Observer-Based Estimation and Hydrostatic Inertia Modeling for Cooperative Transport of Variable-Inertia Loads with Quadrotors

TL;DR

This paper presents a novel observer-based method for estimating load parameters, including variable mass and inertia, in cooperative quadrotor transport of fluid-filled payloads, utilizing geometric control and pre-computed inertia surrogates.

Contribution

It introduces an inertia surrogate model based on fluid mechanics principles to handle variable inertia without real-time tensor identification.

Findings

Effective mass estimation from kinematics and forces.

Inertia surrogate accurately reproduces rotational dynamics.

Method handles fluid payloads with changing fill levels.

Abstract

We address load-parameter estimation in cooperative aerial transport with time-varying mass and inertia, as in fluid-carrying payloads. Using an intrinsic manifold model of the multi-quadrotor-load dynamics, we combine a geometric tracking controller with an observer for parameter identification. We estimate mass from measurable kinematics and commanded forces, and handle variable inertia via an inertia surrogate that reproduces the load's rotational dynamics for control and state propagation. Instead of real-time identification of the true inertia tensor, driven by high-dimensional internal fluid motion, we leverage known tank geometry and fluid-mechanical structure to pre-compute inertia tensors and update them through a lookup table indexed by fill level and attitude. The surrogate is justified via the incompressible Navier-Stokes equations in the translating/rotating load frame: when effective forcing is gravity-dominated (i.e., translational/rotational accelerations and especially jerk are limited), the fluid approaches hydrostatic equilibrium and the free surface is well approximated by a plane orthogonal to the body-frame gravity direction.