Damage-mitigating control with overload injection: Experimental validation of the concept

The goal of damage-mitigating control is to enhance structural durability of mechanical systems (e.g., advanced aircraft, spacecraft, and power plants) while retaining high performance. So far the reported work in damage-mitigating control has focused on reduction of peak stresses to increase structural durability. This paper presents a novel concept that takes advantage of the physical phenomenon of fatigue crack retardation. Overload pulses are intermittently injected into the plant as a feedforward signal through the actuator(s) in addition to robust feedback control. A feedforward sequence of limited overload pulses and a robust feedback control law are designed based on state-space models of fatigue-crack damage and plant dynamics. A series of experiments have been conducted on a laboratory test apparatus to demonstrate feasibility of the overload injection concept for robust damage-mitigating control.