Ground Resonance Mitigation of Rotorcraft with Articulated Robotic Landing Gear: A Preliminary Investigation

Ground resonance is a serious aeromechanical instability in helicopters that results from hub motion coupling with lag motion of the rotor blades when the vehicle is in contact with a surface. Nearly all recent methods to mitigate ground resonance instability rely on a passive or semi-active lag damper. These lag dampers, however, are generally undesirable for rotorcraft design and maintenance. Current innovations in rotorcraft landing gear have created an alternative approach to ground resonance mitigation. Recent work has demonstrated the capabilities of an articulated landing gear system as a feasible device for navigating irregular terrain. Adding articulated robotic landing gear to a rotorcraft can possess an additional function as a device for stability augmentation and act as a unique, built-in alternative to lag dampers. The current work presents a linear ground resonance analysis of a fully articulated rotor for a variety of helicopter characteristics. Rotor conditions that induce instability are identified and it is demonstrated that a legged robotic landing gear system can actively mitigate ground resonance.