Robust driveshaft torque observer design for stepped ratio transmission in electric vehicles

Knowledge of driveshaft torque is very important to powertrain oscillation damping control as well as gear shift quality improvement. However, the driveshaft torque cannot be easily measured by using affordable sensors. This paper provides a robust driveshaft torque observer design for electric vehicle equipped with stepped ratio transmission. The proposed observer is constructed using the measurable angular velocity signals and designed to be robust against modeling error, system uncertainties as well as external load disturbance. Torsion angle of the driveshaft is selected to be estimated instead of direct torque observation, which can be further used to calculate the driveshaft torsion based on driveshaft׳s spring–damper model. The H∞ performance is adopted in the observer design to minimize the effect of the disturbance on the estimation error. Furthermore, the decay rate of the estimation error and transient response of the observer are also considered by using an eigenvalue placement technique. The observer gain is derived by solving the linear matrix inequality while simulation results are adopted to show the effectiveness of the proposed observer design.