Integrated powertrain control of gearshifts on twin clutch transmissions

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Integrated powertrain control of gearshifts on twin clutch transmissions

Goetz, M. / Levesley, M.C. / Crolla, D.A.

In this paper a gearshift controller for clutch-to-clutch shifts on twin clutch transmissions has been developed. The controller makes use of a closed loop clutch slip control for better control of the engine torque transfer in the torque phase of both upshift and downshift. The advantage of this clutch slip control in avoiding harsh changes in transmission output torque with subsequent torque vibration have been demonstrated based on simulation results. A further key feature of the presented controller was the consequent utilization of engine control in both upshift and downshift control strategies. Simulation results have shown that the transmission output torque trajectory on an upshift can be smoothed out in the inertia phase compared to a conventional pressure-based upshift control. On a downshift increasing the throttle angle during the inertia phase can aid synchronization thus avoiding reduction in wheel traction on fast shifts. A main feature employed on both upshift and downshift control as an optional extension to the existing control was the closed-loop control of transmission output torque. The advantages of such a control are manifold ranging from a direct influence of the gearshift character to added robustness. The feature is especially useful for an integrated torque management schema where all powertrain components are controlled based on calculated reference profiles for wheel torque thus reflecting the request of the driver for propulsion power. Torque control has been employed in the inertia phase of the upshift and in the torque phase of the downshift. Simulation results have demonstrated the advantages of such a torque control particularly for the downshift where the torque increase due to the change in gear ratio could be effectively controlled by choosing the appropriate reference profile.