Seating System Research Articles

Characterisation of the human-seat coupling in response to vibration

Characterising the coupling between the occupant and vehicle seat is necessary to understand the transmission of vehicle seat vibration to the human body. In this study, the vibration characteristics of the human body coupled with a vehicle seat were identified in frequencies up to 100 Hz. Transmissibilities of three volunteers seated on two different vehicle seats were measured under multi-axial random vibration excitation. The results revealed that the human-seat system vibration was dominated by the human body and foam below 10 Hz. Major coupling between the human body and the vehicle seat-structure was observed in the frequency range of 10–60 Hz. There was local coupling of the system dominated by local resonances of seat frame and seat surface above 60 Hz. Moreover, the transmissibility measured on the seat surface between the human and seat foam is suggested to be a good method of capturing human-seat system resonances rather than that measured on the human body in high frequencies above 10 Hz.Practitioner Summary: The coupling characteristics of the combined human body and vehicle seat system has not yet been fully understood in frequencies of 0.5–100 Hz. This study shows the human-seat system has distinctive dynamic coupling characteristics in three different frequency regions: below 10 Hz, 10–60 Hz, and above 60 Hz.

Design concepts for an integrated whiplash mitigating head restraint and seat

ABSTRACTThis paper presents design of a concept for an integrated head restraint and car seat system to mitigate whiplash in rear-end vehicle collisions. The main emphasis is on a concept, which combines a reactive head restraint with a reactive seat. The chosen concept is developed in the form of mechanical linkages using linkage analysis software, SAM 6.1. A human model positioned in a ‘good’ driving posture is used to show how the head restraint and seat would operate using a typical crash pulse used for dynamic sled testing of automotive seats. The head restraint system is capable of translating into an optimal position of 40 mm forwards and 60 mm upwards in 12 ms, before whiplash-induced injuries start to take place. The reactive seat is also capable of reclining 15 degrees. The combination of reducing the backset and reclining the seat to reduce the relative motion between the head and torso has the potential to reduce the whiplash-effect-related injuries in rear-end collisions.

Local Pressure Application Effects on Discomfort, Temperature, and Limb Oxygenation.

Despite significant investment into the development and improvement of military helicopter seat systems, military aviators continue to report seat system related pain and discomfort during prolonged missions. Using a factorial repeated measures design, 15 healthy subjects completed the study, in which focal pressure was applied to two locations on the sitting surfaces of the body (ischial tuberosity and middle of the posterior thigh). Pressure was applied using a purpose-built pressure application system allowing subjects to sit in a position mimicking the sitting position in the UH-60 Black Hawk helicopter. The researchers measured pain using the Category Partitioning Scale and McGill Pain Questionnaire and vascular function using dynamic infrared thermography in the lower leg and pulse oximetry at the great toe. Data were collected before and during a 10-min application of focal pressure applied to either the ischial tuberosity or middle of the posterior thigh and at two different pressure magnitudes (36 or 44 kPa). We found that during a 10-min pressure application, superficial skin temperature increased by 0.61°C, suggesting a decreased venous return during pressure application. We found that lower extremity blood oxygenation remained unchanged during pressure application. Subjects' reported pain increased during pressure application and was greater with 44 kPa of application compared to 36 kPa. These results support the hypothesis that locally high pressure creates symptoms of discomfort and paresthesia. Research examining the effects of local pressure application on physiological and neurological function is needed. Games KE, Lakin JM, Quindry JC, Weimar WH, Sefton JM. Local pressure application effects on discomfort, temperature, and limb oxygenation. Aerosp Med Hum Perform. 2016; 87(8):697-703.

Effects of different seating equipment on postural control and upper extremity function in children with cerebral palsy.

Adaptive seating supports for cerebral palsy are recommended to develop and maintain optimum posture, and functional use of upper extremities. To compare the effectiveness of different seating adaptations regarding postural alignment and related functions and to investigate the effects of these seating adaptations on different motor levels. Prospective study. A total of 20 children with spastic cerebral palsy (Gross Motor Function Classification System 3-5) were included. Postural control and function (Seated Postural Control Measure, Sitting Assessment Scale) were measured in three different systems: standard chair, adjustable seating system and custom-made orthosis. In results of all participants ungrouped, there was a significant difference in most parameters of both measurement tools in favor of custom-made orthosis and adjustable seating system when compared to standard chair ( p < 0.0017). There was a difference among interventions in most of the Seated Postural Control Measure results in Level 4 when subjects were grouped according to Gross Motor Function Classification System levels. A difference was observed between standard chair and adjustable seating system in foot control, arm control, and total Sitting Assessment Scale scores; and between standard chair and custom-made orthosis in trunk control, arm control, and total Sitting Assessment Scale score in Level 4. There was no difference in adjustable seating system and custom-made orthosis in Sitting Assessment Scale in this group of children ( p < 0.017). Although custom-made orthosis fabrication is time consuming, it is still recommended since it is custom made, easy to use, and low-cost. On the other hand, the adjustable seating system can be modified according to a patient's height and weight. Clinical relevance It was found that Gross Motor Function Classification System Level 4 children benefitted most from the seating support systems. It was presented that standard chair is sufficient in providing postural alignment. Both custom-made orthosis and adjustable seating system have pros and cons and the best solution for each will be dependent on a number of factors.

Hybrid modeling of seat-cab coupled system for truck

For the complex structure and vibration characteristics of the seat and cab system of truck, there is no reliable theoretical model for the suspensions design at present, which seriously restricts the improvement of ride comfort. In this paper, a 4 degree-of-freedom seat-cab coupled system model was presented; using the mechanism modeling method, its vibration equations were built; then, by the tested cab suspensions excitations and seat acceleration response, its parameters identification mathematical model was established. Combining the tested signals and a simulation model with the parameters identification mathematical model, a new method of hybrid modeling of seat-cab coupled system was presented. With a practical example of seat and cab system, the parameters values were identified and validated by simulation and test. The results show that the model and method proposed are correct and reliable, and lay a good foundation for the optimal design of seat suspension and cab suspensions to improve ride comfort.

Editorial: Wheeled Mobility Biomechanics

Editorial: Wheeled Mobility Biomechanics

Exploring the functional impact of adaptive seating on the lives of individual children and their families: a collective case study

Purpose: This study examined parent-reported change in the functional performance of four school-aged children with wheeled mobility needs who had used a new adaptive seating system for 6 weeks.Methods: The collective case study involved four mothers whose children, ages 6–9 years, received a new adaptive seating system for a manual wheelchair or stroller. Mothers completed the Family Impact of Assistive Technology Scale for Adaptive Seating (FIATS-AS) at the time their child received a new seating system, and then after 6 weeks of daily use. Other questionnaires, health records, and semi-structured interviews provided additional data about the seating interventions and their functional effects on individual children and their families.Results: The FIATS-AS detected overall functional gain in one family, and both gains and losses in 2–7 dimensions for all families. Functional status and change scores showed consistency with measures of seating intervention satisfaction, global functional change, and home participation. Interview themes also suggested consistency with change scores, but provided a deeper understanding of important factors that influenced adaptive seating outcomes.Conclusion: This study supports the need to explore further the complexity, temporality and meaningfulness of adaptive seating outcomes in individual children and their families.Implications for RehabilitationAssistive technology practitioners need to adopt practical measurement strategies that consider the complexity, temporality, and meaningfulness of outcomes to make evidence-informed decisions about how to improve adaptive seating services and interventions.Health measurement scales that measure adaptive seating outcomes for service applications must have adequate levels of reliability and validity, as well as demonstrate responsive to important change over time for individual children and their families.Needs-specific measurement scales provide a promising avenue for understanding functional outcomes for individual children and youth who use adaptive seating systems.

Damping collaborative optimization of five-suspensions for driver-seat-cab coupled system

Both the seat and cab system of truck play a vital role in ride comfort. The damping matching methods of the two systems are studied separately at present. However, the driver, seat, and cab system are one inseparable whole. In order to further improve ride comfort, the seat suspension is regarded as the fifth suspension of the cab, a new idea of “Five-suspensions” is proposed. Based on this idea, a 4 degree-of-freedom driver-seat-cab coupled system model is presented. Using the tested cab suspensions excitations as inputs and seat acceleration response as compared output, the simulation model is built. Taking optimal ride comfort as target, a new method of damping collaborative optimization for Five-suspensions is proposed. With a practical example of seat and cab system, the damping parameters are optimized and validated by simulation and bench test. The results show the seat vertical frequency-weighted RMS acceleration values tested for the un-optimized and optimized Five-suspensions are 0.50 m/s2 and 0.39 m/s2, respectively, with a decrease by 22.0%, which proves the model and method proposed are correct and reliable. The idea of “Five-suspensions” and the method proposed provide a reference for achieving global optimal damping matching of seat suspension and cab suspensions.

Measuring the psychosocial impact of mobility assistive products with elderly people: Findings from Italian surveys

Purpose. In 2014 and 2015 the authors surveyed two samples of 79 and 65 users who had obtained mobility assistive devices from the National Health Service in Italy. The first sample was composed of powered wheelchair users, 71% of them being over 65 years old [1]. The second sample included users of seven different mobility assistive devices: powered wheelchairs, tilting manual wheelchairs, manual wheelchairs with seating system, tracked and wheeled stair-climbing devices, trans-femoral and trans-tibial lower limb prostheses); 42% of them were over 65 years old. Follow-up interviews were conducted in order to collect information about usage, effectiveness, usefulness and economic impact of their assistive device. Method. The instruments used in the interviews, which were conducted at the users’ homes, included an introductory questionnaire and other widely known assessment instruments, one of them being the PIADS (Psychosocial Impact of Assistive Devices Scale) [2], [3]. Results & Discussion. In both samples elderly people (those aged 65 or more) answered the PIADS items in greater numbers than those under 65. Some difficulties in answering the PIADS questions were noticed, which seem to be related to the kind of assistive device rather than to the age of the interviewed person. In the 2015 survey the number of subjects who did not answer the whole PIADS questionnaire was greater among users of assistive devices maneuvered by caregivers (tilting wheelchairs, manual wheelchairs with seating system, tracked and wheeled stair-climbing devices) than among users of devices providing full independence (powered wheelchairs, trans-femoral and trans-tibial lower limb prostheses). Another noteworthy finding is that, although all average scores obtained in the PIADS subscales were positive (about +1 in both samples), for elderly people the scores were a bit lower than those obtained from younger users. This does not occur for electronic wheelchairs users, whose scores don't differ in relation to the age of the interviewed subjects. Building on experience gained during these and previous studies, in the next two years a battery of outcome measurement instruments will be prepared to be used in clinical practice. References. 1. Salatino C, Andrich R, Converti RM, Saruggia M. An observational study of powered wheelchair pro-vision in Italy. Assistive technology 28(1) (2015) 41-52. 2. Andrich R, Pedroni F, Vanni G. Psychosocial Impact of Assistive Devices: Italian localization of the PIADS instrument. In: Craddock G et al (eds), Assistive technology: Shaping the future (AAATE 2003). Amsterdam: IOS Press (2003) 917–921. 3. Jutai J, Day H. Psychosocial Impact of Assistive Devices Scale (PIADS). Technology and Disability 14(3) (2002) 107–111.

Hybrid modelling and damping collaborative optimisation of Five-suspensions for coupling driver-seat-cab system

ABSTRACTFor the complex structure and vibration characteristics of coupling driver-seat-cab system of trucks, there is no damping optimisation theory for its suspensions at present, which seriously restricts the improvement of vehicle ride comfort. Thus, in this paper, the seat suspension was regarded as ‘the fifth suspension’ of cab, the ‘Five-suspensions’ for this system was proposed. Based on this, using the mechanism modelling method, a 4 degree-of-freedom coupling driver-seat-cab system model was presented; then, by the tested cab suspensions excitation and seat acceleration response, its parameters identification mathematical model was established. Based on this, taking optimal ride comfort as target, its damping collaborative optimisation mathematical model was built. Combining the tested signals and a simulation model with the mathematical models of parameters identification and damping collaborative optimisation, a complete flow of hybrid modelling and damping collaborative optimisation of Five-suspensions was presented. With a practical example of seat and cab system, the damping parameters were optimised and validated by simulation and bench test. The results show that the model and method proposed are correct and reliable, providing a valuable reference for the design of seat suspension and cab suspensions.

Seating System with Adjustable Sheet and Body Surface Measurement

[abstFig src='/00280001/08.jpg' width=""220"" text='Wheel chair with adjustable sheets' ]The seat is an important interface between many types of machines and their users, able-bodied and disabled users alike. In this work, new seating system with adjustable sheets and body surface measurement is developed to improve the sitting postures and pressure distributions for patients with deformed backbones. A basic structure and adjustment method for the adjustable sheet is proposed. In addition, a way of using a Microsoft Kinect sensor to measure lengths is also developed and utilized to adjust the seating system. Evaluation tests are conducted on a healthy subject with different mock spinal deformations, and pressure distributions and postures of the subject are evaluated. The proposed method successfully averages pressure on the model and also adjusts his posture, simultaneously reducing pressure and increasing the contact area of the back.

Strapping rowers to their sliding seat improves performance during the start of single-scull rowing

ABSTRACTIn this study, the effect of strapping rowers to their sliding seat on performance during 75 m on-water starting trials was investigated. Well-trained rowers performed 75 m maximum-effort starts using an instrumented single scull equipped with a redesigned sliding seat system, both under normal conditions and while strapped to the sliding seat. Strapping rowers to their sliding seat resulted in a 0.45 s lead after 75 m, corresponding to an increase in average boat velocity of about 2.5%. Corresponding effect sizes were large. No significant changes were observed in general stroke cycle characteristics. No indications of additional boat heaving and pitching under strapped conditions were found. The increase in boat velocity is estimated to correspond to an increase in average mechanical power output during the start of on-water rowing between 5% and 10%, which is substantial but smaller than the 12% increase found in a previous study on ergometer starting. We conclude that, after a very short period of adaptation to the strapped condition, single-scull starting performance is substantially improved when the rower is strapped to the sliding seat.

Identification and optimisation of surrogate model parameters of the bus driver's seat suspension

For the driver's seat system of buses, its design often needs trial and error, which usually has longer periods, higher cost, and larger waste. In this paper, a three degrees-of-freedom driver's seat system model was built. Based on the tested seat suspension excitation and cushion acceleration response, its parameters identification model and damping identification model were established, respectively. Combining the mechanism modelling with the parameters identification model and damping identification model, an integrated and convenient method of modelling, damping optimisation, and accompanying verifications for the driver's seat system was presented. With a practical example, the method and the dynamic model were validated by simulation and test. The measured cushion vertical frequency-weighed RMS acceleration values of the driver's seat system for the un-optimised and the optimised are 0.588 m/s2 and 0.533 m/s2, respectively, with a decrease of 9.35%. The results show that the method and the dynamic model presented are correct and workable.

Identification and optimisation of surrogate model parameters of the bus driver's seat suspension

For the driver's seat system of buses, its design often needs trial and error, which usually has longer periods, higher cost, and larger waste. In this paper, a three degrees-of-freedom driver's seat system model was built. Based on the tested seat suspension excitation and cushion acceleration response, its parameters identification model and damping identification model were established, respectively. Combining the mechanism modelling with the parameters identification model and damping identification model, an integrated and convenient method of modelling, damping optimisation, and accompanying verifications for the driver's seat system was presented. With a practical example, the method and the dynamic model were validated by simulation and test. The measured cushion vertical frequency-weighed RMS acceleration values of the driver's seat system for the un-optimised and the optimised are 0.588 m/s2 and 0.533 m/s2, respectively, with a decrease of 9.35%. The results show that the method and the dynamic model presented are correct and workable.

A study on the Horizontal Control of a Seat for Heavy Machinery using a Phase Adjusting Technique

This study proposes a dynamic plant model to simulate the performance of a heavy equipment vehicle seat system. The system controls the transmission of vibration using a phase adjustment control method. First, a dynamic model for the flexible heavy equipment seat is proposed using a commercial multi-body dynamic analysis tool, ADAMS. This model is used as a plant model. Then a phase adjustment control mechanism for reducing the vibration and shock transmitted by the seat is applied to the driving dynamics control plant model. Angle control using the phase adjustment control was confirmed. This technique is expected to be the basis for a future commercial system.

Design concepts for an integrated whiplash mitigating head restraint and seat

ABSTRACTThis paper presents design of a concept for an integrated head restraint and car seat system to mitigate whiplash in rear-end vehicle collisions. The main emphasis is on a concept, which combines a reactive head restraint with a reactive seat. The chosen concept is developed in the form of mechanical linkages using linkage analysis software, SAM 6.1. A human model positioned in a ‘good’ driving posture is used to show how the head restraint and seat would operate using a typical crash pulse used for dynamic sled testing of automotive seats. The head restraint system is capable of translating into an optimal position of 40 mm forwards and 60 mm upwards in 12 ms, before whiplash-induced injuries start to take place. The reactive seat is also capable of reclining 15 degrees. The combination of reducing the backset and reclining the seat to reduce the relative motion between the head and torso has the potential to reduce the whiplash-effect-related injuries in rear-end collisions.

Interface pressure mapping pilot study to select surfaces that effectively redistribute pediatric occipital pressure

AimThe aim of this pilot study was to better inform clinical decisions to prevent pediatric occipital pressure ulcers with quantitative data to choose an appropriate reactive support surface. MaterialsA commercially available capacitive pressure mapping system (XSENSOR, X3 Medical Seat System, Calgary, Canada) was used to evaluate a standard pediatric mattress and four commercially available pressure-redistributing support surfaces. MethodsThe pressure mapping system was validated for use in the pediatric population through studies on sensitivity, accuracy, creep, and repeatability. Then, a pilot pressure mapping study on healthy children under 6 years old (n = 22) was performed to determine interface pressure and pressure distribution between the occipital region of the skull and each surface: standard mattress, gel, foam, air and fluidized. ResultsThe sensor was adequate to measure pressure generated by pediatric occipital loading, with 0.5–9% error in accuracy in the 25–95 mmHg range. The air surface had the lowest mean interface pressure (p < .005) and lowest peak pressure index (PPI), defined as the peak pressure averaged over four sensels, (p < .005). Mean interface pressure for mattress, foam, fluidized, gel, and air materials were 24.8 ± 4.42, 24.1 ± 1.89, 19.4 ± 3.25, 17.9 ± 3.10, and 14.2 ± 1.41 mmHg, respectively. The air surface also had the most homogenous pressure distribution, with the highest mean to PPI ratio (p < .005) and relatively high contact area compared to the other surfaces (p < .005). ConclusionThe air surface was the most effective pressure-redistributing material for pediatric occipital pressure as it had the lowest interface pressure and a homogeneous pressure distribution. This implies effective envelopment of the bony prominence of the occiput and increasing contact area to decrease peak pressure points.

Effects of adjustment devices on the fore-and-aft mode of an automobile seat system: headrest, height adjuster, recliner and track slide

The automobile seat is an important and unique device in the automobile system, which directly contacts the human body. The dynamic characteristics of the automobile seat are the key parameters for its vibration security and dynamic performance. Both experiments and finite element simulations are conducted to analyse the fore-and-aft operating modes of a new type of automobile seat system in this paper. The results and their correlation analysis between the experimental data and the computational models are given. By using finite element simulations, the computational results of the modes with the first 12 orders for the automobile seat are in the range 0–100 Hz, including the integral modes and the local modes of the automobile seat. An experimental method was designed to measure the seat frame mode using an impact hammer, a triaxial accelerometer, uniaxial accelerometers and a 24-channel LMS vibration test system. The experimental data were analysed by estimating the frequency response function and the modal parameters and validated using LMS Test.Lab software. The experimental results for five integral modal parameters of the automobile seat between 0 Hz and 100 Hz are given. The orthogonal experimental method is used to design nine different working states of the automobile seat with variations in the positions of different adjustable devices (the headrest, the height adjuster, the recliner and the track slide). Finally, the influences of the above-mentioned adjustable devices on the fore-and-aft operating mode are analysed by the single-factor analysis method using finite element simulations.

Tissue Changes During Operational Load Bearing in UH-60 Aircrew Using Magnetic Resonance Imaging.

Warfighters involved in mounted operations often experience prolonged periods of tissue loading, leading to injury. Determining how anatomical structures are affected during loading aids in the prevention and treatment of injury. The purpose of this study was to develop a magnetic resonance imaging (MRI) compatible seat system that simulates a UH-60 Blackhawk in-flight sitting posture. Eight men were scanned with a 3.0 Tesla MRI. Scans were collected with and without 6.38 psi of pressure applied to the buttocks via two air bladders and an MRI-compatible robot controller system. Scans revealed that 6.38 psi of pressure applied to the buttocks significantly decreases total soft-tissue thickness beneath the left and right ischial tuberosities by 3.6 and 3.8 mm, respectively. At operational load bearing pressures seen in the UH-60, the soft tissue structures of the buttocks are compressed. These findings aid in our understanding of the etiology of repetitive trauma disorders in aircrew due to prolonged sitting. This study serves as the foundation for future work examining the anatomical changes associated with prolonged restricted sitting and other operational activities. A better understanding of the anatomical characteristics associated with mounted operations is invaluable to the prevention and treatment of injuries reported by warfighters and civilian populations.

Adaptive seating systems in children with severe cerebral palsy across ICF‐CY domains: a systematic review

Adaptive seating systems in children with severe cerebral palsy across ICF‐CY domains: a systematic review