Multi-objective Parameter Optimization of Automatic Transmission Shift Control Profiles

This paper proposes a method for multi-objective parameter optimization of piecewise linear time profiles for control of Automatic Transmission (AT) shifts and presents results obtained on an example of a powertrain with a 10-speed automatic transmission. The paper first outlines the powertrain dynamics model. Then, the AT control trajectory optimization approach is outlined and employed with the aim of getting insights into the optimal shift control profiles and related performance. The parameter optimization problem is to find parameters of piecewise linear shift control profiles, which provide a trade-off between the shift comfort and performance. The optimization problem is solved by using the multi-objective genetic algorithm MOGA-II incorporated within modeFRONTIER environment. As an extension of the parameter optimization approach, a method for robust parameter optimization is proposed, which aims at ensuring high shift quality and robustness in the presence of transmission actuation parameter variations. The objective is to find shift control profile parameters that simultaneously minimize mean values of vehicle jerk and shift duration indices as well as their standard deviations for improved robustness against change of transmission parameters. The overall optimization approach is demonstrated first on an example of a single-transition power-on upshift, and the obtained optimization results are analyzed and compared to the control trajectory and non-robust parameter optimization results. The analysis points out that the shift robustness can be improved by sacrificing comfort. Finally, the method is applied to a double-transition power-on downshift to illustrate its applicability for more demanding transmission control tasks.