| Vehicle braking performance is an important factor in safe driving. The GB7258—2004 legislate that all of the motor vehicle must be regularly tested their braking performance. The roller opposite force type brake tester is the main equipment to test the motor vehicle's running and parking brake performance. So, only keep the brake testers' metrological performance good, can ensure the testing results accurate and reliable. Therefore, it is necessary to make the verification for break testers regularly to check their metrological performance. JJG906—2009 has seven requirements of metrological performance for break testers and provide the corresponding verifying methods. The most important one is the verification of indication error. Use the lever to load standard force values on the force sensor and then compare the measured value with the standard value. If the relative error within±5%, the brake testers are considered to be qualified. The outstanding feature of this method is static. However, the actual testing brake force is a dynamic process. So, sometimes, a qualified brake tester, verified by the metrological executive branch, will still give a wrong judgment. The main reason is that static calibration can not reflect the actual dynamic measurement performance of brake testers.The main purpose of this paper is to design a dynamic calibration equipment for roller opposite force type brake testers to achieve the dynamic calibration of the brake testers.This paper's research includes mainly the following aspects:1. First, this paper introduced the basic structure and working principle of roller opposite force type brake testers, and made the stress analysis of the wheels when the brake testers was working. The difference between static calibration and dynamic measurement was analyzed at the condition of force transferring process when the brake tester was testing the force. Then made the stress analysis of this dynamic process of force transferring and proposed the theory of dynamic calibration. Through the design of a dynamic calibration equipment, let the roller rotate when calibrating the brake testers. The dynamic calibration equipment loads the force changing according to a pre-set curve on the gearbox. Then the force lever transfers the force to the force sensor. Thus, simulate the actual measuring situation when the brake tester is testing. The measurement system of brake testers can also get a braking force curve. Then compare the two curves, we can know the actual dynamic measuring performance of the brake testers. In short, load a known force curve on the brake testers and let the brake testers to measure, then compare error of the two curves.2. According to the dynamic calibration theory, on the SolidWorks platform, this paper has designed two dynamic calibration equipments for roller opposite force type brake testers and explains their working principle. The main difference between the two sets of calibration equipments is on the devices of providing power. The power of one's providing power device is provided by a servo motor and the other's is provided by the hydraulic servo force mechanism. According to the servo motor's dynamic calibration equipment, this paper has illustrated the selection of related parts.3. Describes the hardware units of dynamic calibration system. This paper has reasonable selections on the digital input & output I/O cards, A/D cards, and signal conditioning modules. Use the programming language Visual C++6.0 to realize the export of testing data. Elaborate the proximity switch's classifications and its work principle, and also make a reasonable selection. In terms of software, in order to achieve the purpose of automatic calibration, use a modular idea in the software designing. The main part of the software system is automatic calibration module. In this paper, the flow chart of the entire calibration system for calibrating has been showed.4. Using the dynamic calibration theory, this paper has put forward some new metrological performances including the maximum loss of braking force, the braking force difference, the repeatability, and the response time of fast step on the brake. The accuracy of the dynamic calibration equipment and its main error sources have been analyzed in this paper. And the calibration experiment has been carried out. First, carry the static calibration for a brake tester, then carry the dynamic calibration. Finally, the processed and analyzed experimental data showed that the dynamic calibration system can make reasonable judgments on the dynamic performance of break testers.
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