Adaptive Fuzzy Logic Controller for Vehicle Active Suspensions with Interval Type-2 Fuzzy Membership Functions

Elicited from the Least Means Squares optimal algorithm (LMS), an adaptive fuzzy logic controller (AFC) based on interval type-2 fuzzy sets is proposed for vehicle non-linear active suspension systems. The interval membership functions (IMF(2)s) are utilized in the AFC design to deal with not only non-linearity and uncertainty caused from irregular road inputs and immeasurable disturbance, but also the potential uncertainty of expert's knowledge and experience. The adaptive strategy is designed to self-tune the active force between the lower bounds and upper bounds of interval fuzzy outputs. A case study based on a quarter active suspension model has demonstrated that the proposed type-2 fuzzy controller significantly outperforms conventional fuzzy controllers of an active suspension and a passive suspension.