Charge-based robust position estimation for low impedance piezoelectric actuators

[Display omitted] •Charge-position relation is not linear for low impedance piezoelectric actuators.•Conventional charge-based position estimation methods cannot be applied.•The charge leakage and other uncertainties are considered as a sensor fault.•A combination of charge measurement and fault tolerant observer is proposed.•This method is robust to uncertainties and can be used in long time measurement. Charge measurement is a common position estimation method for piezoelectric actuators. It resorts to the linear charge-position characteristic to estimate the actuator position. But in low impedance actuators, charge-position relation is not linear and there is a leakage due to piezoelectric internal resistance. This resistance can be highly nonlinear which makes its compensation too complicated. Therefore, conventional charge-based methods cannot be effectively applied. In this research, a new compound estimation method is proposed by considering the charge leakage and other uncertainties as a sensor fault. Therefore, a simple charge measurement method and a fault tolerant robust observer are merged together to estimate the actuator position through the faulty charge output. Experimental results show the effectiveness of proposed method for 100 μm p-p quasi-static and multi frequency trajectories in short and long time (300 s) measurements. The achieved absolute mean error is about 0.1907 μm, 0.1453 μm and 0.1135 μm, respectively.