| Automobile detective & diagnostic technique is a method which examines automobile's status of technology and abilities of work , judging places and reasons of broken-down synthetically using machine electronic acoustics optics technique and so on through the variety of parameter curve and wave form etc . It also can use computer to collect data , to analyze and estimate automatically , to print result of measure . The points of this technique is nicety , credibility , speediness and can be quantitative analysis . That under the process of fast development of automobile industry and along with automobile capability enhancement of people's needs , it urges kinds of high and new technologies such as electronics , optics , computer , sensor , new material to apply on automobile .People describe automobile as a chip of super great type because the applications of these new technologies make the configurations of auto change greatly and increase the quantities of modern electronic components . The services of auto have been changed from machine to electronic diagnoses and replacing parts . New type auto must be examined and maintained through new type equipments . The conventional methods such as watching touching listening that examine automobile's status of technology and abilities of work ,judging places and reasons of broken-down can't adapt the needs of auto technique's fast developments . The application and development of automobile detective & diagnostic technique must be not only in the wake of steps of automobile's fast developments , but also matched with collective direction of auto's progress . Just so , the method can get better effects and check effectively . Inspection technic is one of the concernful parts of the modern manufacture technic. With the development of electricity and mechanism industry it is becoming modern automobile diagnose and inspect technic. Automobile inspection usually means that to inspect automobile's status by modern inspecting technic and instrument and even with the help of the technic of computer and auto control. It is a integrative technology based on engineering mathematics, fault physics, reliability theory, electronics, electron technic and information controlling theory and so forth. There are essential meanings to guarantee traffic safety , protect the environment , enhance carrying capacity and decrease production cost . There is practical meaning to choose automobile performance inspecting as a researching task . Automobile braking capacities is one of auto's main capacities , which means braking abilities under steam of man-made reducing speed to park basing on demand . The choiceness of braking capacities is related to securities of automobile directly . This shows that it is very important to study automobile's braking detective & diagnostic technique . This thesis designs automobile braking performance inspecting and control system. Some primary technic qualification of automobile braking has been brought forward in .inspecting item and correlate criterion of table inspection braking performance has been prescripted in it. The hardware and software are designed according to practical need. In order to restrain the noise, the design of hardware anti-interference and digital filter is necessary. Firstly , establishing the blue print of auto braking performance inspecting and control system The hardware has been designed according to the characteristic of the parameter . Then the thesis introduces the working principle of every part. At last , the software is designed according to detective items and functions . The signals of sensors must be rectified firstly before these are collected by data collecting equipments accurately and credibly . This processing of former end is called signal adjustment which includes universal function such as signals'magnifying , filtering , insulation . The thesis designs circuits of signals'adjustment according to different signals of sensors output . The signal's range of tension sensor is 0 ~ 20mV , voltage signal . There are kinds of jamming such as strong electricity , So , the convertor of V/I is designed , which converts signal from voltage to current . At the end of controlling machine , signal ofcurrent must be converted to voltage and magnified . The design chooses precise current loop receiver-RCV420 which is a production of Rurr-Brown company to achieve this function . This chip which has high capacity and price ratio is used to change 4-20 mA input signal to 0-5 V output signal . There are one high operation amplifier , one in-chip precise resistance network and one precise voltage benchmark of 10V . It's conversion precision is 0.1% , CMR reaching 86dB . The signal's amplifier is AD1674 which is 12bit comparison expression speed A/D switcher of AD company .It is a substitute of AD574 . In order to measure the power of the automobile braking and protect the electromotor , we must measure both braking power and wheel speed . The process of it consists of real time data collection and real time controlling . The real time is quality meanly incarnated in the speed of data collecting and measurement for the wheel speed signal . Speed measurement is used to realized to turn on and off the electromotor in the table . To reach this, one must both collect power data and measure speed signal simultaneously . Speed sensor's output is pulse signal . After amplified and adjusted , it is carried to timing / countering to count the value of speed . The second part is the software and hardware reliability and anti-jamming has been researched . There are kinds of multi-frequencies jamming noise signals in the sensors'signal because infection of strong electromagnetism in industry locale and sensors and processing circuits of amplifying . In this situation , the measure of filtering is needed to get rid of unnecessary noises . Useful signals are in low frequency segment ,noises in high frequency part . So , low frequency signals must be passed and high frequency signals be controlled or attenuated . In order to achieve function ,low-pass filter is designed . The third part is about data processing method including digital filtering arithmetic and data synthesizing techinic . Digital filtering , recuring to some count or estimate program , reduces noise jamming ratio which mix in useful signals in order to enhance signals'qualities . Curve which is drown by simple digital filtering data is not as clean as a whistle . It means that there are noise in... |
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