Load Alleviation Control using Dynamic Inversion with Direct Load Feedback

Scaramal, Mariano; Horn, Joseph F.; Saetti, Umberto

doi:10.4050/f-0077-2021-16792

Cited by 2 publications

(1 citation statement)

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“…The flight control law used in this work to track the desired flare trajectory is nonlinear dynamic inversion (NDI), a popular model-following scheme among aircraft and rotorcraft manufacturers, and within the aerospace flight control community in general. Application of NDI control laws to rotorcraft can be found in, e.g., [17][18][19][20][21][22][23][24][25][26]. One convenient feature of NDI is that it inverts the plant model in its feedback linearization loop, which, compared to other more conventional model-following control strategies such as explicit model following (EMF), eliminates the need for gain scheduling.…”

Section: Introductionmentioning

confidence: 99%

Tau Theory-Based Flare Control in Autonomous Helicopter Autorotation

Saetti,

Rogers,

Alam

et al. 2023

Aerospace

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A novel trajectory generation and control architecture for fully autonomous autorotative flare that combines rapid path generation with model-based control is proposed. The trajectory generation component uses optical Tau theory to compute flare trajectories for both longitudinal and vertical speed. These flare trajectories are tracked using a nonlinear dynamic inversion (NDI) control law. One convenient feature of NDI is that it inverts the plant model in its feedback linearization loop, which eliminates the need for gain scheduling. However, the plant model used for feedback linearization still needs to be scheduled with the flight condition. This key aspect is leveraged to derive a control law that is scheduled with linearized models of the rotorcraft flight dynamics obtained in steady-state autorotation, while relying on a single set of gains. Computer simulations are used to demonstrate that the NDI control law is able to successfully execute autorotative flare in the UH-60 aircraft. Autonomous flare trajectories are compared to piloted simulation data to assess similarities and discrepancies between piloted and automatic control approaches. Trade studies examine which combinations of downrange distances and altitudes at flare initiation result in successful autorotative landings.

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Section: Introductionmentioning

confidence: 99%

Tau Theory-Based Flare Control in Autonomous Helicopter Autorotation

Saetti,

Rogers,

Alam

et al. 2023

Aerospace

Self Cite

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On the effects of rotor induced vibrational stability on helicopter flight dynamics

Saetti,

Horn,

Berger

2024

CEAS Aeronaut J

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This article investigates vibrational stabilization effects in rotorcraft flight dynamics. This study is motivated by recent results in flapping-wing flight, which showed that the time-varying aerodynamic and inertial loads due to the insect wing periodic motion induce a vibrational stabilization mechanism in hover. The dynamics of flapping-wing flyers and rotary-wing vehicles are both described by time-periodic systems so vibrational stabilization mechanisms can also have an effect on stability characteristics of rotary-wing vehicles. The article extends the use of the harmonic decomposition method to vibrational stability analysis of rotorcraft. Two cases are considered: vibrational stability due blade imbalance at hover, and vibrational stability due to number-of-blades-per-rotor-revolution ($$N_b$$ N b /rev) in high-speed forward flight. Results show that while vibrations induced by rotor blade imbalance do not stabilize the hovering dynamics of a helicopter, these vibrations can still have a significant effect on the hovering dynamics. Rotor blade imbalance results in a symmetric effect on the roll and pitch axes, in that it tends to decrease the frequency of the subsidence modes of the hovering cubic, while the unstable oscillatory modes tend to increase in frequency and decrease in damping (destabilizing effect). On the other hand, the yaw/heave dynamics are relatively unaffected compared to the lateral and longitudinal axes. Moreover, $$N_b$$ N b /rev rotor loads in forward flight are shown to reduce the damping of the coupled roll/pitch oscillation mode.

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Load Alleviation Control using Dynamic Inversion with Direct Load Feedback

Cited by 2 publications

References 0 publications

Tau Theory-Based Flare Control in Autonomous Helicopter Autorotation

Tau Theory-Based Flare Control in Autonomous Helicopter Autorotation

On the effects of rotor induced vibrational stability on helicopter flight dynamics

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