| Automobile brake performance is so important that it is safeguard for safety traffic. It is the automobile brake performance that a automobile is able to stop in a short distance with directional stability or a automobile or a automobile is able to run under a certain speed on a slope. It is show that almost 1/3 traffic accident is caused from bad automobile brake performance. So automobile brake performance is related with the traffic security, it is undoubted that automobile brake performance is very important for traffic security. That is why to select "automobile security performance detecting research" as research subject.It is automobile detecting that to detect the working condition and working capability for a automobile without disassembly it or part of it. It is called modern automobile detecting technique to detect a automobile with advanced equipment & modern technique by computer. It is a syntheses applied science based on engineering mathematics malfunction physics reliability theory electronics & electronics information control theory.We shall detail more on how to collect and processing the datum of automobile brake system in a automobile safety test. This article consist three parts.Firstly we introduce how to design the hardware and software for automobile safety performance testing system. It is defined to compare the brake force with the weight of a car or axle load when detecting the brake performance for a automobile with brake force in GB7258 2004《Security specification for auto car》.The max brake force happens when the wheels stop rotating in detecting automobile brake performance test, we must stop the motor as soon as possible it happens to avoid quartz sand damaging tyres. That is why we need to collect axle load brake force and wheel speed in the test. In order to get this performance index we designed the automobile safety performance testing program based on the logic control theory for the system & requirement for the automobile safety performance test. We designed the automatic control system, data acquisition system and communication program for the testing system.We designed the switching value board, input and output switch and control the drum and motor to react properly timely Moreover we realized the automation during testing with a monitor to display the orders for the inspector.The following are the datum to be colleted in the system: 1.Axle load for left/right axle; 2.Brake force for left/right wheels; 3.Velocity of left/right wheels. We designed different detecting circuits according the different parameter including axle load measuring device, signal processing circuit for force sensor, signal processing circuit for speed sensor and A / D modulus of conversion. At the same time we detailed the principle of operation system and how to design the software according to the requirement for the test and detected datum. The automobile safety test procedure can be divided into real-time control procedure and real-time data acquisition procedure. The real time data acquisition mostly incarnates by data acquisition as well as the real time measuring for drum speed. The real-time detected analog signals shall be translated into digital signals by AD 1674 chip and be transferred into the PC based on the requirement for accuracy of measurement. Hardware is the physical basis for the whole testing system but the software to control the different hardware to teamwork realizing the different functions in the system. We designed the software by C language for the system. The software consist detection system, Primary Control Programming, data acquisition system program, communication software program.We also do some research on the anti-interference measures etc. in the automobile safety performance detecting system in the second part of the article. There are four ways for disturbs to whisk into the system including electromagnetic radiation disturb, power supply system disturb, process door disturb and printed electronic circuits disturb. We take the interference-free capability into consideration when designing the hardware. We found the way to avoid and reduce the interference in the system such as shielding or isolation measure. We introduced the self-check program, redundancy technique, software trap technique into the system to avoid the interference. We processed the collected datum using the software algorithm to improve the reliability for the datum based on the research with numeric filtering technique. For most of the collected datum in the system are digital value by A/D conversion, we have to resolve them into relevant parameter dimensions to display record and print. It is so-called scale conversion. We detailed more on the linear scale transform and non-linear scale transform in this article.Digital filter is that decreasing the noise interference mixed in the useful signal by certain means such as calculation or judgment program, so that we can improve the quality for collected signals. Digital filter is realized by software program having no use for the hardware. We use different filtering means or filtering parameter according to different signals and it proves stable and powerful. We introduced several different common digital filter techniques and balanced them. We determined the detection frequency for brake force signal by experiment and computational comparison and determined to use linear scale means to calibrate the axle load testing system and brake testing system and use anti-impulse interference filtering & low pass filtering technique for digital processing, and we get the outcome conformed by GB7258 -2004《safety specification for auto car》.Experimental evidence proves that the automobile safety testing system is reliable and datum is exact, all these prove the system to be a success.This subject is based on theory incorporated with on-site testing and laboratorial experiment. The automobile safety performance testing system bears high detecting-precision, high reliability & real-time advantage. It also proves satisfied in the in practical situations; it bears more useful-value in automobile brake performance testing and such detecting equipment developing. |
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