WO2022007382A1 - 基于偏相干函数求解非燃烧激励信号贡献度的方法 - Google Patents

基于偏相干函数求解非燃烧激励信号贡献度的方法 Download PDF

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WO2022007382A1
WO2022007382A1 PCT/CN2021/071201 CN2021071201W WO2022007382A1 WO 2022007382 A1 WO2022007382 A1 WO 2022007382A1 CN 2021071201 W CN2021071201 W CN 2021071201W WO 2022007382 A1 WO2022007382 A1 WO 2022007382A1
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signal
excitation
vibration
combustion
contribution
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赵秀亮
王丽梅
潘邦雄
汪若尘
杨政宇
赵明明
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Jiangsu University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M15/00—Testing of engines
    • G01M15/04—Testing internal-combustion engines
    • G01M15/12—Testing internal-combustion engines by monitoring vibrations

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  • the invention relates to a method for calculating a contribution degree, in particular to a method for calculating the contribution degree of a non-combustion excitation signal based on a partial coherence function, and belongs to the technical field of internal combustion engines.
  • the vibration signal of the internal combustion engine is the result of the combined action of combustion excitation and non-combustion excitation such as reciprocating inertial force, valve seating impact force, piston reversing impact force, piston side pressure and crankshaft main journal load.
  • combustion excitation and non-combustion excitation such as reciprocating inertial force, valve seating impact force, piston reversing impact force, piston side pressure and crankshaft main journal load.
  • non-combustion excitation is coupled with the combustion excitation in the time and frequency domains, which makes it difficult to eliminate the non-combustion excitation response signal, and even affects the integrity of the combustion excitation response signal.
  • Contribution degree refers to the ratio of the spectral amplitude of the vibration velocity signal when the main excitation is applied alone to the amplitude of the vibration velocity signal when all excitations are applied at a certain frequency.
  • the characteristics of the excitation and its response signals are comprehensively analyzed, the coupling relationship between the excitation and response signals is studied, and the contribution of the main excitation response signals in the vibration signal is verified, which will eliminate the non-combustion excitation response signals and realize the acquisition of combustion information. and combustion process control to provide a theoretical basis.
  • the present invention provides a method for solving the contribution degree of the non-combustion excitation signal based on the partial coherence function. Analyze the characteristics and intensity of non-combustion excitation sources to determine the main non-combustion excitation sources; determine the non-combustion excitation that plays a primary role in the vibration signal by analyzing the characteristics of the vibration signal; use the partial coherence function to calculate the contribution and variation of the combustion excitation .
  • Step 1 Determine the main non-combustion excitation source, analyze the time domain characteristics of valve opening and closing excitation and adjacent cylinder combustion excitation, solve the excitation source strength of reciprocating inertial force and piston commutation impact force, and obtain excitation sources sensitive to the influence of vibration signals ;
  • Step 2 Determine the non-combustion excitation that plays a primary role in the vibration signal, simplify the actual internal combustion engine structure, retain the body and cylinder head, and establish an engine simulation model; select the measuring point on the model to apply a force hammer, and compare the simulation vibration signal and Measured vibration signal to verify the validity of the model;
  • each excitation vibration response signal is analyzed by compressive wavelet transform technology, and the non-combustion excitation which plays a primary role in the vibration signal is obtained;
  • Step 3 According to the primary non-combustion excitation determined in Step 2, use the partial coherence function to calculate the contribution of the excitation signal to the vibration signal at a specific frequency.
  • the method for solving the excitation source strength of the reciprocating inertial force and the reversing impact force of the piston in the step 1 is as follows: according to the measured pressure signal in the cylinder, the excitation curve of the reciprocating inertial force and the excitation curve of the reversing impact force of the piston, respectively obtain their maximum value.
  • a 10-node tetrahedral mesh is used when establishing the engine simulation model.
  • the body is fixed on the test bench through 4 brackets, and the brackets are restricted to be rigid bodies without deformation. degrees of freedom of orientation.
  • the method for verifying the validity of the simulated vibration signal and the measured vibration signal model in the second step is:
  • the method of analyzing the time-frequency characteristics of each excitation vibration response signal through the compressive wavelet transform technology is as follows:
  • the time-frequency analysis of the excitation response signal is performed to obtain the time-frequency distribution of the vibration displacement, vibration velocity and vibration acceleration signals, and the vibration signal characteristics caused by the reciprocating inertial force excitation and the piston commutation excitation alone are obtained;
  • Two inputs x 1 (t), x 2 (t), the partial coherence function of a single output signal y(t) can be defined as:
  • the present invention determines the contribution of non-combustion excitation signals to the vibration signal, which is the basis for research to eliminate interference in the vibration signal, and helps to repair part of the combustion information in the vibration signal, which is helpful for realizing the extraction of combustion information by using the vibration signal, and the internal combustion engine.
  • Working condition monitoring, closed-loop control of combustion process and fault diagnosis have important theoretical significance and practical value.
  • Fig. 1 is the working phase diagram of valve opening and closing of an internal combustion engine of the present invention
  • Fig. 2 is the measured vibration acceleration signal diagram of the present invention
  • Fig. 3 is the pressure signal in the cylinder of the present invention and the reciprocating inertial force excitation curve obtained by calculation;
  • Fig. 4 is the motive simulation model diagram of the present invention.
  • Fig. 5 is the graph of the vibration acceleration signal obtained by the actual measurement vibration acceleration signal of the present invention and simulation
  • Fig. 6 is the time frequency spectrum diagram of the reciprocating inertial force signal of the present invention.
  • Fig. 7 is the time-frequency distribution diagram of the reciprocating inertial force excitation response signal of the present invention; wherein, Fig. 7 (a), (b) are the time-frequency distribution diagrams of vibration displacement and vibration velocity signals respectively, Fig. 7 (c) is The time-frequency distribution diagram of the vibration acceleration signal, Fig. 7(d) is a partial enlarged view of Fig. 5(c);
  • Fig. 8 is a statistical diagram of the contribution degree of the second-order reciprocating inertial force of the present invention
  • Fig. 8(a) is a statistical diagram of the contribution degree when the torque is 40N m and the rotational speeds are respectively 800rpm, 1200rpm, 1650rpm and 2200rpm
  • Fig. 8( b) shows the contribution statistics when the rotational speed is 1650rpm and the torque is 20N ⁇ m, 40N ⁇ m, 60N ⁇ m, 80N ⁇ m, and 100N ⁇ m, respectively;
  • valve opening and closing excitations are also important excitation sources of vibration response signals.
  • FIG. 2 it shows the measured vibration acceleration signal at 2200 r/min and 60 N m.
  • the working process of the two-cylinder engine is that the two cylinders are alternately performed.
  • the firing time of cylinder 1 lags behind the firing time of cylinder 2 by 180 °C A
  • the ignition time of cylinder 2 lags behind cylinder 1 by 540°CA. It takes a certain amount of time for the vibration signal to recover from excitation. The higher the rotational speed, the shorter the interval between the occurrences of each excitation.
  • the measurement is performed at the rated speed.
  • the vibration acceleration signal of the cylinder head surface is taken and analyzed.
  • A1 is the surface vibration acceleration of the 1-cylinder cylinder head
  • A2 is the surface vibration acceleration of the 2-cylinder cylinder head.
  • the vibration signal waveforms of the cylinder head surface measured by the two cylinders should be the same, with only a fixed deviation in phase.
  • A1 and A2 have similar variation laws, and the vibration acceleration signal energy is the strongest near their respective combustion top dead centers.
  • the vibration acceleration signal has recovered to be stable, indicating that the combustion excitation of the adjacent cylinder does not affect the combustion process of the current cylinder.
  • FIG. 5 it shows the hammer excitation signal, the measured vibration acceleration signal, the measured vibration acceleration signal after 20 points of smoothing, and the vibration acceleration signal obtained by simulation.
  • the force hammer excitation was applied at point 2, and the hammer signal and the cylinder head vibration acceleration signal at measuring point 1 were measured; at the same time, the measured force hammer signal was applied to the model measuring point 2, and the vibration at measuring point 1 was simulated. acceleration signal.
  • the results in the figure show that the simulated vibration acceleration signal and the measured vibration acceleration signal have a similar trend in waveform, and the amplitude and phase are basically the same, which indicates that the established engine model can be used to analyze the characteristics and coupling relationship of each excitation response signal.
  • the invention adopts the compression wavelet transform technology to analyze the time-frequency characteristics of each excitation vibration response signal.
  • Figure 7 it is the time-frequency analysis result of the reciprocating inertial force excitation response signal.
  • Figures 7(a) and (b) are the time-frequency distributions of the vibration displacement and vibration velocity signals, respectively.
  • the time-frequency distributions of the vibration displacement signals and vibration velocity signals in the frequency domain are similar to the time-frequency distribution of the reciprocating inertial force signal.
  • the frequencies of the reciprocating inertial force and the second-order reciprocating inertial force radiate from the center to the surroundings;
  • Fig. 7(c) is the time-frequency distribution of the vibration acceleration signal, and
  • Fig. 7(d) is a partial enlarged view of Fig. 7(c).
  • the vibration acceleration signal also has a strong energy distribution around the frequencies of the first-order reciprocating inertial force and the second-order reciprocating inertial force. In addition, there are also some energy around 1000Hz and 2000Hz. It can be seen that the energy of the reciprocating inertial force excitation response signal is relatively concentrated in the frequency band, and runs through the entire working cycle of the internal combustion engine. In other words, both the reciprocating inertial force excitation response signal and the combustion excitation vibration response signal are coupled in the time-frequency domain.
  • the simulation After analyzing the characteristics of the vibration signal caused by the reciprocating inertial force excitation and the piston reversing excitation, it is believed that the main influence on the vibration response signal is the reciprocating inertial force excitation.
  • the simulation obtains the vibration velocity signal when the three excitations of piston reversing impact, reciprocating inertia force and cylinder pressure signal act together, and the simulation obtains the vibration velocity when the other two excitations work together without considering the piston reversing impact Signal, the vibration velocity signal when the other two excitations work together without considering the reciprocating inertial force.
  • the present invention takes the vibration velocity signal as an example, and further studies the correlation variation law between the reciprocating inertial force and the vibration signal at the key frequency.
  • the invention utilizes the partial coherence function to approximately determine the contribution of the reciprocating inertial force excitation response signal to the vibration signal.
  • Two inputs x 1 (t), x 2 (t), the partial coherence function of a single output signal y(t) can be defined as:
  • Figure 8(a) shows the contribution when the torque is 40N ⁇ m and the rotational speed is 800rpm, 1200rpm, 1650rpm, and 2200rpm, respectively.
  • Figure 8(b) shows that the rotational speed is 1650rpm, and the torque is 20N ⁇ m and 40N ⁇ m, respectively. , 60N ⁇ m, 80N ⁇ m, 100N ⁇ m contribution.
  • the contribution of the reciprocating inertial force is defined as: at a certain frequency, the ratio of the spectral amplitude of the vibration velocity signal when the reciprocating inertial force is applied alone to the amplitude of the vibration velocity signal when all excitations are applied. It can be seen from the figure that as the rotational speed increases, the contribution of the reciprocating inertial force to the vibration velocity signal increases significantly, and the contribution decreases slightly as the torque increases. This is because the relationship between the reciprocating inertial force and the rotational speed is a quadratic function.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Testing Of Engines (AREA)

Abstract

一种基于偏相干函数求解非燃烧激励信号贡献度的方法，包括步骤一、确定主要非燃烧激励源；步骤二、确定对振动信号起首要作用的非燃烧激励；步骤三、根据步骤二中确定的首要非燃烧激励，利用偏相干函数计算该激励信号在特定频率处对振动信号的贡献度。确定非燃烧激励信号对振动信号的贡献度，是研究剔除振动信号中干扰的基础，而且有助于修复振动信号中的部分燃烧信息，对实现利用振动信号提取燃烧信息、内燃机工作状态监测、燃烧过程闭环控制和故障诊断具有重要的理论意义和实用价值。

Description

基于偏相干函数求解非燃烧激励信号贡献度的方法 技术领域
本发明涉及一种贡献度的计算方法，特别涉及一种基于偏相干函数求解非燃烧激励信号贡献度的方法，属于内燃机技术领域。
背景技术
内燃机振动信号是燃烧激励与往复惯性力、气门落座冲击力、活塞换向撞击力、活塞侧压力及曲轴主轴颈负荷等非燃烧激励共同作用的结果。且非燃烧激励在时域和频域上和燃烧激励存在耦合，导致非燃烧激励响应信号的剔除存在一定得困难，甚至会影响燃烧激励响应信号的完整度。
山东大学唐娟在《内燃机学报》第29卷(2011)第5期中发表的《非燃烧激励对缸盖燃烧激励振动影响模拟分析》一文中模拟了活塞换向撞击、侧压力、曲轴主轴颈负荷单独作用及各激励和燃烧激励共同作用时引起的缸盖表面振动信号，并对各激励振动响应信号的时频特点进行了分析。结果表明，各激励引起的缸盖表面振动位移主要反映了2KHz以下的低频振动，振动速度和加速度能同时反映系统的低频及高频振动，在时域和频域上各激励振动响应存在耦合。但活塞侧压力、曲轴主轴颈负荷对燃烧激励振动响应的影响可以忽略，活塞换向撞击对燃烧激励引起的振动位移和振动速度的影响可以忽略；但对燃烧激励引起的振动加速度的影响不能忽略。
贡献度是指在某一频率处，单独施加主要激励时振动速度信号的频谱幅值与施加所有激励时振动速度信号幅值的比值。
为此，对激励及其响应信号特性进行全面分析，研究各激励响应信号间耦合关系，探明振动信号中主要激励响应信号贡献度，将为非燃烧激励响应信号的剔除，实现燃烧信息的获取和燃烧过程控制提供理论依据。
发明内容
发明目的：针对现有技术中对各激励响应信号间耦合关系以及振动信号中主要激励响应信号贡献度研究不足，本发明提供了一种基于偏相干函数求解非燃烧激励信号贡献度的方法，根据非燃烧激励源特性和强度分析，确定主要非燃烧激励源；通过对振动信号特性进行分析，确定对振动信号起首要作用的非燃烧激励；利用偏相干函数计算该燃烧激励的贡献度及变化规律。
技术方案：一种基于偏相干函数求解非燃烧激励信号贡献度的方法，包括以下步骤：
步骤一、确定主要非燃烧激励源，分析气门开启关闭激励和相邻缸燃烧激励的时域特点， 求解往复惯性力和活塞换向撞击力的激励源强度，得到对振动信号影响敏感的激励源；
步骤二、确定对振动信号起首要作用的非燃烧激励，对实际内燃机结构进行简化，保留机体和缸盖，建立发动机仿真模型；在模型上选定测点施加力锤，通过对比仿真振动信号和实测振动信号验证模型有效性；
通过压缩小波变换技术对各激励振动响应信号的时频特点进行了分析，得到对振动信号起首要作用的非燃烧激励；
步骤三、根据步骤二中确定的首要非燃烧激励，利用偏相干函数计算该激励信号在特定频率处对振动信号的贡献度。
所述步骤一中求解往复惯性力和活塞换向撞击力的激励源强度的方法为：根据测得的缸内压力信号、往复惯性力的激励曲线和活塞换向撞击力的激励曲线分别获取其最大值。
所述步骤二中建立发动机仿真模型时采用10节点四面体网格，机体通过4个支架固定在试验台架上，约束支架为刚性体不发生变形，对支架上各节点进行约束，限制其各个方向的自由度。
所述步骤二中仿真振动信号和实测振动信号模型有效性验证方法为：
首先、在实际发动机上选择施力点施加力锤激励，测取力锤信号和测点处的振动加速度信号；
然后，将测取的力锤信号施加到模型的相应的施力点上，仿真得到测点处的振动加速度信号；
最后、得出力锤激励信号、实测振动加速度信号、20点光顺后的实测振动加速度信号和仿真得到的振动加速度信号图，得出验证结论。
所述步骤二中通过压缩小波变换技术对各激励振动响应信号的时频特点进行了分析的方法为：
首先、测得往复惯性力信号和活塞换向撞击力的时频谱图，得出能量主要分布的频率范围；
然后、对激励响应信号时频分析，得到振动位移、振动速度和振动加速度信号的时频分布，得到单独施加往复惯性力激励和活塞换向激励引起的振动信号特性；
最后、模拟施加活塞换向撞击、往复惯性力和缸内压力信号三个激励共同作用时的振动速度信号，同时模拟不考虑活塞换向撞击时其他两个激励共同作用时的振动速度信号，不考虑往复惯性力时其他两个激励共同作用时的振动速度信号；得到在所有的非燃烧激励中起首要作用的非燃烧激励。
利用偏相干函数计算该激励信号在特定频率处对振动信号的贡献度的方法为：
两个输入x 1(t)、x 2(t)，单输出信号y(t)的偏相干函数可以定义为：
Figure PCTCN2021071201-appb-000001
Figure PCTCN2021071201-appb-000002
称为x 2(t)与y(t)之间的偏相干函数，其中x 1(t)的影响已排除掉，S 2Y1(f)为x 2(t)与y(t) 的条件互功率谱，S 221(f)和S YY1(f)分别为去掉x 1(t)影响后x 2(t)与y(t)的条件自功率谱，且满足不等式：
Figure PCTCN2021071201-appb-000003
根据计算结果得出特定频率时贡献度的统计结果，最终得出结论。
有益效果：本发明确定非燃烧激励信号对振动信号的贡献度，是研究剔除振动信号中干扰的基础，而且有助于修复振动信号中的部分燃烧信息，对实现利用振动信号提取燃烧信息、内燃机工作状态监测、燃烧过程闭环控制和故障诊断具有重要的理论意义和实用价值。
附图说明
图1为本发明内燃机气门开启、关闭工作相位图；
图2为本发明实测振动加速度信号图；
图3为本发明缸内压力信号及计算得到的往复惯性力激励曲线；
图4为本发明动机仿真模型图；
图5为本发明实测振动加速度信号和仿真得到的振动加速度信号的曲线图；
图6为本发明往复惯性力信号的时频谱图；
图7为本发明为本发明往复惯性力激励响应信号时频分布图；其中，图7(a)、(b)分别为振动位移和振动速度信号的时频分布图，图7(c)为振动加速度信号的时频分布图，图7(d)是图5(c)的局部放大图；
图8为本发明二阶往复惯性力的贡献度统计图；其中，图8(a)是扭矩为40N·m，转速分别为800rpm、1200rpm、1650rpm、2200rpm时的贡献度统计图，图8(b)显示了转速为1650rpm，扭矩分别为20N·m、40N·m、60N·m、80N·m、100N·m时的贡献度统计图；
具体实施方式
下面结合附图以及具体实施例对本发明作进一步的说明，但本发明的保护范围并不限于此。
如图1所示，SD2100TA柴油机工作循环中两个缸气门开启、关闭时刻示意图。气门开启、关闭激励也是振动响应信号的重要激励源，对多缸机而言，相邻缸气门开启、关闭激励振动响应和燃烧激励振动响应还可能存在耦合。由图可见，两个缸在着火前都不存在其他非燃烧激励信号。因此，气门开启、关闭激励与燃烧激励在时域上不存在同步性，其响应信号的特性可以忽略。
如图2所示，显示了2200r/min，60N·m工况时实测的振动加速度信号，两缸机工作过程是两个缸交替进行，工作相位上，1缸发火时刻滞后2缸180℃A，2缸发火时刻滞后1缸540℃A。振动信号从激起到恢复需要一定的时间，转速越高，各激励出现时刻的间隔时间越 短，为验证相邻缸的燃烧激励是否对当前缸燃烧激励响应信号产生影响，在额定转速下测取了缸盖表面振动加速度信号并进行了分析。图中A1是1缸缸盖表面振动加速度，A2是2缸缸盖表面振动加速度。理论上，两个缸测得的缸盖表面振动信号波形应当相同，只会在相位上出现固定偏差。从图2中可以看出，A1、A2具有相似的变化规律，在各自的燃烧上止点附近振动加速度信号能量最强。从图中还可以看出，A1在270-300℃A转角范围内，振动加速度信号已经恢复平稳，表明相邻缸燃烧激励并未影响到当前缸的燃烧过程。
如图3所示，转速为1200r/min，扭矩为40N·m时缸内压力信号及计算得到的往复惯性力激励曲线，该工况下往复惯性力峰值与缸内压力峰值的比值为5.3％。由于随着转速的增加，往复惯性力增大，缸压也会发生变化。经计算，相同扭矩下，800r/min,1200r/min,1650r/min,2200r/min时，往复惯性力峰值与缸内压力峰值的比值为2.4％，5.3％，10.6％，20.7％，呈增大趋势，由此可见，往复惯性力激励对振动信号的影响，尤其是在中高转速时的影响难以忽略不计。类似的，计算了活塞换向激励的强度，通过与缸内压力信号对比，认为，二者对振动信号的影响不能忽略，仍需进一步分析。
如图4所示，为了定量研究各激励响应信号特性和耦合关系，本文对实际柴油机结构进行简化，保留机体和缸盖，利用ABAQUS软件建立了发动机仿真模型，计算中采用10节点四面体网格，机体通过4个支架固定在试验台架上，假定约束支架为刚性体不发生变形，对支架上各节点进行约束，限制其各个方向的自由度。
如图5所示，显示了力锤激励信号、实测振动加速度信号、20点光顺后的实测振动加速度信号和仿真得到的振动加速度信号，为了对所建立发动机模型进行验证，本文在实际发动机测点2施加力锤激励，测取了力锤信号和测点1处的缸盖振动加速度信号；同时，将测取的力锤信号施加到模型测点2处，仿真得到测点1处的振动加速度信号。图中结果表明，仿真振动加速度信号和实测振动加速度信号在波形上有近似的趋势，幅值和相位基本一致，这表明所建立的发动机模型可用于分析各激励响应信号的特点和耦合关系。
为了对激励信号经机体后的激励响应信号特性进行分析，本发明采用压缩小波变换技术对各激励振动响应信号的时频特点进行了分析。
如图6所示，为往复惯性力信号的时频谱图，往复惯性力激励的能量主要分布在27.5Hz和55Hz周围，表明一阶和二阶往复惯性力起主要作用。
如图7所示，为往复惯性力激励响应信号时频分析结果。图7(a)、(b)分别为振动位移和振动速度信号的时频分布，频域上振动位移信号和振动速度信号的时频分布和往复惯性力信号的时频分布相似，以一阶往复惯性力和二阶往复惯性力频率为中心向周围发散；图7(c)为振动加速度信号的时频分布，图7(d)是图7(c)的局部放大图，从这两张图中可以看出，振动 加速度信号在一阶往复惯性力和二阶往复惯性力频率周围也有较强的能量分布，除此之外，在1000Hz和2000Hz附近也有部分能量。由此可见，往复惯性力激励响应信号的能量在频带上分布较为集中，且贯穿整个内燃机工作周期。换而言之，往复惯性力激励响应信号和燃烧激励振动响应信号在时频域上都存在耦合。
对往复惯性力激励和活塞换向激励引起的振动信号特性分析后认为，对振动响应信号起主要影响的是往复惯性力激励，为进一步分析往复惯性力激励对燃烧激励振动响应信号输出结果的影响，模拟得到了施加活塞换向撞击、往复惯性力和缸内压力信号三个激励共同作用时的振动速度信号，同时模拟得到了不考虑活塞换向撞击时其他两个激励共同作用时的振动速度信号，不考虑往复惯性力时其他两个激励共同作用时的振动速度信号。结果表明，各激励共同作用和燃烧激励单独作用时振动信号输出结果的差异主要是由往复惯性力激励引起的，也就是说，在所有的非燃烧激励中，往复惯性力是其首要作用的。
本发明以振动速度信号为例，进一步研究关键频率处往复惯性力与振动信号间的相关性变化规律。本发明利用偏相干函数近似确定往复惯性力激励响应信号对振动信号的贡献。
两个输入x 1(t)、x 2(t)，单输出信号y(t)的偏相干函数可以定义为：
Figure PCTCN2021071201-appb-000004
Figure PCTCN2021071201-appb-000005
称为x 2(t)与y(t)之间的偏相干函数，其中x 1(t)的影响已排除掉。S 2Y1(f)为x 2(t)与y(t)的条件互功率谱，S 221(f)和S YY1(f)分别为去掉x 1(t)影响后x 2(t)与y(t)的条件自功率谱。且满足不等式：
Figure PCTCN2021071201-appb-000006
如图8所示，显示了在二阶往复惯性力频率处，往复惯性力的贡献度统计结果。其中，图8(a)是扭矩为40N·m，转速分别为800rpm、1200rpm、1650rpm、2200rpm时的贡献度，图8(b)显示了转速为1650rpm，扭矩分别为20N·m、40N·m、60N·m、80N·m、100N·m时的贡献度。往复惯性力贡献度定义为：在某一频率处，单独施加往复惯性力时振动速度信号的频谱幅值与施加所有激励时振动速度信号幅值的比值。从图中可以看出，随着转速升高，往复惯性力对振动速度信号贡献度有明显增加，随着扭矩增加贡献度略有减小。这是由于往复惯性力与转速之间是二次函数关系，因此，随着转速增加，往复惯性力权重增加较大；而转速固定时，随着扭矩增加，往复惯性力保持不变，其他激励能量稍微增加，导致往复惯性力贡献度略有减小。
所述实施例为本发明的优选的实施方式，但本发明并不限于上述实施方式，在不背离本发明的实质内容的情况下，本领域技术人员能够做出的任何显而易见的改进、替换或变型均属于本发明的保护范围。

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  1. 一种基于偏相干函数求解非燃烧激励信号贡献度的方法，其特征在于，包括以下步骤：
    步骤一、确定主要非燃烧激励源，分析气门开启关闭激励和相邻缸燃烧激励的时域特点，求解往复惯性力和活塞换向撞击力的激励源强度，得到对振动信号影响敏感的激励源；
    步骤二、确定对振动信号起首要作用的非燃烧激励，对实际内燃机结构进行简化，保留机体和缸盖，建立发动机仿真模型；在模型上选定测点施加力锤，通过对比仿真振动信号和实测振动信号验证模型有效性；
    通过压缩小波变换技术对各激励振动响应信号的时频特点进行了分析，得到对振动信号起首要作用的非燃烧激励；
    步骤三、根据步骤二中确定的首要非燃烧激励，利用偏相干函数计算该激励信号在特定频率处对振动信号的贡献度。
  2. 根据权利要求1所述的基于偏相干函数求解非燃烧激励信号贡献度的方法，其特征在于，所述步骤一中求解往复惯性力和活塞换向撞击力的激励源强度的方法为：根据测得的缸内压力信号、往复惯性力的激励曲线和活塞换向撞击力的激励曲线分别获取其最大值。
  3. 根据权利要求1所述的基于偏相干函数求解非燃烧激励信号贡献度的方法，其特征在于：所述步骤二中建立发动机仿真模型时采用10节点四面体网格，机体通过4个支架固定在试验台架上，约束支架为刚性体不发生变形，对支架上各节点进行约束，限制其各个方向的自由度。
  4. 根据权利要求1所述的基于偏相干函数求解非燃烧激励信号贡献度的方法，其特征在于，所述步骤二中仿真振动信号和实测振动信号模型有效性验证方法为：
    首先、在实际发动机上选择施力点施加力锤激励，测取力锤信号和测点处的振动加速度信号；
    然后，将测取的力锤信号施加到模型的相应的施力点上，仿真得到测点处的振动加速度信号；
    最后、得出力锤激励信号、实测振动加速度信号、20点光顺后的实测振动加速度信号和仿真得到的振动加速度信号图，得出验证结论。
  5. 根据权利要求1所述的基于偏相干函数求解非燃烧激励信号贡献度的方法，其特征在于：所述步骤二中通过压缩小波变换技术对各激励振动响应信号的时频特点进行了分析的方法为：
    首先、测得往复惯性力信号和活塞换向撞击力的时频谱图，得出能量主要分布的频率范围；
    然后、对激励响应信号时频分析，得到振动位移、振动速度和振动加速度信号的时频分布，得到单独施加往复惯性力激励和活塞换向激励引起的振动信号特性；
    最后、模拟施加活塞换向撞击、往复惯性力和缸内压力信号三个激励共同作用时的振动速度信号，同时模拟不考虑活塞换向撞击时其他两个激励共同作用时的振动速度信号，不考虑往复惯性力时其他两个激励共同作用时的振动速度信号；得到在所有的非燃烧激励中起首 要作用的非燃烧激励。
  6. 根据权利要求1所述的基于偏相干函数求解非燃烧激励信号贡献度的方法，其特征在于，利用偏相干函数计算该激励信号在特定频率处对振动信号的贡献度的方法为：
    两个输入x 1(t)、x 2(t)，单输出信号y(t)的偏相干函数可以定义为：
    Figure PCTCN2021071201-appb-100001
    Figure PCTCN2021071201-appb-100002
    称为x 2(t)与y(t)之间的偏相干函数，其中x 1(t)的影响已排除掉，S 2Y1(f)为x 2(t)与y(t)的条件互功率谱，S 221(f)和S YY1(f)分别为去掉x 1(t)影响后x 2(t)与y(t)的条件自功率谱，且满足不等式：
    Figure PCTCN2021071201-appb-100003
    根据计算结果得出特定频率时贡献度的统计结果，最终得出结论。
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