Design of nonlinear shaft torque observer for trucks with Automated Manual Transmission

Knowledge of drive axle shaft torque improves the longitudinal dynamic performance of vehicles. An axle shaft torque observer is proposed for vehicles with stepped ratio transmissions, which is a class of switching systems. Model uncertainties, including the steady state error and the unmodeled dynamics, are considered as an additive disturbance input and the observer is designed such that the error dynamics is input-to-state stable for all gear positions. The lowest possible gain of the designed observer is achieved by solving a set of LMIs. In the designed reduced-order observer, the complex nonlinear characteristics of powertrain systems are included and appears as their usual form of MAPs. Finally, the proposed observer is tested on an AMESim powertrain simulation model of a medium-duty truck.