Research on Automobile Detection and Fault Diagnosis Technology
Abstract: With the rapid development of modern automobile technology, the structure of automobile is becoming more and more complicated, and high technology, especially electronic technology and computer technology, is more and more widely used in automobiles. Automobile fault diagnosis technology has developed from traditional empirical diagnosis methods such as asking, seeing, listening, smelling and touching to modern automobile fault diagnosis technology based on information technology.
Classification number of China Library: f407.45438+0 Document ID number: A document number:1009-914x (2016)13-0364-01.
I. Definition:
The car broke down? Diagnosis? And then what? Testing? Broadly speaking, there is not much difference between these two words, but if we pay attention, there will be a little difference. Diagnosis is a process of analyzing and judging vehicle faults (including fault codes and symptoms) and determining fault parts, devices and circuits by using necessary means (including appearance, smell, vibration, sound, feeling and electrical reality and instruments) and knowledge and experience. The process of diagnosis is a complete process. Detection refers to the process of accurately measuring the identified fault parts, devices and circuits according to the judgment to confirm whether the judgment is correct and accurately determine the fault parts, devices and circuits.
Second, the technical characteristics of fault diagnosis
1, and the means of fault analysis are diversified. The complexity of modern automobile structure makes the fault state show diversity, fuzziness and uncertainty. Wavelet analysis, fuzzy set theory, rough set theory, grey relational analysis, waveform analysis, fusion technology and neural network technology are applied to fault diagnosis.
2. Modernization of fault diagnosis equipment. The development of on-board diagnosis system and on-board diagnosis system integrates mechanical, electronic, fluid, acoustic, optical and other technologies, and also has the function of automatic analysis, judgment and printing results, and is constantly developing towards integration and intelligence.
3. Networking of fault diagnosis methods. With the development of modern network technology, modern communication technology can be used for automobile fault diagnosis, and can integrate various components such as management software, diagnosis and maintenance technical information system and expert system of maintenance enterprises, so as to realize the sharing of software and hardware among maintenance enterprises.
Third, the technical methods of automobile fault diagnosis
1, artificial experience diagnosis method: The diagnostician relies on rich practical experience and theoretical knowledge, and uses simple tools to check, test and analyze at the same time by means of seeing, hearing, touching and smelling, and then makes a judgment on the technical condition of the automobile. There are direct detection method, substitution method, condition change method, sequence check method, segmentation exclusion method and so on. Especially for random faults in automobile operation, it is still an effective diagnosis method until now. But it can only make qualitative analysis of faults, and it is difficult to diagnose complex faults caused by various factors. The accuracy and speed of diagnosis depend on the technical level of diagnostic technicians. After continuous accumulation, summary and improvement, empirical diagnosis methods have developed towards artificial intelligence analysis and logical reasoning. When using this method, it is generally necessary to understand the use and maintenance of the car first, make clear the fault characteristics and its accompanying phenomena, and then make reasoning analysis and judgment from the simple to the complex. Diagnostic methods can be roughly divided into observation, inspection, hearing, smelling, touching and testing.
2. Diagnostic methods of instruments and equipment
Based on the traditional manual experience diagnosis method, the diagnosis method of instruments and equipment is gradually developed with the progress of society and science and technology. Compared with manual experience diagnosis method, its differences are as follows: first, it needs the help of instruments; Second, the inspection results can be quantified.
At present, the available instruments and equipment include: multimeter, ignition timing lamp, cylinder pressure gauge, vacuum gauge, oil pressure gauge, sound level meter, flowmeter, oil consumption meter, oscilloscope, cylinder leakage detector, crankcase blowby detector, gas analyzer, smoke meter, dynamometer with relatively complete functions, four-wheel locator, brake test bench, sideslip test bench, engine comprehensive detector, chassis dynamometer and so on. These instruments and equipment provide reliable tools for people, and make the automobile fault diagnosis develop from qualitative diagnosis to quantitative diagnosis.
The diagnosis method of modern instruments and equipment has the advantages of fast detection speed, high precision, quantitative analysis and rapid diagnosis. Modern electronic instruments and equipment controlled by microcomputer can automatically analyze, judge, store and print out various performance parameters of automobiles. However, its disadvantages are large investment, special workshop, training of operators and high testing cost. This diagnosis method is suitable for automobile inspection stations and large and medium-sized maintenance enterprises. It is an inevitable trend for the development of automobile diagnosis and detection technology to adopt modern instruments and equipment diagnosis methods.
3. Self-diagnosis method of automobile fault.
With the progress of modern science and technology, especially computer technology, the auto fault self-diagnosis technology developed with the development of auto electronic control technology at the end of 20th century. The complexity of the mechanism and structure of automobile electronic control system requires it to establish a reliable fault self-diagnosis system. 1979, GM first applied the ECU self-diagnosis system to automobiles. The system consists of software stored in ECU and corresponding hardware. When the car is running, ECU constantly monitors the working conditions of all components in the system. If there is a fault, ECU will first enter the fail-safe mode according to the nature and degree of the fault, so that the car may drive to a nearby maintenance point to troubleshoot. At the same time, it stores fault information in the form of code. When the vehicle is in maintenance, special instruments and methods are used to extract the fault code, and then the fault is cleared. This auto fault self-diagnosis system is also called OBD.
Four, fault diagnosis and detection process
1, fault description. Ask carefully about the fault status, such as time, temperature, cold car, hot car, acceleration and deceleration, mileage, sunny or rainy day. In the whole maintenance process, the fault description is very important and can not be ignored.
2. First visit
2. 1 According to the understanding of fault symptoms, fault system and accumulated experience, we can make a preliminary judgment on the center of the fault. For example, what system, where, equipment related to fault symptoms, etc. For example, the extension subsystem has many subsystems. Which systems are the failures related to? This judgment is a preliminary judgment, but the judgment has a rational understanding, which is based on your understanding of the fault and your experience and knowledge. It is not an objective thing, but a stage created by your brain thinking. Is this conclusion correct? We must test it.
2.2 Use appropriate instruments and equipment for simple and rapid detection of preliminary judgments, such as related fault codes.
2.3 Relevant technical data, this is very important, because with the upgrading of vehicles and the acceleration of technological changes, technical data is also essential, and specialized factories directly receive technical support in time.
Step 3 Replace the test
3. 1 substitution has two principles. One is to use parts with good performance instead of new parts, and new parts are not equal to good parts. Good performance means that there is no problem in correct use on similar vehicles. Second, when replacing, we should change them one by one. Some people keep changing, and in the end, you don't know which one is wrong.
3.2 The replaced experiment should be consistent with the fault state, and the replaced experiment must be equal to the fault state, otherwise it is meaningless to replace the experiment.
4, road test, there is a principle, who must accompany the customer to test, by him to accompany the customer to experiment.
4. 1 A good test driver should be very familiar with the car condition and road conditions.
4.2 All functions of the system must be verified. Nowadays, cars pay attention to not only good gear shifting, but also quality control, gear shifting process, forced car changing process and TOC control process, including engine functions. It can't be said that people have eight functions, and car owners won't agree if they repair three functions. So no matter which system you fix, all the functions have to be tested.
Five, diagnosis, detection methods and skills
1, proficient in the use of various test instruments. Mastering the model, connection, selection and use of instruments skillfully, the application of a function depends on people's understanding of instruments.
2, understand the location of the measuring device, circuit (such as interface, pin, line color, signal type, etc. ), press it to the circuit diagram and find the location diagram. 60-80% faults in the circuit can be analyzed on the circuit diagram according to the phenomenon, and the measuring points can be analyzed according to the circuit diagram. Now all repairmen can't see clearly the stress on the circuit, which is feasible.
3. Select appropriate and reasonable measuring components, connect the test equipment correctly, and record the test data comprehensively and truly. Some things, if it is very difficult to measure by hand, and many things have to be dismantled, but you can't get rid of them, then you can also measure with the same equipment at this time.
4, comprehensive and correct analysis of the information obtained, if the measurement is wrong, you may come to the wrong conclusion, but there are always people who do not admit their mistakes. Therefore, when recording data, it is also necessary to be comprehensive and true. At the beginning of the measurement, we didn't know what use these data were. In the process of analysis, we need various data.
Conclusion: By discussing the methods of automobile detection and fault diagnosis, it is helpful for automobile maintenance workers to quickly diagnose the cause and location of the fault when the automobile breaks down, carry out maintenance in time, improve the efficiency of automobile maintenance and automobile use, and make the automobile benefit mankind.
References:
Wu Bo. Research on automobile engine fault and diagnosis [J]. Heilongjiang science and technology information; 20 10.(0 1)
[2] Zhen Ruidong. Automobile engine fault detection and maintenance [J]. Management and technology of small and medium-sized enterprises; 2009; 28
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