Active disturbance rejection control of tractor cab suspension with a multi-state adjustable damper

This study presents an advanced semi-active vibration control strategy for tractor cab suspension systems based on active disturbance rejection control (ADRC). A novel multi-state adjustable damper, capable of real-time switching between four damping modes via dual solenoid valves, is developed to adapt to varying vibration conditions. A comprehensive 7-degree-of-freedom (7-DOF) dynamic model of the tractor cab, incorporating vertical, pitch, and roll motions, is established to characterize the vibration behavior. Based on this model, an ADRC controller is designed to suppress cab vibrations caused by both road surface irregularities and the engine-induced profile. The control forces computed by ADRC are allocated to four corner dampers through a decoupling-based force distribution method, enabling mode switching through solenoid valve control signals. Simulation results under the ISO Class D road profile demonstrate that the proposed ADRC strategy significantly reduces the RMS values of vertical, pitch, and roll accelerations by up to 57.1 %, 67.1 %, and 65.4 %, respectively, compared with conventional fuzzy PID and skyhook control methods. Furthermore, according to the ISO 2631-1 evaluation, the overall frequency-weighted acceleration was reduced by 60.2 % and 46.7 % compared with fuzzy PID and skyhook control, respectively, confirming a significant improvement in ride comfort classification. Additionally, the proposed system effectively limits dynamic suspension travel and avoids excessive valve switching, demonstrating improved ride comfort and strong system robustness.