A Hierarchical Type-2 Fuzzy Logic Control Architecture for Autonomous Mobile Robots

TLDR

Autonomous mobile robots operating in dynamic, unstructured outdoor settings face significant uncertainties that traditional type‑1 fuzzy logic controllers cannot fully manage, whereas type‑2 fuzzy logic offers improved handling of such uncertainties. The study proposes a reactive control architecture that employs a type‑2 fuzzy logic controller to realize basic navigation behaviors and their coordination, forming a hierarchical type‑2 FLC. The architecture was implemented on various indoor and outdoor mobile robots navigating unstructured, challenging environments. The type‑2 based system outperformed its type‑1 counterpart while achieving a substantial reduction in rule complexity.

Abstract

Autonomous mobile robots navigating in changing and dynamic unstructured environments like the outdoor environments need to cope with large amounts of uncertainties that are inherent of natural environments. The traditional type-1 fuzzy logic controller (FLC) using precise type-1 fuzzy sets cannot fully handle such uncertainties. A type-2 FLC using type-2 fuzzy sets can handle such uncertainties to produce a better performance. In this paper, we present a novel reactive control architecture for autonomous mobile robots that is based on type-2 FLC to implement the basic navigation behaviors and the coordination between these behaviors to produce a type-2 hierarchical FLC. In our experiments, we implemented this type-2 architecture in different types of mobile robots navigating in indoor and outdoor unstructured and challenging environments. The type-2-based control system dealt with the uncertainties facing mobile robots in unstructured environments and resulted in a very good performance that outperformed the type-1-based control system while achieving a significant rule reduction compared to the type-1 system.