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A new generation of a planetary-gear-based automatic transmission system is designed with an increasing number of ratio steps. It requires synchronous operation of one or more wet clutches, to achieve a complex shift event. A missed synchronization results in drive torque disturbance which may be perceived by vehicle occupants as an undesirable shift shock. Accurate knowledge of clutch behaviors in an actual vehicle environment is indispensable for achieving precise clutch controls and reducing shift calibration effort. Wet clutches are routinely evaluated on an industry-standard SAE#2 tester during the clutch design process. While it is a valuable tool for screening relative frictional behaviors, clutch engagement data from a SAE#2 tester do not correlate well with vehicle shift behaviors due to the limited reproducibility of realistic slip, actuator force profiles, and lubrication conditions.

The design discipline of Design For Six Sigma (DFSS) has been applied to many areas of product development and manufacturing. As DFSS application has recently been extended to upfront automotive engineering areas such as research and advanced development, more robust and optimized technologies can be achieved in the pre-production stage, reducing cost, exhibiting superior quality and performance, and shortened development cycle. This paper describes the application of the DFSS process, Define, Characterize, Optimize, and Verify (DCOV) to develop an automotive technology that begins from the conceptual phase and continues up through the implementation phase. The role of DFSS in the automotive industry is to provide a framework for more rigorous upfront engineering. It provides guidelines to a more effective and efficient development of new technologies.

In a step-ratio automatic transmission system, wet friction components are widely utilized to alter planetary gear configurations for automatic shifting. Thus, their engagement characteristics have a direct impact on shift quality or drivetrain NVH. A vehicle design process can benefit from predictive friction component models that allow analytical shift quality evaluation, leading to reduced development time. However, their practical application to shift analysis is seldom discussed in the literature although there are many references available for friction component modeling itself. A successful shift analysis requires a balance of model complexity, predictability and computational efficiency for a given objective. This paper reviews three types of friction component models found in today's open literature, namely, first principle based, algebraic, and empirical models. Model structure, assumptions, computational efficiency, and utilities are discussed.