Seat Comfort Study With Consideration Of Body Pressure Distribution Of Boundary Manikins

Seating comfort improvement has been paid more attention today, which can not onlybring more driving pleasure, but also can delay fatigue and reduce the safety problems causedby driving fatigue. Therefore, it is necessary to study subjective and objective evaluation dataassociated with seating comfort, and provide a theoretical basis for the design of a comfortseat. During the seat design process, how to meet the comfort needs of more users is a keyfactor in the evaluation of seat comfort design besides meeting functional requirements suchas driving and manipulation. So individual factors should be considered. A significantquantitative correlation has been showed between pressure distribution and seat comfortevaluation. Therefore, this article will research the influence of individual factors on seatcomfort through researching variation of pressure distribution mode. Pressure distributionvariation is visually acquired using experimental methods, and pressure, stress or otherchanges of the interface between human and seat can be showed more effectively and morecomprehensively through the use of simulation methods. This two methods were combinedand variation regulations of objective evaluation of data were summed to study the comfortseat design in this thesis.Accurate, representative anthropometric data is a prerequisite for the research of humanfactors. Height, weight and sitting height, which can best reflect differences of statures, wereselected to predict human dimensions.10,000samples, which contained U.S. humandimension data was generated through Monte Carlo simulation. Confidence limits formultidimensional human dimension distribution was established with principal componentanalysis and three typical human were selected, which represent boundary manikins. Thelength of the arms, legs and other human dimensions that affect the driving postures of thethree human models was calculated, which formed the data basis of human factor research ofthis thesis. Pressure distribution experiment is the basis of the simulation study. Ten drivers ofdifferent statures were selected according to the predicted human dimensions. Experiments onpressure distribution were done in an experimental car with fixed layout parameters. Contactarea, peak contact pressure and average contact pressure were obtained and then the trendsover the human dimensions were summarized. Measured layout parameters, the position of Hpoint and driving postures were also gained through experiment, which guaranteed theaccuracy of the simulation study.It is essential to establish biomechanical models before pressure distribution simulation.Human models from Poser can reproduce the real outline of human body surface and skeleton.Three boundary manikin models,5th%tile male,50th%tile male and95th%tile male withpredicted anthropometric database were developed using dimension scaling. In order toremove the effect of posture factors, postures of this three digital human body models wereadjusted according to the CPM, which was known as optimum driving posture predictionmodel. The skin was modeled as a linearly-elastic isotropic nearly-incompressible materialdescribe its mechanical properties. Bones were constructed using linear elastic isotropicmaterial. Soft tissue was modeled as Mooney-Rivlin model and seat foam was modeled ashyper foam. Several connectors were used to represent the joints connecting adjacent bones.Suitable boundary conditions were added to ensure the accuracy of the seating process. Thetrends of contact area and contact pressure gained from simulation match good accuracy withexperimental results of pressure distribution. The fatigue process had also been explained fromthe stress data of soft tissue.Researches show that lumbar support can improve seating comfort. Lumbar supportfactor was also contained in this thesis. Subjective evaluation scores of10driver’s support thisview. Peak pressure increased and pressure distribution showed better symmetry after lumbarsupport was added. This conclusion was gained both through experiment and simulation andexplained the role of the lumbar support objectively. Experiment on the adjustment travel oflumbar support was conducted. Drivers were more likely to choose the prominence height of20mm of the lumbar support and the adjustment travel of up and down was70mm which provided a reference for the design of the lumbar support.