Research On Cab Package Optimization Based On Joint Load Evaluation Of Driving Posture Comfort

A driver's main posture is very important to the layout of a cab. It is crucial to evaluate main driving posture accurately and objectively on simulating driving posture, which is also a guarantee to the layout quality of an excellent cab. This thesis presents a study on the theory of objective evaluation and technical problems of the drivers'main driving postures; including anthropometry prediction, main driving posture prediction, man-machine interface force and joint loads calculation model of driving postures, and model of discomfort of driving posture. By adopting these results, the multi-objective optimization of the cab's layout design was further studied.Anthropometry measurement was usually taken with heavy costs, but with limited data gained. For application conveniently, the constant ratios of body parts were often analyzed, so as to predict detailed body dimension based on only a few body dimensions. However, this method adopts only few predicate factors and can only forecast average dimension. In order to conquer these shortages, this thesis studied how to measure body scale accurately. Anthropometry data were collected by measuring in a simulating way in CATIA-V5 software. And then, body height, hip height and body mass index were adopted as predictors in body dimensions prediction study, and by bringing back residuals to regression equations, the revised anthropometry prediction models were established. By comparing the predicated values with measured values, the validation and effectiveness of anthropometry prediction models had been testified.In the past, discomfort evaluation had often been done subjectively, which was not accurate and objective, and difficult to be connected with simulation and optimization. In this thesis, an evaluation method of driving posture comfort based on joint load was studied, including skeleton kinematics modeling, driving posture prediction as well as man-machine interface forces and joint loads quasi-static calculation models. A simplified representation of human skeleton system was built with reference to human anatomy and biomechanics, and human kinematics model was constructed by using D-H method. Forward direction kinematics and reverse kinematics normally could not acquire real driving posture easily, so prediction models were used to analyze and calculate the main driving posture. By inputting the layout parameters of real car and anthropometry information predicted into the OPM(Optimization Prediction Model) of UMTRI (University of Michigan Transportation Research Institute), the main driving posture can be calculated. After analyzing of the interaction forces between human body, seat, footplate, steering wheel and floor, man-machine interface force and joint load quasi-static solving models of main driving posture were established. And then, the man-machine interface forces and joints loads were calculated by using the theory of static mechanics, reverse dynamics and numerical calculation methods, which form the basis for joints loads based posture comfort modeling.Finally, the multi-objective layout optimization of the cab of a occupant car was carried on. The Hard Points Dimension such as H70, A18, H17, L11 and A27 were selected as design variables, and then experiments were designed based on them. The driver's downward vision was used as constraint of optimization. The optimization calculation was mainly towards 95-percentile male and 5-percentile female driver population. Several joints loads were selected by correlation analysis as the predictors of postural discomfort, and also their weights. Static discomfort evaluation model for mixed-gender population based on joints loads was built, with consideration of the probability of the male and female occurrence. By using postural discomfort and H-Point horizontal travel as optimization objectives, the packaging of the cab was optimized.There was some progress on anthropometry prediction and evaluation of main driving posture comfort. The anthropometry prediction model greatly improved its accuracy and flexibility. The evaluation method of static driving posture discomfort based on driver's joint load greatly improved its objectivity and practical value. For the convenience of application, all the results of study had been integrated under V.Fortran platform. More stress had been laid on the application of cab package in this thesis. It provided guarantee to identify cab layout parameters objectively and accurately while shortened the cycle of product development and cut down the costs. Therefore, based on the methods above mentioned, preliminary study of the optimization of cab package had been carried on, with the result of meeting the requirements of forward vision and sitting comfort. Cab layout parameters that were gained by optimization may improve driving environment tremendously, and embodied the human-centered design ideas of cab design, which improved the product's competitiveness in market.