Development of a 2-DoF nonlinear fuzzy PI–PD controller for a tractor active suspension system

This study focuses on developing an efficient active suspension system for the Kubota M110X tractor to address the challenges posed by varying field disturbance profiles and parameter variations. A nonlinear fuzzy proportional-integral–proportional-derivative (PI–PD) controller, utilizing the center of area/gravity (CoA/G) defuzzification, is proposed to enhance the ride quality and robustness by mitigating vibrations caused by field-level fluctuations. The proposed fuzzy PI–PD controller yields significant system performance improvement in comparison to linear proportional–integral–derivative (PID), linear PI–PD, and fuzzy PID controllers, not just under nominal conditions but also with parameter variations. To provide comprehensive and detailed comparative analyses, the performance of the proposed controller is evaluated against existing state-feedback controllers (SFCs) designed for the same tractor active suspension system. While a real-time demonstration on the tractor active suspension system is beyond the scope of this study, the practicality of the proposed fuzzy PI–PD controller is substantiated through an application study on a magnetic levitation (MagLev) system. The experimental results underscore the proposed controller's versatility as well as provide a more complete understanding of its potential for real-world applications.