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.     

Malaysian sitting anthropometry for seat fit parameters

This article presents sitting anthropometry data for Malaysians focusing on seat fit parameters. It offers additional data regarding seat design requirements as there have been only a few efforts made to establish anthropometry data in Malaysia. An analysis using a measurement composed of 16 common and important dimensions in seat design was done with 216 subjects. Data collection was done by using direct measuring methods with standard equipment. Malaysian automobile seat fit parameters, namely backrest width, backrest height, cushion width, and cushion length were established from collected anthropometric dimensions: interscye breadth (5th percentile female and 95th percentile male), sitting shoulder height (5th percentile female), hip breadth (95th percentile female), and buttock–popliteal length (5th percentile female), respectively. From the data collected, this study finds that the fit parameter dimensions are bigger than other Asians' 95th percentile values but smaller than the Filipino and the Thai data being compared in this study. The female 5th percentile values for cushion length and cushion width are the smallest. In addition, two local automobile seats were measured and compared with the data. It was observed that the cushion lengths of both seats were too long for the 5th percentile female of the current data. This study provides seat fit parameters–the most fundamental part of automotive seat design, especially for the Malaysian population. © 2010 Wiley Periodicals, Inc.     

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.     

Thermal comfort of aeroplane seats: influence of different seat materials and the use of laboratory test methods

This study determined the influence of different cover and cushion materials on the thermal comfort of aeroplane seats. Different materials as well as ready made seats were investigated by the physiological laboratory test methods Skin Model and seat comfort tester. Additionally, seat trials with human test subjects were performed in a climatic chamber. Results show that a fabric cover produces a considerably higher sweat transport than leather. A three-dimensional knitted spacer fabric turns out to be the better cushion alternative in comparison to a moulded foam pad. Results from the physiological laboratory test methods nicely correspond to the seat trials with human test subjects.     

Factors affecting static seat cushion comfort

To improve the understanding of factors affecting automobile seat cushion comfort in static conditions (i.e. without vibration), relationships between the static physical characteristics of a seat cushion and seat comfort have been investigated. The static seat comfort of four automobile cushions, with the same foam hardness but diOEerent foam compositions, was investigated using Scheffe?s method of paired comparisons. The comfort judgements were correlated with sample stiOEness, given by the gradient of a force-deflection curve at 490 N (= 50 kgf). Samples with lower stiffness were judged to be more comfortable than samples with greater stiffness. A similar comfort evaluation was conducted using five rectangular foam samples of the same composition but different foam hardness (and a wider range than in the first experiment). There was no linear relationship between the sample stiffness and seat comfort for these samples. Static seat cushion comfort seemed to be affected by two factors, a ‘bottoming feeling’ and a ‘foam hardness feeling’. The bottoming feeling was reflected in the sample stiffness when loaded to 490 N, while the foam hardness feeling was reflected in foam characteristics at relatively low forces. The pressures underneath the buttocks of subjects were compared with the comfort judgements. The total pressure over a 4 cm × cm area beneath the ischial bones was correlated with static seat comfort, even when the differences among samples were great; samples with less total pressure in this area were judged to be more comfortable than samples with greater total pressure. It is concluded that the pressure beneath the ischial bones may reflect both comfort factors: the bottoming feeling and the foam hardness feeling.     

Factors affecting static seat cushion comfort.

To improve the understanding of factors affecting automobile seat cushion comfort in static conditions (i.e. without vibration), relationships between the static physical characteristics of a seat cushion and seat comfort have been investigated. The static seat comfort of four automobile cushions, with the same foam hardness but different foam compositions, was investigated using Scheffe's method of paired comparisons. The comfort judgements were correlated with sample stiffness, given by the gradient of a force-deflection curve at 490 N (= 50 kgf). Samples with lower stiffness were judged to be more comfortable than samples with greater stiffness. A similar comfort evaluation was conducted using five rectangular foam samples of the same composition but different foam hardness (and a wider range than in the first experiment). There was no linear relationship between the sample stiffness and seat comfort for these samples. Static seat cushion comfort seemed to be affected by two factors, a 'bottoming feeling' and a 'foam hardness feeling'. The bottoming feeling was reflected in the sample stiffness when loaded to 490 N, while the foam hardness feeling was reflected in foam characteristics at relatively low forces. The pressures underneath the buttocks of subjects were compared with the comfort judgements. The total pressure over a 4 cm x 4 cm area beneath the ischial bones was correlated with static seat comfort, even when the differences among samples were great; samples with less total pressure in this area were judged to be more comfortable than samples with greater total pressure. It is concluded that the pressure beneath the ischial bones may reflect both comfort factors: the bottoming feeling and the foam hardness feeling.     

Ergonomics modelling and evaluation of automobile seat comfort

Automobile seats are developed in an iterative manner because subjective feedback, which is usually of questionable quality, drives the design. The time and cost associated with iteration could be justified if the process was guaranteed to produce a comfortable seat. Unfortunately, this is not the case. Current practices are based on the premise that seat system design teams need objective, measurable laboratory standards, which can be linked to subjective perceptions of comfort. Only in this way can predictions be made regarding whether or not a particular design will be viewed by the consumer as comfortable. This type of forecasting ability would effectively improve the efficiency with which automobile seats are designed. In this context, the research reported, developed, and validated a stepwise, multiple linear regression model relating seat interface pressure characteristics, occupant anthropometry, occupant demographics, and perceptions of seat appearance to an overall, subjective comfort index derived from a survey with proven levels of reliability and validity. The model performance statistics were: adjusted r(2)=0.668, standard error of estimate=2.308, F (6, 38)=15.728, p=0.000, and cross-validated r (15)=0.952, p=0.000. From the model, human criteria for seat interface pressure measures were established. These findings could not have been attained without first demonstrating that (1) the data collection protocol for seat interface pressure measurement was repeatable and (2) seat interface pressure measurements can be used to distinguish between seats.     

In-vehicle vibration study of child safety seats

This paper reports experimental measurements of the in-vehicle vibrational behaviour of stage 0&1 child safety seats. Road tests were performed for eight combinations of child, child seat and automobile. Four accelerometers were installed in the vehicles and orientated to measure as closely as possible in the vertical direction; two were attached to the floor and two located at the human interfaces. An SAE pad was placed under the ischial tuberosities of the driver at the seat cushion and a child pad, designed for the purpose of this study, was placed under the child. Four test runs were made over a pave’ (cobblestone) surface for the driver's seat and four for the child seat at both 20?km?h^?1 and 40?km?h^?1. Power spectral densities were determined for all measurement points and acceleration transmissibility functions (ATFs) were estimated from the floor of the vehicle to the human interfaces. The system composed of automobile seat, child seat and child was found to transmit greater vibration than the system composed of automobile seat and driver. The ensemble mean transmissibility in the frequency range from 1 to 60 Hz was found to be 77% for the child seats systems as opposed to 61% for the driver's seats. The acceleration transmissibility for the child seat system was found to be higher than that of the driver's seat at most frequencies above 10 Hz for all eight systems tested. The measured ATFs suggest that the principal whole-body vibration resonance of the children occurred at a mean frequency of 8.5, rather than the 3.5 to 5.0 Hz typically found in the case of seated adults. It can be concluded that current belt-fastened child seats are less effective than the vehicle primary seating systems in attenuating vibrational disturbances. The results also suggest the potential inability of evaluating child comfort by means of existing whole-body vibration standards.     

Some observations regarding the vibrational environment in child safety seats

A growing issue in the area of vehicular ride comfort is that of child safety seats. Postural, thermal and vibrational comfort considerations are finding their way into child seat design. This paper makes some observations regarding the current state of child safety seat design, then goes on to present the results of vibration tests performed over two road surfaces using two child seats and two children. The vibration levels measured at the interfaces between the children and their seats were found to be higher than the vibration levels between the driver and the driver's seat. Calculated power spectral densities and acceleration transmissibility functions showed that the vibration transmission characteristics of the coupled system consisting of the automobile seat, child seat and child were different from those of the driver/seat system. Whereas, automobile seats normally reduce vibrational disturbances at most frequencies, the child seats tested amplified vibration at most frequencies up to 60 Hz.     

In-vehicle vibration study of child safety seats

This paper reports experimental measurements of the in-vehicle vibrational behaviour of stage 0&1 child safety seats. Road tests were performed for eight combinations of child, child seat and automobile. Four accelerometers were installed in the vehicles and orientated to measure as closely as possible in the vertical direction; two were attached to the floor and two located at the human interfaces. An SAE pad was placed under the ischial tuberosities of the driver at the seat cushion and a child pad, designed for the purpose of this study, was placed under the child. Four test runs were made over a pave' (cobblestone) surface for the driver's seat and four for the child seat at both 20 km h(-1) and 40 km h(-1). Power spectral densities were determined for all measurement points and acceleration transmissibility functions (ATFs) were estimated from the floor of the vehicle to the human interfaces. The system composed of automobile seat, child seat and child was found to transmit greater vibration than the system composed of automobile seat and driver. The ensemble mean transmissibility in the frequency range from 1 to 60 Hz was found to be 77% for the child seats systems as opposed to 61% for the driver's seats. The acceleration transmissibility for the child seat system was found to be higher than that of the driver's seat at most frequencies above 10 Hz for all eight systems tested. The measured ATFs suggest that the principal whole-body vibration resonance of the children occurred at a mean frequency of 8.5, rather than the 3.5 to 5.0 Hz typically found in the case of seated adults. It can be concluded that current belt-fastened child seats are less effective than the vehicle primary seating systems in attenuating vibrational disturbances. The results also suggest the potential inability of evaluating child comfort by means of existing whole-body vibration standards.     

A subjective framework for seat comfort based on a heuristic multi criteria decision making technique and anthropometry

Consumer expectations for automobile seat comfort continue to rise. With this said, it is evident that the current automobile seat comfort development process, which is only sporadically successful, needs to change. In this context, there has been growing recognition of the need for establishing theoretical and methodological automobile seat comfort. On the other hand, seat producer need to know the costumer’s required comfort to produce based on their interests. The current research methodologies apply qualitative approaches due to anthropometric specifications. The most significant weakness of these approaches is the inexact extracted inferences. Despite the qualitative nature of the consumer’s preferences there are some methods to transform the qualitative parameters into numerical value which could help seat producer to improve or enhance their products. Nonetheless this approach would help the automobile manufacturer to provide their seats from the best producer regarding to the consumers idea. In this paper, a heuristic multi criteria decision making technique is applied to make consumers preferences in the numeric value. This Technique is combination of Analytical Hierarchy Procedure (AHP), Entropy method, and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS). A case study is conducted to illustrate the applicability and the effectiveness of the proposed heuristic approach.     

A subjective framework for seat comfort based on a heuristic multi criteria decision making technique and anthropometry

Consumer expectations for automobile seat comfort continue to rise. With this said, it is evident that the current automobile seat comfort development process, which is only sporadically successful, needs to change. In this context, there has been growing recognition of the need for establishing theoretical and methodological automobile seat comfort. On the other hand, seat producer need to know the costumer’s required comfort to produce based on their interests. The current research methodologies apply qualitative approaches due to anthropometric specifications. The most significant weakness of these approaches is the inexact extracted inferences. Despite the qualitative nature of the consumer’s preferences there are some methods to transform the qualitative parameters into numerical value which could help seat producer to improve or enhance their products. Nonetheless this approach would help the automobile manufacturer to provide their seats from the best producer regarding to the consumers idea. In this paper, a heuristic multi criteria decision making technique is applied to make consumers preferences in the numeric value. This Technique is combination of Analytical Hierarchy Procedure (AHP), Entropy method, and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS). A case study is conducted to illustrate the applicability and the effectiveness of the proposed heuristic approach.     

Ergonomics modelling and evaluation of automobile seat comfort

Automobile seats are developed in an iterative manner because subjective feedback, which is usually of questionable quality, drives the design. The time and cost associated with iteration could be justified if the process was guaranteed to produce a comfortable seat. Unfortunately, this is not the case. Current practices are based on the premise that seat system design teams need objective, measurable laboratory standards, which can be linked to subjective perceptions of comfort. Only in this way can predictions be made regarding whether or not a particular design will be viewed by the consumer as comfortable. This type of forecasting ability would effectively improve the efficiency with which automobile seats are designed. In this context, the research reported, developed, and validated a stepwise, multiple linear regression model relating seat interface pressure characteristics, occupant anthropometry, occupant demographics, and perceptions of seat appearance to an overall, subjective comfort index derived from a survey with proven levels of reliability and validity. The model performance statistics were: adjusted r ²?=?0.668, standard error of estimate?=?2.308, F (6, 38)?=?15.728, p?=?0.000, and cross-validated r (15)?=?0.952, p?=?0.000. From the model, human criteria for seat interface pressure measures were established. These findings could not have been attained without first demonstrating that (1) the data collection protocol for seat interface pressure measurement was repeatable and (2) seat interface pressure measurements can be used to distinguish between seats.     

Coach design for the Korean high-speed train: a systematic approach to passenger seat design and layout

Proper ergonomic design of a passenger seat and coach layout for a high-speed train is an essential component that is directly related to passenger comfort. In this research, a systematic approach to the design of passenger seats was described and the coach layout which reflected the tradeoff between transportation capacity and passenger comfort was investigated for the Korean high-speed train. As a result, design recommendations and specifications of the passenger seat and its layout were suggested. The whole design process is composed of four stages. A survey and analysis of design requirement was first conducted, which formed the base for designing the first and second class passenger seats. Prototypes were made and evaluated iteratively, and seat arrangement and coach layout were finally obtained. The systematic approach and recommendations suggested in this study are expected to be applicable to the seat design for public transportations and to help modify and redesign existing vehicular seats.     

Effects of heated seats in vehicles on thermal comfort during the initial warm-up period

Eight subjects participated in a subjective experiment of eight conditions to investigate the effects of heated seats in vehicles on skin temperature, thermal sensation and thermal comfort during the initial warm-up period. The experimental conditions were designed as a combination of air temperature in the test room (5, 10, 15, or 20 °C) and heated seat (on/off). The heated seat was effective for improving thermal comfort during the initial warm-up period when air temperature was lower than 15 °C. Use of heated seats prevented decreases in or increased toe skin temperature. Heated seats also increased foot thermal sensation at 15 and 20 °C. Optimal thermal sensation in contact with the seat was higher when air temperature was lower. Optimal skin temperature in contact with the seat back was higher than that with the seat cushion. Moreover, these optimal skin temperatures were higher when air temperature was lower.     

Police officer in-vehicle discomfort: Appointments carriage method and vehicle seat features

Musculoskeletal pain is commonly reported by police officers. A potential cause of officer discomfort is a mismatch between vehicle seats and the method used for carrying appointments. Twenty-five police officers rated their discomfort while seated in: (1) a standard police vehicle seat, and (2) a vehicle seat custom-designed for police use. Discomfort was recorded in both seats while wearing police appointments on: (1) a traditional appointments belt, and (2) a load-bearing vest/belt combination (LBV). Sitting in the standard vehicle seat and carrying appointments on a traditional appointments belt were both associated with significantly elevated discomfort. Four vehicle seat features were most implicated as contributing to discomfort: back rest bolster prominence; lumbar region support; seat cushion width; and seat cushion bolster depth. Authorising the carriage of appointments using a LBV is a lower cost solution with potential to reduce officer discomfort. Furthermore, the introduction of custom-designed vehicle seats should be considered.     

The postural support of seats: a study of driver preferences during simulated tractor operation

The overall comfort of four current production tractor seats and some individual features of seat design have been assessed by a method of paired comparisons. The experiment was carried out under both static and dynamic conditions and subjects had to adopt natural postures similar to those adopted when ploughing. The results suggest that operators can differentiate seat comfort differences reliably. Subjects' posture has proved important particularly when assessing the height of the back rest. On the other hand most appraisals were not significantly affected by the conditions (dynamic or static) of the simulation. An exception to this was the cushion length. This experiment has finally produced enough information on the relative importance of various aspects to enable us to design an experimental seat to be used in a series of experiments to assess specific features of seat aspects. The ultimate objectives of this investigation are to determine what aspects of seat and workplace design affect the comfort of the operator and how these can be altered to improve the tractor driver's posture.     

Evaluation of the seating of Qantas flight deck crew

In 1985 Qantas Airways (Australia) requested an ergonomics assessment of three pilots' seats so that one could be selected for fitting in all new aircraft as well replacement in existing aircraft. The Ipeco seat was chosen. In 1991, after all aircraft were fitted with the Ipeco seats, the company then requested a further evaluation of the seat to see if it was acceptable to the pilots and if there were any outstanding problems. A seat feature checklist plus a body chart discomfort rating scale was given to the total crew of 1030 pilots. The results from the 202 respondents indicated that although the pilots found the Ipeco seat an improvement on the Weber seat there were some modifications required. The main problems included insufficient adjustment range of the lumbar support area and the thigh supports, and infrequent replacement of the seat cushion. The body charts supported the checklist results in that the main areas of discomfort indicated were the buttocks and low back. Recommendations for improvements in design of the Ipeco seat, training in use and maintenance are presented. The method used in this study has application for field assessment of seating in a wide range of occupations, particularly bus drivers, truck drivers and train drivers, who spend long hours seated without being able to take breaks.     

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.     

The effect of 17-inch-wide and 18-inch-wide airplane passenger seats on comfort

The pitch and width of airline seats are crucial factors on the comfort of passengers. The aim of this study is to measure the comfort feeling of passengers regarding different widths and together with data from a previous study, to offer suggestions on the aircraft interior design. 311 participants were recruited and were asked to sit in 17-inch-wide and 18-inch-wide aircraft seats in a Boeing 737 fuselage for 10 min, respectively. Questionnaires on psychological comfort and overall discomfort, as well as an additional questionnaire on the discomfort of different body parts, were used to evaluate the comfort and discomfort experience of participants. Experiment results indicated that the comfort scores were significantly higher, and the discomfort scores were significantly lower for sitting in the 18-inch-wide seats than that of sitting in the 17-inch-wide seats. It was also found that rather than the buttock, the shoulders, knees, lower legs and feet contributed significantly to the reduction in overall discomfort by providing more space for movements. Regarding anthropometric measurements, participants with smaller hip-breadth felt more comfort while sitting the 18-inch-wide seat, which highlights the importance of the freedom of movement. By synthesizing the results of a previous study on the relations of the seat pitch and comfort, it was found that given the same amount of additional floor area, widening the seat is more effective on comfort than increasing the pitch.Relevance to industry: This discovery might be useful for the airline industry for a more effective and efficient usage of floor area.