A Comparison of Non-stationary, Type-2 and Dual Surface Fuzzy Control

TL;DR

This paper compares various fuzzy control methods, including type-1, interval type-2, non-stationary, and dual surface type-2 controllers, highlighting their performance under environmental uncertainty in a simulated sailing task.

Contribution

It provides a comparative analysis of advanced fuzzy control approaches and examines how FOU size impacts their effectiveness in uncertain conditions.

Findings

More sophisticated controllers can outperform type-1 control.

FOU size significantly affects controller performance.

Performance gains are not guaranteed with advanced fuzzy methods.

Abstract

Type-1 fuzzy logic has frequently been used in control systems. However this method is sometimes shown to be too restrictive and unable to adapt in the presence of uncertainty. In this paper we compare type-1 fuzzy control with several other fuzzy approaches under a range of uncertain conditions. Interval type-2 and non-stationary fuzzy controllers are compared, along with 'dual surface' type-2 control, named due to utilising both the lower and upper values produced from standard interval type-2 systems. We tune a type-1 controller, then derive the membership functions and footprints of uncertainty from the type-1 system and evaluate them using a simulated autonomous sailing problem with varying amounts of environmental uncertainty. We show that while these more sophisticated controllers can produce better performance than the type-1 controller, this is not guaranteed and that selection of Footprint of Uncertainty (FOU) size has a large effect on this relative performance.