Seat Cushion Research Articles

Effect of Air Cushion Seating in Passenger Car on different Road Conditions

Objectives: To improve the ride comfort of the passenger car driver using an air-inflated cushion on top of the conventional polyurethane foam seat. Methodology: The acceleration between the base of the driver and the seat interface in a small passenger car is measured in all the three Cartesian directions for three different drivers each of different weights, on four different types of roads using SV106 Whole Body Vibration (WBV) measurement equipment. The car is driven at different speeds within the range of 20 kmph to 80 kmph on smooth road like highways and a limited maximum speed of 40 kmph on the other roads. The obtained results are used to calculate the percentage Seat Effective Amplitude Transmissibility (%SEAT) to estimate the ride comfort. Findings: The results proved that by using the air-inflated seat cushion placing over the polyurethane seat cushion has decreased the vibration that is transmitted to the driver and the ride comfort is enhanced rather than using only polyurethane foam cushion that is provided by the manufacturer. The air-inflated cushion used is of compartmental celled model which will not get deflated easily assuring comfort for a long period of safe drive. Keywords: Air-celled Cushion, Seat, Transmissibility, Ride-comfort, Whole Body Vibration.

Designing Ergonomic Study Chair Using Quality Function Deployment Method with Anthropometry Approach

Increasing the high number of under-fives entering the age of study, commonly called early childhood education (Pendidikan Anak Usia Dini–PAUD), creates an opportunity to design a product that supports learning activities for the toddlers, namely folding study desks. This research aims to make a redesign of folding table-chair products specially designed for toddlers by considering ergonomic aspects that prioritize function and comfort using Quality Function Deployment (QFD) method through anthropometry approach of toddler’s body. This study focuses on toddlers aged 3 yr to 5 yr who are students of the playing group and kindergarten at Integrated Islamic Kindergarten (Taman Kanak-kanak Islam Terpadu-TKIT) “Rabbani”. Different body sizes of toddlers with adults are the main consideration in determining anthropometric approach, but it is also expected to produce ergonomic products both in terms of materials and product size to a child’s sitting position. The results of this study obtained a comfortable chair table, soft and comfortable backrest, strong seat resistance, comfortable padded seat cushion, has a place to store bag/footrest, has a place to store stationery, has an attractive color and seats safe to use, and has additional features for gadget. As for the changes made in terms of the dimensions of the chair that prioritize ergonomic values, the seat height is 60 mm, the back height is 33.2 mm, the width of the backrest is 30 mm, the length of the seat is 26.6 mm, and the seat width is 26.6 mm. All these additions are additional tolerance for comfort, especially for large children.
 Keywords: ergonomic product design; quality function deployment; toddler study chair design

Adaptive Automobile Seat Design Based on Ergonomic Principle

In order to improve the comfort of automobile seat, it is necessary to analyse and study the design method of automobile seat. A design method of adaptive automobile seat based on ergonomics principle is proposed. The height, width, depth, backrest, seat inclination and backrest inclination of automobile seat as well as the sitting posture physiology and body pressure distribution of human body are analysed. The frame of automobile seat is designed by using aluminium alloy in PROE software, the size of the energy absorption of headrest, cushion and seat are determined according to national regulations. By analyzing the back force, pillow force, seat belt force and seat belt locking, the force of automobile seat, the strength of back, head pillow and seat cushion of automobile seat are designed and the design of adaptive automobile seat is completed. The experimental results show that the proposed method has high comfort, low processing cost and high production efficiency.

Cushion seat design on manual wheelchair for people with paralysis using value engineering method to improve activity comfort: A preliminary study

Many people with paralysis feel discomfortness in their activities on wheelchair. Assistive device which can increase comforness is cushion seat wheelchair, but cushion seat with special specification for people with paralysis has high prices. This research is a preliminary study to design alternative cushion seat which comfortable and affordable price for manual wheelchair using value engineering method. There are three criteria and eight subcriteria were raised which were processed by Analytical Hierarchy Process (AHP). Three subcriteria were selected for the priority of requirement design, there is user’s maneuver support as selected subcriteria 1 weighing 0.64221, lumbal protection as selected subcriteria 2 weighing 0.72054 and suitability of cushion seat material to maintain the gluteal temperature as selected criteria 3 weighing 0.83333. Based on selected subcriteria, three alternatives designs were raised which were processed with AHP. Selected alternative is cushion seat with backrest, foam and gel modification which were measured based on selected subcriteria that selected subcriteria 1 weighing 0.70536, selected subcriteria 2 weighing 0.68032, selected subcriteria 3 weighing 0.74084.

Design of assembly tools at woodworking and upholstery workstations with PUGH’s Method to improve productivity

This study is a research on manufacturing processes field, especially in the assembly process with a single workstation. This research was conducted on the implementation of manufacturing process of making lecture chairs at the Industrial Engineering Department at Sebelas Maret University. In this research, an assembly tool was designed to solve the problem of high time needed to complete the assembly process of the backrest and cushion seat components and work stations that are not ergonomic. The assembly tool design stages are based on a structured approach of Ulrich and Eppinger (2015) so that it’s good to develop new products and concept selection using the PUGH method to find out the concepts with the highest ranking and best fit the design criteria. This research involved 3 stakeholders, namely operator, lecturer, and assistant. The alternative concept chosen using components are pull-push toggle clamp, gas spring, M6 bolt, multiplex, cam buckle tie down, self-aligning ball bearings, aluminum extrusion 3030. Data on work productivity were tested with Paired T-Test at a significance level of 5 percent. The results showed that by using an ergonomic assembly tool design on woodworking and upholstery workstations, assembly cycle time increased significantly by 63.78 percent.

Enhancement of Driver Ride-Comfort through Reduction of Transmitted Vibrations by using Different Materials for Car Seat Cushion

The aim of this work is to simulate reduction of whole-body vibration represented by acceleration that is transmitted through seat to the driver in a passenger car by studying different cushion materials for the seat. The accelerations at the interface of driver and seat are studied for an exposure period of eight hours as per ISO 2631-1(1997) standards. The entire study is done using FEA analysis in ANSYS 19.2. The simulation has been carried out for three different base accelerations representing three different road conditions and also for three different weights of drivers which are assigned to the manikin model sitting on the seat. Two cushion materials namely melamine foam and rebonded foam, in addition to regufoam which is commonly used in the cars have been taken up for study. For 65 kgf, 75 kgf and 85 kgf driver weights, rebonded foam results in an average A(8) reduction by 13.8%, 19.48% and 30.34% respectively whereas melamine foam has reduced it by 5.19%, 5.80% and 14.54% respectively for the same conditions. It is therefore suggested that rebonded foam gives better comfort compared to the existing regufoam and melamine for seat cushioning of the car studied.

Model construction and analysis of ride comfort for high-speed railway seat cushions.

More and more people choose to travel by high-speed railway. The seats in these vehicles are an important contact point and comfort of the seat cushions needs attention. The aim of this study is to choose among three seat cushions, the one that creates most comfort for a high-speed train. Twelve healthy volunteers were selected to participate in the experiment. Three different surface shape models of high-speed railway seat cushions were used. The Seat Pressure Distribution Index (SPD%) was calculated and analysed. A 7-point Likert scale questionnaire was applied for subjective evaluation. The evaluation is based on subjective and objective data. The results showed that the front protruding cushion made the pressure distribution more even, while the flat cushion had the smallest SPD% and the static pressure was most evenly distributed. This knowledge was beneficial for the design of comfortable high-speed railway seat cushions.

Comparative study of body pressure distribution on the user-cushion interface with various support elasticity

Comfortable sitting plays an important role in reducing the risk of musculoskeletal disorders and is linked with the continuous increase of the prolonged computer aided office work. This explains the intensification of research focusing on healthy chair development. The majority of the body's weight is placed upon the supporting area of the seat pan; therefore, special attention should be paid to the seat cushions. The main objective of this research is to evaluate the influence of support geometry and elasticity on the sitting comfort and to compare the real and simulated pressure distribution data. For data acquisition, the Tekscan's CONFORMAT body pressure distribution measuring system was used. The effect of geometry, flexibility, load pad shape and body build was evaluated with the peak pressure and contact surface values. Research data and analysis revealed that seat cushion structure and cushion support characteristics significantly influence the body pressure distribution, an important factor in seat comfort determination.

Investigation of risk factors affecting injuries in reclining seat under frontal impact

In autonomous vehicles, passengers often recline their seatbacks for a more comfortable posture. Such a reclined posture greatly increases risk of submarining and other injury concerns due to the unfavourable geometrical configuration of occupant, seat and seatbelt. In this paper, numerous simulations with a modified computational dummy model are proposed to analyse effects of various occupant restraint systems in frontal impact, including seatbelt, pretensioner, load limiter, locking tongue, airbag, knee bolster and so on. After the sensitivity analyses, four concepts for designing anti-submarining countermeasures are proposed: (1) increase the lap belt-to-pelvis friction coefficient; (2) reduce the shoulder belt force along with the use of the locking tongue; (3) increase the lap belt angle; (4) reduce the H point forward and downward displacement. Sled tests with anti-submarining countermeasures were conducted to verify the effectiveness of the anti-submarining concepts for reclining seats. Four anti-submarining countermeasures are suggested to prevent the submarining with no other auxiliary hurts: load limiter plus locking tongue, anchor pretensioners plus anti-submarining bar, seat cushion airbag, and retractor plus buckle pretensioner. This paper could give better understanding of submarining mechanism and eligible vehicle design.

Nonlinear vibration of knitted spacer fabric under harmonic excitation

Knitted spacer fabrics can be an alternative material to typical rubber sponges and polyurethane foams for the protection of the human body from vibration exposure, such as automotive seat cushions and anti-vibration gloves. To provide a theoretical basis for the understanding of the nonlinear vibration behavior of the mass-spacer fabric system under harmonic excitation, experimental, analytical and numerical methods are used. Different from a linear mass-spring-damper vibration model, this study builds a phenomenological model with the asymmetric elastic force and the fractional derivative damping force to describe the periodic solution of the mass-spacer fabric system under harmonic excitation. Mathematical expression of the harmonic amplitude versus frequency response curve (FRC) is obtained using the harmonic balance method (HBM) to solve the equation of motion of the system. Parameter values in the model are estimated by performing curve fit between the modeled FRC and the experimental data of acceleration transmissibility. Theoretical analysis concerning the influence of varying excitation level on the FRCs is carried out, showing that nonlinear softening resonance turns into nonlinear hardening resonance with the increase of excitation level, due to the quadratic stiffness term and the cubic stiffness term in the model, respectively. The quadratic stiffness term also results in biased vibration response and causes an even order harmonic distortion. Besides, the increase of excitation level also results in elevated peak transmissibility at resonance.

Experimental investigation on shear properties of warp-knitted brush fabrics

Warp-knitted brush fabrics are composed of an outer surface formed by weaving the front and rear needle beds with spacer yarns interposed between them. Warp-knitted brush fabrics can be used as a non-slip cover for car seat cushions; the adhesion between non-slip fabric and car seat is related to the shear strength of warp-knitted brush fabrics. In this article, to study the factors affecting the shear force of warp-knitted brush fabrics, three different processing methods and four different stretching speed intervals were used to find the effects of stiffeners and action of different speed intervals on shear properties of fabrics. The experimental results show that the stiffener treatment can improve the shear resistance of the warp-knitted brush fabrics, and the effect of different speed intervals can affect the shear resistance of fabrics. These findings will have a guiding significance in the design and production of warp-knitted brush fabrics applied to fabrics such as car seat cushions, and the results can also help to study the shear properties of warp-knitted brush fabrics for wider applications.

EXPERIMENTAL AND NUMERICAL STUDY OF SEWING SEAMS OF AUTOMOBILE SEAT COVERS UNDER UNIDIRECTIONAL AND MULTIAXIAL LOADING

In industrial textiles, knowing the exact characteristics and behaviour of materials is important. A several precise studies and numerical models of material structures of fabrics, foams, and threads have been developed, but the behaviours of entire functional parts have been researched to a lesser extent. For car seats, industrial textiles not just cover the underlying foam but also increase rigidity of the seat cushion and influence viscoelastic behaviours of foams. Moreover, strength of sewn seams is one of the main quality parameters. Herein, four polyester and polyamide threads were sewn on a material used for car seat covers through lockstitch sewing. Combinations of these materials were studied using static tests in the unidirectional and multiaxial variants. The experimental measurements recorded using a high-speed camera and computer tomography were used to create CAD models. Numerical simulations were conducted using these models and the obtained material models. These model studies help predict and describe the stresses emerging within various types of textile and the threads in their connections. The simulation results agree well with the experimental results

A numerical investigation of factors affecting lumbar spine injuries in frontal crashes

Recent field data analyses have shown that lumbar spine fractures occurred more frequently in late model vehicles than the early ones in frontal crashes. Therefore, the objective of this study was to investigate risk factors associated with lumbar spine fractures in frontal crashes.Parametric simulations were conducted using a set of validated vehicle driver compartment model, restraint system model, and a HIII mid-size male crash test dummy model. Risk factors considered in the study included occupant seating posture, crash pulse, vehicle pitch angle, seat design, anchor pre-tensioner, dynamic locking tongue, and shoulder belt load limiter. ANOVA and ANCOVA were used to test the statistical significance (p < 0.05).Simulation results showed that all the factors that reduced the risk of submarining increased the lumbar spine forces, indicating a direct conflict between submarining and lumbar spine fractures. Among all the factors selected, seat structure is the most significant factor in determining the lumbar spine force (p < 0.001). Crash pulse severity, time at which the peak crash deceleration reached, and pitch angle are also crucial for lumbar spine force. Specifically, increase in vehicle pitch angle increased lumbar spine force, but reduced injury measures to other body regions; while a crash pulse with early peak produced greater lumbar spine force than that with a late peak. On average, more reclined posture increased the lumbar spine force compared to upright posture, and decreases in the coefficient of friction between the pelvis and the seat cushion reduced the lumbar spine force. However, they are not statistically significant.This study provided better understanding of effects from design countermeasures to reduce occupant lumbar spine injuries in new generation of vehicle models.

Frontal crash seat belt restraint effectiveness and comfort accessories used by older occupants

Objective: Around a quarter of older occupants use some type of comfort or orthopedic aftermarket accessory on the vehicle seat while traveling in a vehicle. The aim of this study was to investigate the effect of comfort accessories on the performance of the seat belt restraint system in a frontal crash in terms of potential injury implications for older occupants.Methods: Eight frontal sled tests (43 km/h, 32 g) were carried out on a deceleration sled fitted with a three-point lap-sash seat belt and a front passenger seat from a common Australian passenger car for each test. A 5th percentile Hybrid III anthropometric test device (ATD) was positioned in the seat and measurements were recorded for head center of gravity acceleration, chest acceleration, neck forces and moments and sternal deflection. Tests were carried out in a baseline condition and with seven comfort accessories. Each comfort accessory was inserted between the ATD and vehicle seat as it is intended to be used, with the ATD otherwise positioned as close as possible to the baseline test position.Results: Initial distance between the seat belt anchor and ATD hip was associated with a statistically significant decrease in Head Injury Criterion and increase in sternal deflection. Submarining was related to the ATD torso recline angle and angle of the lap belt from the seat belt anchor.Conclusions: Accessories placed between the seat back and the lumbar region of an occupant have the potential to increase the risk of submarining due to a change in posture and should be avoided if such a change in posture when seated with an accessory is excessive. Sitting on seat cushions resulted in the greatest increase in seat belt anchor to hip distances and hence largest increase in sternal deflection. Given the fragility, frailty and particular importance of chest injuries among older vehicle occupants, further investigation is needed to determine whether these changes in ATD sternal deflection observed with seat cushion use results in injury threshold limits being exceeded and whether pretensioners and load limiters would ameliorate these effects without causing other negative changes in occupant response or kinematics.

Recycling of bio-polyurethane foam using high power ultrasound

Three different types of waste bio-polyurethane foams (bio-PUFs) made of castor oil-based polyol, castor oil-based polyol with isosorbide-based isocyanate, and soybean oil-based polyol were ultrasonically decrosslinked, and blended with a traditional PUF formula for fabrication of automotive seat cushions. The seating comfort of recrosslinked PUFs was quantified by calculating the hardness, hysteresis loss, and sag factor as derived from the indentation force deflection test, and found to exhibit improved seating comfort. In this regard, the ultrasonically decrosslinked bio-PUFs were examined by gel fraction, crosslink density, FT-IR spectroscopy, and thermal property, and the improvement of comfort was attempted to explain by analyzing the morphological changes of recrosslinked PUFs using SEM.

Implementing local cooling to increase skin tolerance to ischemia during normal seating in people with spinal cord injury

The purpose of this study was to investigate the effectiveness of local cooling in reducing reactive hyperemia after ischemia at the ischial tuberosities for people with spinal cord injury (SCI) during normal seating. The degree of the reactive hyperemic response is indicative of the extent of cellular stress caused by the ischemia. We hypothesized that reactive hyperemic skin blood flow (SBF) responses will be lower when local cooling is implemented by the wheelchair seat cushion. This study used a repeated measures design, and each subject underwent two conditions: normal seating with temperature control ‘on’ (cooling) and ‘off’ (non-cooling) for 30 min. Twenty-three participants with traumatic SCI were recruited. SBF and skin temperature were collected before, during and after seating. SBF signals were processed with short-time Fourier analyses to examine the underlying vascular control mechanisms, including the following (corresponding frequency bands): metabolic (0.0095–0.02 Hz), neurogenic (0.02–0.05 Hz), and myogenic (0.05–0.15 Hz) spectral densities. Our results showed that with cooling, skin temperature decreased (range −0.4 ~ −3.1 °C, p = 0.002), and reactive hyperemia parameters (normalized peak SBF and perfusion area) were reduced (p = 0.02, p = 0.033, respectively). In addition, changes in normalized peak SBF (non-cooling – cooling) was moderately correlated with changes in normalized metabolic and neurogenic spectral densities. Our findings suggested that local cooling has a positive effect on reducing the cellular stress caused by ischemia during normal seating. Metabolic and neurogenic SBF control mechanisms may play a minor role. Further exploration of the effect of temperature control on pressure injury prevention is warranted.

The Effect of Automotive Seat Cushion Stiffness Distribution on the Subjective Comfort

When body pressures are concentrated, sense of fatigue is increased. To confirm this, correlation analysis between the difference in stiffness of seat and comfort using multiple linear regression analysis has been conducted. For the selected three types of seats which are small-, mid-, and large-size seats, respectively, static tests were con-ducted to measure the distribution of the subject's body pressure on the cushion, through which local stiffness distribution were derived. Also, a subjective comfort evaluation was conducted, and analyzed. According to the present analysis results, the correlation coefficients between stiff-ness of hip area and comfort of hip area were observed to be 0.713 and 0.789, respectively, indicating a strong positive correlation. Thus, the comfort of seat perceived by the driver could be seen to have the largest linear correlation with the stiffness of hip area. Selection of variables for the multiple linear regression analysis was implemented by a backward removal method. Differences of stiffness by areas were selected as independent variables, and subjective comfort evaluation results were selected as dependent variables. According to multiple regression analysis, the comfort of the cushion increased when the left and right balance of the stiffness distribution was maintained even if the body pressure distribution of the hip area was concentrated on one side. According to the analysis results, the stiffness of hip area could be seen to have the greatest linear relationship with the overall satisfaction of comfort, in which comfort is planned to be confirmed by actual production of seats

Fabrication and Testing of Auxetic Foams for Rehabilitation Applications

Negative Poisson’s ratio or auxetic foams were fabricated and studied for use in prosthetic applications. A thermomechanical process was used to convert conventional polyurethane (PU) foam into auxetic PU foam. Two types of auxetic PU foams were made using two different volumetric compression ratios, 3.02 and 3.86. Chemical composition analysis showed that chemical structure of the converted auxetic foam remained the same as the conventional PU foam after the thermomechanical process. Compression tests showed that the auxetic foams had higher stiffness than conventional foams, implying that the auxetic foams could be potentially used in seat cushions, shoe soles, and as liners in prosthetic applications. Compression fatigue tests showed that percentage loss in thickness in auxetic foam fabricated using lower compression ratio had loss in thickness that is comparable to conventional foam, whereas auxetic foam fabricated using higher compression ratio had greater loss in thickness. Our study indicates that the auxetic foams made using lower compression ratio need to be further explored for suitability in various rehabilitation applications.

Design and operation verification of an automated pressure mapping and modulating seat cushion for pressure ulcer prevention

A sensorized air cell-based seat cushion system was developed to address the issues of loading magnitude and duration at a sitting interface to aid in reducing risk of sitting acquired pressure ulcers. This system is capable of pressure mapping, redistribution, and offloading which were verified using an anthropomorphic model and a human subject. The system is comprised of an air cell array cushion, a pneumatic control unit, and a graphical user interface. ISO load deflection testing confirmed that the cushion's loading response is comparable to commercial air cell-based seat cushions. Testing demonstrated that the internal pressure of the air cells are indicative of interface pressure and can be used as input to pressure modulating algorithms. Uniform pressure distribution was achieved through automated pressure redistribution algorithm implementation where the immersion of a subject into the seat cushion increased and interface pressure decreased. High pressure point identification and automatic offloading were performed in which newly created high pressure points were addressed using subsequent redistribution. Pressure mapping enabled offloading and redistribution can objectively manage the effects of loading magnitude and duration at the sitting interface.

Biodynamic Modeling Techniques for Rotorcraft Comfort Evaluation

This work shows how different occupant biodynamic modeling techniques are integrated in a rotorcraft design environment and discusses the resulting differences in comfort assessment. Three modeling techniques, that are used for biodynamic characterization, are considered: lumped parameter, finite element and multibody dynamics. These models are identified for the same gender, age, weight and height, and then integrated into a virtual helicopter environment with a seat–cushion interface. A generic helicopter model is used to demonstrate the approach. For each of the three techniques, the vertical acceleration levels at the human–helicopter interface, as required by vibration regulations, and at the head are evaluated up to 30 Hz. At a first glance, it is observed that the lumped parameter is the easiest to implement in terms of model set-up. However, the use of lumped parameter models is limited to the population groups that they are identified from, and thus are not as flexible as the finite element and multibody ones in developing biodynamic models for individuals of an arbitrary population percentile. Furthermore, through numerical analysis, it is found that the differences are not very significant in terms of accelerations at the human–seat interface. Therefore, for comfort-related issues, the use of more complex models is not justified, unless complicated comfort assessments other than human interface accelerations are required. On the other hand, it is observed that the spine dynamics can play a significant role in estimating the acceleration of head; therefore, the sophisticated finite element and multibody dynamics models redeem their higher modeling cost and computation time when the head–neck health of occupants is considered.