Geometric Control of Quadrotor Attitude in Wind With Flow Sensing and Thrust Constraints

Abstract

Quadrotor vehicles show great potential over a range of tasks, but effective control in windy environments continues to be a challenge. This paper develops a thrust-saturated controller on the Lie group SO (3) that uses flow sensing in order to reduce the effect of gusts on the vehicle. Designing the controller on SO (3) establishes almost-global exponential stability, and avoids the pitfalls of representing rigid-body kinematics using Euler angles. We prove that exponential stability is retained in the presence of thrust saturation. Aerodynamics are incorporated into the dynamics and control through a model of the blade-flapping phenomena experienced by rotorcraft. Numerical examples show that the system control remains effective despite thrust saturation, and that flow sensing improves both the initial response and steady-state error of the system in wind.

Geometric control of a quadrotor in wind with flow sensing and thrust constraints: Attitude and position control

“…By using flow measurements as well as inertial sensing, the controller can react to the wind before the resulting moment has propagated to the quadrotor's dynamics, which yields benefits compared to relying on inertial sensing alone. Work validating the benefit of flow feedback was performed in [15] for a one degree-of-freedom pitching test stand, and in [16] for a three degree-of-freedom attitude test stand. The flow sensor package consists of fore and aft, and left and right facing probe pairs connected to a microcontroller unit through flexible tubing [4].…”

“…The contributions of this paper are (1) a nonlinear, feedback-linearizing attitude and position controller on SE(3) using flow sensing and accounting for saturated thrust inputs; and (2) an experimental demonstration of the benefit of flow probes on a quadrotor, including an assessment of the relative merits of adding flow sensing to the vehicle controller versus using inertial feedback alone. This paper extends the three degree-of-freedom attitude-only control in [16] to a six degree-of-freedom free-flight quadrotor.…”

“…We model the aerodynamic moment on the quadrotor as a result of the blade-flapping phenomena in rotorcraft, which occurs due to uneven lift on the advancing and retreating blades as the vehicle flies forward and/or is subject to wind [11]. We follow the single-propeller analysis in [26] to develop the aerodynamic moment M aer o acting on the quadrotor, derived in [16].…”

“…However, we ignore the hinge offset and blade pitching moment contributions because the spring force provides the majority of the moment at the hub. When solving for the total aerodynamic moment on the quadrotor, counter-rotating pairs cancel the u 1 component to yield the moment used for attitude control [16]…”

A Dynamics-Agnostic State Estimator for Unmanned Aerial Vehicles Using Ultra-Wideband Radios

“…Disturbances may include aerodynamic effects (see e.g. [14,[17][18][19][20]) as well as other effects due to e.g. misaligned actuators.…”