Optimizing a tractor frame for improved cabin NVH

To address an aging agricultural workforce and modern ergonomic guidelines, researchers at Doshisha University and Kubota modeled medium- and large-sized agricultural tractors to reduce vibration and noise and increase comfort.

New emphasis is being placed on agricultural vehicles for improved safety, comfort, and functionality. The monocoque-type frame of today's tractors consists of the engine, power transmission case, and differential case in modular assemblies. Main vibration sources are the engine, drive system, and exhaust system. Vibrations travel into the cabin through the frame and are amplified when transmissions from excitation sources coincide with the natural frequency of the frame. To decrease vibration and noise of the tractor, it is necessary to improve the dynamic characteristics of the frame.

From measuring tractor part vibration characteristics and cabin noise characteristics, researchers at Doshisha University and Kubota Corp. determined that the bending mode of the frame influences the vibration characteristics of the tractor. Knowing that, the full frame was separated into sub-structures of cases and joint parts, and each was modeled. Model tuning with sensitivity analysis improved accuracy, and a dynamic model for the frame was constructed. Comparing the analytical result with experimental data confirmed the dynamic model. Finally, the design change of the frame was carried out with the object of increasing stiffness while reducing weight.