Improvement of Shift Quality in Power-On Upshift using Motor Torque Control
Examensarbete för masterexamen
Automotive engineering (MPAUT), MSc
The transmission is a very crucial part of a vehicle, especially if the prime mover is a combustion engine, since such a power source has a rather low torque at low engine speeds. There would not be enough torque to accelerate the vehicle at an acceptable rate while still reaching acceptable top speed. There is a need for several gears to achieve this, thus making the transmission mandatory in such vehicles. Increasing demands on modern vehicles for minimizing the environmental impact are putting high requirements on transmissions. Hybrid solutions integrating electric motors are not only reducing the carbon footprint but also opening up possibilities for improving transmission shift quality. In this thesis a dual clutch transmission propelled by an electric motor is analysed in the simulation software AVL Cruise 2015 and Matlab Simulink 2010a in order to investigate and improve the shift quality of the transmission using motor torque control. The transmission is an automatic, powershifting, transmission which means that the torque interruption during the shift procedure is minimal. The four different phases of a shift procedure: filling phase, torque phase, inertia phase and completion phase are studied. A Simulink program was developed including a proportional integrator (PI) controller for comparing the output torque of the transmission to the desired value and control the electric motor torque in order to achieve a smooth torque curve during the power-on upshift procedure. It was found in the results from the simulations that the controller is effective in reducing the torque fluctuations during the power-on upshift procedure both for a low and a high load signal applied to the electric motor. In order to reduce the fluctuations even more, a special strategy aiming to improve the fluctuations during inertia phase, was applied. The result was satisfying but can be further improved and is hence a scope for future development.
Farkostteknik , Hållbar utveckling , Transport , Vehicle Engineering , Sustainable Development , Transport