Piloted Simulation Evaluation of Damage Tolerant Control for a Coaxial Compound Helicopter

Advanced rotorcraft configurations currently being considered for Future Vertical Lift and Advanced Air Mobility applications typically feature redundant control effectors, which bring new opportunities for control design, including the ability to re-allocate control in response to failure or damage. This paper presents the design of damage tolerant control (DTC) for a generic utility-class lift-offset coaxial compound helicopter using weighted pseudo-inverse control allocation. Consideration was given to tip clearance between the upper and lower rotors of the coaxial configuration in the design of DTC. The damage tolerant control was then integrated into full flight envelope control laws, and tested in a piloted simulation using several mission task elements and one operational scenario. Results showed that DTC significantly reduced aircraft coupling in the presence of stuck actuators and maintained sufficient rotor tip separation even during aggressive maneuvers. Furthermore, for all damage cases tested, DTC received better or similar ratings than the baseline case. This work was done in support of the Adaptive Digital Automated Pilotage Technology (ADAPT^TM) program which aims to develop a flight control software package to take advantage of redundant controls to improve safety, survivability, and performance for advanced vertical takeoff and landing capable aircraft.