# Distributed Global Output-Feedback Control for a Class of Euler-Lagrange Systems

## TL;DR

This paper develops a distributed output-feedback control method for Euler-Lagrange multi-agent systems with only position measurements, overcoming nonlinearities and lack of separation principle to achieve global exponential stability.

## Contribution

It introduces a novel coordinate transformation and velocity observers to enable distributed control with only position measurements in complex nonlinear systems.

## Key findings

- Achieves uniform global exponential stability in multi-agent systems
- Validates the control scheme through theoretical analysis and simulations
- Provides a new approach to output-feedback control for nonlinear Euler-Lagrange systems

## Abstract

This published paper investigates the distributed tracking control problem for a class of Euler-Lagrange multi-agent systems when the agents can only measure the positions. In this case, the lack of the separation principle and the strong nonlinearity in unmeasurable states pose severe technical challenges to global output-feedback control design. To overcome these difficulties, a global nonsingular coordinate transformation matrix in the upper triangular form is firstly proposed such that the nonlinear dynamic model can be partially linearized with respect to the unmeasurable states. And, a new type of velocity observers is designed to estimate the unmeasurable velocities for each system. Then, based on the outputs of the velocity observers, we propose distributed control laws that enable the coordinated tracking control system to achieve uniform global exponential stability (UGES). Both theoretical analysis and numerical simulations are presented to validate the effectiveness of the proposed control scheme. Followed by the original paper, a typo and a mistake is corrected.