# Quad-rotor Flight Simulation in Realistic Atmospheric Conditions

## TL;DR

This paper presents a realistic, real-time quad-rotor flight simulation framework that incorporates advanced atmospheric models and validated aerodynamics, enabling improved trajectory planning and control in low-altitude conditions.

## Contribution

It introduces an integrated simulation environment combining validated aerodynamic models, atmospheric boundary layer simulations, and nonlinear control for quad-rotors, with open-source code for community use.

## Key findings

- Wind model accuracy significantly affects trajectory predictions.
- Simplified rotor aerodynamics impact flight performance.
- Open-source simulation tools facilitate research and development.

## Abstract

In trajectory planning and control design for unmanned air vehicles, highly simplified models are typically used to represent the vehicle dynamics and the operating environment. The goal of this work is to perform real-time, but realistic flight simulations and trajectory planning for quad-copters in low altitude (<500m) atmospheric conditions. The aerodynamic model for rotor performance is adapted from blade element momentum theory and validated against experimental data. Large-eddy simulations of the atmospheric boundary layer are used to accurately represent the operating environment of unmanned air vehicles. A reduced-order version of the atmospheric boundary layer data as well as the popular Dryden model are used to assess the impact of accuracy of the wind field model on the predicted vehicle performance and trajectory. The wind model, aerodynamics and control modules are integrated into a six-degree-of-freedom flight simulation environment with a fully nonlinear flight controller. Simulations are performed for two representative flight paths, namely, straight and circular paths. Results for different wind models are compared and the impact of simplifying assumptions in representing rotor aerodynamics is discussed. The simulation framework and codes are open-sourced for use by the community.