关 键 词：

货车 驱动 三维设计

资源描述：

某型货车驱动桥三维设计,货车,驱动,三维设计

内容简介：

本科毕业设计中期检查报告课题名称 某型货车驱动桥三维设计学 号 20052199 姓 名 孟德浩 专 业 机械设计 指导教师 张义民 评阅教师 检查时间 2009 年 5 月 18 日东北大学机械工程与自动化学院1填表说明1、 中期检查报告作为过程考核的依据，将作为资料存档；2、 表内容在导师指导下如实填写；3、 学生在通过中期检查后一周内将经导师签字的材料交到研究所，集中上报学院（包括电子文档）；4、 按毕业设计管理规定，中期检查成绩将计入学生最终毕业设计成绩。一、毕业设计（论文）研究工作主要进展情况（开题报告预计研究内容完成情况，未完成的原因）序号工作内容进展约占所占全部工作的比例1准备阶段（搜集资料，完成开题报告，翻译外文文献）完成10%2初步设计计算阶段（整理已获得的材料，完成总体方案分析和总体参数设计和计算）完成15%3详细设计计算阶段（主减速器总成，差速器总成和驱动桥壳的设计）完成20%4三维设计（用SolidWorks对驱动桥壳进行三维建模）正在进行40%5678二、下一步论文工作进度安排和预期成果序号工作内容进度安排预期成果1三维设计（完成零件的三维设计，并装配在一起）5月18日5月25日完成三维设计2完成装配图的绘制，并请老师初步检查 5月25日6月1日完成装配图的绘制3完成设计说明书，请老师检查并做最后修改6月1日6月10日完成说明书的撰写4为答辩做准备（做PPT）6月10日以后567三、存在问题及需要说明的情况 刚拿到题目时，自己对所要做的设计还很不了解。但经过老师的细心指导和我的努力，整个毕业设计有了很大进展。三维建模基本完成，我一直在查跟课题相关的资料以求设计能更合理，更符合实际应用。由于没有相关的二维图纸，所以设计参数都是根据相关资料自己设定的，但由于实践经验缺乏，难免有些不合理之处，我已认识到这一点，并积极向老师请教以尽量避免可能出现的错误。 我先根据查到的相关书籍，利用SolidWorks对驱动桥做了三维建模。进行完三维建模和装配后，再画出装配图。我想通过三维建模和二维画图结合，可以更好的发现问题，完善设计。四、评审意见指导教师对学生论文工作评价意见： 导师： 日期：评阅人对学生论文工作评价意见： 评阅人： 日期： 正导师所在基层负责人： 日期：4 本科毕业设计开题报告课题名称 某型货车驱动桥三维设计学 号 20052199 姓 名 孟德浩 专 业 机械设计 指导教师 张义民 评阅教师 开题时间 年 月 日 东北大学机械工程与自动化学院一、 立论依据1 本课题的目的和意义新中国成立以前，我国没有汽车制造工业，自1953年在长春兴建第一汽车制造广(以下简称“一汽”)，1956年制造出第一辆“解放”牌运输车，宣告了中国不能生产汽车历史的结束。中国汽车行业到现在已经获得了长足发展。现在中国汽车工业已成为世界汽车工业的重要组成部分。改革开放20年来，与国际上各大汽车及零部件制造商相继建立了600余家中外合资企业，积累了资本200多亿美元；引进了1000多项汽车技术，绝大部分都与国外处于同等水平；2002年，汽车进出口贸易总额达100亿美元，占世界汽车市场的1/20的份额。2010年我国汽车产量的目标是600万辆，占世界汽车市场的1/10；若按5%的增长率计算，2020年我国的汽车产量将达到1000万辆，将占世界汽车市场的1/5，中国的汽车工业将由生产大国走向强国。中国的本土的设计能力跟国际先进水平还有一定差距，在国内汽车专利的申请还是跨国公司占绝大多数。所以中国要进一步发展汽车的行业，应该在自主设计和创新方面做出更大努力。驱动桥设计是汽车设计重要组成部分，汽车的驱动桥位于传动系的末端，其基本功用是增大由传动轴或直接由变速器传来的转矩，将转矩分配给左、右驱动车轮；并使左、右驱动车轮具有汽车行驶运动学所要求的差速功能. 同时驱动桥还要承受作用于路面和车架或承载式车身之间的力和力矩。汽车车桥的结构型式和设计参数除对汽车的可靠性与耐久性有重要影响外，也对汽车的行驶性能如动力性、经济性、平顺性、通过性、机动性和操作稳定性等有直接影响。通过本课题可以达到以下目的：1) 通过对汽车驱动桥的学习和设计实践，可以锻炼查阅收集资料并进行实际设计操作的能力，掌握机械设计的方法和过程。2) 通过对汽车驱动桥的学习和设计实践，可以更好的学习并掌握现代汽车设计与机械设计的全面知识和技能。3) 通过对汽车驱动桥结构的研究并查阅了解多种三维制图软件，熟练掌握及操作三维设计软件SolidWorks，利用已掌握的机械制图技能利用三维软件完成汽车驱动桥结构设计。4) 通过查阅汽车驱动桥的相关资料，可以对汽车行业的发展有新的认识。二、文献综述1 国内外研究现状、发展动态随着汽车工业的发展及汽车技术的提高，驱动桥的设计、制造工艺都在日益完善。驱动桥也和其他汽车总成一样，除了广泛采用新技术外，在结构设计中日益朝着“零件标准化、部件通用化、产品系列化”的方向发展及生产组织的专业化日标前进。应采用能以几种典型的零部件、以不同方案组合的设计方法和生产方式达到驱动桥产品的系列化或变型的目的，或力求做到将某一基型的驱动桥以更换或增减不多的零件，用到不同性能、不同吨位、不同用途并由单桥驱动到多桥驱动的许多变型汽车上。例如，驱动桥主减速齿轮以几种典型的主减速比形成系列，就能达到以不同动力性要求为目的的汽车变型。为了防止功率循环现象的产生。在现代多桥驱动的汽车上泞往装有轴间差速器。后者也可显著地减少多桥驱动汽车主减速器出现过载的情况。但在安装轴问差速器的汽车上，必须考虑到能充分利用备驱动桥牵引力的要求。随着发动机转速及汽车行驶速度的提高，降低汽车的噪声已成为汽车设计中的一个重要课题。驱动桥的噪声主要来自齿轮及其他传动机件。提高齿轮反其他传动零件的加工精度、装配精度增强齿轮的支承刚度，采用运转平稳、无噪声的双曲面齿轮作主减速器齿轮等等。汽车驱动桥是汽车的重要总成，驱动桥设计是汽车设计的重要组成部分之一。目前国内外驱动桥设计出现了一下一些变化：1、主要部件和功能向驱动桥的中部集中有些厂家开始把主减速器, 制动器和行星减速机构等集合在桥的中部, 但其优点尚待考证。2、桥壳采用球墨铸铁, 以提高整桥外观质量 桥壳采用球墨铸铁, 加工成本低, 其铸造及加工后的外观质量均比现在大多采用的铸钢桥有了很大的提高。3、适应特种要求的多功能驱动桥为适应主机产品的特殊要求, 驱动桥产品供应厂家设法在桥上增加引进了一些特殊功能:自动充气功能、超载报警功能、增添转向油缸功能等, 增加了驱动桥产品的适应性。 2 所阅文献的查阅范围及手段范围：汽车设计、汽车底盘构造、汽车构造、汽车车桥设计手段：从图书馆电子资源下载；从图书馆借阅相关书籍参考文献1. 刘惟信. 汽车车桥设计M, 北京: 清华大学出版社, 2004, 339-346.2. 常明. 汽车底盘构造M, 北京: 国防工业出版社, 2005, 77-86.3. 王望予主编. 汽车设计(第四版) M, 北京:机械工业出版社, 2004, 20-21.4. 刘惟信. 论现代汽车设计及其发展趋势J, 汽车与社会, 1996, 1（1）: 40-41.5. 长春汽车研究所. 驱动桥设计(上)J, 汽车技术, 1972(03): 45-55.6. 长春汽车研究所. 驱动桥设计(下)J, 汽车技术, 1972(04): 56-60.7. 余志生. 汽车理论M, 北京: 机械工业出版社, 1981, 105-106.8. 陈家霸主编. 汽车构造M, 北京: 人民交通出版社, 1993, 10-12.9. 王聪兴,冯茂林. 现代设计方法在驱动桥设计中的应用J, 公路与汽运，2004, (4): 6-8.10. Reimpell J, Stoll H. The Automotive Chassis: Engineering PrinciplesM，Warrendale, PA 15096, USA, SAE, 199611. 鲍晓东. 44载货汽车的设计要点技术分析J, 北京工业职业技术学院学报, 2007, 6(4), 6-7.12. Muro T. Comparison of the traffic performance of a two-axle four wheel drive(4WD),rear wheel drive(RWD),and front wheel drive(FWD) vehicle on loose sandy sloped terrainJ， Journal of Terramechanics,1997,No.1:37-55.13. Baxter, John. Infocus: DRIVE AXLESJ , Carrier Journal, 2006, No.5:38.14. 汽车百科全书编纂委员会. 汽车百科全书M, 北京: 机械工业出版社, 1992, 66-70.15. 杨朝会, 王丰元, 马浩. 基于有限元方法的载货汽车驱动桥壳分析J, 农业装备与车辆工程, 2006, （10）: 19-21.16. 汽车工程手册编写组. 汽车工程手册M, 北京:人民交通出版社, 2001, 160-165.17. 胡迪青, 易建军, 胡于进等. 基于模块化的越野汽车驱动桥设计及性能综合评价J,机械设计与制造工程, 2000,（3）: 8-11.18. 常曙光. 重载汽车驱动桥齿轮用钢的成分设计J, 现代零部件, 2006, （1）: 90-95.三、研究内容1课题的构想与思路本课题通过给定的参数，首先进行了总体方案分析，确定出了驱动桥的各个部分的结构型式。然后按驱动桥的四个主要部分分别进行了详细设计和校核，确定出了驱动桥各个部分的主要参数。确定出参数后，用SolidWorks进行了各个零部件的三维建模和装配。 三维建模完成后，又根据三维模型画出了二维装配图。同时在画二维装配图的过程中对三维模型中的不合理之处进行了修改。当一切完成之后，对驱动桥进行了运动仿真，通过动画形式更好的展示设计的产品。2 主要设计内容1）进行总体方案分析，总体参数设计和计算，完成总体设计全部内容。2）进行零部件设计和校核计算、标准件选择和校核等。3）完成该驱动桥总体和零部件三维设计，进行装配和运动仿真并画出装配图。4）撰写毕业设计说明书。5）翻译外文文献。3 拟解决的关键技术1）完成驱动桥的参数计算和强度校核。2）用SolidWorks把驱动桥的三维模型建立起来，并且进行装配和运动仿真。3）采用全浮式半轴结构使半轴仅受到转矩,而不承受其它的路面反力(径向力、轴向力、弯矩等)。4 总体设计方案总体设计方案可用以下流程图表示总体方案分析设计计算和强度校核二维图纸运动仿真三维建模和装配修改搜集资料五、工作计划序号阶段及内容工作量估计（天）起止日期阶段成果形式1准备阶段（搜集资料，完成开题报告，翻译外文文献）103.103.20完成开题报告，翻译完外文文献2初步设计计算阶段（整理已获得的材料，完成总体方案分析和总体参数设计和计算）203.204.10整理已获得的材料，完成总体方案分析和总体参数设计和计算3详细设计计算阶段（主减速器总成，差速器总成，半轴和驱动桥壳的设计）204.104.30完成主减速器，差速器总成，半轴及桥壳的设计和校核4三维设计（用SolidWorks对驱动桥壳进行三维建模，完成零件的三维设计，并装配在一起）204.305.20做出三维实体并完成装配5装配图的绘制155.206.1完成装配图的绘制6设计说明书的编写106.1-6.10完成设计说明书合计工作量：95天六、评审意见指导教师对本课题的评价 指导教师签名 年 月 日评阅教师对本课题的评价 评阅教师签名 年 月 日 Proceedings of the IEEE International Conference on Mechatronics & Automation Niagara Falls, Canada July 2005 0-7803-9044-X/05/$20.00 2005 IEEEA Way to Detect the Quality of Main Retarder in Automobile Drive Shaft with Vibration Analysing Jia Huang, Jiexiong Ding and Zhenhua Tang School of Mechatronics Engineering University of Electronic Science and Technology of China No4.2ndSection, Jianshebei Road, Chengdu, Sichuan, China orginal Abstract As a part of comprehensive estimate method, this article describes a new way to evaluate the quality of the main retarder in automobiles drive shaft. The proposed system uses vibration signal analysing instead of the noise signal analysing with the main retarder. It performs the wavelet transform with the collected vibration signal of the drive shaft shell and analyses it by using the tool of MATLAB. A simulated signal is taken into the system and analysed using the method aforementioned as an example. According to the analysing results, the conclusions for evaluating the quality of main retarder can be drawn more rapidly and rationally. Index Terms - main retarder; noise; vibration analysing; wavelet transform. I. INTRODUCTIONAs various automobiles come into daily life, the noise caused by automobile is in majority of the citys noise. Contacting noise long, it not only affects health of those people but also causes traffic accidents indirectly. Thus, the noise is one of the significant targets in weighing the quality of automobile. Besides the engine and exhaust system, the main retarder is another primary noisemaker in automobile. To reduce the noise of main retarder is an important aspect to realize low noise automobile. The main retarder is often manufactured separately 1. It is assembled firstly as retarder assembly according to the technical demands. And then it is put into the drive shaft housing. The retarder assembly consists of three main segments: driving cone gear assembly, differential assembly and retarder housing. Fig. 1 shows the retarder assembly of a camion and its fixed into the drive shaft shell. A comprehensive test has been taken when the assembly of main retarder finishes, for ensuring the pair of screwy bevel gears keeping relative location correctly. Its a key means to guarantee the quality of those productions and prevent the rejects entering into the next working procedure. The noise of main retarder is an important aspect in the comprehensive evaluating for it reflects the meshing conditions of the pair screwy bevel gears. The conventional method for noise testing in the old ones is that, the operators listen to the sound from the pair of screwy bevel gears when they are meshing, and make decisions according to their own experiences. Obviously, the efficiency and accuracy are low via using this old method. There is another improved method which detects the noise signal of the main retarder directly and analyses it using noise pressure analysing method. It advances the old one in a certain extent. However, the request conditions for realising the measuring and analysing of noise are high. Even a silencer room is needed some times. As Fig.1 denoting, the test is usually taken in the workshop where the environment noise are loud. The improved method is obvious not suitable for such an industrial circumstance. Fig.1 The retarder assembly and drive shaft shellAccording to the research on the vibration and noise of the main retarder, the vibration and noise signal are in close relationship. When the frequency of vibration varies from 20 to 20000Hz, the vibration source is the noise source either. This vibration transmits in form of wave in solid and radiates noise in the meanwhile. The vibration of drive shaft housing reflects the meshing impact of the pair of screwy bevel gears ultimately. That is to say, the vibration signal of drive shaft shell contains abundant dynamic information of the meshing screwy gears. Thus, this article brings up that analysing the vibration signal instead of measuring noise signal directly. II. INFORMATION ABOUT WAVELETAs all know, there are many ways and means in the field of signal processing, and the conventional Fourier Transform (FT) is more often used. FT represents a signal by a family of complex exponents with infinite time duration. Therefore, FT is useful in identifying harmonic signals. However, it is weak in analysing transitory signals. The reason is that shape of wave of the signal in time domain doesnt contain the information in frequency domain, and the Fourier spectrum is a statistical characteristic of the signal, which isnt provided with function of localization. There is another developing method called Short Time Fourier Transform (STFT). The 782Authorized licensed use limited to: Northeastern University. Downloaded on May 27, 2009 at 02:45 from IEEE Xplore. Restrictions apply.essential idea of STFT is that it divides signal into many interval of time at first, then implements FT in each divided time zone for obtaining the frequency information included in this interval. Obviously, it contains the information both in time and frequency. However, for the invariable of the time intervals, it is difficult to detect the signals which have short time duration and high frequency. It is really only suit to analysis of signals where all of the patterns appear at approximately the same size. Wavelet Transform (WT) is a time-frequency localization analysis method, whose shape of window changes but the magnitude keeps invariable. For its ability of alterable extension of window essentially, WT can take a long time to obtain information about low-frequency more exactly, and take a shorter time to get information about high-frequency. On the other hand, the most important characteristic of WT is that, it can perform multiresolution analysis of the signals. Thus, it is useful in detecting the signal which carries instantaneous abnormal components. Generally, wavelet is a family of functions satisfying the condition expressed as follow: 12( , )( )( )( )(),xtWTatx tx tdtaaa=? (1) Where indicates the inner product; the asterisk * represents the complex conjugate; the factor 12a is used to ensure energy conservation;( ),tadenotes the daughter wavelets that are derived from the mother wavelet ( ) t by continuously varying both the scale factora, and the translation or time shift factor, and the mother wavelet ( )tshould satisfy the condition shown as follow: ( )0Rt dx=? (2) WhereR denotes the set of real numbers. III. SCHEME OF THE ANALYZING SYSTEMA. Frame of the system There is a vibration signal analysing and supervising system in low cost, which uses the sound card of computer instead of a data acquisition card, and analyses signal using Matlab program 2. It uses common personal computer and analysing software which is programmed by themselves. It predigests the analysing system in a certain extent. For the comprehensive testing takes place in product line, the environment should be wicked and the influencing factors are uncertainty. On the other hand, the analysing system will be embedded into the comprehensive testing system, and the effects which come from the other parts of the whole system are inevitable. The data acquisition system aforementioned can not solve those problems well. Thus, an approximate but different system is adopted in this article. The vibration signal of the drive shaft shell should be firstly obtained via an accelerometer, then the transformed signal should be processed via a signal modulated module, at last the inspected signal is inputted to a personal computer via a data acquisition card. Fig. 2 shows the frame of the system.Fig.2 The frame of the analysing systemNowadays, the accelerometer of piezoelectric material is commonly used for its small size, light weight and favourable sensitiveness. The main function of transducer is that changing the physical signal into electric signal. Its a sense organ of force. When under the effects of stress, press and acceleration, charges are generated on the surface of the electric medium. Thus, it tests the acceleration on the vibrating drive shaft shell to get the needed electric signal. This output signal is proportion to the acceleration. The general range of the vibration signal is from 10 to 1000Hz. However, an impulse signal may up to 10KHz while the fault occurs. This should be taken into consideration as well as the measurement when choosing the accelerometer. In this provided system, a piezoelectric transducer is adopted. As the data acquisition system using in more widely fields, the involved type of signal and source becoming more and more, and the demanded precision getting higher, ordinary acquisition modules are difficult to satisfy those conditions at one time. To accommodate the different measuring situations, various series of signal modulated module with singularity function have been manufactured, which can be assembled neatly and expediently according to the actual instance. Thus, the appropriative signal modulated modules are adopted in modern data acquisition system. The main functions of them are magnifying, linearizing or filtering the signals collected by transducer. In the provided system, it must get through a signal modulated module before processed, for the charge signal outputted from the accelerometer is very faint. Data acquisition is the most important approach in signal processing. In order to conveniently cooperate with the personal computer, the adoptive data acquisition card is USB (UNIVERSAL SERIER BUS) card. USB card not only connects the computer and external fixtures simply, but also takes us into a bran-new PC age. Firstly, a normal port takes place of all the other different serial ports and parallel ports. Secondly, it possesses of the function with plug and play. Finally, the transmission rate of it is up to 100 kHz with 12 bit resolution that it can well achieve high speed data acquisition which the industrial platform needs. 783Authorized licensed use limited to: Northeastern University. Downloaded on May 27, 2009 at 02:45 from IEEE Xplore. Restrictions apply.This system works at testing situations that to simulate the different conditions, which are caused by tuning around of the automobile or the roughness of the road. Considering the automobile running as usual, turning or braking, there are four simulated testing phases in this provided system. And the parameters which are concerned in those four phases are listed as in Table I. Table I The parameters in 4 phases Testing phase Loading situation Rotating orientation Rotating speed I No load Right 940(r/min) IILoad the right side gear till it stops Right 940(r/min) IIILoad the left side gear till it stops Right 940(r/min) IVKeep load both of the side gears Left 540(r/min) The vibration signal of the drive shaft housing should be measured in those four phases respectively. Then it will be analysed via the arithmetic motioned latter. And the cue information should be displayed on the screen of the personal computer according to the analysing results when they are caused by anomalous signals. B. Select of the wavelet for analysis In a number of publications, WT is widely recognized as an effective tool for vibration-based machine fault diagnosis, for it can detect both stationary and transitory signals. In actual application, especially in realizing of computer, it needs to disperse the continuous wavelets and its transform. The discrete wavelet transform (DWT) is built up mainly based on binary wavelet transform. It disperses the scaleaas exponential progression. That is to say, order scale factora=00a,10a,20a,0ja,j=1, 2, N. When the scale magnifies0jatimes, which means the frequency reduce the same times, so the sampling interval magnifies 0ja times accordingly. A more natural notion is, disperse the time shift as 0ja times. According to Nyquist sampling theorem, it wont lose information of the original signal by doing this. Dispersing the signal as exponential progression is an effective dispersing method. For the exponential indexjvaries in a small degree, it will induce the scale varying a lot. In this provided system, makea=2, which is suitable for analysing and the calculating of the computer. For the series of wavelets are derived from mother wavelets and choosing the different wavelet basis would obtain different results, the wavelet basis is important for analysing. There are several properties for the choosing of a wavelet basis that one could want to be fulfilled: 1)orthogonality; 2)compact support: )rational coefficients; 4)symmetry; 5)smoothness; 6)interpolation. The problem concerned in the provided system is vibration of the drive shaft shell. The configuration of drive shaft housing is complex. For there are many vibration excited sources, the signal is made up of periodic components which generated by the meshing of the screwy bevel gears and the instantaneous components that generated by the other excited source. Considering those factors aforementioned, the Daubechies wavelet is chosen in analysing. The series of Daubechies wavelets are marked as dbN in MATLAB. Where N is the serial number, and N=2, 3,10. There is no specific expression for it. The effective compact support length of the wavelet function ( )t and scale function is 2N-1, and the vanishing length is N. C. Analysing process with a simulated signal Before practical measurement, the adopted analysing system should be tested. The frame of the system is testified to be reasonable by many other data processing systems. The only different is that this vibration analysis is a part of the comprehensive evaluating for the main retarder. The analysing system should be embedded into the whole evaluating system. Thus, the chosen wavelet analysis should be tested. A simulated signal is taken into the provided system as shown in Fig.3. It consists of periodic signal which is used to simulate the signal generated by the meshing of screwy bevel gears, random noise signal and impulse signal which are used to simulate the signals generated by the fault of the gears or other interferential complications. Fig. 3 The simulated original signal A common phenomenon has been observed when decomposing a given signal, within a selected time frame, if a daughter wavelet, which is generated by a particular scale, has the largest value of the wavelet coefficient, it often implies that the shape of that daughter wavelet can match the shape of the inspected signal better than other daughter wavelets generated by other scales 6. According to the principle mentioned above and the shape of the simulated signal, the db10 is chosen for the simulated analysing system. The scale function and the wavelet function of db10 are showed as in Fig.4. Fig.4 The scale function and wavelet function of db10784Authorized licensed use limited to: Northeastern University. Downloaded on May 27, 2009 at 02:45 from IEEE Xplore. Restrictions apply.The time-frequency characteristics of the chosen wavelet basis db10 are listed as follow: the effective compact support length N is 20; the support zone is 0, 20; the vanishing moment is 10. At the point of multiresolution, DWT is equivalent to a band-pass filter and a low-pass filter. The original signal is decomposed into two sub-signals each time, and it equivalent to the signals in frequency zone 0,2j are decomposed into two components that in the frequency zones 0,12j and 12j,2j, which named as approximation and detail signal respectively. The decomposed components should be decomposed in frequency zone 0,12j approximately as the previous step does. And the Nth level of the wavelet analysing result can be obtained via N times decomposition, therefore, the results can match the analysing demands of the system well. Fig.5 denotes the tree of the decomposing. Fig. 5 The wavelet decomposing tree Where S indicates the original signal, cA is the wavelet coefficient of the low-pass filter, and cD is the wavelet coefficient of the band-pass filter. The simulated signal is decomposed by performing the chosen wavelet basis. And the results are shown as in Fig.6. Obviously, when the decomposition achieves 5th level, both the approximation and detail component represents the raw simulated signal well. Because the range of normal vibration signal is usually smaller than the impulse signal, the former is the details compared with the later in the collected signals. The approximation component shown as in (a) contains the anomalous information which is used to simulate the fault situations usually generated in high frequency zones, and the detail component shown as in (b) denotes the periodic information which is used to simulate the meshing of the screwy bevel gears. When testing in an actual application, it can be performed with a threshold while the wavelet coefficient over a certain value as in Fig.6 (a). The practical threshold can be obtained from the statistical datum of the approximate coefficients. Thus, the conclusions can be drawn with the remained signal. For example, if the fault appears at the driving screwy bevel gear, the periodic information would be accord with the rotating information of the driving bevel gear. And the same conclusions also can be drawn according to the fault information from driven screwy bevel gear or factors affected by the other parts of the drive shaft. (a) (b)Fig. 6 The decompositions of the simulated signal (a)The wavelet coefficients of the low-pass filter (b)The wavelet coefficients of the band-pass filter IV. CONCLUSIONThe proposed vibration analysing is complementary to the comprehensive evaluating analysis with the main retarder of the automobile drive shaft. In old method, the operator makes the estimations only according to their experiences. Both the efficiency and dependability are low. Besides, for the environmen