Ride Simulation of Passive, Active, and Semi-Active Seat Suspensions for Off-Road Vehicles

ABSTRACT MATHEMATICAL models were developed for passive, active, and semi-active seat suspension systems. Each suspension model was combined with a three degree of freedom model of the vehicle operator to formulate models of the ride systems of off-road vehicles. Ride performance of the suspensions were computer simulated using the ride models at the various natural frequencies and damping ratios of the suspension systems. The input vibrations for the simulation were obtained by measuring a real time history of accelerations at the base of the seat suspension of agricultural tractors during transport and moldboard plowing operations. The output of the simulation was presented in terms of the ISO frequency weighted root mean square accelerations of the operator's head, body, and pelvis at the preferred one third octave frequency bands. The acceleration levels were evaluated in the criteria of the ISO 8 h fatigue-decreased proficiency boundary. Absorbed power of the operator was also computed for assessing relative ride performance of the suspension systems.