essential property that there is trend term in angular vibration signal caused by unstable operating condition of ICE, and the effects of trend term on angular vibration analysis and its elimination approaches is studied. When the random measuring error of angular vibration resulted by different reasons is relatively large, it can be eliminated by using the A/D sampling fitting refinement algorithm—multi-point average in one cycle method.Through analysis on the basic characteristic of inference signal in angular vibration signal of crankshaft, a distorted point filtering method (DPF) is presented that only attenuates the errors of distorted point but not affects the real value of non-distorted point in periodic signal. Also it has demonstrated the critical steps of DPF, made a deduction the attenuation rule of the error value of distorted point, and estimated the calculated amount of DPF. Furthermore in order to adapt the calculation speed demands of online measurement or real time control, it also bringsforward fast DPF method. The DPF method and the fast algorithm can be used not only in signal filtering of crankshaft angular vibration signals, but also in other periodic signals and damped harmonic signals. Moreover, for the sake of filtering out the distorted point in damped harmonic signal, it puts forward an idea that changing the damped harmonic signal to simple harmonic signal firstly and then filtering out the distorted point in damped harmonic signal using DPF method. The negative damping Fourier transformation method presented in the paper can be used to transform the damped harmonic signal to simple harmonic signal. It is also a new precise mode parameter identification method.Based upon the dynamics of ICE and Fourier transformation theory, it has studied in depth the relationship between the input excitation moment and the output angular vibration response of crankshaft, and firstly deduced the function relationship of simple harmonic angular vibration of arbitrary measurement point with respective simple harmonic moment of each cylinder in multi-cylinder ICE, namely the basic relationship. Aiming at the present limitations of the rigid and elastic model, by virtue of the orthogonality of simple harmonic vibration, the single order quasi-rigid body model is presented from the point of view of simple harmonic analysis firstly, and two cases satisfying the condition of single order quasi-rigid body model is discussed. Single order quasi-rigid body model is the accurate and simple and practical angular vibration diagnosis kinetic model. Accord to the basic relationship and single order quasi-rigid body model, five deductions are deduced which can be applied in fault diagnosis, and a new angular vibration simple harmonic diagnosis method is established which has the advantages of powerful commonality, accurate diagnosis, simple application, independent of configuration parameters of crankshaft or a great deal of experiments. The new diagnosis method is applied successfully in operation condition monitoring, the misfire cylinder diagnosis, the misfire cylinder rate diagnosis, the gas leakage cylinder diagnosis and the operation uniformity diagnosis of each cylinder.All new methods in this paper are not only deduced theoretically and proved strictly, but tested and verified sufficiently by a great deal of simulated and experimental studies.The research efforts develop the key technology of fault diagnosis system of ICE based on crankshaft angular vibration, has use values on the diagnosis system. Furthermore some generalized meaning research results can also be used to resolve the problems in other relevant fields, and enriches the theories of ICE dynamics, engineering signal processing, measurement techniques, parameter identification of vibration mode and other interrelated subjects.更多还原