Research On The Simulation Of Heavy Commercial Vehicle Driver's Seating Posture Comfort

This dissertation is based on the "Development of Heavy Commercial Vehicle Cab" project, the sub item of national 863 project(National High-technology Research and Development Project) "Advanced Technology in Heavy Commercial Vehicle Integration and Development".The researches in this thesis are mainly used for evaluation and optimization of drivers' posture,which is important part of SHOVED(System for Heavy Commercial Vehicle Ergonomic Design) established on earlier stage.In this paper,research background and state of art of developments of computer aided ergonomics in automobile industry were reviewed,especially in the aspect of driver posture comfort study.While digital technique is widely used in present car design,the basic element for evaluating the rationality of driver operation in virtual world is posture.Whether static or dynamic operation,the analysis and evaluation of drivers' operations can finally be quantized as the checking of driving posture.As driving posture is usually referred as the posture adopted by driver in certain driving environment for carrying out the driving tasks, the posture discomfort prediction model is aimed to mathematically express the relationship between the influencing factors of posture(joint angle,biomechanical force for maintaining posture,pressure distribution of body contact area with seat,etc.) and discomfort. Several popular approaches of discomfort modeling were studied and summarized in detail. In these models,discomfort was usually evaluated by subjective way,which may be influenced by many exterior factors.In this paper,a new posture discomfort evaluation method was proposed by using joint load(joint force and joint torque).That is,the discomfort of posture was calculated by joint load as an objective measurement,while was predicted by posture variables.Based on this idea,discomfort models of driver posture for heavy commercial vehicle design were established.The kinematics description of human body is the base of the posture comfort evaluation. Since there are strong relationships exist between joint load and posture,using limbs angle as measurement of posture has many virtues such as discomfort can be related to posture easily,and muscles changes can also be seen directly when analyzing the discomfort caused by the changes of posture.In this background,simplified skeleton model was built using limbs angles to describe the human body structure and kinematics.And the characteristics of driving behavior were analyzed,so as to understand deeply the relationships among driver operation,posture variables,joint loads and discomfort.The hypothesis,that drivers with different stature,weight and shape have similar law of joint load distribution in posture variable space,was validated by simulation.On the basis of this hypothesis,simulative experiments of lower extremity,torso and upper extremity were designed and performed,and the joints load and coordination data for the creation of discomfort model were acquired.By analyzing the experimental data,the reasonable factors of joint load for calculating the discomfort of lower extremity,upper extremity and trunk were choosed.And then discomfort data were calculated using these factors.By performing relation analysis and regression analysis of discomfort and posture data,discomfort prediction model of these body parts were established.In addition,relationship between torso joint position kinematics and posture were studied,to overcome the inaccurate problem of simple rigid modeling and simulation of torso skeleton.These discomfort models had already been integrated in SHOVED.By using SHOVED and these models,the packaging of driver H-point was studied,with good effect.And also in a heavy commercial driving environment design,by comparing the comfort of driver posture,a better design was selected.By simulation of ergonomics,a lot of human-machine factors can be analyzed and evaluated in earlier stage. Building up virtual humans and products in computer,simulating different motions with more and more biophysiology consideration,and then visualizing these man-machine interaction process,so the human-machine factors for design can be analyzed quantificationally,which on one hand decreased the cost and strongly supported the innovation of product,on the other hand improved the quality of design,shortened the time, and reduced the risk of certain dangerous products testing.But the key of ergonomic simulation is the establishment of a set of accurate and objective criteria for evaluation.The methods in this paper will greatly enhance the objectivity of the posture evaluation and be of a highly applicable worth.