System Identification and $\mathcal{H}_{\infty}$ Control of a Fatigue Structural Testing Rig

This paper considers system identification and $\mathcal{H}_{\infty}$ control of a load-controlled fatigue structural test rig. The test rig is comprised of an aluminum-composite structure and hydraulic actuators that apply desired loads. Fatigue tests must be performed using closed-loop control in order to avoid damaging the test article. Therefore, three closed-loop system identification methods are considered, the direct method, indirect method, and dual-Youla method. The best identified models in terms of variance accounted for are then used to design two degree-of-freedom $\mathcal{H}_{\infty}$ controllers. Reduced-order versions of the $\mathcal{H}_{\infty}$ controllers are implemented on the test rig and used to track a load profile. The system identification and $\mathcal{H}_{\infty}$ controller synthesis methods are presented, along with identification and tracking results.