Load allocation for risk management in overactuated systems experiencing incipient failure conditions

This paper examines the fault tolerant control problem for a generic class of incipient failure modes that grow in severity as a function of component loading. Assuming that a prognostic model is available to evaluate the risk of incipient fault modes growing into catastrophic failure conditions, then fundamentally the fault adaptive control problem is to adjust component loads to minimize risk of failure, while not overly degrading nominal performance. A methodology is proposed for posing this problem as a finite horizon constrained optimization, where constraints correspond to maximum risk of failure and maximum allowable deviation from nominal performance. Simulation results are given for an example system with an active redundant DC motor configuration. The fault mode simulated in this system is temperature dependent motor winding insulation degradation.