Real Time Rotor Component Load Limiting via Model Predictive Control

This paper explores the use of Model Predictive Control (MPC) as a viable solution for real time load limiting for critical helicopter components that are subjected to significant fatigue loading. The development of the (structural) load limiting controller is posed as an optimal control problem where given a desired user defined max limit, the estimate of control margin associated with the component load limit is found and is provided as a cue to the pilot. The proposed load limiting via MPC, which makes use of an on-board reduced order model derived from a higher order Linear Time Invariant (LTI) model of helicopter coupled body/rotor/inflow dynamics, is described in detail. The proposed scheme is evaluated using nonlinear model simulations for its ability to limit harmonic pitch link loads and indirectly limit the peak-to-peak of the total pitch link load.