A Dual-strategic Adaptive Switching method for high-accuracy speed regulation in piezoelectric stepping motor

Piezoelectric stepping motors (PSMs) are widely employed in ultra-precision nanopositioning applications, where highly accurate speed regulation is paramount. However, traditional Frequency-Controlled Speed Regulation (FSR) methods are constrained by their inability to compensate for frequency-related nonlinearities. Furthermore, a pronounced stair-step output emerges in the low-speed range, further degrading positioning performance. To overcome these limitations, this paper introduces a Dual-Strategic Adaptive Switching (DAS) method for PSM speed regulation. The DAS method is underpinned by a modified velocity formula that accounts for these nonlinearities. In the standard speed range, an Improved Frequency-Controlled Speed Regulation (IFSR) method is employed, compensating for frequency-related nonlinearities via a phenomenological model. As the target speed decreases into the low-speed range, the system seamlessly transitions to an Improved Step-Controlled Speed Regulation (ISSR) method. The ISSR method mitigates nonlinearities in the step length-Shear Stack Voltage (SSV) relationship using a polynomial model. A switching criterion ensures a smooth transition between the IFSR and ISSR methods. Experimental results demonstrate that the DAS method significantly enhances speed regulation accuracy compared to the traditional FSR method, reducing real-time positioning errors by 2.1% to 6.0%. The proposed DAS method effectively addresses the speed regulation requirements of the PSM across its entire operational speed range.