Research On Simulation Of The Pressure Distribution Between Driver And Seat

Static seating comfort is important for drivers and other passengers, which mainlyreflected by the level of muscle activity and the pressure distribution between drive and seat.Using biomechanics method to study the mechanism of seating comfort has become a hottopic of ergonomics. At present, contact pressure distribution between human and seat isoften used for objective evaluation of seat comfort. The public-domain researches show thatdifferent driving postures can cause changes of contact pressure distributions, while thedriving postures will change with the variation of packaging parameters as certain law.Therefore the comforts of driver seats used to match different cars are different. To improveseating comfort and to meet driving requirements, characteristics of body pressuredistribution under specific driving posture must be studied and used in design. With the aidsof human anthropometric dimensions prediction and driving posture prediction methods, thepressure distribution of specific driver under specific driving posture and its influence onpostural comfort were studied in this thesis.Since pressure distribution simulation should represent realistically the actual situation,it is one of the key points of accurate simulation of the interaction between driver and seat toset driving postures corresponding to different cab packaging parameters precisely. Whenseat is determined, it not only needs to consider the influence of posture but also needs toreflect the impact of individual factors. In order to introduce the posture and individualfactors into pressure distribution simulation properly, the drivers,driving posture predictionmodels and boundary manikin anthropometric models were established by usingEmpirical-Statistical method and principal component analysis method respectively. Withthese models, the driving postures under packaging environments can be achieved throughdriving posture prediction models, and the boundary manikin could be used to study theinfluence of individual factors on pressure distribution. Another difficult point lies in the establishment of driver human body model. In order to guarantee the accuracy of simulationresult and the authenticity of simulation, a detailed biomechanical model of seated driverhuman body model was developed in present work using Poser human data. The establishedmodel was verified using height, body weight and chest circumference, and some partswhich ever with small differences also were readjusted according to some macroscopic bodysizes. Then a detailed finite element model of human body was developed. The tissue of thehuman-body was modeled using the Mooney-Rivlin hyperelastic isotropic material model.This model is capable of accounting for large (non-linear) elastic deformations that issuitable for the simulation of soft tissue of the seated human. The pressure distribution of50thpercentile driver under specific posture was studied using the above human finiteelement model, with the boundary conditions of the simulation set by using surface tosurface contact between driver and seat. The simulation result was validated by comparingwith pressure distribution experiments. The simulation result showed that the maximumstress of buttocks locates under the ischial tuberosity which was also greater than the stressof the skin layer, and the maximum stress of body back occurred at the back of scapula andthe lower waist. Due to the fact that posture has an important influence on the pressuredistribution, the pressure distributions under different packaging parameters were studied inpresent work, and a comfort evaluation method based on linear regression analysis wasestablished. The results showed that maximum pressure distribution decreases with theincrease of seat height (H30). Currently, only the relationships between a few of thepackaging parameters and pressure distribution were studied, which should be updated andvalidated by more experimental studies in the future, so as to find the relationship betweenpressure distribution and those packaging parameters. It was found from the sitting comfortstudy that the average shear force and maximum cushion pressure were the two mainlycomfort affecting factors. Finally in this thesis, the H-point position of the seated H pointmachine is studied using both simulation and trial methods. According to prediction result ofthe simulation, and by writing simulation program in the Visual C++6.0platform, thedistribution of the body back characteristic points of seated boundary driver manikin were simulated combining with the boundary manikin and the posture prediction models. Byadopting the pressure distributions of seated boundary manikins and the distributions ofbody back characteristic points of seated boundary manikin, the forward design method ofseat was studied..