Robust and fast non-singular terminal sliding mode control for piezoelectric actuators

Piezoelectric actuators (PEAs) are essential elements in many systems that require high precision and accuracy. However, the difficulty with the use of PEAs is their actuator uncertainties including the highly non-linear behaviour which is a consequence of the hysteresis property inherently within PEAs. Therefore, a robust control system is essential for such actuators. This study proposes a systematic control method that utilises a fast non-singular terminal sliding mode (FNTSM) for PEAs. Unlike the conventional sliding mode (CSM), the FNTSM control method is characterised by chatter free. Besides, a zero error convergence can be guaranteed in finite time in the presence of disturbance and system uncertainties. The design of the FNTSM control is based on the bounded information of parametric uncertainties. The feedback velocity is provided for the FNTSM controller by using the a model-free velocity estimator. Theoretical analysis and experimental results reveal that the FNTSM controller can achieve faster and higher precision performance in comparison with either a CSM or a linear controller.