An optimal vibration control logic for minimising fatigue damage in flexible structures

One of the most common applications of active control on flexible structures is the mitigation of vibrations to reduce stresses and consequently increase lifetime. However, except for a few particular cases, the fatigue phenomenon has never been taken into account in the design of the control algorithm. Moreover, since fatigue is mainly a local effect, in some cases active control could even worsen the structure's integrity (e.g. consider local damage close to the actuators caused by control strategies requiring high control forces). For this reason, control is not able to achieve the best performance in terms of damage reduction and lifetime maximisation. This paper proposes an optimal active control designed to minimise fatigue damage on the structure. A model of the fatigue phenomenon is introduced and included in the definition of the control parameters. The solution is firstly described from a theoretical point of view and then tested both numerically and experimentally, showing a significant improvement over state-of-the-art techniques.