Bench Detection Approach And Experimental Study For Auto Anti-lock Braking System

In order to improve the active safety of automobile, Anti-lock Braking System (ABS) isgenerally installed. It can prevent the automobile from deviation brake, rear axle sideslip andsteering failure caused for wheels lock by controlling and adjusting the wheel brake pressure.And enable the automobile to make the best use of the ground braking force to slow down andstop, therefore, the braking performance and active safety of automobiles are effectivelyimproved. Currently, the main approach to detect the performance of auto ABS is the roadexperiment. However, the disadvantages of large area occupation, high construction cost of thetest site, long test time, dangerous, susceptible to environment influences and poorreproducibility make it difficult to implement. So, the road experiment is only suitable for ABStype-match experiment of special automobiles or ABS sampling inspection and not suitablefor the periodic testing of a large number of automobiles.To solve the problems above, a novel ABS indoor bench detection approach is proposedin this paper. Translational inertia of automobile and different adhesion coefficients aresimulated on the bench. The real-time speeds of the wheels and the automobile are collectedduring braking process, and technical parameters that can reflect the ABS performance arecalculated. Then, data analysis is performed based on Principal Component Analysis (PCA)and neural network, and ultimately the realization of entire automobile ABS detection andautomatic determination of the ABS detection results are achieved. Compared with the roadexperiment, the ABS bench detection approach has the advantages of small area occupation,low cost, high efficiency, high safety, good repeatability and insusceptible to environmentinfluences, etc.The main research contents are described as follows:(1) An indoor bench detection approach for auto ABS is proposed. The rolling drums areused to simulate the continuously moving road. Translational inertia of the automobilebraking on the road is simulated by the moment of inertia of flywheel on the bench. Differentadhesion coefficients of road surface are dynamically simulated through loading different torques to the drums by the torque controllers. The mathematical model of different adhesioncoefficient simulation is built based on study of the structure and working principles of thetorque controller. The value of flywheel moment of inertia needed on the test bench isdetermined according to the translational inertia of braking on the road.(2) Computer simulation for ABS bench detection approach is studied. According to theABS bench detection theory, the vehicle model, wheel model, brake system model, slip ratio-adhesion coefficient model, braking force model, ect. on the test bench are established. AndMatlab/Simulink simulation model of a quarter-vehicle braking on the test bench is builtaccording to the relationship of each sub-model. Simulations under a variety of simulatedroad conditions are conducted in order to verify the correctness and feasibility of the benchdetection theory.(3) The technical solutions and the overall structure of the ABS test bench andmeasurement&control system are studied. The test bench has the functions of axle loadmeasurement, normal brake performance test, ABS performance test and speedometer test.The front and rear axle of an automobile can be detected at the same time for the ABSperformance, and the drum center distance between the the front and the rear bench can beautomatically adjusted according to the automobile wheelbase information. The system canoffer different road adhesion coefficient for each wheel at the same time. The measurementand control system is proposed based on CAN bus structure, and the communication protocolamong host computer and the intelligent modules is designed and realized. Proper detectionprocess and application software are designed and realized according to the ABS auto-testrequirement.(4) Comparative analysis between ABS bench test and road experiment is performed.Experiments with several types of automobile are conducted on the ABS detection benchproposed in this paper, including the experiments on single high adhesion coefficient road,single low adhesion coefficient road, split-μ surface road and connection-μ surface road. ABSroad experiments with the same automobile under the same braking conditions are performed,and the results are compared and analyzed with those from bench test. The results show that the bench tests achieve good compliance with road experiments under the same brakingconditions. And the proposed ABS bench detection approach can correctly simulate the roadexperiment conditions and realize the entire automobile ABS performance detection.(5) A judgment method for ABS test results based on principal component analysis andBP neural network is proposed. Firstly, the principal component analysis is adopted to processthe technical parameters of the test results to remove the correlation and redundantinformation among them, and the dimension of feature vectors is reduced at the same time.Then a classifier model based on BP neural network is built and the structure of network,neuron number of the input layers, output layers and hidden layer are determined. At last,ABS test results judgment algorithm based on principal component analysis and BP neuralnetwork classifier is put forward, and a small number of principal components withcomprehensive information is input into neural network classifier to complete the test resultsjudgment.The research of this paper is a frontier research topic in automobile performance testfield. The research results can effectively solve the problem of testing the performance of autoABS by the existing automobile test platform and have a great significance for promoting thedevelopment of automobile detection technology and equipment of China.