Design of Adaptive Voltage Dither Control Framework Based on Spectral Analysis for Nonlinear Piezoelectric Actuator

Advances in miniaturization of micromachines are receiving considerable industrial attention, with a crucial aspect of research being on precision positioning and manipulation at the micro-nanoscale. Nanopositioners are precision mechatronic systems designed to deal with objects at extremely precise resolution wherein piezoelectric actuators have a high potential to impact emerging markets. However, the major bottleneck in harvesting the advantages of piezoelectric actuator for nanopositioning is the presence of inherent nonlinearity, mostly hysteresis, along with the presence of external dynamical disturbance, and traditional feedback controller cannot handle. Dithering has been used in the parlance of piezoelectric actuation as a surprisingly simple yet powerful means of enhancing system performance. This research presents the design framework of an adaptive voltage dither control logic based on spectral analysis of the system output using normalized harmonic ratio. The proposed controller adaptively tunes the intensity of dither amplitude depending on the system response to an optimum value that yields satisfactory results. A commercially available piezo-actuator has been used to model the system along with hysteresis using Dahl model, and system parameters have been identified experimentally. Performance of the proposed controller has been investigated by subjecting the plant model to several real-time perturbations like plant parameter variation, sinusoidal motion tracking, multi-amplitude multi-frequency input signal, external disturbances like Gaussian and impulse, step response, etc., and with the results showing better control performance and disturbance rejection capability as compared to traditional feedback control.