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Technical Paper
C Venkatesan, V Faustino, S Arun, S Ravi Shankar
Abstract The automotive industry needs sustainable seating products which offer good climate performance and superior seating comfort. The safety requirement is always a concern for current seating systems. The life of the present seating system is low and absorbs moisture over a period of time which affects seat performance (cushioning effect). Recycling is one of the major concerns as far as polyurethane (PU) is concerned. This paper presents the development of an alternative material which is eco-friendly and light in weight. Thermoplastic Polyolefin (PO) materials were tried in place PU for many good reasons. It is closed cell foam which has better tear and abrasion resistance. It doesn't absorb water and has excellent weathering resistance. Also it has a better cushioning effect and available in various colours. Because of superior tear resistance, it is possible to eliminate upholstery and would reduce system level cost. The development involves testing and characterization of the materials, making of prototypes and validations.
WIP Standard
This recommended practice describes boundaries of hand control locations that can be reached by a percentage of different driver populations in passenger cars, multi-purpose passenger vehicles, and light trucks (Class A vehicles). This practice is not applicable to heavy trucks (Class B vehicles).
WIP Standard
This recommended practice is a source of information for body and trim engineers and represents existing technology in the field of on-highway vehicle seating systems. It provides a more uniform system of nomenclature, definitions of functional requirements, and testing methods of various material components of motor vehicle seating systems.
WIP Standard
Methods will be developed to characterize In Flight Entertainment (IFE) component impact performance separate from seat design. These methods will address both initial seat head impact criterion (HIC) testing and subsequent IFE component changes. Methods will evaluate head blunt trauma, post-impact sharp edges, and egress impediment. Criteria development will involve defining test methods, test parameters, measurements, and acceptance criteria. Particular emphasis on evaluating IFE changes that require coordination and evaluation per SAE ARP 6448, Appendix B.
This document provides informational background, rationale and a technical case to allow consideration of the removal of the magnesium alloy restriction in aircraft seat construction as contained in AS8049B. The foundation of this argument is flammability characterization work performed by the FAA at the William J. Hughes Technical Center (FAATC), Fire Safety Branch in Atlantic City, New Jersey, USA. The rationale and detailed testing results are presented along with flammability reports that have concluded that the use of specific types of magnesium alloys in aircraft seat construction does not increase the hazard level potential in the passenger cabin in a post-crash fire scenario. Further, the FAA has developed a lab scale test method, reference DOT/FAA/TC-13/52, to be used as a certification test, or method of compliance (MOC) to allow acceptability of the use of magnesium in the governing TSO-C127 and TSO-C39C. Other flammability studies are also cited in the AIR document to substantiate the FAA findings.
WIP Standard
This SAE Aerospace Recommended Practice (ARP) provides guidance for the design and location of flight attendant stations, including emergency equipment installations at or near such stations, so as to enable the flight attendant to function effectively in emergency situations, including emergency evacuations. Recommendations regarding design of flight attendant stations apply to all such stations; recommendations regarding location apply to those stations located near or adjacent to floor level exits.
This SAE Recommended Practice encompasses the significant factors which determine the effectiveness of a seat system in limiting spinal injury during vertical impacts between the rider and the snowmobile seat system. The document is intended to provide a tool for the development of safer snowmobile seats. It is recognized that the seat is only a portion of the entire vehicle protective suspension system. It is, however, usually required that the seat serve as added protection to the suspension system, since the latter may "bottom out" during a severe impact. The term "seat" refers to the occupant-supporting system not normally considered part of the vehicle suspension or frame system. In some cases, it may include more than the foam cushion. This document provides the minimum requirements for performance of a general seat system, and a description of specific means of evaluating the shock-absorbing characteristics of foam seat cushions using a specific testing procedure and a companion seat evaluation chart.
Technical Paper
Prasad Kumbhar, Ning Li, Peijun Xu, James Yang
In vehicle driving environment, the driver is subjected to the vibrations in horizontal, vertical, and fore-aft directions. The human body is very much sensitive to whole body vibration and this vibration transmission to the body depends upon various factors including road irregularities, vehicle suspension, vehicle dynamics, tires, seat design and the human body's properties. The seat design plays a vital role in the vibration isolation as it is directly in contact with human body. Vibration isolation properties of a seat depend upon its dynamic parameters which include spring stiffness and damping of seat suspension and cushion. In this paper, an optimization-based method is used to determine the optimal seat dynamic parameters for seat suspension, and cushion based on minimizing occupant's body fatigue (occupant body absorbed power). A 14-degree of freedom (DOF) multibody biodynamic human model in 2D is selected from literature to assess three types of seat arrangements. The human model has total mass of 71.32 kg with 5 body segments.
Technical Paper
Sung Young Shin, Sang Dong Lee, Bong Chul Go
Abstract In terms of the responsive quality of cars, reducing the vibration of car seats is very important, as this vibration is transmitted directly to the driver. Here, a sensitivity analysis method was used to reasonably reduce the vibration of car seats at minimal cost. A laboratory test was conducted under two excitation conditions: first, vibration in idle state; second, random vibration not exceeding 100 Hz. To determine the reliability of the laboratory test, the actual vibration in idle state was simulated in a multi-axial simulation table for the idle excitation environment of cars that are sensitive to even the smallest changes in the environment. The frequencies of interest were selected by adding the sums of frequency response functions measured at the 24 nodal points of interest under the two excitation conditions. Sensitivity factors were derived at the 24 nodal points of interest and a design modification plan with relatively large sensitivity factors was suggested to reinforce the overall rigidity of the part modules containing the points of interest.
Technical Paper
Se Jin Park, Seung Nam Min, Murali Subramaniyam, Dong-Hoon Lee, Heeran Lee, Dong Gyun Kim
Abstract Seating comfort is one of the most important indicators of the performance of automotive seats. The objective and subjective evaluation of seating comfort plays an important role in the development of seating systems. Objective methods are primarily based on evaluating the influence of vibrations on the driver's seat and assessing the seat pressure ratio. The primary goal of this study was to evaluate the comfort of two car seats (sedan and compact) by comparing a subjective technique with an objective technique like body pressure ratio for a sample of 12 subjects. The results show that the pressure ratio for IT (ischial tuberosity) and L4/L5 were significantly greater for the seat of a compact car than the seat of a sedan car. The subjective comfort was significantly greater for the seat of the sedan car and females than the seat of the compact car and males, respectively. The combination of valid objective measures with subjective ratings of comfort and discomfort may give information of use to seat designers.
Technical Paper
Se Jin Park, Seung Nam Min, Murali Subramaniyam, Heeran Lee, Dong Gyun Kim, Cheol Pyo Hong
Abstract Vibration is both a source of discomfort and a possible risk to human health. There have been numerous studies and knowledge exists regarding the vibrational behavior of vehicle seats on adult human occupants. Children are more and more becoming regular passengers in the vehicle. However, very little knowledge available regarding the vibrational behavior of child safety seats for children. Therefore, the objective of this study was to measure the vibrations in three different baby car seats and to compare these to the vibrations at the interface between the driver and the automobile seat. The test was performed on the National road at the average speed of 70 km/h and acceleration levels were recorded for about 350 Sec (5.83 min). One male driver considered as an adult occupant and a dummy having a mass of 9 kg was representing one year old baby. Four accelerometers were used to measure the vibration. All measured accelerations were relative to the vertical direction. Vibration Analysis Toolset (VATS) was used for time domain analysis.
Technical Paper
Scott Allen Ziolek
Abstract Seat comfort is an important factor in the development of a vehicle; however, comfort can be measured in many ways. Many aspects of the experimental design such as the duration of the drive test, the questions asked, and the make-up of the test subjects are known to influence comfort results. This paper provides the background methodology and results of a Seat comfort study aimed at assessing long-term driving seat comfort.
Technical Paper
Ankang Jin, Weiguo Zhang, Shihu Wang, Yu Yang, Yunqing Zhang
The suspension system of a heavy truck's driver seat plays an important role to reduce the vibrations transmitted to the seat occupant from the cab floor. Air-spring is widely used in the seat suspension system, for the reason that its spring rate is variable and it can make the seat suspension system keep constant ‘tuned’ frequency compared to the conventional coil spring. In this paper, vibration differential equation of air-spring system with auxiliary volume is derived, according to the theory of thermodynamic, hydrodynamics. The deformation-load static characteristic curves of air-spring is obtained, by using a numerical solution method. Then, the ADAMS model of the heavy truck's driver seat suspension system is built up, based on the structure of the seat and parameters of the air-spring and the shock-absorber. At last, the model is validated by comparing the simulation results and the test results, considering the seat acceleration PSD and RMS value.
Technical Paper
Vincent Laurent, Christophe Then, Gerhard Silber
Comfort is a main factor in customer's decision when buying a car. The seat plays a very important role, as it is the interface between occupant and vehicle. Pressure distribution is today's most common approach to characterize seat comfort, but it shows limitations. Analysis of human inter-tissue stress tends to be relevant for an objective comfort assessment. This paper presents the construction and validation of a CAE human model, based on Magnetic Resonance Imaging scans and in-vivo tests data. Correlation between objective criteria and subjective evaluation will be investigated, comfort performance of a real seat will be predicted.
Technical Paper
Chuqi Su, Zhengzhong Chu
Driving comfort is one of the most important indexes for automobile comfort. Driving posture comfort is closely related to the drivers' joint angles and joint torques. In present research, a new method is proposed to identify the most comfortable driving posture based on studying the relation between drivers' joint angles and joint torques. In order to truly reflect a driving situation, the accurate human driving model of 50 percent of the size of Chinese male is established according to the human body database of RAMSIS firstly. Biomechanical model based on accurate human driving model is also developed to analyze and obtain dynamic equations of human driving model by employing Kane method. The joint torque-angle curves of drivers' upper and lower limbs during holding wheel or pedal operation can be obtained through dynamic simulation in the MATLAB. Through curve-fitting analysis, the minimum joint torque of a driver' limb and the optimal joint angel can be found. As an important reference, these parameters can be used to optimize driving seat structure and offer an important support for the optimization of cab package.
Technical Paper
Yousof Azizi, Vaidyanadan Sundaram, Patricia Davies, Anil Bajaj
Flexible polyurethane foam is the main cushioning element used in car seats. Optimization of an occupied seat's static and dynamic behavior requires models of foam that are accurate over a wide range of excitation and pre-compression conditions. In this research, a method is described to estimate the parameters of a global model of the foam behavior from data gathered in a series of impulse tests at different settling points. The estimated model is capable of describing the responses gathered from all the impulse tests using a unique set of parameters. The global model structure includes a nonlinear elastic term and a hereditary viscoelastic term. The model can be used to predict the settling point for each mass used and, by expanding the model about that settling point, local linear models of the response to impulsive excitation can be derived. From this analysis the relationship between the local linear model parameters and the global model parameters is defined. A series of experiments are conducted using different sized masses on the foam block.
Technical Paper
Seishiro Murata, Hiroyuki Ito, Steven Sopher
Flexible polyurethane (PU) foam has been widely used for seat cushions in automotive passenger vehicles due to the excellent cushioning performance and the ability to shape mold. Originally introduced in the late 1950's, it has been used for more than 50 years. However, there is a limitation using polyurethane foam with efforts to reduce the weight and address ever increasing risks to environment. This paper provides information about a new automotive seat concept which does not use polyurethane foam at all. Expanded polyolefin foam is used for this application to replace polyurethane foam and achieve comparable cushioning performance. Other features of the material include 100% recyclability, and no VOC's. By replacing polyurethane foam with expanded thermoplastic foam, hazardous outgassing is eliminated during the seat cushion production, thus improving workplace environmental health and safety.
Technical Paper
Brian Pinkelman
Abstract Experience tells us that one can develop a technically comfortable seat where the seat fits and supports the occupant. The pressure distribution is optimized and the seat and packaging are such that a good posture is attainable by many. The dynamic characteristics of the seat and the vehicle are technically good. Despite all this the customer is not satisfied. Despite it being a technically comfortable seat, it does meet the customers' expectations and/or priorities and thus the comfort provided is lacking. This paper seeks to explore that gap between the seat and the user by modeling comfort using techniques similar to those found in the social sciences where models often focus on user or individual behavior. The model is built upon but diverges from the Cobb Douglas consumer utility model found in economics. It is presented as theory and presents a very different perspective on comfort. The model should be used not as a replacement but a complement to the more traditional technical models of comfort that model the seat.
Technical Paper
Sivapriya Balasubramanian, Santosh Gosavi
Vehicle floor vibration is the resultant of different road inputs damped through various transfer paths. Seat comfort, which depends on these floor vibrations, can be evaluated with a single input signal “Pink noise”; which constitutes various road inputs. Transmissibility of seat structure on a vibration shaker with pink noise input includes all possible responses of road inputs. Still, transmissibility profile at vehicle end and component level varies. This is due to the utilization of “dummy” on component level testing on vibration shaker, which acts as a dead weight with dissimilar damping characteristics of human. A transmissibility correlation between human and dummy is attained by replacing the dummy in place of human and actuating it to find the difference in contribution between them for different class of vehicles. This contribution extrapolation from the damping effects of human and dummy is applied on dummy transmissibility. This results in a complete solution for attaining real time vehicle level seat structure transmissibility at component level testing.
Technical Paper
R.A. Antonelli, L.C.C. Costa, A.M.N. Eustachio, R.C. Queiroz, F. S. Martins, A.P.S. Mello
Safety, Ergonomics and comfort are inseparable concepts and of greater relevance to the full exercise of professional drivers, being the seat, one of the most important components to be considered, when designing their workplace. This work presents initiatives taken by Mercedes-Benz do Brasil Ltda. (MBBras) in partnership with GRAMMER do Brasil Ltda. (Grammer) and Oficio Ergonomia e Design Ltda. concerning the improvement of a SAE Class 8 Heavy-truck Driver Seat. Proposals involved seat design improvement at driver reach and posture, design and constructive characteristics (seat-bottom foam and frame) Upholstery, seat-controls ergonomics and the vibration response, due to the introduction of independent shock-absorbers. A user centered approach was employed to promote the necessary interaction between the major synergic areas: ergonomics, engineering, manufacturing and design, in order to guarantee that the greatest number of demands coming from future customers - here represented by a selected group of drivers - was brought to reality.
Technical Paper
Erik Telles Pascoal, Gustavo de Souza Lima
A frequent situation in the national automobile industry is the each time bigger rapidity that just-launched models are evolved (the so called face-lifts). Within this highly dynamic context, the solutions and technical proposals developed by the local product engineering have two main guidelines. The first one is to work on product evolutions which goal is to make the vehicles far more attractive and differentiated with respect to the competition and also to the previous model. The second one is to constantly search the standardization or the modularization of parts between the different models and versions of vehicles, thus reducing the costs of investments and providing scale profits. This article aims to present, through a case study of the front seat structures, a practical and innovative example of the application of a modular solution developed by the local product engineering that allowed the conciliation of these two apparently antagonistic objectives, the one of obtaining scale economies and, at the same time, the other of preserving the style and the identity of each one of the final products.
Seating solutions steer toward steel Zoomy-looking designs and alternative materials are eye-catching and save weight, but steel keeps getting lighter.
This SAE Standard provides a method to obtain consistent force-deflection data of finished (or unfinished, when specified) cushioned components of seats for off-road work machines as listed in SAE J1116. This data may be helpful in maintaining seat comfort characteristics and quality control. There is no intent to establish any acceptance criteria.
WIP Standard
This document establishes the minimum requirements for seats and restraint systems for the flight deck. Due to limitations that it would place upon basic aircraft design, it is not considered practical for these requirements to apply fully to the observer seat. However, it is emphasized that every effort should be made to provide the observer seat position with an equivalent level of comfort and safety. This document is also intended to make recommendations for flight crew restraint systems. A properly designed crew restraint system will mminimize injury or debilitation during a survivable crash and enable post crash assistance to occupants and escape from the aircraft. Crew member safety is the primary objective, with appropriate provisions for crew comfort taken into consideration. The criteria established herein are designed to standardize restraint systems without hindering the development of new, improved systems.
WIP Standard
The scope of the SAE Heated Seat Committee is to develop a recommended practice to promote an acceptable operating condition for heated vehicle seats. The design guidelines are established in order to mitigate risk to the human skin when using heated seats. The guidelines may include the definition of maximum operating temperatures and durations, the location/visibility and type of indicators and/or telltales, and a procedure to measure certain test temperatures.
Technical Paper
Saed T. Amer, Landon Onyebueke
Traditionally, seat comfort analyses are performed on physically produced seats and, in most cases, human subjects are asked to sit for a period of time to obtain personal subjective and objective comfort measurements. When performed in the seat comfort research laboratory at Tennessee State University, such procedures required close to 900 hours of testing to achieve feasible results. Besides, the costs of the procedures were noticeably high. One of the studies performed in the Lab employs computer driven techniques to avoid physical prototyping for seat comfort analyses. This technique is sought to eliminate the dependence on the traditional techniques and reduce resources consumptions. This study presents the crucial procedures needed to validate and authenticate the new technique by comparing its outcomes to those obtained by the traditionally established techniques. The validation process examines the CAD based system under diverse circumstances that accentuate the predominant factors of seat comfort.
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