Enhancing Ride Comfort and Stability of a Large Van Using an Improved Semi-active Stability Augmentation System

In large vehicles, controlled suspension systems play a vital role in balancing the trade-off between ride comfort and vehicle stability. This article attempts to improve the semi-active stability augmentation system (S-SAS) to provide enhanced passenger comfort and vehicle stability irrespective of the road terrain. A type-1 (T1) fuzzy attitude control strategy is developed to mitigate the loop interactions and limitations in optimizing control gains between the heave and pitch with roll motions. The inner loop called ride control uses a Mamdani interval type-2 (IT2) fuzzy logic control (FLC) to accommodate the system uncertainties and nonlinearities. Semi-active type voice-oil-actuated electrohydraulic (EH) dampers are used to provide controlled damping to suspension systems. The algorithm is deployed in a microcontroller-based hardware, and its performance is tested outdoor for bumpy road conditions at different speeds. A realistic model of the large van in CarSim is also used to investigate the robustness and reliability of the controller in roll-dominated terrains. The proposed fuzzy S-SAS (FS-SAS) is compared with standard S-SAS and passive suspension system for different road inputs. For instance, the outdoor test results on a bumpy road at 5 km/h speed show heave acceleration and roll rate reduction by 53.85% and 51.23% against the passive suspension. The simulation and experimental results indicate the capability of FS-SAS in achieving superior ride comfort, good roll stability, better road-holding, and avoiding the possibility of an untripped vehicle rollover.