"LQI control of dual-clutch transmission systems in hybrid vehicles with P2 architecture"

The automotive industry is facing many challenges related to different fields, in particular it is becoming more and more important the improvement of the technologies related to the reduction of emissions, fuel consumption and driving comfort. Considering all these factors, that are becoming crucial for the success of a new product, the companies are giving particular attention to the developement of more efficient transmission systems. The environmental needs and legislative pressure for a significant CO2 emissions reduction in the coming years forces the automotive industry to optimize every single component of the next generation vehicles. In this dissertation, realized in collaboration with Centro Ricerche Fiat (CRF), a Linear Quadratic Integral approach is implemented in order to control a Dry Dual Clutch Transmission system in hybrid vehicles with P2 architecture, during the slipping phase. The main objectives of the control are related to an improvement of the vehicle comfort, drivability and robustness; a better gearbox/clutch maneuver smoothness and the minimization at the same time of vibrations and abrupt movements. In particular, the analysis is focused on the Dry Dual Clutch Transmission (DDCT) developed by Fiat Power-train Technologies. The aim of the control is that to ensure that the slipping speed, that is the speed difference between the disks of the clutch, reaches the zero value in a smooth way, after following a given reference. The clutch engagement problem is here analysed, focusing on the Dual Clutch Transmission (DCT) system, in the following operational conditions: one DCT clutch is in slipping phase, the other is opened, while the combustion engine is ON. The necessity to optimize the transmission is related to the fact that it allows the engine’s energy to flow directly to the wheels. A simplified model of the transmission is here implemented with clutch actuator, dynamic engine model and elasticity of the transmission shafts. Some uncertainties have to be considered in the control: the delays of the clutch and engine actuators, the clutch transmissibility, vehicle mass and the drive shaft torsion effects. Firstly a Linear Quadratic Integral controller for the plant without actuators is simulated: both the engine and clutch torques are considered as inputs computed by the controller and the outputs are equal to the states - engine speed, slipping speed, drive shaft torsional speed and angle. Then, with the aim of improving the model making it more realistic, the actuators and delays are introduced in the model and some techniques are introduced together with the LQI control strategy in order to compensate them, obtaining a more complex state space representation of the plant that in this case, being more accurate, gives more reliable results. The impossibility to measure the actuators states, makes necessary the introduction of a state estimation with the Kalman Filter that results to be the best way to manage the uncertainties related to the presence of the delays. In conclusion, the Linear Quadratic Integral approach for the clutch slipping control turns out to be advantageous in terms of performances that are assessed in terms of Standard deviation and Root Mean Square Error (RMSE) and also for its flexibility that makes possible the introduction of other control strategies suitable for the actuators management.