All Wheel Drive Hardware Dependant Control

Abstract: Haldex Traction AB designs and manufactures an all wheel drive system called Haldex Limited Slip Coupling. A slip controller controls the speed differences between the front and rear shafts in the all wheel drive vehicle. The product exists in three generations and a fourth, with some major hardware differences, is under development. The variations in hardware lead to widely different demands on the control software of the slip controller. This master thesis presents a well-founded comparison between Generation I and IV from a control design perspective. Two models were made of the coupling, one for the two generations respectively, and simulated together with a simple vehicle model and a PID controller. The control parameters were tuned for a normal driving condition and then tested for different disturbances. The simulations show that the slip controller in Generation IV can be made faster due to less embedded delay in the coupling. Generation I on the other side is more robust to changes in friction between the tyres and the surface and is more stable for time delays from the CANbus.