The inadequate effect of automobile seating on foot posture and callus development

Driver posture is an important factor to be considered in the ergonomics design process of automobiles. Most decisions during automobile design and manufacture are informed by studying the intricate biomechanical components of human musculoskeletal systems to ensure maximum comfort, safety and well-being during driving. A case study is presented that confirms inappropriate foot position as a causative factor for the development of abnormal lateral/plantar heel callosities when driving a 4 × 4-style vehicle. The driver's foot position was influenced by the seat geometry of the vehicle. Cessation of driving the 4 × 4-style vehicle and driving of an alternative automobile while on holiday for a period of 4 weeks resolved the condition. On return to the 4 × 4-style vehicle, however, the abnormal callus patterns redeveloped while using the same footwear and no change in any other parameters. It is therefore suggested that seat and consequent foot position is an important ergonomic factor that should be addressed in the future design of automobile seating.     

An ergonomics investigation into human thermal comfort using an automobile seat heated with encapsulated carbonized fabric (ECF).

This report presents the results of an ergonomics investigation into human thermal comfort using an automobile seat heated with an encapsulated carbonized fabric (ECF). Subjective and objective thermal comfort data were recorded while participants sat for 90 min in a heated and a non-heated automobile seat in an environmental chamber. Eight male participants each completed eight experimental sessions in a balanced order repeated measures experimental design. The conditions in the chamber were representative of a range of cool vehicle thermal environments (5, 10, 15 and 20 degrees C; in the 20 degrees C trial participants sat beside a 5 degrees C 'cold wall'). Participants in the heated seat condition used the heating controller with separate temperature control over the back of the seat (squab) and bottom of the seat (cushion) in an effort to maintain their thermal comfort while wearing the provided clothing, which had an estimated insulation value of 0.9 Clo. The trials showed that participants' overall sensations remained higher than 'slightly cool' in the heated seat at all temperatures. Participants' overall discomfort remained lower (i.e. more comfortable) than 'slightly uncomfortable' at temperatures ranging down to nearly 5 degrees C in the heated seat. Hand and foot comfort, sensation and temperature were similar in both seats. Asymmetric torso and thigh skin temperatures were higher in the heated seat although no significant discomfort was found in the front and back of the torso and thigh in either seat. Participants reported no significant difference in alertness between the control and heated seat.     

A statistical method for predicting automobile driving posture

A new model for predicting automobile driving posture is presented. The model, based on data from a study of 68 men and women in 18 vehicle package and seat conditions, is designed for use in posturing the human figure models that are increasingly used for vehicle interior design. The model uses a series of independent regression models, coupled with data-guided inverse kinematics, to fit a whole-body linkage. An important characteristic of the new model is that it places greatest importance on prediction accuracy for the body locations that are most important for vehicle interior design: eye location and hip location. The model predictions were compared with the driving postures of 120 men and women in five vehicles. Errors in mean eye location predictions in the vehicles were typically less than 10 mm. Prediction errors were largely independent of anthropometric variables and vehicle layout. Although the average posture of a group of people can be predicted accurately, individuals' postures cannot be predicted precisely because of interindividual posture variance that is unrelated to key anthropometric variables. The posture prediction models developed in this research can be applied to posturing computer-rendered human models to improve the accuracy of ergonomic assessments of vehicle interiors.     

Modeling of human model for static pressure distribution prediction

Vehicle comfort, the key factor that influences the purchase of automobile products, is becoming increasingly important. However, the processes of traditional empirical and experimental approaches to design a new, more comfortable seat is complicated, time consuming and costly. The finite element method could facilitate, accelerate and economize this process. In the present work, a complete human FE model is established based on the Hybrid III dummy, the appropriate element size of 10 mm was ascertained. The body segment mass was verified by comparing segment mass percentages obtained from this model with previous data. The further validation study of the human model was achieved via the human pressure distribution experiments over human-rigid seat interaction under three postures, the validation reveals that the simulation results agree well with the experimental data. On this basis, the human model was applied to predict the interactions between human body and an automobile seat, then the contact pressure distribution, additional information about the contact shear stresses distribution and stress distribution within the soft tissue were obtained through simulation. The human model presented in this paper can reflect the interaction between human body and automobile seat precisely.Relevance to industryThe results deduced that the model is capable of realistically predicting pressure distribution, the present model allows the evaluation of seating comforts in a virtual phase of seat development, and the study can be taken as reference for vehicle seat design and biomechanical evaluation.     

Effects of vehicle interior geometry and anthropometric variables on automobile driving posture

The effects of vehicle package, seat, and anthropometric variables on posture were studied in a laboratory vehicle mockup. Participants (68 men and women) selected their preferred driving postures in 18 combinations of seat height, fore-aft steering wheel position, and seat cushion angle. Two seats differing in stiffness and seat back contour were used in testing. Driving postures were recorded using a sonic digitizer to measure the 3D locations of body landmarks. All test variables had significant independent effects on driving posture. Drivers were found to adapt to changes in the vehicle geometry primarily by changes in limb posture, whereas torso posture remained relatively constant. Stature accounts for most of the anthropometrically related variability in driving posture, and gender differences appear to be explained by body size variation. Large intersubject differences in torso posture, which are fairly stable across different seat and package conditions, are not closely related to standard anthropometric measures. The findings can be used to predict the effects of changes in vehicle and seat design on driving postures for populations with a wide range of anthropometric characteristics.     

Assessment of the static fit of automobile lap-belt systems on front-seat passengers

While automobile seat belts are recognized as reducing injury in frontal collisions, the lap belt can cause injury to the abdominal contents during impact. A lap belt which is malpositioned, i.e., above the anterior superior iliac spines (ASIS) of the pelvis before impact, is suggested as a causative factor in many of these injuries. A questionnaire was completed by 198 adult passengers on lap-belt fit as well as vehicle, anthropometric and behavioural factors. All measures were self-reported. The fit of automobile seat belts was also investigated in the laboratory to determine some of the factors thought important in the pre-impact position of the lap belt. Seven factors, subject size, subject sitting posture, clothing thickness, vehicle configuration, vehicle seat position, seat back angle and the handling of the belt by the occupant, were assessed on 51 subjects sitting in six simulated vehicles. The sample purposely included a disproportionate number of tall, short, heavy and thin subjects.

The questionnaire responses indicated that a high proportion (49%) of lap belts were found to be malpositioned in a normal sitting posture. Moving around in the seat, especially slouching, greatly increased the proportion of malpositions. It was noteworthy that wearing a heavy winter coat did not cause belt malposition. A high incidence of malpositioned lap belts was also found in the laboratory study with 42% of the belts having their centre-lines above the ASIS and 89% having part of the belt overlying the ASIS in a normal upright seated position with the seat in the middle of its fore/aft movement. Slouching in the seat significantly increased this proportion. The malposition rate was adversely affected by a forward seat position in a significant manner. There was a large increase in the malposition rate when the occupant attached the belt compared to when the experimenter attached it, with malposition rates of 43% and 19% respectively in the rearmost seat position. There was no statistically significant effect of clothing thickness on belt fit. Although statistically significant correlations between belt inclination and malposition were found, no clear-cut belt-angle existed above which satisfactory fit existed.     

The effect of posture and seat suspension design on discomfort and back muscle fatigue during simulated truck driving

Several studies have shown a relationship between low-back problems and exposure to seated whole-body vibration. The amount of vibration transmitted to the operator is influenced by the posture of the subject in the vehicle. The aim of this study was to determine whether a truck seat with a gas spring in its suspension is superior to the standard spring seat in slowing the onset of muscle fatigue and reducing the level of discomfort experienced during road vibrations while maintaining typical driving postures. The experiment used a 2 x 3 (2 seats x 3 postures) repeated measures design. It was conducted on six males free from low-back pain. Subject comfort was rated before and directly after exposure to typical vibrations. Muscle fatigue using centre frequency was determined during vibration exposure, and the magnitude and phase of acceleration transfer were calculated from the base plate to the seat pan and from the seat pan to the bite bar. None of comfort, fatigue rate or fatigue average were affected by seat type or seat suspension design in the short term, 10 min vibration exposure. Fatigue and comfort measures could continue to be used to detect postural defects, but the more sensitive measures of seat/driver interactions remain mechanical ones using motion-measuring techniques such as accelerometry and correcting for the heavily damped nature of the system. Until more sophisticated manikins are available the characteristics of vibration-attenuating seats should be confirmed using live humans.     

Evaluation of an intelligent seat system

This study was conducted to evaluate the effect of an intelligent seat system, a microprocessor-based interactive seat that automatically adjusts itself to fit a seated individual by making pressure-sensitive adjustments on its own. First, a standard American automobile seat ('baseline' seat) was assessed for comfort. Subjective ratings of comfort, pressure distribution and seated anthropometric measurements were recorded for 20 test subjects. These measurements were recorded while the subjects maintained a simulated driving position in a seat buck. The comfort scale was based on a rating of 1 to 10, with 1 corresponding to 'very poor' and 10 corresponding to 'very good.' Based on a nonlinear, multiple regression model that had been previously developed, the comfort rating of the seat was predicted based on the subjective ratings and the recorded values of 450 pressure measurements from 20 subjects. The predicted comfort value was 7.46 for the baseline seat. Following the baseline assessment, the intelligent seat system was installed into the standard American automobile seat. The objective and subjective assessments were then repeated for 17 subjects and the new predicted comfort rating was 8.06. A t-test performed on the subjective and objective measures indicated that this was a significant improvement in seat comfort. Overall, subjects felt the self-adjusting seat was more customized and more comfortable, providing a better fit.     

The prediction of car driver size and position to enhance safety in crashes

The positions which car drivers adopt when driving will depend on their anthropometric characteristics, the range and type of adjustment available from the vehicle package and their preferred driving posture. The design and testing of systems to protect occupants in car crashes assumes that the size and position of the driver is ‘normal’ or ‘average’, although there is some accommodation for adjustability. If, however, the occupant protection system had information on the driver's chosen seat position, on whether the driver was particularly large or small and on whether the driver was sitting close to or further from the steering wheel, in a crash the system could tailor its performance and enhance the protection offered. This study investigated whether it was possible to predict the physical characteristics of the driver and the driver's position in relation to the steering wheel, from data that could be collected by sensors in the seat and seat mounting. In order to do this, anthropometric characteristics of drivers and their usual seated position in their own vehicle were measured and analyses were undertaken to identify whether there were any relationships between the driver-related and the vehicle-related measures. The results showed that it was possible to predict drivers' head and chest positions relative to injury-producing features of the vehicle such as the steering wheel (and hence the airbag) and to predict some physical dimensions of drivers.     

Haptic perceptions in the vehicle seat

The perceptual overloads of visually and auditorily based information and their interference phenomena within vehicles led to research for the applicability of haptically based information and the haptic interfaces to intelligent vehicles. Because seats are the interface that touches the largest area of the driver's body, the driver's seat in vehicles has been the focus of a promising haptic interface that can improve the safety of drivers and the effectiveness and efficiency of the information transfer between vehicles and drivers. This study aims to provide practical guidelines as a building block for designing the haptic (or vibrotactile) interface in a vehicle's driver's seat by investigating, through four experiments, 1) proper intensity of vibration, 2) minimum distance of spatially distinguishable vibrations, 3) proper position and direction of vibration, and 4) proper rhythm of vibration. Twenty participants took part in the experiments, which were conducted in driving simulation environments. These environments consisted of a real car seat, commercial vibration actuators (i.e., the eccentric motors), and a monitor that showed scenes of the road while driving. This study recommended the proper intensity (approximately 26 to 34 Hz and 2.0 to 3.4 G), position (seat pan or back support), direction (horizontal or indirect), intervibration distance (8 to 9 cm), and rhythm of vibration (3‐s duration with 0.5‐s interval), and showed how the characteristics of drivers, such as gender and age, had effects on setting the design variables of the haptic interface in the vehicle seat. © 2010 Wiley Periodicals, Inc.     

Technical note: spine loading in automotive seating

For car manufacturers, seat comfort is becoming more important in distinguishing themselves from their competitors. Therefore, many studies on participative seat comfort are carried out. In this paper, an objective assessment approach is reported which evaluates the concept of "optimal load distribution", based on the identification of a close relationship between the pressure on the seat and the discomfort felt by the person sitting. An in vivo measurement of the pressure in the spinal disc, which is an indicator of the load in the spine, was performed. For this research, a pressure sensor was implanted with a canula in the middle of the disc intervertebralis of a participant. The local pressure on the disc was established for the participant in an automobile seat set in various seat positions. The results indicate that in the seat position with the pressure distribution corresponding to the most comfortable posture the pressure in the intervertebral disc is lowest. The pressure in this position is 0.5 bar, while in the upright seated position the pressure is 1.6 bar.     

基于动作捕捉的汽车座椅坐姿自动化装配方法研究

针对汽车座椅坐姿自动化装配过程存在人体动作干扰等因素,提出基于动作捕捉的汽车座椅坐姿自动化装配方法。结合视觉动态特征分析方法,进行汽车座椅坐姿自动化装配的动作图像采集,对采集的汽车座椅坐姿动作图像进行降噪处理,采用分区域特征匹配方法进行汽车座椅坐姿动作图像的模板特征匹配,提取汽车座椅坐姿动作图像的边缘轮廓特征量,结合模糊像素区域性融合技术实现对汽车座椅坐姿自动化装配过程中的动作捕捉,根据动作捕捉结果进行汽车座椅坐姿的动态调节,实现汽车座椅坐姿自动化装配优化。仿真结果表明,采用该方法进行汽车座椅坐姿动作捕捉的性较高,动态调节能力较好,提高了汽车座椅坐姿自动化装配水平。     

Postural implications of obtaining line-of-sight for seated operators of underground mining load-haul-dump vehicles

Operators of load-haul-dump (LHD) vehicles use awkward postures that may be held statically and at extreme ranges of motion for long shift periods to spot hazards in underground mining. This study examined postural variables associated with three amounts of seat rotation intended to maximize line-of-sight during forward driving. Three different models, representing the 1st, 50th and 99th percentile male for height and weight, were positioned with appropriate hand and foot constraints in the virtual LHD cab modelled in Classic JACK v4.0. A total of 15 virtual movement strategies were developed to model the postural behaviour of typical workers and each virtual subject was tested, first with the seat in a neutral 0 degrees position and then with it rotated counter-clockwise to 20 degrees and 45 degrees . Results revealed that reductions in trunk rotation, trunk lateral bend and neck rotation were associated with the seat rotation intervention. The general relationship observed was that as seat rotation increased, view of critical visual attention locations and visible line-of-sight area increased while postural load variables decreased. For the most part, 20 degres of seat rotation was beneficial but 45 dgrees produced significantly greater changes to postural load and visible visual attention locations.     

Effect of lumbar support on seating comfort predicted by a whole human body-seat model

Automobile seat greatly affects the ride comfort of drivers in a prolonged driving. Not only the layout parameters of automobile seats, such as seat height, cushion inclination angle, backrest inclination angle, etc, but also the backrest surface related with lumbar support all affect the seating comfort. The human body-seat system includes the three-dimensional data of body based on anatomy and anthropometry, three-dimensional data of seat and adjustable assembly interaction between body and seat based on human body kinematics. Body height and driving posture are adjusted in POSER software, then the solid model of human skin, skeleton and muscle are created in ANSA software, and the integrated model of body-seat system is created in ABAQUS software. The adjustment of the lumbar support parameters is achieved by setting boundary condition of lumbar support region of seats. The finite element model of human body-seat system is validated by comparison to available literature results. At last the finite element model is applied to analyze the effect of lumbar support parameters of seats on the interaction between body and seat under the action of gravity. The pressure value and distribution, contact area, total force of backrest and intervertebral disc stress are obtained. The result shows that the optimal thickness of seat's lumbar support size for the seating comfort is 10 mm after comprehensive comparison and evaluation.Relevance to industry: This study investigated the effects of lumbar support on seating comfort, and can be used to protect the lumbar health. The modeling and simulation method can be applied for the optimization design of vehicle seats.     

汽车电动座椅自动控制系统的研制

一种汽车电动座椅自动控制系统的设计方法。系统以C8051F311单片机为核心,通过控制直流电动机,经蜗轮蜗杆传动机构牵引座椅移动,使汽车座椅具有自动测量极限位置、手动调节、位置记忆以及自动恢复功能。该系统使汽车座椅便于安装,位置调节方便、快捷。     

Driver sitting comfort and discomfort (part II): Relationships with and prediction from interface pressure

Pressure at the driver–seat interface has been used as an objective method to assess seat design, yet existing evidence regarding its efficacy is mixed. The current study examined associations between three subjective ratings (overall, comfort, and discomfort) and 36 measures describing driver–seat interface pressure, and identified pressure level, contact area, and ratio (local to global) variables that could be effectively used to improve subjective responses. Each of 27 participants was involved in six separate driving sessions which included combinations of two seats (from vehicles ranked high and low on overall comfort), two vehicle classes (sedan and SUV), and two driving venues (lab-based and field). Several pressure variables were identified as more effective for assessing sitting comfort and discomfort across a range of individual statures. Based on the results, specific approaches are recommended to improve the sitting experience: (1) lower pressure ratios at the buttocks and higher pressure ratios at the upper and lower back; and (2) balanced pressure between the bilateral buttocks, and between the lower and upper body. Finally, separate analyses supported that human–seat interface pressure was more strongly related with overall and comfort ratings than with discomfort ratings.

Relevance to industry

Several interface pressure variables were identified that showed associations with subjective responses during sitting. Use of these measures is suggested to improve the quality of car seats.     

基于卷积神经网络的驾驶辅助系统设计

为了减轻驾驶员在行驶过程中的操作负担,进而降低误差判断事件的出现几率,设计一种基于卷积神经网络的驾驶辅助系统。在执行良好的汽车导航架构中,限定Learning Navigation模块与Learning Controller模块的连接位置,再根据辅助驾驶传感器对于行驶画面的采集情况,对车辆巡航能力进行定向控制,抑制监测仪表中辅助波的过渡振动,完成驾驶辅助系统的需求与设计分析。在此基础上,确定辅助激活函数、约束仪表中的行车图像,建立标准化的卷积神经网络。按照驾驶辅助数据的学习结果,对其进行传输处理,进而连接驾驶辅助系统的Job请求,实现系统的顺利运行。利用卷积神经网络平台设计实车实验结果表明,应用驾驶辅助系统后,车辆监测仪表中辅助波振动幅度的最小值处于36-61Hz之间,平均波长偏移量明显减小,驾驶员的行驶操作负担得到有效缓解。     

Haptic Seat Interfaces for Driver Information and Warning Systems

The implementation of haptic interfaces in vehicles has important safety and flexibility implications for lessening visual and auditory overload during driving. The present study aims to design and evaluate haptic interfaces with vehicle seats. Three experiments were conducted by testing a haptic seat in a simulator with a total of 20 participants. The first experiment measured reaction time, subjective satisfaction, and subject workloads of the haptic, visual, and auditory displays for the four signals primarily used by vehicle navigation systems. The second experiment measured reaction time, subjective satisfaction, and subjective workloads of the haptic, auditory, and multimodal (haptic + auditory) displays for the ringing signal used by in-vehicle Bluetooth hands-free systems. The third experiment measured drivers' subjective awareness, urgency, usefulness, and disturbance levels at various vibration intensities and positions for a haptic warning signal used by a driver drowsiness warning system. The results indicated that haptic seat interfaces performed better than visual and auditory interfaces, but the unfamiliarity of the haptic interface caused a lower subjective satisfaction for some criteria. Generally, participants showed high subjective satisfaction levels and low subjective workloads toward haptic seat interfaces. This study provided guidance for implementing haptic seat interfaces and identified the possible benefits of their use. It is expected that haptic seats implemented in vehicles will improve safety and the interaction between driver and vehicle.     

Analysis and study of an automobile rear seat by FEM

The aim of this work is to carry out the design of an automobile rear seat and the simulation by finite element method (FEM) on its performance using different standard tests. The design is intended for the rear seats of a four-seat vehicle: two front seats and two rear seats. The rear seat set comprises the right and the left seats. Each of these seats is individual and independent so that it can house only a person and is structurally independent of the other one. Two main parts of this work are: (1) design; and (2) analysis by FEM. We carry out the design of the rear seat of a generic automobile, using the CAD Catia V4 software [P. Carman and P. Tigwell, CATIA Reference Guide, OnWord Press, New York, 1998; F. Karam and C.D. Kleismit, Using CATIA, OnWord Press, New York, 2003]. The seat is composed of two very different parts: (a) framework which is the internal structure of the seat, supporting the weight of the occupants and the seat itself, in order to allow the different positions and to assure the durability and correct operation throughout the vehicle's useful life, and (b) foam rubber whose function is to distribute the load, to provide comfort and to give the most aesthetic possible finish to the seat. During the design we have kept in mind criteria such as resistance, safety, durability, aesthetic and lightness; this last property is necessary to achieve fuel economy and a lower inertia in the event of a collision. The standard rules demand that the automobile seats are able to overcome a series of tests, implying the security in the event of a road accident. In this study the tests were carried out by finite element simulations. The software used was Pam-Crash, a well-known non-linear explicit solver of finite elements. From the computer simulation of these tests, stresses and displacement data are obtained for the seat's framework in order to check the correct execution of the demands of the standard rules, carrying out, if necessary, changes in the design within the allowed limits. In this way the use of this tool makes possible to carry out an optimisation of the geometry, materials, etc. of the product before the construction of the prototype, minimising costs and manufacturers’ development time.     

Postural implications of obtaining line–of–sight for seated operators of underground mining load-haul-dump vehicles

Operators of load–haul–dump (LHD) vehicles use awkward postures that may be held statically and at extreme ranges of motion for long shift periods to spot hazards in underground mining. This study examined postural variables associated with three amounts of seat rotation intended to maximize line-of-sight during forward driving. Three different models, representing the 1st, 50th and 99th percentile male for height and weight, were positioned with appropriate hand and foot constraints in the virtual LHD cab modelled in Classic JACK v4.0. A total of 15 virtual movement strategies were developed to model the postural behaviour of typical workers and each virtual subject was tested, first with the seat in a neutral 0° position and then with it rotated counter-clockwise to 20° and 45°. Results revealed that reductions in trunk rotation, trunk lateral bend and neck rotation were associated with the seat rotation intervention. The general relationship observed was that as seat rotation increased, view of critical visual attention locations and visible line-of-sight area increased while postural load variables decreased. For the most part, 20° of seat rotation was beneficial but 45° produced significantly greater changes to postural load and visible visual attention locations.