Tuning controllers against multiple design requirements

In this paper, we introduce a new technique for tuning arbitrarily structured controllers against multiple control requirements. Control requirements encompass soft or hard design constraints in the usual H₂ and H_∞ design metrics as well as supplemental requirements such as (1) μ constraints on MIMO margins at specified opening sites (2) constraints on the closed-loop dynamics (3) loop-shaping constraints at specified loop opening sites (4) controller stability enforcement. Our algorithmic approach is a non-smooth technique relying on a one-parameter driving function which leads to locally optimal solutions of the design problem. This has been implemented in the MATLAB-based tool SYSTUNE which can be regarded as an extension of HINFSTRUCT from the Robust Control Toolbox. The new SYSTUNE retains the same flexibility and simplicity as HINFSTRUCT to specify control structures but is tailored to handle multiple models and requirements. Two challenging applications are discussed to illustrate the capabilities of the new technique.