Testing, control and modeling of a pneumatic active seat suspension and ride comfort evaluation

Good handling of heavy vehicles such as tractors, trucks or buses require large roll stiffness at the front axle of the truck, which causes large vertical accelerations in the driver's seat. Exposure to vibration is a major concern to vehicles operators. Most of these drivers over time develop serious spinal musculoskeletal and discs problems causing low back injuries.Adding a secondary suspension mechanism to the seat is one of the solutions that were found to minimize the human body vibration. In this thesis, the performance of a pneumatic semi-active seat suspension under development at the Vehicle Technology Laboratory at the University of Illinois at Chicago is investigated. Experimental testing of the design was performed varying different design parameters and control strategies. In addition, two suspension models were created and validated against the experimental data. The two simulations differed on the way the dynamic of the actuator is modeled.Ride dynamics and safety of operators have for years been evaluated and achieved through measurements of accelerations at the interface between the seat and the passenger or simply through subjective means of operators/drivers feedback. The correlation between the two methods has yet to be proven reliable and in most cases lead to drastically different answers. Lower back pain being the main health issue in whole body vibration, the authors believe that a better understanding of the energy and vibration transmission through the lumbar spine could potentially lead to a better correlation between physical and subjective measurements.As a result, two human body models were developed to quantify the energy transmission from the seat to the operator. The first model consisted of a lump mass model. Since lower back issue is the main health issue for whole body vibration, a second dynamic model in 3D was created. It includes a refined model of the lumbar area based a finite element model of the lumbar spine.Field data collected on an off-road vehicle were applied to the resulting human body model. The level of acceleration and absorbed power for each body segment were compared. The results undermine the importance of the lumbar region when it comes to energy and vibration transmission.