Research On The Test System Of Roller Opposite Forces Type Automobile Braking Tester

The test of automobile braking performance is one of the importantparts in automobile safety test. Whether the choiceness of brakingcapacities or not is related to securities of automobile directly.Automobile braking capacity is one of automotive main capacity,whichmeans braking ability under steam of man-made reducing speed to parkbasing on demand. Automobile braking performance not only depends onthe performance of the braking system,but also relates to theperformance of automobile driving, tyres mechanical characteristics,road conditions clinged to the ground and the characteristics of thehuman body engineering related to braking operation closely. Therefore,the researches on the test system of automotive braking performanceprovide technical support and guidance for the science research and testof the test system. So it is of great significance to research onautomobile braking test system with high precision and high automaticdegree.Test technology is one of the important parts of the modernmanufacture technology. With the development of electronic technologyand mechanical processing industries, it is gradually becoming modernautomobile diagnostic and test technology on the basis of thetraditional test methods. Automobile test usually means to inspectautomobile's conditions by modern test techniques and equipments withthe help of the computer and automation and other high-tech. It is aintegrative technology based on engineering mathematics, fault physics,reliability theory, electronics, electron technic and informationcontrolling theory and so forth. There are essential meanings toguarantee traffic safety,protect the environment, enhance carryingcapacity and decrease production cost. There is practical meaning tochoose automobile performance test as a researching task. The content of this thesis is research on the test system of rolleropposite forces type automobile braking tester. First of all, the thesisnarrates domestic and foreign actuality and the future direction ofdevelopment on the automobile braking tester. Based on main technicqualification of automobile braking system which has been broughtforward in GB7258-2004, thethesis analyzes and evaluates the test items and related standards. Theyhave been analysed and narrated that the overall structure and workingprinciple of the automobile braking test. To anlalyze the forces whichautomobile braking tester has been taken,and then analyze the impactfactors on braking performance. The methods to choose roller dimension,rotational speed and surface materials of automobile braking testerhave been given. It has also been given to choose the basis andparameters about the motor and retarder.According to the automobile braking tester, it has been designedthat the hardware circuit of the test system based on AT89C52single-chip microcomputer, including A/D circuits for sensorinterfaces, circuits for indicating and display device, driving orswitch circuits to control motors, the communication interface circuitsbetween the single-chip microcomputer and PC, etc. The signals ofsensors must be rectified firstly before they are collected by datacollecting equipments accurately and reliably. This beginningprocessing is called signal adjustment which includes universalfunction such as signals magnifying,filtering,insulating and so on.The thesis designs adjusting circuits of signals according to differentsignals of sensors output. There are many kinds of interfering signalssuch as high voltage or big current interfering. Therefore, V/I circuitis designed, which converts signals from voltage to current. At the endof controlling machine, signal of current must be converted to voltageand magnified. In order to measure the performance of the automobilebraking accurately and protect the electromotor,we must measure both braking force and wheel speed. The process of test system is consistedof real time data collection and real time control. The real time ismainly incarnated in the speed of data collecting and measurement forthe wheel speed signal. Speed measurement is used to control turningon and off the electromotor in the tester. To realize this, test systemmust both collect braking forces data and measure speed signalsimultaneously. In order not to loss braking forces data and guaranteereal time signal of the speed measure, there is a F/V circuit in thisthesis to convert frequency signal to voltage signal, and then it isconverted to digital signal by A/D convertor. According to therequirements of measure precision, high-performance A/D converter chipAD1674 is adopted as the core data collection.According to the requirements of test items and the functions,software has been designed in the test system. The programs are compiledby senior language. The functions of the programs are test system entry,data test, data inquiry and print and so on. The communication protocolbetween the single-chip computer and the PC has been set up. The paperincreases the system of data processing in the automotive braking testsystem to constitute an automatic diagnosis system which can realizeautomatic diagnosis to automotive malfunctions. Because of infectionof strong electromagnetism in industry locale and sensors andprocessing circuits, there are kinds of multi-frequenciesinterferential noise signals in the sensors'signals which aretransmitted to test system across circuitries. In the serious situation,these kinds of noise signals will cover the input signals that are readyto be extracted, and the system can't get the measured signals. In orderto eliminate and restrain the interferential signals in the test system,the software to resist interference is designed for the system. Thedesign of the software to resist interference is mainly self-diagnosisand error-correcting program, it enhances self-defense capability ofthe computer system, and it can obviously enhance stability and reliability of system, and may also farthest reduce the hardware costof the test system to realize the anti-jamming requirement.This task depends mainly on the theory. But it is completed withthe help of practical debugging and test. This automobile braking testsystem is good at high precision, good reliability and its real time.Furthermore it works well in practical condition. It has banausic valuein inspecting automobile braking performance and the development of theinspecting instrument.