Vertical Seat Research Articles

Finite Element Analysis of the Main Structure for a New Conceptual Aircraft Passenger Vertical Seat Design

Standing cabin is a new design concept of aircraft passenger cabin whereby passengers are transported in the standing position throughout flight as opposed to current seated position. An important element of this cabin concept is the design of the vertical seat to support the passengers, which has to be in compliance with requirements of aviation regulation. In commercial aircraft applications, weight of passenger seat is a significant factor that can affect flight performance of the aircraft. Meanwhile, the seat’s structure should have adequate strength to ensure proper safety provision to passengers. Hence weight and strength are potentially two conflicting design requirements for the vertical seat, and the optimum structural design should have the best compromise with regards to these two requirements. In this study, parametric study on primary structural design of the proposed vertical seat concept is done to obtain an optimized design that satisfies the strength requirements for safety of passengers without causing high penalty to the overall aircraft weight and performance. The simulation analysis for the main structures of the vertical seat design is conducted through finite element method using ABAQUS software. From the results of the analysis, main structural parts made from aluminium alloy with diameter 90 mm and thickness 3 mm are selected for the optimum vertical seat design. This standing seat design has also been shown to have adequate strength and can satisfy the safety regulation requirement without failure. The maximum stress on the seat’s structure under 9-g forward loading is found to be 147.5 MPa, which is lower than ultimate strength of aluminium. Moreover, the seat’s weight is estimated to be 9.5 kg and the maximum deflection of its main structures under forward 9-g loading is 28.42 mm. All in all, the stress analysis results highlight that the structural strength of the optimal vertical seat design can satisfy the requirements of the governing aviation regulations to provide safety to passengers.

Nonlinear Dynamic Modelling of a Suspension Seat for Predicting the Vertical Seat Transmissibility

Suspension seats are widely used in heavy vehicles to reduce vibration transmitted to human body and promote ride comfort. Previous studies have shown that the dynamics of the suspension seat exhibits nonlinear behaviour with changed vibration magnitudes. Despite various linear seat models developed in the past, a nonlinear model of the suspension seat capturing the nonlinear dynamic behaviour of the seat suspension and cushion has not been developed for the prediction of the seat transmissibility. This paper proposes a nonlinear lumped parameter model of the suspension seat to predict the nonlinear dynamic response of the seat. The suspension seat model comprises of a nonlinear suspension submodel integrated with a nonlinear cushion submodel. The parameters of the submodels are determined by minimizing the error between the simulated and the measured transmissibility of the suspension mechanism and the force-deflection curve of the seat cushion, respectively. The model of the complete seat is then validated using the seat transmissibility measured with inert mass under vertical vibration excitation. The results show that the proposed suspension seat model can be used to predict the seat transmissibility with various excitation magnitudes.

Cardiovascular response to whole-body vibration on an automobile seat

The study aim was to determine whether a relationship exists between the cardiovascular response, measured by HR and HRV and the magnitude of whole-body vibration. Cardiovascular response of sixty male participants in four groups, was measured during three states i.e. (1) no vibration, (2) a reference vibration and (3) an alternative vibration. The reference vibration was the same for all groups with the alternative vibrations different for each group. Weighted vertical seat vibration was 0.66 m.s−2, root-mean-square for the reference and 0.70, 0.73, 0.76, and 0.79 m.s−2, root-mean-square for the alternative vibrations. Vibrations only differed in magnitude with the difference between alternative vibrations based on relative difference thresholds. Nonparametric tests compared cardiovascular indicators between groups at State 3 adjusted for state of departure i.e. State 2. No significant differences between groups were found for most of the indicators, suggesting no relationship between cardiovascular response and the magnitude of whole-body vibration. Practitioner summary: The cardiovascular response to the magnitude of whole-body vibration on an automobile seat was investigated. Results suggest that no relationship exists between the magnitude and cardiovascular response and that the latter may not be as effective as other objective measures (e.g. acceleration) in evaluating the human’s response to whole-body vibration.

Design of a linear motor-based shaker rig for testing driver's perceived ride comfort

In autonomous vehicles the driver will become a passenger. By ensuring a high level of ride comfort through active suspensions, the driver's ability to perform various tasks such as reading, drawing and texting can be enhanced. A high-performance shaker rig can conveniently be used to test the ride comfort improvement by means of various active suspensions under laboratory conditions. The paper deals with the design of such a rig, which employs a linear electric servomotor to impose accurately controlled vertical vibrations of driver seat. The reference time profiles of seat acceleration, velocity and displacement are generated off-line by using a half-car vehicle model and LQR control with a road preview option. The selection of linear motor comes from assessment of three characteristic shaker rig drive designs (hydraulic and two electric ones). To ensure high-precision seat motion, the proposed shaker control system includes: acceleration feedforward and feedback control loops, a state controller-like compensator of accelerometer offset to prevent drift of seat position and velocity, and feedforward compensation of linear motor cogging force mode. The designed shaker rig application is demonstrated through a case study related to ride comfort evaluation of various active suspension configurations and a drawing task. The drawing task results are employed to determine the root-mean-square vertical seat acceleration threshold, below which the active suspension drawing task performance remains similar to that obtained under standstill conditions.

Analysis of bio-dynamic model of seated human subject and optimization of the passenger ride comfort for three-wheel vehicle using random search technique

Ride comfort is the major concern to the roadway vehicle passengers, travelling in as it affects their health and efficiency to work. In the present study, a 9 DoF model of a three-wheel vehicle is developed with Lagrangian approach to investigate its ride behavior when subjected to random surface irregularities. The irregularities of the track are measured with a three-wheeled setup equipped with profilometer known as opto-coupler. The present model is validated in two ways, first by comparing the vertical-lateral PSD acceleration received from simulation and actual testing and second by comparing vertical seat to head transmissibility obtained from analysis (VSTH) with past reported studies. A 7 DoF bio-dynamic model of the seated human subject is formulated and integrated with the vehicle model, ride comfort of the vehicle and human body segments are assessed based on ISO specifications. Passenger Ride Comfort is optimized through non-linear optimization using Random Search Technique. The modified values of vehicle suspension parameters are presented to obtain optimum passenger comfort based on ISO-2631-1 criteria.

An Analysis of Vibration Reduction Design on the Bicycle Frame Based on Multi-Body Dynamics Simulation

In recent years, the awareness of environmental protection has risen, and modern people’s quality of life has improved. Bicycles are no longer just general transportation and carrying tools, but evolved into the need to emphasize comfortable riding, energy-saving and carbon reduction, and physical fitness. In this study, the different vehicle-to-weight ratio and road bumpiness before and after designing the bicycle frame’s damping and stiffness parameters were considered. The simulation results designate that the seat acceleration in both the y and z-axis is adequate constant, and the seat velocity gradually increases, whereas the vertical seat displacement of damped has significantly reduced compared with undamped.

Modelling and simulation of an integrated human-vehicle system with non-linear cushion contact force

Driver comfort is related to human-seat interaction forces and the seat suspension system. For a human body subjected to vertical seat vibration, the head exhibits vertical as well as fore-aft motion, which leads to high forces in the neck. In order to capture these effects, a detailed 12 degrees of freedom two-dimensional seated human body model with inclined backrest support is developed to study direct and cross-axis seat to head transmissibility. The human model is then integrated with a non-linear cushion-human interaction model. The cushion parameters are obtained using a genetic algorithm and a global criterion-based scheme to minimize the least square difference between experimental contact force-time signal and analytical results. Subsequently, the human body model, along with a non-linear seat cushion model, are incorporated into a full vehicle model. Seat suspension parameters are obtained by minimizing the seat effective amplitude transmissibility and human body comfort factors. Both random road excitation and sudden bumps on the road have been studied. The influence of the human body's position in the vehicle and parameter sensitivity with respect to cushion-human interaction force, vertical and fore-aft head acceleration are investigated for multi-compression damper with an inclined damper-seat suspension system. The angle of inclination of the damper has been found to be the parameter with the highest sensitivity. These results and the modelling methodology are expected to lead to a better way of analyzing biodynamic response of the driver.

Seat cushions made of warp knitted spacer fabrics influence seat transmissibility

The aim of this study was to compare the application of different warp knitted spacer fabrics on a car seat shell to a standard seat in terms of vertical seat transmissibility. Furthermore, the results obtained by human subject tests were compared to results of an anthropodynamic dummy test. Experiments were conducted on a vertically actuated platform under laboratory conditions with 16 human subjects and an anthropodynamic dummy. Seat Effective Amplitude Transmissibility of the seat pan and the seat backrest were calculated to evaluate ride quality. Seat transmissibility ranged between 73.6% for backrest and 177.7% for pan. Based on the results of statistical tests, the hypothesis that the transmissibility of a seat would be influenced by seat cushion conditions was accepted (p < 0.05). It was also shown that an anthropodynamic dummy test could replace tests with human subjects (r2 = 0.907) if the target population was matched sufficiently.

Design of optimum vibration absorbers for a bus vehicle to suppress unwanted vibrations against the harmonic and random road excitations

Unwanted vibrations of the vehicles are regarded as harmful threats to the human health from various biomechanical and psychophysical aspects. Road roughness has been considered as the main cause of unwanted vibrations in bus vehicles. Vertical seat vibrations have been found via simulation of a ten degree of freedom (10-DOF) model of an intercity bus vehicle under harmonic and random excitations caused by road roughness. To suppress undesirable vibrations, mass-spring-damper passive absorbers are proposed in a thirteen degrees of freedom (13-DOFs) model of the bus. By optimizing the characteristics of the embedded passive absorbers under each seat, and implementation of the designed absorbers, it is observed that the vertical displacement amplitudes in the frequency response of the seats are reduced especially near the bus resonance frequencies. In addition, the vertical displacement and acceleration amplitudes are decreased in the random excitation of the road roughness. According to the results, optimized mass-spring-damper absorbers are suggested as a practical solution to suppress the unwanted vibration effects in the bus vehicle.

Seat to Head Transmissibility during Exposure to Vertical Seat Vibration: Effects of Posture and Vibration Magnitude

The low frequency vibration transmitted to the body can affect the comfort, performance, and health of humans. In this paper, the effect of variations in posture and vibration magnitude on the head motion in three translational axes (fore-and-aft, lateral and vertical) has been studied with a vertical seat vibration. Thirty healthy male subjects were exposed to random vibration with three vibration magnitudes of 0.4, 0.8, and 1.2 m/s2 rms over the frequency range of 1–20 Hz. The results are analysed in terms of seat-to-head-transmissibility (STHT) for the head motions in two seated postures (backrest and leaning forward on table). The measurement of the head motion was made with an apparatus (bite-bar) specifically developed for this purpose. The measured responses to a single axis seat vibration have also shown notable cross-axis responses in both vertical and fore-and-aft axes for both postures. The crossaxis fore-aft and vertical STHT responses showed single peak near 5 Hz in both postures. An increasing intensity of vibration yields a non-linear softening effect in the muscle tension, particularly in the presence of back support, however, the body stiffens under a greater upper body motion in the forward leaning posture. The combined effect of the unsupported back and hands support was observed to be more pronounced around the resonance peak in the forward lean posture.

Effect of Tractor Seat Suspension Parameters on Vibration Exposure

India is the largest manufacturer of farm equipment like tractor, harvester and tiller. It accounts one third global tractor production. Tractor sale in the country is expected to increase 11-13 per cent in the financial year 2019 while the tractor industry is expected to grow at 8-10 per cent during 2019-23. In the country, the agricultural tractors used for different farm operations starting from land preparation up to harvesting and transportation of agricultural products. Due to this various types of random vibrations, generated from terrain and tractor engine, is transmitted to the operator through seat suspension. Most of the tractors available in India, are attached with a passive type vertical seat suspension which is found to decrease vibration in vertical direction. Many research works have been done in optimisation/modification of the seat suspension parameters alone and development of new seat suspension. But none of them optimize the seat suspension parameters in combination. Hence, the following study was conducted to determine the optimized value of seat suspension parameters for which the vibration transmitted to the operator could be minimum. For this a seat suspension model was developed in AMESim software. The model requires input signal which was tractor seat mounting vibration data and gives the model output data as seat cushion vibration. When the model output data was compared with the test result data for the same vibration input, it was found to have 77.93 per cent correlation. The optimization result of seat suspension parameters alone, spring stiffness of 12000 N/m damping coefficient of 4225 N.s/m was observed to have minimum vibration. While optimizing both the suspension parameters, the combination of 3000 N/m and 2225 N.s/m was found to have minimum vibration. However, it was only 10.79 per cent less than the measured vibration value which might not be an economical decision though there is reduction in vibration.

Generation of design alternatives of vertical passenger seat for standing cabin concept in commercial transport aircraft

Standing cabin concept, whereby the passengers are transported during flight in their standing position, has been proposed as one of the measures to make flying more affordable to the mass public. The vertical seat, or also known as standing seat, is an essential element for the implementation of this new cabin concept as it will determine the compliance to the governing aviation regulations and also the level of safety and comfort for the passengers. Up until now however, there is no vertical seat design that has been approved for use inside the commercial transport aircraft cabin. Therefore, this study presents the generation of alternative designs for the vertical seat through the use of systematic engineering design methodology with the use of supporting design tools such as Quality Function Deployment (QFD) chart and Morphological Matrix. Five alternative concepts of the vertical passenger seat design have been developed for further assessment study to select the best one among them.

Effect of particle intrusion on rail seat load distributions on heavy haul freight railroads

ABSTRACTThe rail seat load distribution is critical for analysing failure mechanisms associated with rail seat deterioration (RSD), the degradation of concrete surface at the sleeper rail seat. RSD can lead to wide gauge, cant deficiency, and an increased risk of rail rollover. Previous experimentation with matrix-based tactile surface sensors (MBTSS) at the University of Illinois Urbana-Champaign (UIUC) has yielded concern regarding the feasibility of crushing of the concrete material at the rail seat. This paper examines data collected from laboratory experimentation in which the particle size, particle intrusion, vertical rail seat load, and lateral over vertical force ratio were varied to generate extreme loading environments. No pressures exceeded the concrete compressive strength. However, certain loading scenarios yielded pressures exceeding the concrete fatigue strength. It was therefore concluded that accumulated crushing damage due to a high number of repeated load applications is a feasible failure mechanism of RSD initiation.

Market Potential Study for Standing Cabin Concept for Domestic Low-Cost Commercial Airlines in Malaysia

An affordable air transportation has become the operational aim of many airlines these days. This is to cater the growing air travel demands from people of different social and economic status. One of the revolutionary proposals to reduce the operational costs, hence the flight ticket price, is by introducing the so-called standing cabin concept. This concept involves transporting passengers during the entire flight in their standing position with a proper support of a vertical seat. As can be expected with many new inventions, despite its clear advantages, the concept has been met with mixed reactions from the public. This study intends to establish whether the standing cabin concept has a market potential to be implemented for domestic flights in Malaysia. The public perception is determined from collected data through a survey done at two major local low-cost airport terminals. It can be concluded from the results that the concept has a good market potential for application on flights with duration of less than two hours.

Ergonomics Study of Vertical Seat Design for Standing Cabin Concept in Commercial Transport Aircraft

Rapid growth of low-cost airlines has changed the landscape of market competition for the airline industry. Affordability of air travel is the new target that is being sought after by many airlines. Over the years, several suggestions have been made for ways to reduce the flight ticket price and one of them is the new revolutionary concept of a standing passengers cabin. The main idea of this cabin concept is that the passengers will be transported in their standing position during flight instead of the current seated position. By having the passengers standing, this allows more people to be accommodated within the available cabin space. Hence the cost of flying can be distributed to more people and subsequently the ticket price per passenger will be reduced. This paper discusses the standing cabin concept from the ergonomics aspect of the vertical seat design for use in the standing cabin, highlighting some design recommendations to make it more suitable for human body.

Response of the seated human body to whole-body vertical vibration: discomfort caused by sinusoidal vibration

Frequency weightings for predicting vibration discomfort assume the same frequency-dependence at all magnitudes of vibration, whereas biodynamic studies show that the frequency-dependence of the human body depends on the magnitude of vibration. This study investigated how the frequency-dependence of vibration discomfort depends on the acceleration and the force at the subject–seat interface. Using magnitude estimation, 20 males and 20 females judged their discomfort caused by sinusoidal vertical acceleration at 13 frequencies (1–16 Hz) at magnitudes from 0.1 to 4.0 ms− 2 r.m.s. The frequency-dependence of their equivalent comfort contours depended on the magnitude of vibration, but was less dependent on the magnitude of dynamic force than the magnitude of acceleration, consistent with the biodynamic non-linearity of the body causing some of the magnitude-dependence of equivalent comfort contours. There were significant associations between the biodynamic responses and subjective responses at all frequencies in the range 1–16 Hz.Practitioner Summary: Vertical seat vibration causes discomfort in many forms of transport. This study provides the frequency-dependence of vibration discomfort over a range of vibration magnitudes and shows how the frequency weightings in the current standards can be improved.

The Design of Vertical Seat Frame

It is significant to transport hot-rolled steel coil vertically by seat frame in 70t universal gondola for ensuring safety and improving efficiency. According to the basic requirements of loading and reinforcement in railway freight traffic, studies the conditions of coil transported vertically, carries out a rational design of the seat frame combined with the characteristics of 70t universal gondola, finally uses a way of finite element simulation to prove its feasibility.

Off-Road Seat Suspension Optimization by Particle Swarm Algorithm

Due to creating health problems for human by using vehicles in long term, seat suspension design is important especially in off-road vehicles. Recently, intelligent methods are focused by researchers for optimization problems. In this paper, artificial neural network biodynamic model (ANNBM) was used to simulate human body responses to the vertical direction and seat suspension was optimized to reduce vibration transmitted from seat to lower lumbar. Particle Swarm Optimization (PSO) was employed for this purpose. The results of simulation shows 0.6 seat to spine vibration transmissibility (SST), and the efficiency of suspension seems good to remove unwanted vibration.

Conceptual Design of Vertical Passenger Seat for Standing Cabin in Commercial Transport Aircraft

The competition between airlines today is changed towards the affordability of their air transportation service. The airlines are competing to lower their offered flight ticket prices as to capture high demands from leisure and business travelers, who are also price-sensitive customers. Theoretically, by having more passengers onboard the aircraft, the flight ticket price can be lowered since the imposed operational costs can be shared by more passengers per flight. The standing cabin concept has been proposed where the passengers are transported in a cabin of an aircraft in an upright position, similar to standing on buses and trains. This paper explores the conceptual design of vertical seat for the passengers to be applied in such standing cabin concept. 

Comparison of manual rasping and robotic milling for short metaphyseal-fitting stem implantation in total hip arthroplasty: a cadaveric study

Objective: The ROBODOC system offers the theoretical advantage of providing better fit and mechanical stability of the stem in total hip arthroplasty. However, there has been no previous study on short metaphyseal-fitting stem implantation using the ROBODOC system. The aim of the present study was to compare the implant position and primary stability of short metaphyseal-fitting stems implanted by robotic milling and manual rasping in a human cadaveric femoral model.Methods: Eight matched pairs of human cadaveric femora were randomly assigned to a robotic milling group or manual rasping group. Operative time and intraoperative femoral fractures were monitored, and radiographic evaluation of stem alignment was performed by comparison of preoperative planning and postoperative CT data. Stability testing was performed on six matched pairs of femora, excluding two specimens in which intraoperative fractures occurred.Results: The robotic milling procedures took an average of 27 minutes longer than the manual rasping procedures (p < 0.001). The robotic milling group exhibited significantly better anteroposterior alignment and vertical seating, and also showed a significantly reduced variability in both alignment and vertical seating. No intraoperative femoral fracture was detected in the robotic milling group, whereas two femoral fractures and one femoral stem tip perforation were detected in the manual rasping group. Stability testing showed no significant difference in translational and rotational migrations between the two groups, although the robotic milling group showed a trend towards reduced variability of stability.Conclusions: Our cadaveric study suggests that the use of the ROBODOC system for short metaphyseal-fitting stem implantation may have advantages in improving implant fit and reducing the risk of intraoperative femoral fractures without compromising primary stability.