Robust active control of flexible systems with second order sliding

An active vibration controller for flexible systems is developed using a second order sliding manifold approach. Assuming narrow-band disturbances, the crucial point is to increase the damping of those system modes whose frequencies are close to the disturbance frequencies. The stable sliding surface consists of a time-invariant part which eliminates the selected modes without affecting the remaining dynamics, and a time-varying part which bounds the control amplitude in the transient. Moreover, the closed-loop system exhibits strong robustness properties typical of high-gain control systems, avoiding the peaking phenomenon that is one of the main drawbacks of the latter