Software-in-Loop Development and Experimental Testing of a Semi-Active Magnetorheological Coupl­ing for 4WD on Demand Vehicles

In this paper the development and the experimental testing of a magnetorheological coupling for a 4WD vehicle are presented. Unlike most of the active devices use multidisc wet clutches as engagement mechanism, this device does not have any sliding contact and is characterized by an electrical actuation mechanism. The coupling performance is obtained by means of the magnetorheological fluid (MRF), able to change its rheological behaviour when a magnetic field is applied. Therefore the supply current control allows to manage the torque transmitted to the rear drive shaft. So this device can be used to bias the drive torque between the front and rear drive shafts of a 4WD vehicle. In particular the magnetorheological fluid (MRF) employment allows to realize an adaptive system able to improve vehicle directional behaviour and traction. An MRF coupling model and its control logic have been developed and are described. The results of the simulations carried on with these models are reported; they have shown the feasibility of this application in terms of torque transmission and biasing. The above simulation models have been implemented in a Software-In-the-Loop (SIL) scheme together with a vehicle dynamics model. The SIL results are reported and they show the MRF coupling effectiveness on the vehicle dynamical behaviour. A test bench has been realized to test an MRF coupling prototype in order to verify the capability to transmit torque.