Robust actuator multiplicative fault estimation with unknown input decoupling for a wind turbine system

A robust actuator multiplicative fault estimation approach is designed by combining the unknown input-decoupling principle and H_∞ optimization. The fault is constructed as an augmented system state and estimated by the proposed observer. In this observer, the unknown input-decoupling principle is used to decouple the unknown input (the wind force) effect from the fault estimation signal. From the practical point of view, the actuator measurement sensors are corrupted by the sensor measurement noise. An H_∞ approach is used based on the unknown input-decoupling observer to minimize the effect of this sensor noise on the fault estimation signal. In order to estimate the multiplicative fault, a fault model modification is used to reform the multiplicative fault into an additive fault representation by which the fault can be estimated. Finally, the proposed design is used to estimate the hydraulic leakage fault occurring in a wind turbine pitch actuator system based on a non-linear benchmark model.