Improved Integrated Powertrain Control of Gearshifts Using Linear Parameter Varying Control

Automatic transmission designs in automotive powertrains are expected to continue present trends towards higher numbers of transmission gear ratios with wider ratio spreads and smaller ratio steps, owing to their ability to improve fuel economy, while simultaneously satisfying stringent emissions norms. They are also expected to exhibit increased frequency of gearshifting, which requires re-evaluation of various aspects of the control of gearshifts. It is recognized here that clutch-to-clutch gearshift efficiency and quality (comfort) can be improved by minimizing the energy dissipated by the (oncoming) clutch during the speed synchronization (inertia) phase of a power-on upshift, which in turn would require control of both the engine and the (oncoming) clutch during the inertia phase. In order to achieve this control objective in a robust manner, it is proposed that both the engine and the (oncoming) clutch be under feedback control, unlike current practice in transmission control design where only the clutch is under feedback control. Gearshift control is particularly challenging for a 1-2 power-on upshift since the powertrain response is nonlinear due to the open torque converter clutch and, furthermore, a large ratio change is involved. The linear parameter varying (LPV) control technique is used here to design a gain-scheduled observer-based state feedback controller. It is shown through tests on a powertrain simulation that the resulting control solution is effective in controlling the inertia phase of gearshifts at different throttle openings, and is also robust to realistic modeling errors.