Investigation of Tractor Driver Seat Performance with Non-linear Stiffness and On–off Damper

An agricultural tractor seat with non-linear stiffness and on–off damper offers a number of advantages when compared with traditional and currently, commercially available designs. These advantages are discussed within the context of the constraints imposed by the restricted seat travel space. It is known that a soft suspension system with low natural frequency offers more comfort than a stiffer one, and also, that the former requires more travel space. It is also known that conventional dampers tend to be a compromise between limiting seat motion around the natural frequency and having good attenuation of higher-frequency inputs. This work shows that having the damper switched on for low-frequency ‘harsh’ bumps and off for higher-frequency inputs reduces seat accelerations while preventing end stop impacts. Experiments on a non-linear stiffness seat and on-off damper indicate that a 40% reduction in root-mean-square (RMS) acceleration compared to the linear, passively damped seat is obtainable, with no end stop impacts. This design has the additional advantage that it is cheap and robust.