Dynamic Factor Analysis Of Subjective Evaluation Of Vehicle Steering Performance

Vehicle steering performance, as an important part of vehicle chassis performance, hasbecome a “hot” area in current research. The subjective evaluation of steering performanceshould be carried out based on assembly characteristics to meet the design requirement. Inrecent years, the research of subjective evaluation of vehicle steering performance hasattracted much attention from most car enterprises.In the process of subjective evaluation, nearly all of vehicle companies would applyseveral qualified evaluators to evaluate its target. Generally, for subjective evaluation, thetarget is a real car, the test field is a real site and the conclusion is obtained by driver’sfeeling. However, there are some shortcomings for this kind of subjective evaluation, such aslong test period, high cost, uneven level of evaluators, lacking of adjustable parts of test car.In order to solve these disadvantages, the thesis has explored vehicle subjective evaluation ofsteering performance and analyzed dynamic factors of negative phenomena in each item.Different from traditional subjective evaluation which is based on the feeling ofevaluators, the subjective evaluation in this paper is based on dynamic analysis. The authortried to seek physical signals that affect evaluators’ feeling during subjective evaluationprocess. After finding these potential signals, the author tried to transform them intocharacteristic quantities through mathematical methods which can measure the intensity ofnegative phenomena. By signalizing subjective feeling of evaluators, the paper enabledsubjective evaluation to be advanced to development stage. The study is as follows:Firstly, through investigating evaluators in several vehicle companies and referencingsubjective evaluation systems of international vehicle companies and research institutions, alist of subjective evaluation items and their corresponding operating conditions of steeringperformance is established. The steering performance is a vehicle’s dynamic characteristicswhen its steering input exists, including characteristics of steering wheel torque, steering response, steering wheel return, track keeping and rolling. In these characteristics, the paperfocused on aspects concerned with subjective evaluation. According to negative phenomena,the steering performance was divided into11items. For each item, the paper described thenegative phenomena, analyzed principles of dynamics and concluded required operatingconditions.Secondly, after investigating experiences of many evaluators, the paper analyzed andchose physical signals related to each negative phenomenon. These signals are evaluationbasis for measuring intensity of negative phenomena. One phenomenon could have severalrelated signals and different phenomena could share a same signal, but in different analysisangle. It was found that in the process of subjective evaluation, for phenomena reflecting asame steering characteristic, the required signals are always the same as well. Therefore, thepaper discussed the mathematical methods of obtaining characteristic quantities based oneach steering characteristic. The paper then concluded the methods corresponding tonegative phenomena on a case by case basis.Finally, a test on ASCL simulator was carried out. The goal of the test is to verify thephysical signals being stimulated by driver in operating condition of each negativephenomenon and the signals reflecting the intensity of those phenomena. Compared to realcar tests, the test on ASCL simulator has plenty of advantages. For example, the output datais more various and accurate than that of real car test, the test field is undisturbed by severeweather all the time, the test scenarios and kinetic parameters could be set according to theneed and the test is away from danger. Through the test, it is verified that the physical signalsshowed noticeable changes when phenomena were stimulated.