H∞ Loop-Shaping Continuous-Time Controller Design for Nonlinear HDD Systems: A Reduced-Order Approach Using Hankel-Norm Approximation

This study presents the development and examination of a streamlined $H_{\infty }$ loop-shaping continuous-time controller tailored for nonlinear Hard Disk Drive (HDD) systems. Using the Hankel-norm approximation technique, the complexity of the controller is systematically reduced, emphasizing preserving the system’s efficacy while enhancing computational efficiency. The dynamics of the HDD system and the performance of the proposed controller are investigated through MATLAB simulations. The effectiveness of the controller is quantitatively measured by employing the ITAE (Integral of Time multiplied by Absolute Error) criterion. The results indicate that a controller of the 10th-order provides a desirable compromise between maintaining robust control and minimizing disturbances and noise without significant loss in performance. This method illustrates the capacity for implementing more straightforward controllers in complex HDD systems, paving the way for their application in precision-critical industrial settings.