# A New Encounter Between Leader-Follower Tracking and Observer-Based Control: Towards Enhancing Robustness against Disturbances

## TL;DR

This paper introduces a novel observer-based distributed control method for leader-follower multi-agent systems, effectively handling bounded rate disturbances affecting all agents, including the leader, to achieve robust tracking.

## Contribution

It develops the first distributed disturbance observers that enable followers to estimate leader disturbances, enhancing robustness under relaxed disturbance assumptions.

## Key findings

- Achieves bounded-error tracking despite disturbance rate bounds.
- Validates the approach through simulations on first- and second-order MASs.
- Introduces a new disturbance estimation framework for multi-agent systems.

## Abstract

This paper studies robust tracking control for a leader-follower multi-agent system (MAS) subject to disturbances. A challenging problem is considered here, which differs from those in the literature in two aspects. First, we consider the case when all the leader and follower agents are affected by disturbances, while the existing studies assume only the followers to suffer disturbances. Second, we assume the disturbances to be bounded only in rates of change rather than magnitude as in the literature. To address this new problem, we propose a novel observer-based distributed tracking control design. As a distinguishing feature, the followers can cooperatively estimate the disturbance affecting the leader to adjust their maneuvers accordingly, which is enabled by the design of the first-of-its-kind distributed disturbance observers. We build specific tracking control approaches for both first- and second-order MASs and prove that they can lead to bounded-error tracking, despite the challenges due to the relaxed assumptions about disturbances. We further perform simulation to validate the proposed approaches.