DTS (Double Transition Shift) transmission can achieve multiple-speed automatic transmission by using minimum number of planetary gear sets and clutches. Historically DTS transmission has been overlooked because of the complexity to perform high quality shifts.
In this paper, a vehicle model with a traditional AT (Automatic Transmission) is studied first using Matlab/SimDriveline; the simulation results and the vehicle road test data show good agreement. Then a DTS transmission is established based on the same vehicle model. An open-loop control module is developed. All possible parameters which can influence the shift performance are studied. The parametric study shows a double transition shift consists of two inter-action shifts, the parameters which can influence the shift quality include the overlap time of these two inter-action shifts, shifts ending time, downshift parameters and upshift parameters; downshift parameters include initial step of an oncoming brake, pressure slope of an oncoming brake, initial step of an offgoing brake, and pressure slope of an offgoing brake; upshift parameters include initial step of an oncoming clutch, and pressure slope of an oncoming clutch. And finally, the comparison of the vehicle performance with the same vehicle data but different transmissions, one is DTS and the other is traditional AT, is presented. The simulation results indicate that DTS vehicle has a smaller shift shock at lower throttle opening positions, minor shift quality decline and better fuel economy performance at higher throttle opening positions.