Steering U-Joint Non-Unifromity Optimal Design (Master Thesis)

The crossing universal joint has been widely used in the steering system of automobile, due to the demand of the dimensional transmission connection. However, the crossing universal joint has the velocity non-uniformity characteristic, which will not only result in the steering effort fluctuation, but also affect the vehicle response, if not design properly. In addition, the excite fluctuation would generate vibration and noise, make the part wear rapidly, and affect the vehicle steering operation feel negatively. Conversely, if designed properly, appropriate fluctuation, a fast vehicle response on center could benefit the vehicle dynamic and handling performance. By optimizing the design of the steering universal joint non-uniformity characteristic, we can make good use of its advantages to benefit the vehicle dynamic and handling feature, and eliminate its disadvantages.In this paper, the velocity non-uniformity characteristic of the steering system crossing universal joint is studied. According to the transfer function, utilizing the MATLAB programming and its graphics function, the formula was visualized. By adjusting the input parameter, it is easy to observe the influence to the non-uniformity variation including amplitude and phase. The steering non-uniformity of a certain vehicle under development was analyzed and optimized to improve the vehicle steering performance. Meanwhile this paper proposed to use the partial derivative for analyzing the sensitivity of each input parameter based on one certain vehicle geometry, finally it outputs not only the order of the sensitivity for each parameter, but also indicates the affect direction of each parameter. In addition, the variation of the non-uniformity was estimated based on the specific vehicle geometry tolerance utilizing the MATLAB programing. The output will be favorable for the steering non-uniformity optimized design and geometry tolerance design, the study provides the theory guidance for balancing between the steering performance variation and tolerance cost, which will be very valuable practically. Then the original and final steering system design performance was simulated in CarSim, to proof the advantages of the optimized design. Finally the vehicle test result was analyzed and aligned with the theoretical calculation, which proves that the theoretical calculation is correct.