# H2 controller design for a kestrel-inspired ornithopter operating in extreme weather

## TL;DR

This paper designs an H2 controller for a kestrel-inspired ornithopter to improve stability in extreme weather using a bio-inspired gust mitigation system.

## Contribution

The first complete kestrel-inspired ornithopter integrating a bio-inspired GMS with H2 optimal control is presented.

## Key findings

- The H2-augmented GMS reduces gust-induced forces by up to 32%.
- The controller achieves faster state convergence within 1.1 seconds.
- Simulation results align with prior findings, validating the model and control framework.

## Abstract

Unsteady atmospheric disturbances significantly compromise the flight stability of ornithopters, necessitating advanced turbulence-mitigation strategies. Drawing inspiration from the kestrel’s covert feathers, this study presents the modeling, control synthesis, and performance evaluation of a kestrel-inspired ornithopter equipped with an active covert-feather-based Gust Mitigation System (GMS). A reduced-order multibody bond-graph model (BGM) is derived from the full flapping-wing dynamics, capturing the coupled aero-elastic interaction between the main body, rigid wings, propulsion system, and feather actuation mechanism. Stability analysis reveals the presence of unstable internal dynamics, motivating the design of an H₂ optimal controller to ensure robust stability and fast disturbance rejection. The controller’s performance is evaluated against a Linear Quadratic Regulator (LQR) under vertical gust inputs ranging from 0 m/s to 20 m/s using MATLAB/Simulink simulations. Quantitative results indicate that the H₂-augmented GMS installed ornithopter reduces gust-induced forces by up to 32% and achieving faster state convergence within 1.1 seconds. The simulation results exhibit close agreement with previously reported findings, validating the fidelity of the proposed model and control framework. This work represents the first complete kestrel-inspired ornithopter integrating a bio-inspired GMS with H₂ optimal control, offering a validated and scalable foundation for next-generation adaptive ornithopters capable of maintaining stability in unsteady atmospheric environments.