Multi-objective Parameter Optimization of Control Profiles for Automatic Transmission Double-transition Shifts

In advanced automatic transmissions (ATs) with a high number of gears, a multi-step, double-transition downshifts (DTS) occur, in which typically two pairs of clutches change their state. This paper proposes different definitions of piecewise linear control profiles for performing such downshifts, which are determined based on insights gained by utilizing previously developed AT control trajectory optimization method. Optimal values of control profiles parameters are determined by using a multi-objective optimization method. This results in a Pareto frontier representing a set of solutions for an optimal trade-off between shift comfort and performance. The effectiveness of the proposed optimization approach is demonstrated first for 10-6 DTS of a 10-speed AT. Next, the optimizations are run for different shift scenarios, i.e. for various DTSs and different shift control profiles, with the final aim of analyzing and verifying the proposed shift control strategies. Finally, the control strategies are assessed based on an equivalent performance index extracted from parameter optimization results. The assessment results, including qualitative and quantitative comparisons with the control trajectory optimization results, show that properly set piecewise linear shift control profiles can provide very good DTS performance for a wide range of shift scenarios.