Abstract
<title>Abstract</title> <p>Ride vibration transmitted to the cabin can degrade operator comfort in agricultural tractors. This study proposed a semi-active cabin suspension control strategy based on sliding mode control (SMC) to reduce ride vibration and improve robustness. A four-degree-of-freedom half-tractor model incorporating measured parameters was developed, and the equivalent damping force of the semi-active suspension was regulated by the SMC controller. A linear quadratic regulator (LQR) was designed for comparison, and both controllers were tuned using the same genetic-algorithm procedure. Simulations were conducted for one reference case and three uncertainty cases representing variations in cabin mass, vehicle-body mass, and tire stiffness at tractor speeds of 3, 5, 7, 15, and 30 km/h. Both controllers reduced the root-mean-square and peak-to-peak values of cabin vertical acceleration compared with the constant-current type under all conditions. The LQR controller showed larger performance-index variations among the uncertainty cases, whereas the SMC controller maintained more consistent reduction performance. For system uncertainty, median robustness-index values of the SMC controller were 8.19% and 7.42% for the root-mean-square and P2P metrics, respectively, compared with 21.70% and 20.10% for the LQR controller. These results indicate that the proposed SMC controller improves robustness against system-parameter variations while maintaining ride-vibration reduction.</p>