Frequency-domain tuning of fixed-structure control systems

This paper presents two new MATLAB-based tools for tuning fixed-structure linear control systems in the frequency domain: hinfstruct and looptune. These tools can directly tune control architectures with multiple feedback loops and multiple fixed-order, fixed-structure control elements. The controller parameters are tuned using non-smooth H_∞ optimization but little a-priori knowledge of the H_∞ theory is required. This makes such tools ideally suited for real-world applications where the control system structure and complexity are constrained. An application to helicopter control is discussed and the results of an extensive benchmark of hinfstruct vs. hifoo are reported.