DIAGNOSING OF CAR ON THE SHORT ROAD

Abstract

This article describes methods of calibrating car speedometer on the road without expensive equipment. The most accurate results are obtained by using marking elements, for instance, the standard road guard fence. The most practical method is synchronous video recording of speedometer and the display of receiver for satellite signals GPS or/and GLONASS. Also, the KhNADU has substantiated methods of checking a car for acceleration and running out onto the road with simple measuring devices - a speedometer and a phone stopwatch. Experiments have shown that the real picture of countermeasures does not fit into generally accepted models, and this should be taken into account when calculating the standards of diagnostic parameters - the path and time of run-outing and acceleration. For check of the car by a known method the horizontal section of the road 2.5...3 km long is necessary. On the most part of the territory of Ukraine such sections are very rare, so it is proposed to check up a car on an acceleration on II and III gears and on a coasting down from 50 or 40 km/h to 20 km/h, using accessible length of 0,5 km. Behavior of car in such conditions was studied, some unknown specificities are discovered and described. The methods of calculation of control values for time of acceleration and time of coasting are offered. The speedometer is a frequency converter of the output shaft of the transmission or the wheels of the car. It inevitably reflects all the errors caused by the uncertainty of the rolling radius of the wheel, including due to atmospheric conditions, the degree of tire warm-up, vehicle loading and its distribution in the longitudinal and transverse directions, etc. Under these conditions, it is necessary to improve the standless diagnostic methods available to ordinary drivers, i.e. on-the-road inspection methods without complicated or prohibitively expensive equipment. So the calibration of the speedometer is a necessary test step and, in critical cases, must be performed at the beginning and end of each test day. Experimentally estimated the error, the required duration of measurement and speed variation when maintaining it by driver or by cruise control. Grading on GPS better when driving south. Calibration equation was obtained for the 2006 Honda Civic: V_GPS = 0,9528 V_speedo. – 0,83.

Keywords: short road, car test, acceleration time, coasting time, GPS, car, speedometer