Seat Surface Research Articles

РЕЗУЛЬТАТЫ ИМИТАЦИОННОГО МОДЕЛИРОВАНИЯ ПРОЦЕССА ПОДАЧИ И РАСПРЕДЕЛЕНИЯ СМАЗОЧНОГО МАТЕРИАЛА В СЕДЕЛЬНО-СЦЕПНОМ УСТРОЙСТВЕ ЛЕСОВОЗНОГО ТЯГАЧА С ПОЛУПРИЦЕПОМ

The necessity of increasing the efficiency of the fifth wheel coupling of hauling tractor with saddle trailer has been substantiated. The analysis of the works of foreign scientists investigating the influence of fifth wheel couplings on the efficiency of functioning of road trains has been carried out. The importance of periodically applying the lubricant recommended by the manufacturer to the rubbing surfaces of the base plate and the saddle of the fifth wheel coupling of hauling tractor has been described. The goal of the work is formulated to determine the optimal number of outlets in the seat for supplying the minimum amount of lubricant that ensures full coverage of the seat surface, as well as long-term retention on it. To achieve this goal, a mathematical model and a computer program based on it have been developed. The schemes of representation in the model of the mounting plate of the hauling tractor and the base plate of the saddle trailer, the interface form with the results of modeling the supply and distribution of lubricant over the rubbing surfaces of the fifth wheel coupling, as well as a diagram of the main input and output parameters of the simulation model are given. The time dependences of the coefficient of lubricant coverage of the mounting plate of the fifth wheel coupling seat with different periodicity of lubricant supply through a variable number of outlet openings are obtained. It was found that the increase in the coefficient of coverage of the mounting plate of the fifth wheel coupling with a lubricant over time occurs according to an exponential law. The optimum number of openings for the lubricant supply is 5-7

A Generalized Index for the Assessment of Helicopter Pilot Vibration Exposure

Helicopters are known to exhibit higher vibratory levels compared to fixed-wing aircraft. The consequences of vibrations depend on the affected helicopter component or subject. Specifically, pilots are in contact with several parts of the helicopter; vibrations can spoil the pilot-vehicle interaction. To evaluate the effects of vibration exposure on pilots, comfort levels resulting from whole-body vibration are computed. However, specific body parts and organs, e.g., hands, feet, and eyes are also adversely affected, with undesirable effects on piloting quality. Therefore, a detailed assessment is necessary for a more accurate estimation of pilot vibration exposure when comparing different configurations, tracking changes during design, and determining the safety of the flight envelope. A generalized assessment is presented by considering vibrations at the seat surface, hand-grip of controls, eyes, and feet. The suggested vibration measure includes comfort, handling, feet-contact, and vision in a single formulation. It is illustrated by coupling a high-fidelity biodynamic model of the pilot to a helicopter aeroservoelastic model in a comprehensive simulation environment. Using appropriate modeling techniques, vibration exposure of helicopter pilots could be evaluated during all stages of design, to achieve a more comfortable and safer flying environment.

Quantifying parameters of the seat-occupant interface during simulated low speed rear-impact collisions

The influence of supplemental lumbar support on automobile seat surface pressures was measured during simulated rear impact collisions with human volunteers. Men and women (age = 25.4 ± 3.4 years; BMI = 25.2 ± 3.9; stature = 1.73 ± 0.06 m) experienced two low-velocity rear impact collisions. Simulated collisions with and without a lumbar support were conducted in random sequence. Using a pressure sensing mat that contained 2288 ferroresistive sensors, seatback pressure was recorded at a rate of 500 Hz. These data were used to compute the total seatback force, area of force concentration, and centre-of-force (CoF). Total seatback force was not significantly different from body mass for either men or women (≈1.2 × body mass). Average contact area of the occupant's back with the seatback (i.e., area of force concentration) was approximately 221.3 cm2 and 100.1 cm2 greater without supplemental lumbar support for men and women, respectively. With respect to the L4 spinal level, the CoF had a greater vertical distance without lumbar support and a greater horizontal distance with lumbar support. In conclusion, the lumbar support used in this study altered the location and distribution of seatback forces applied to the occupant's back.

Effectiveness of the Movable Seat Surface Evaluated from the Difference in the Start Time of Muscle Activity and Anticipatory Postural Adjustment

Effectiveness of the Movable Seat Surface Evaluated from the Difference in the Start Time of Muscle Activity and Anticipatory Postural Adjustment

Modeling of vehicle seat in lumped network model for ride comfort simulation

Compared to the mesh-based finite element modeling, the lumped-network modeling is more useful for the multi-physical system and the simulation of many design variants. A non-uniform discretization of the seat surface into planar multi-patches is introduced for reproducing beneficial features of FEM by a lumped-network approach. These multi-patches are individually attached to the seat frame by visco-elastic polyurethane (PU) foam elements, which can handle the strain rate effect and the hysteresis. This approach is a mimicking the FEM concept while keeping the computational robustness of the Modelica solution.

IMPROVED REPAIR TECHNOLOGY OF AUTOMOBILE AND TRACTOR ELECTRO-HYDRAULIC FUEL INJECTORS

The actual service life of electrohydraulic injectors of automotive diesel engines with a high-pressure battery system of the Common Rail type in operation is significantly lower than the claimed one, and its restoration by repair is relevant from a technical and economic point of view. One of the most wearable elements of electrohydraulic injectors is the contact surface of the ball valve seat. (Research purpose) The research purpose is in developing an improved technology for repairing electro-hydraulic injectors of automotive diesel engines with a vibration-rivet of the contact surface of the ball valve seat. (Materials and methods) The article presents the carried out theoretical substantiation of the process of vibration riveting of the ball valve seat of electrohydraulic injectors and its laboratory and bench studies using serial stands for testing electrohydraulic injectors, checking their elements and restoring the seat geometry by lapping, an electronic digital microscope. (Results and discussion) Authors confirmed the working hypothesis about the possibility of forming the ring contact surface of the ball valve of electrohydraulic injectors reinforced with a vibration riveting by creating certain hydraulic and electrical modes of its operation during the required time. For the model 0445110376 electrohydraulic injectors of the Cummins ISF 2.8 diesel engine, the total area of the hardened surface of the regular ring shape was 0.07 square millimeters, and the depth was about 0.003 millimeters with a process time of 45 minutes. The parameters of the experimental electrohydraulic injectors met the requirements of the test plan, and they are currently successfully undergoing operational tests. (Conclusions) The use of a valve seat vibration rivet will increase the life of repaired injectors at a low cost for its implementation.

Smart-Cover: A real time sitting posture monitoring system

Prolonged asymmetrical sitting is common and can exacerbate musculoskeletal back pain and spinal deformities. Monitoring sitting posture can help maintain correct posture and prevent health problems. Currently posture is assessed by expert clinicians using subjective visual observation. More objective methods involve the use of a gold-standard motion capture system in Laboratories, which is expensive and not widely available. We develop a Smart-Cover, an automatic system to provide real time visualization and information about sitting posture. A Sitting Pressure Sensor (SPS) is built using Velostat, conductive fabric and foam to collect pressure distribution information within the seat surface. The data are collected from 10 healthy young subjects where each subject sits for 30 min and are transferred to a cloud server using Internet-of-Things (IoT). A rule-based classifier is used to provide timely notification to users about sitting duration and level of asymmetry. A new end-point device application is developed to show sitting balance. Dial based displays show level of asymmetry, active and static sitting, and daily summary score. Our system is user friendly, inexpensive, automatic and quantitative method for evaluating posture in real time, which has the capability of providing quantitative information about sitting behaviour. The results show that our system can be used for objective monitoring of sitting posture which has medical and social benefits. Smart-Cover can support the management of patients during their rehabilitation by monitoring pressure areas and balance when seated. In addition, it offers users at home, schools and offices the means to improve their sitting posture.

Application of Goertzel Algorithm to Piezoresistive Pressure Sensing Fabric for Custom Fitting of Wheelchair Cushions

Abstract Pressure sores are a costly, painful problem for wheelchair users, caused by prolonged periods of mechanical loading. A common location of pressure sores in wheelchair users is the tissue between the ischial tuberosities and the seating surface. The pressure exerted on the tissue, or interface pressure, can be measured using piezoresistive fabric. This work demonstrates the use of the Goertzel algorithm for efficiently acquiring interface pressure data from a fabric assembly consisting of a layer of piezoresistive fabric between two layers of fabric with conducting and non-conducting stripes. The Goertzel algorithm was used to sample sums of sine waves from the conductive columns of the fabric assembly and calculate the amplitudes of each component sine wave corresponding to the local interface pressure. The Goertzel algorithm is more efficient for this application than a fast Fourier transform due to the limited number of calculated frequency bins needed for this application and more freedom in choice of sample size. The algorithm was successfully used to generate two-dimensional, 32 × 32 sensel interface pressure maps once per second. The Goertzel algorithm can be used in tandem with generated sine waves to measure interface pressure from piezoresistive fabric. Low-cost, accurate interface pressure measurements will help lessen the risk of pressure sores in wheelchair users.

Failure of a Pressure Regulator System by Crevice Corrosion: Attributed to Improper Material Selection

A pressure regulator in a system of the base shroud failed during service. The pressure regulator is intended to regulate the inlet pressure of 275 to 50 kg/cm2 outlet pressure. The working medium is stated to be nitrogen gas. On disassembly of the system, a brown layer was observed on the seating surface of poppet of the main regulator. A brown layer was also observed on the spring pocket and on the spring end surface which was in contact with the poppet. Metallographic tests and hardness measurement were carried out on the components to reach to the cause of failure. The poppet of the pressure regulator failed to function in service due to rusting of its seating surface by crevice corrosion and partial closure of the holes. The crevices at contact surface between the poppet and the spring seems to have formed by settlement of a stagnant condensed moisture along the surface. Partial closure of the holes was due to the presence of condensed moisture as well as rust. Spring made of AISI 302 austenitic stainless steel did not corrode at all, while poppet made of AISI 420 martensitic stainless steel corroded heavily.

Analysis of Co-Relation Between Objective Measurement and Subjective Assessment for Dynamic Comfort of Vehicles

The assessment of vehicle dynamic comfort to human body vibration varies from person to person. Even though the dynamic comfort rating can be obtained by placing measurement devices over the cabin, passengers may have dissimilar sensations. For many car manufacturers, both subject and objective measurements are used together at development of new cars. To effectively assess the dynamic comfort of vehicle, this research explores the correlation between the objective measurement of the whole body vibration, hand-transmitted vibration and subjective assessment. The whole body vibration is measured from the backrest, seat surface and vehicle floor, whereas the hand-transmitted vibration is measured from the steering wheel. Four different vehicles are driven at various speeds on five types of pavements. Both simple linear regression and polynomial regression models based on Stevens’s power law from psychophysics are built to correlate the subjective and objective data. The regression results show that (1) the seat surface is more reliable than other positions for assessing the human body vibration; (2) the hand transmitted vibration on rough roads is more trustful for dynamic comfort evaluation than on smooth roads; (3) the overall dynamic comfort value is the most reliable index for dynamic comfort evaluation.

International Roughness Index Thresholds Based on Whole-Body Vibration in Passenger Cars

This study analyzed whole-body vibration (WBV) on a car seat (seat surface and feet) in passenger cars as a function of longitudinal road roughness. Measurements were provided on nine different cars in six categories and included a total travel distance of 1,860 km. The root mean square (RMS) of the frequency-weighted acceleration was used to quantify WBV. The relationship between seat acceleration response and comfort reactions according to the ISO 2631-1 and the International Roughness Index (IRI) was estimated. IRI thresholds were proposed as a function of vehicle speed and road category. Proposed IRI thresholds decreased with vehicle velocity and were similar with published IRI threshold proposals based on simulation. IRI thresholds as a function of speed limit should decrease with power by approximately –0.75. Substantially lower (by ~ 40%) IRI thresholds were calculated for the total vibration value (six signals) in comparison with vertical vibration on the seat surface.

Active Cloth Fabricated by a Flat String Machine and its Application to a Safe Wheelchair System

In this study, a pneumatically contracting active cloth has been developed; its application is proposed for a safe sitting-posture recovery system for wheelchair users to avoid fall-related accidents. The active cloth consists of thin artificial muscles knitted via a flat string machine. The safe wheelchair system is configured with an active cloth and seating pressure sensor. The seating pressure sensor, located on the seating surface of the wheelchair, estimates the inclination of the upper body of the user; when this reaches an angle that is dangerous for falling from the wheelchair, the active cloth contracts to correct the posture of the upper body. In this paper, we clarify the fabrication process and fundamental characteristics of the active cloth and indicate its potential as a mechanical element for welfare apparatuses by demonstrating a safe wheelchair system.

Ergonomics of a Chinese folk bamboo lounge chair

Bamboo is an environmentally friendly sustainable resource and is commonly used in furniture production in China. Limited research has been conducted in the field of ergonomics of bamboo furniture, which can greatly affect the seating experience. This study provides a qualitative and quantitative analysis of the main effects of seat surface curve, bending deflection of bamboo strips of seat, functions, and usability in a bamboo lounge chair provided in Zhejiang Province. The shape of the seat surface curve of the bamboo lounge chair included the seat-back angle of 134°, and the slope of the bamboo lounge chair seat was 16°. The deflection of bamboo strips of seat under vertical loading force of 336 N was 30.7 mm. In addition, the angles, deflection characteristic, and functions of the bamboo lounge chair were all human-centered design and suitable for human comfort, which can reduce maximum pressure and maintain normal lumbar spine curve in adult.

Spatial seated occupancy detection in offices with a chair-based temperature sensor array

Sensors used to monitor indoor environmental conditions and utility consumption can result in well-defined working and living spaces. Real-time spatiotemporal occupancy detection techniques used to track humans indoors paired with these data can be used to better understand the role of occupants on indoor air quality and building energy consumption. This study introduces a novel occupancy sensing technique whereby a chair-based temperature sensor array is used to detect the presence of occupants seated in a living laboratory open-plan office. Seat surface temperatures were tracked for twenty individuals over seven months using K-type thermocouples with battery-powered dataloggers secured to office chairs in known locations. The temperature differential between the occupant and seat surface enables for rapid conduction and thus detection of one's seated presence. Seat surface temperature time-series were converted to binary seated occupancy for each chair and totaled to achieve a spatial map of room seated occupancy with a time resolution of 15 s. Trends in spatiotemporal seated occupancy profiles in the office were evaluated for seven months using the novel technique. This highly localized form of occupancy detection offers several advantages compared to delocalized sensing techniques, including visualization of spatial occupancy patterns over time; determination of individual seated occupancy histories visualized in the form of “occupancy barcodes; ” quantification of total seated hours per occupant in different spatial zones across varying time-scales; and characterization of diurnal and weekly trends in seated occupancy probabilities categorized by an occupant's relative level of presence.

Shotgun metagenomics of dust microbiome from flight deck and cabin in civil aviation aircraft.

Microbial exposure is related to the health of passengers on commercial aircraft, but no studies characterized the microbial composition at the species level and identified their ecological determinants. We collected vacuum dust from floor and seat surfaces in flight decks and cabins of 18 aircraft, and amplification-free shotgun metagenomics was conducted to characterize the microbial composition. In total, 7437 microbial taxa were identified. The relative abundance for bacteria, eukaryote, viruses, and archaea was 96.9%, 1.8%, 0.3%, and 0.03%, respectively. The top bacterial species mainly derived from outdoor air and human skin included Sphingomonas, Corynebacterium, Micrococcus luteus, Variovorax paradoxus, Paracoccus dentrificans, and Propionibacterium acnes. The abundance of NIAID-defined pathogens was low, accounted for only 0.23% of total microbes. The microbial species and functional composition were structured by the indoor surface type (R2 =0.38, Adonis), followed by the manufacturer of the aircraft (R2 =0.12) and flight duration (R2 =0.07). Indoor surfaces affected species derived from different habitats; the abundance of dry skin and desiccated species was higher on textile surfaces, whereas the abundance of moist and oily skin species was higher on leather surfaces. The growth rates for most microbes were stopped and almost stopped.

Relationship between seat surface shape and pressure distribution in school seat models.

Students remain in a sedentary position inside classrooms for 60% to 80% of their school day. As such, research has associated students' prolonged seated posture on school furniture with their discomfort and musculoskeletal pain. The correlation between the shape of the seat surface and the zones of the body making contact with these surfaces constitutes an essential factor in determining comfort-enhancing seat design. This study's primary aim lies in contrasting the standard, current school chair against two seat prototypes, both designed and built from digital models, comparing seat-user pressure distribution and contact area during students' performance of different school tasks. Participants (n = 13), ages 7 to 19, performed school tasks sitting on three different chairs' seat surfaces during the test: the current seat used in schools and two seat prototypes, each designed based on body anatomy. The seats were evaluated through a force-sensing array pressure-mapping system. The measurements from designed seat prototypes provide a better distribution of pressures and greater contact area with the students' anatomical areas (buttocks and thighs) than the seat currently used in the specified schools. The improvement in pressure values and contact area as seen in the second designed seat prototype is due to its inclination angle and contact with students' sacral zone. This research work found that a seat's shape based on human anatomical features (buttocks and thighs), compared to a completely flat seat, creates a higher reduction of body pressures and an increase in the body contact area, with the intent to increase comfort and reduce musculoskeletal pain.

Comfort seat design: Thermal sensitivity of human back and buttock

In recent years, comfort seat design has received widespread attention from researchers. One of the factors that could contribute to comfort is the thermal influence due to the interaction between the human and the seating surface, for which literature is limited.In this paper, a laboratory experimental setup was used to detect and analyse the temperature changes at interface between seated subjects and a sensorized automotive seat. Acquired temperatures were processed in order to identify a mathematical model for describing the temperature changes at the interface.The main target of the study was the identification of the most sensitive areas of the human body to temperature variation while seated and its effect on local and overall perceived thermal comfort.Statistical analysis showed that the effects of temperature were most perceived in the “Upper Body” (UB) and less in the “Lower Body” (LB). The shoulders, the sides of the back, the back and the buttocks were most sensitive to temperature changes at the interface. Differences have been highlighted also between male and female subjects. Relevance to industryThe identification of the most sensitive areas of the human body to temperature variation, while seated, and the identification of the logarithmic model for describing the temperature changes should allow seat designers to define targets and strategies in developing cooling and heating systems for car seats, taking into account, in a preventive evaluation, the most probable perceived thermal comfort.

Reduced Power Seat Heater System Using Thermal Wave Technology

<div class="section abstract"><div class="htmlview paragraph">This paper presents a method of controlling the seat heater using intentional oscillations between multiple, independently controlled temperatures (each with its own tolerance range). The amplitude and frequency of these oscillations can be changed based on secondary trigger events such as changes in the interior temperature. The benefits of using this technique to heat the seat surface are improved thermal sensation and reduced energy usage over the typical drive time.</div></div>

Lateral Transfer Assist Robot (LTAR): Development of a proof-of-concept prototype.

Falls during transfer to and from a wheelchair are associated with numerous problems. Factors responsible for difficulty in transferring include horizontal/vertical gaps between surfaces; obstacles, such as armrests; and complicated brake/footrests configurations before transferring. Moreover, controlling a wheelchair sufficiently close to the transfer surface within the confined home space is difficult. We described the design of the novel Lateral Transfer Assist Robot (LTAR) for solving problems during transfer. Furthermore, the effectiveness and usability of the robot were preliminary examined in healthy adults. The transfer problems and basic designs were organized. The effectiveness of the prototype was measured by three-dimensional motion analysis and questionnaire. The prototype LTAR was developed. With just a push on a button, the footplate lowers to the floor and the seat and armrest lowers to the height of the seating surface to fill the gap between the surfaces. Using these features, users can transfer by simply shifting their buttocks sideways. Additionally, LTAR has omnidirectional wheels that help move it within a narrow space. The LTAR was confirmed to reduce the physical and subjective burden, except for maneuverability. The LTAR was found to be effective for home use and reducing burden of transfer.

Do the Types of Seat Surface influence the pulmonary Functions during Prolonged Sitting?

Purpose: The purpose of this study was to identify the effects of the types of seat surface (static or dynamic seat surface) on the pulmo nary functions during prolonged sitting. Methods: Thirty-four participants (20 males and 14 females) were recruited, and distributed randomly into dynamic prolonged sitting (DPS, n=17) and static prolonged sitting (SPS, n=17) groups. The DPS group was seated on a chair with a dynamic air cushion, and the SPS group was seated on a chair without a dynamic air cushion. The pulmonary function was assessed before sitting, and after partici pants had been seated for one hour. The pulmonary function [forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and Peak expiratory flow (PEF)] was measured using a spirometer. Results: Statistical analyses revealed significant differences in the time x group interactions of FVC, FEV1, PEF, and FEV1/FVC. The DPS group were significantly different in FVC, FEV1, PEF, and FEV1/FVC after prolonged sitting for one hour, compared to the SPS group (p<0.05). Conclusion: These findings suggest that dynamic sitting can prevent a decrease in the physiological function, such as pulmonary func tions, rather than static sitting during prolonged sitting.