Research On The Methods Of Subjective Evaluation For Handling And Stability Of A Car

Chinese rapid economic development and comprehensive national strength growing have promoted the development of the auto industry, one of the Chinese pillar industry, as a result that Chinese vehicle production output and consumer market are expanding rapidly. However, due to the late begining of the automobile industry, the corporate R & D base is relatively weak, as results in a disparity between our owns and foreign brands in product performance and the international reputation. At the same time, Chinese own automotive products are facing unprecedented competitive pressure from the joint-stock brands products. At present, during the automotive product development process of the international well-known automobile manufacturers, the subjective evaluation are applied as the ultimate test of product development, being formed a mature subjective evaluation system of automotive performance and quality; while At present, Chinese automobile self-developing capacity is relatively weak, especially in the automotive performance tuning of chassis, and the tasks are mostly commissioned to the foreign design companies. In order to improve self-developing capacity of Chinese automobile products, especially in the chassis tuning capability, learning from the mature experience of foreign countries and establishing a subjective evaluation system suiting to China's auto enterprises are imperative.According to the reality of China's automobile industry, this paper researches and practices the subjective evaluation method of passenger cars. First, the paper analyzes, summarizes and classifies the mature foreign subjective evaluation method; on this basis, it puts forward a complete set of subjective evaluation system for passenger cars. According to this system, the subjective evaluation test with several drivers and cars was carried out. In allusion to the situation that our Chinese subjective evaluators are with limited average abilities, this paper puts forward a method to appraise the evaluator's subjective evaluating ability and the one to test the credibility of the subjective evaluation results, as well as the one to simplify the evaluation system. Based on the situation that it is difficult for our evaluators to give the overall ratings to the vehicles handling and stability, the paper as well proposes the method to determine the weighting factor of the individual subjective evaluation index with applying the FAHP theory.I. Analysis and summary of the mature foreign subjective evaluation methodThrough the analysis of vehicle development process, it was found that the evaluation of the vehicle performance plays an important role on the development of the cars, while the subjective evaluation of vehicle handling and stability is one of the most important steps in the process. This paper has collected the mature foreign subjective evaluation and rating methods, and analyzed and summarized these evaluating methods, testing method and rating method.II. The establishment of the subjective evaluation system of passenger car handling and stabilityTo establish the subjective evaluation system, the first thing to do is to classify the vehicle chassis performance reasonably. This paper passenger separates the cars chassis performance generally into the performance indicators and the quality of the dynamic process to make the subjective and objective evaluation respectively independent; and whereas the indicators of the subjective evaluation of vehicle are comparatively too may, based on the maneuverability and driving stability of vehicles, the subjective evaluation system is divided into the steering handling and the handling stability. On the basis of the reasonable division of the cars chassis performance, learning to the experience and lessons of the collected methods of subjective evaluation, this paper originally puts forward a complete set of subjective evaluation system for passenger cars and also explains the test method, the scoring method but also the dynamics principle and the effect of the indicators.III. A method to appraise the evaluator's subjective evaluating abilityOn the basis of the completed and reasonable subjective evaluation system established, the ability of the evaluators becomes the determination factor of the reasonability and reliability of the evaluation results. This paper proposes to use the sensory evaluation index for appraising the individual evaluator's subjective evaluating ability, and to use SN method for testing the evaluator's subjective evaluating repeatability. The paper has given an exhaustive introduction to the steps of methods above. Based on the test data, the methods have been validated, computing results have been analyzed and a well conclusion is got.IV. Simplification of the evaluation system and the testing of the evaluation reliabilityBecause there are too many factors which will have an effect on the results of the subjective evaluation and all these factors will more or less effect the exertion of the evaluators'subjective evaluating ability, testing the evaluators'ability only could not assure the reasonability and reliability of the evaluation results. Therefore filtration of the evaluation results is one of the most important steps of the treatment of the results. Based on this reason, the correlation analysis method is used for filtering the results of evaluation and the evaluator with bad ratings is eliminated and the reasonable result ia got.In addition, the indicators of the subjective evaluation are in the state of with great number, as a result it is easy for the evaluators to get an similar comprehension, furthermore the more complex the indicators are, the longer the development process will last. This will result in more cost. So it is necessary to simplify the evaluation system. This paper applies the Correlation Analysis Method to analyzing the evaluators'ratings and finds the indicator with a high correlation coefficient then analyzes the reason from the aspect of dynamics and puts forward the proposal for simplification of the system.V. Determination of the weight factors of the subjective evaluation indicatorsThrough the analysis of the important effect of the subjective evaluation in the developing process and the level of our evaluators, this paper discusses the important effect of the weight factors of subjective evaluation on the development process and the carrying-out of the subjective evaluation. The FAHP method is originally used for determining the weight factors of the subjective evaluation indicators and analyzing the results. At the beginning, the theoretical fundament and the basic steps of FAHP were briefly introduced, and then a FAHP method on the basis of the complementary matrix with triangle fuzzy numbers was focused on. After that a hierarchical structure model of the subjective evaluation was established. Three evaluators were asked to weigh each pair of the indicators and then comparison matrixes on the basis of fuzzy numbers were established. All the evaluators are with great experience and good understanding of the evaluation system and the FAHP scale. According to the testing data, the weight factors were analyzed and tested and a reasonable conclusion has been got. These factors provide the basis of quantifying the subjective evaluation and the developing process.In summary, this paper carries out the comprehensive and in-depth research on the establishment of the evaluation system, the appraisal of the evaluator, the treatment for the evaluation results and the weight factors of the evaluation index. The innovations are as follows:i. Through the research on the mature subjective evaluation method of vehicles handling and stability, a complete set of subjective evaluation system of handling and stability for passenger cars has been put forward.ii. The paper has proposed to use the sensory evaluation index and SN method for appraising the individual evaluators'subjective evaluating ability. iii. This paper has put forward a method of simplifying the system and filtering the evaluators'ratings by applying the Correlation Analysis Method, which has eliminated the effect of the bad ratings and improved the credibility of the results.iv. The paper has proposed to use the FAHP for determining the weight factors of the subjective evaluation indicators. Via the evaluation test, the reasonability of the factors have been proof-tested.