Seat Effective Amplitude Transmissibility Research Articles

Coupled occupant-suspension-seat system analysis and vehicle-specific design optimization

A suspension seat is generally designed to achieve attenuation of low frequency whole-body vibration for a broad range of vehicles. Owing to the strong dependence of its vibration isolation performance on the nature of vibration excitation, an optimal performance could be realized via optimal tuning of suspension for specific classes of vehicles. In this study, a coupled occupant suspension seat model is developed and analyzed to identify optimal design parameters for different classes of vehicles. The multibody dynamic model of the air suspension seat is formulated considering kineto-dynamics of the suspension system and the elastic motion-limiters. The component models, namely, air spring with auxiliary air volume, hydraulic damper, and cushion, are identified from the laboratory-measured static and dynamic characteristics. A two-degree-of-freedom occupant model, is integrated to the suspension seat model to account for contribution due to occupant biodynamics. Model validity is examined using the laboratory-measured responses with a rigid load and a human occupant of similar body weight, and analyzed for different body weights and excitation spectra. The results suggest strong dependency of the suspension resonance frequency on nonlinear behavior of the air spring and the seated body mass. The model is subsequently employed to identify optimal coordinates of the air spring to achieve nearly constant natural frequency for a broad range of body masses. Furthermore, the model is used to identify optimal linkage and suspension design parameters with an objective to minimize the SEAT (Seat Effective Amplitude Transmissibility) for different spectral classes of earth moving machines defined in the ISO-7096 standard, while limiting the suspension travel. It is shown that the optimal coordinates of air spring could yield nearly constant natural frequency for different body weights, while damper could help limit the suspension travel, in addition to notable reductions in SEAT, ranging from 9% to 31% for different spectral classes of vehicles.

Ride comfort analysis of vehicle seat suspension systems: A co-simulation study

In this study, the vehicle seat suspension system installed with a semi-active magnetorheological (MR) damper is excited by the power spectral density (PSD) and its vibration control performance is evaluated using finite element analysis (FEA). The control system receives the velocity of the sprung and unsprung mass from the seat mounting locations and calculates the desired controllable damping forces available from MR damper. The effectiveness of the control systems is demonstrated by adopting ride quality evaluation method. To predict a better ride comfort and ride quality, co-simulation methodology is utilized considering the dynamic behavior of the real-world seat system. In this case, the multi-body dynamics and control system are coupled by solving the mechanical equations and the control logic. Then, the computed damping force is exchanged between the dynamics and controller in an iterative manner by passing state variables. The simulation results achieved from co-simulation methodology associated with the controller are analyzed by comparing with ISO 2631-1. The co-simulation results studied using vibration dose value (VDV), crest factor (CF) and seat effective amplitude transmissibility (SEAT) in terms of percentage improvement were found to be 44.33%, 26.66% and 17.65% respectively which were better than that for the passive suspension for a random rough road profile. Modified skyhook controller delivers superior performance for vibration suppression of the vehicle seat suspension as compared to other control policies. The application of co-simulation methodology can reduce time and cost for the development of a semi-active seat suspension system.

COMFORT ANALYSIS COMPARISON BETWEEN ALFAPENDULAR AND INTERCITY PORTUGUESE TRAINS AT THE NORTH RAIL

Nowadays, trains are one of the most used public transportation modes. Comfort is the key to keeping and attracting new users. Vibration highly influences comfort levels and, once it is derived from the train motion it is stated as a primary concern. Due to contact with the seat and floor, passengers are subjected to whole-body vibration. ISO 2631 standard is fully dedicated to the evaluation of this type of vibration. Following its approach, the present research evaluates the comfort levels of Alfapendular and Intercity trains operating in Portugal at the Porto Campanhã – Lisbon Oriente connection. Measurements were performed at the beginning, middle, and end of the train, allowing a comparison between seat types within the same train and the same types from different trains. Results showed higher comfort levels for the Alfapendular trains, while for the Intercity train, both middle and end of train locations were ranked as “Little uncomfortable”. As a complementary analysis, it was observed the vibration transmission of the seat based on the Seat Effective Amplitude Transmissibility (SEAT). Results were above 100%, showing vibration amplification by all tested seats. Higher SEAT values were found for the Intercity train seat. This was the first study conducted on Portuguese trains regarding comfort analysis and vibration transmission. Keywords: Railways, Whole-body vibration, Vibration transmission, SEAT.

Sensitivity Analysis of a Driver’s Lumped Parameter Model in the Evaluation of Ride Comfort

The ride comfort provided by a vehicle to the driver and the passengers is an important feature, directly correlated to the technical characteristics of the suspension system of the vehicle. In the literature, several lumped-parameter models simulating the vehicle and the driver are proposed for the computational evaluation of ride comfort. In order to quantify ride comfort, other than the values of acceleration, metrics such as seat effective amplitude transmissibility (SEAT) and seat-to-head transmissibility (STHT) are utilized. In this paper, a quarter car model is coupled with a six-degree-of-freedom lumped-parameter model, consisting of the driver’s seat and the driver. A sensitivity analysis is performed on the values of the lumped parameters of the seated human body with regard to ride comfort in order to evaluate the effect of their accuracy relative to the ride comfort evaluation. The results of the sensitivity analysis revealed that the values of the mass, the stiffness and the damping parameters of the seated human model influence the ride-comfort metrics to a different extent. Furthermore, it was depicted that ride-comfort metrics were affected in different manners depending on the characteristics of the excitation of the vehicle, yet less than 10% Finally, the importance of the consideration of single-disturbance excitations in such sensitivity studies emerged.

Transmission of vertical vibration through a seat cushion at the seat pan: Effect of foam physical properties during different excitation magnitudes

The vibration characteristics of car seats directly influence the ride comfort. Polyurethane foam is the key part of a seat, and its physical parameters have an important impact on the seat. In this study, the influence of the foam thickness and foam hardness on the vibration characteristics of seat cushion with different excitation magnitudes was investigated by using transmissibility and seat effective amplitude transmissibility (SEAT) value. First, vibration tests were carried out at a vertical vibration simulator with width-limited white noise vibration frequencies from 0.5 to 20 Hz with root-mean-square (r.m.s.) values of 0.4, 0.8, and 1.2 m/s2, the acceleration at the platform and the body-foam interfaces were measured to calculate the transmissibility, and the influence of the foam physical properties on the transmissibility was analyzed. Then, the SEAT value was introduced to assess the vibration isolation efficiency of the foam cushion, and the influence of the foam physical properties of the foam cushion on the vibration isolation efficiency was analyzed. With increasing thickness of the foam and decreasing hardness of the foam at the seat pan, the peak transmissibility increased and the resonance frequency decreased. The SEAT values show that increasing the foam thickness is beneficial to the improvement of the vibration isolation efficiency of the seat, but there is a diminishing return; the combination of physical parameters of low hardness and high thickness could make the vibration isolation performance of the seat better. In addition, the nonlinearity of human-seat system during different vibration magnitude was found.

Transforming farming with intelligence: Smart vibration monitoring and alert system

During the evolution towards digital agriculture, the pivotal role of tractor riding necessitates a focus on improving operator performance and well-being. While most research has centered around vibration analysis, tangible solutions to control elevated vibration levels remain rare. The study aims to introduce an intelligent ThingSpeak-Enabled IoT (Internet of Things) solution that provides real-time monitoring and generates prompt warning alerts for tractor operators when vibrations exceed safe thresholds. The initial phase involved the real-time measurement of WBV (whole-body vibration) and SEAT (seat effective amplitude transmissibility). Following this, the secondary phase encompassed the analysis and validation of the system in cases where WBV and SEAT exceeded the recommended limits. The experimental design comprised 135 trials by systematically varying tractor ride parameters, including average speed (m/s), average depth (m), and pulling force (kN) levels. Daily vibration exposure response ranged from 0.43 m/s² to 0.87 m/s² with a mean exposure of 0.64 m/s2, surpassing the EAV (exposure action value) threshold of 0.5 m/s². The SEAT values ranged between 91.37 and 133.08 with a mean of 108.35, that indicates insufficient seat isolation capacity, i.e., < 100. Statistically, the study ascertained a significant influence of average speed and average depth WBV and SEAT responses at a 5% significance level. It underscores the potential efficacy of altering speed and depth parameters to attenuate vibration exposure levels. Further, the effectiveness of the system was tested through the automatic transmission of warning alerts via emails, text messages, and flashing red LED light on the IoT system. This critical feature provides considerable utility for tractor operators to adjust ride settings, ensuring that the ride remains within safe vibration limits. Furthermore, adopting such an advanced warning system in tractor manufacturing signifies a pioneering step towards sustainably enhancing operator well-being.

Exposure to Whole-Body Vibration in Commercial Heavy-Truck Driving in On- and Off-Road Conditions: Effect of Seat Choice.

Trucking is a key industry in Canada with around 180 000 professional drivers. As an industry it has a disproportionately high injury claim rate, particularly for back injuries. Whole-body vibration (WBV) can contribute to the onset and development of low back disorders, and is a well-documented exposure among driving professions. A widely adopted WBV mitigation measure focuses on hydraulic and/or pneumatic passive suspension systems both in the driver's seat and underneath the vehicle cab. Passive suspension 'air-ride' seats are the current industry standard but new technologies such as the electromagnetic active vibration cancelling (EAVC) seats offer potentially substantial improvements in WBV reduction. In this paper, we evaluate and compare four commonly used truck seats (three air-ride, one EAVC) for their vibration damping characteristics and WBV exposure attenuation in on- and off-road conditions. We recruited 24 professional truck drivers who drove 280 km (mixed on-road and off-road) in ore-haul trucks under four different seating conditions. Following the ISO 2631-1 WBV standard, vibration measurements were made on the cab floor and seat pad, and 8-h average weighted vibration (A(8)) and 8-h vibration dose values (VDV(8)) were calculated, as well as the Seat Effective Amplitude Transmissibility (SEAT), and daily vibration action limits (DVALs). These measures were compared between seat types, as well as road conditions. The EAVC seat gave best performance for both A(8) (0.27 m s-2) and VDV(8) (6.6 m s-1.75). The EVAC seat had the lowest SEAT tested (36.2%) and the longest DVAL. However, among the three passive air-suspension seats, two showed significantly reduced A(8) (0.43 and 0.44 m s-2) and VDV(8) (9.1 and 9.3 m s-1.75) exposures relative to the third passive air-suspension seats [A(8) (0.54 m s-2) and VDV(8) (11.1 m s-1.75)]. These differences in exposures among the three passive air-suspension seats resulted in varying DVAL times, with the worst performing seat reaching the DVAL after only 6.3 h of driving. There was also a seat by road type interaction; there were performance differences between the passive air-suspension seats on-road, but not off-road. The observed reduction of the WBV exposures measured from the EAVC seat was consistent with previous results. But we showed that there can also be substantive differences among seats that are the current industry standard. These differences were more evident on-road than off-road, which suggests that more work needs to be done to understand seat performance characteristics, and in matching the correct seat technology to the driving task. We demonstrated that WBV exposures in current industry conditions may exceed health-based exposure limits; this has policy relevance because WBV exposures are linked to prevalent and costly adverse health conditions in a working population that is ageing. Increased WBV measurement collection is recommended to ensure the anticipated exposure attenuations are achieved when seats are relied upon as an engineered control against WBV.

Evaluation and Analysis of Whole-Body Vibration Exposure during Soil Tillage Operation

This study investigated whole-body vibration (WBV) response in real field harrowing operations at different tractor ride conditions i.e., average speed, front harrow pin angle (FHPA), and rear harrow pin distance (RHPD). Taguchi’s L27 orthogonal array was used to formulate a systematic design of experiments. WBV exposure was measured along the three translational axes to compute overall daily vibration magnitude i.e., A(8). Tractor’s seat isolation capacity was assessed in terms of Seat Effective Amplitude Transmissibility i.e., SEAT%. Raw acceleration data was analysed to obtain dominant frequencies using Fast Fourier Transform (FFT). A(8) was found to range between 0.43 to 0.87 m/s2 in the experimental trials. Seat isolation capacity was found to be poor in 89% of the experiments i.e., SEAT% &gt; 100%. Average speed and FHPA was found to have a significant impact (p ≤ 0.05) on A(8) and SEAT%. FFT response showed a range of primary and secondary dominant peaks within a frequency range of 0.2 to 11 Hz. In conclusion, the majority of experimental trials (67%) exceeded the Directive2002/44EU recommended exposure action value (EAV) limit i.e., 0.5 m/s2. The harrowing operation was found to exhibit vibration exposure at low frequencies in the vicinity of natural frequencies of the human body and may consequently affect ride comfort.

Prediction of the driver’s head acceleration and vibration isolation performance of the seating suspension system using the time and frequency domain modeling

Long-time exposure to low-frequency vibration will negatively impact human health.A rapid biodynamic system modeling method has been proposed to study the human body’s response to the low-frequency vibration excitation in the whole vehicle environment. The sensitivity of design parameters of the seating suspension system to the vibration isolation performance will be studied. The dynamic model consists of a lumped parameter mass-spring-dashpot model of seven degrees of freedom (7DOF) and used for the prediction of the head acceleration in the time domain and peak transmissibility ratio in the frequency domain under a sinusoidal wave excitation and random road profile excitations of different road classes and vehicle speeds. A calculation formula has been established to predict the seat effective amplitude transmissibility (SEAT) from the transmissibility ratios and frequency weighting function of the ISO 8606, while the transmissibility ratios can be calculated from the frequency response analysis of the seven degrees of freedom system dynamic equations. The simulation results in the frequency domain have been verified by those in the time domain for the linear system assumption. The change trends of the driver’s head acceleration, SEAT value, and peak transmissibility ratio from the driver’s head to the seat base with respect to the stiffness and damping coefficients of the seat and cushion have been compared with and verified by one another.It is proved that in the vehicle system, individually, reducing the individual stiffness and damping coefficients of the seat structure, reducing the individual seat cushion stiffness, and increasing the individual seat cushion damping coefficient one by one will be able to reduce the driver’s head acceleration, peak transmissibility ratio, and SEAT value from the head to seat base, and improve the ride comfort. Simultaneously reducing the stiffness and damping coefficients of the seat and cushion will be able to reduce the driver’s head acceleration, peak transmissibility ratio, and SEAT value from the head to seat base and improve the ride comfort. The reduction effect of the driver’s head acceleration is more substantial under the Class E road profile of a large profile roughness than that under the other road classes.

A nonlinear seat suspension with high-static low-dynamic stiffness based on negative stiffness structure for helicopter

One of the most important issues for the helicopter pilots is the health risk due to the vibration transmitted to the pilot through the seat. In this article, a seat suspension based on negative stiffness structure is presented to decrease the vibration transmitted to the pilot in both vertical and lateral directions without losing the loading capacity of the system. Here, an integrated model of the suspension–cushion–occupant is derived. To generalize the results of system analysis and its usability in other applications, the impact of parameters on the system performance is studied in dimensionless form. Despite coupling between the lateral and vertical directions, the design parameters of the seat suspension are determined in such a way that the system responds simultaneously as a negative stiffness structure in both directions. The system efficiency in vibration damping is assessed by seat effective amplitude transmissibility and transmissibility criteria. In addition, the whole body vibration and impact of the vibration on the pilot body are evaluated using ISO-2631. To verify the system efficiency in more realistic situation, the simulations are performed using the measured vibration data of a Bell-412 helicopter. The results indicate that the vibration amplitude is decreased by about 45% and 48% in the lateral and vertical directions, respectively. The frequency spectrum comparison of the seat and cabin floor reveals 80% reduction of amplitude in fundamental frequency in the vertical direction, whereas it is about 93% in the lateral direction. Furthermore, the level of pilot’s comfort and perception is improved that demonstrates better riding quality and reduced vibration environment.

Effect of fatigue on muscle latency, muscle activation and perceived discomfort when exposed to whole-body vibration

Whole-body vibration and muscle fatigue have both been shown to delay the trunk muscle reflex response and increase trunk muscle activation, leading to an increased risk of low back injuries. However, the effects of whole-body vibration on previously fatigued trunk muscles have never been tested, despite studies showing that prolonged exposure to whole-body vibration can lead to muscle fatigue. The purpose of this research was to investigate the effects of muscle fatigue on muscle latency, muscle activation and perceived discomfort when exposed to whole-body vibration. The results showed that a fatigued muscle state resulted in increased muscle latency, muscle activation and perceived discomfort, which all escalate the risk of low back injuries. Additionally, the ISO 2631-1 comfort ratings did not increase with fatigue, showing a disconnect between these comfort ratings and the perceived discomfort ratings in a fatigued muscle state. Practitioner summary: When exposed to whole-body vibration, fatigued back muscles result in delayed muscle contraction, higher overall muscle activation and increased perceived discomfort, all of which are known to increase low back injury risk. ISO 2631-1 comfort ratings are unable to increase with fatigue, showing a disconnect with perceived discomfort ratings. Abbreviations: EMG: electromyography; EO: external oblique; IO: internal oblique; LE: lumbar erector spinae; LEO: left externaloblique; LIO: left internal oblique; LLE: left lumbar erector spinae; LTE: left thoracic erector spinae; MVC: maximum voluntarycontraction; REO: right external oblique; RIO: right internal oblique; RLE: right lumbar erector spinae; RTE: right thoracicerector spinae; SEAT: Seat Effective Amplitude Transmissibility; TE: thoracic erector spinae; WBV: whole body vibration

Modelling and simulation of active and passive seat suspensions for vibration attenuation of vehicle occupants

Literature on biodynamic modelling of the occupant in a vehicle associates riders’ comfort with human-seat interaction forces and vibration attenuation capabilities of the suspension system. Though the superiority of active suspension systems over passive ones is well established in literature, quantification of this superiority by using the best possible passive suspension system has not been reported. This work attempts to do this. It integrates a nonlinear cushion seat contact force model and a 12 degrees of freedom two-dimensional seated human body model supported by an inclined backrest with a full vehicle model through the seat suspension system. The passive and active proportional integral derivative suspension system parameters are obtained by simultaneously minimizing the seat effective amplitude transmissibility, cushion contact force and head motion using a multi-objective genetic algorithm in MATLAB-SIMULINK co-simulation. The time responses of cushion contact force, head vertical and fore-aft motion are studied for two road profiles—random and bump. Comparative analyses were also done with regard to internal forces, absorbed power and the effect on vehicle chassis. Human body response to different grades of road roughness and vehicle speeds were investigated. The results establish the clear superiority of the active system in all aspects with rise in suspension travel and acceleration of vehicle chassis in the vertical direction for a random road profile. A parameter sensitivity analysis allowed us to identify spring stiffness as the component which needs greatest care during fabrication.

Attenuation of Mechanical Vibration During Transmission to Human Body Through Mining Vehicle Seats

Operators of mining vehicles are exposed to high levels of whole-body vibration (WBV) and are therefore at risk of developing vibration-related health disorders. For implementing an effective control strategy, it is imperative to locate the source(s) of vibration, and the specific changes that might occur to the vibration signals during its transmission through the seats to the recipient human body. With this objective, Seat Effective Amplitude Transmissibility (SEAT) values of seat modules used in dumpers (n = 10) and other heavy earth-moving machines (n = 11) were evaluated in an iron ore mine. Vibration was measured simultaneously on the seat and on the cabin floor beneath the seat using tri-axial and uni-axial accelerometers. The study aims at determining the quality of seat modules of the transport and non-transport vehicles from the perspective of their natural resonance frequencies and capability of any such seat in reducing harmful vibration. The highest acceleration values were observed in the z-axis for all the dumpers. SEATrms values ranged from 78 to 133% and SEATvdv values ranged from 72 to 130% for the dumpers. For other HEMMs, SEATrms values ranged from 55 to 125% and SEATvdv values ranged from 56 to 123%. Mechanical vibration contains multiple frequency components. To understand the changes taking place to the different signals at these frequencies, 1/3 octave band analysis was carried out for the signals recorded both on the seat and the floor. There was significant attenuation (38 to 57%) at 4 Hz for three Dumper seats, whereas they resonated in the range of 1.6–2.5 Hz. The transmissibility(%) in the resonating frequencies ranged from 108 to 156%. Resonance frequencies for the remaining seven dumpers ranged from 3 to 8 Hz. The spine has been reported to resonate at 4 Hz, whereas resonance at 1.6 Hz has little significance to human beings in regard to WBV of a seated person. Hence, the characteristic resonant frequency of 4 Hz of seats as observed in the present study has the potential of causing adverse impacts on spinal health. Evaluation of SEAT factors and resonance characteristics of seats are therefore recommended to be examined while selecting a mining vehicle for regular deployment in mines.

Parameter identification and robust vibration control of a truck driver’s seat system using multi-objective optimization and genetic algorithm

This paper has developed a 5-DOF driver and seat suspension system model for active vibration control. A novel fast system parameter identification method from vibration measurement data has been proposed for the seat-occupant system based on the multi-objective Genetic Algorithm optimization (GA). This system parameter identification method can identify the seat system parameters of a 5-DOF lumped mass-spring-dashpot biodynamic seat-occupant model from vibration test results quickly and accurately. Without calculation and measurement of materials, the physical parameters of the seat suspension system such as masses (m), stiffness (k), and damping coefficients (c) are estimated through matching the measured resonant frequency and transmissibility amplitude at a specific frequency with the simulated ones. This is one of the main contributions of this paper. The characteristics of the human body vibration in the low-frequency range are analyzed through the seat to head transmissibility (STHT) ratio. The experimental and simulation results of the STHT values have been calculated and compared to verify each other. The sensitivity analysis of the seat effective amplitude transmissibility (SEAT) values over the seat system parameters have been conducted and validated by the measured results of the transmissibility ratios. A full state feedback controller has been developed to reduce the human body vibration in the seat suspension system, which is another new contribution of this paper. The simulation results show that the proposed controller has better vibration attenuation performance than the conventional PID controller.

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.

The effect of posture and vibration magnitude on the vertical vibration transmissibility of tractor suspension system

The efficiency of suspension seat can be influenced by several factors such as the input vibration, the dynamic characteristics of the seat and the dynamic characteristics of the human body. The objective of this paper is to study the effect of sitting postures and vibration magnitude on the vibration transmissibility of a suspension system of an agricultural tractor seat. Eleven (11) healthy male subjects participated in the study. All subjects were asked to sit on the suspension system. Four (4) different sitting postures were investigated – i) “relax”, ii) “slouch”, iii) “tense”, and iv) “with backrest support”. All subjects were exposed to random vertical vibration in the range of 1–20 Hz, at three vibration magnitudes - 0.5, 1.0 and 2.0 m/s2 r.m.s for 60 s. The results showed that there were three pronounced peaks in the seat transmissibility, with the primary resonance was found at 1.75–2.5 Hz for every sitting postures. The “backrest” condition had the highest transmissibility resonance (1.46), while the “slouch” posture had the highest Seat Effective Amplitude Transmissibility (SEAT) values (64.7%). Changes in vibration magnitude for “relax” posture from 0.5 to 2.0 m/s2 r.m.s resulted in greater reduction in the primary resonance frequency of seat transmissibility. The SEAT values decreased with increased vibration magnitude. It can be suggested that variations in posture and vibration magnitude affected the vibration transmission through the suspension system, indicating the non-linear effect on the interaction between the human body and the suspension system.Relevance to industry: Investigating the posture adopted during agricultural activities, and the effects of various magnitudes of vibration on the suspension system's performance are beneficial to the industry. The findings regarding their influence on the human body may be used to optimize the suspension system's performance.

Vibration Behaviour Control of a Fabricated One-Passenger Electric Vehicle with Either Mechanical or Air Suspension

Vehicle vibration transmission associated with the dynamic system depends on the frequency and direction of the input motion and the characteristics of vehicle suspension system and the seat from which the vibration exposure is received. A fabricated one-passenger electric vehicle equipped by a coil spring (mechanical) suspension system is introduced in this study. An air suspension system is used to replace the coil spring suspension system to improve ride comfort performance and intelligent classical adaptive neuro-fuzzy inference system controller is used to control the vehicle seat performance parameters. Accelerometers are mounted on the seat pan and seat base (floor) when measuring vertical acceleration. Data is frequently weighted according to standard BS 6841 in order to model the human response to vibration in terms of location and direction. The Simulink model is developed in Matlab software with the adaptive neuro-fuzzy inference system controller for the vehicle seat weighted vibration acceleration control. The results indicate that the predicted vibration acceleration can track the target vibration acceleration very well. Moreover, the values of the crest factor and kurtosis for the vehicle equipped by air suspension system are lower than those for the vehicle equipped by mechanical suspension system. Furthermore, the seat effective amplitude transmissibility for the fabricated vehicle with air suspension behaves lower value than that for mechanical suspension.

Vibration control of an active horizontal seat suspension with a permanent magnet synchronous motor

This paper describes the control design of an active horizontal seat suspension with an electromagnetic actuator. First, physical and mathematical models of an active vibration reduction system with a seated human body are established. Then, a novel control strategy for the permanent magnet synchronous motor is developed to improve the vibro-isolation properties of the horizontal seat suspension. A multi-criteria optimisation is employed to obtain control system parameters that allow simultaneous minimisation of two conflicting vibro-isolation criteria, i.e. the seat effective amplitude transmissibility (SEAT) factor and the suspension travel. Finally, a laboratory investigation of the effectiveness of the active system is conducted and the dynamic performance of the system is compared with that of a corresponding conventional passive suspension system.

A comparative study of transmissibility factors of traditional and pneumatic dumper seats using one-third octave band analysis

Severity of exposure to whole-body vibration of vehicle drivers depends on multiple factors including type of vehicle suspension or quality of seats. The study presents analysis of seat vibrations of two different types of dumpers in opencast mines. Since health guidance provided in ISO 2631-1997 are only indicative, seat effective amplitude transmissibility factors along with one-third octave-band analysis of vibration signals have been considered as more effective information for control measures. Vibration characteristics of conventional seats ( n = 3) with rigid frame and those with pneumatic suspensions ( n = 3) have been compared during their use in mines. A(8) values ranged from 0.66 to 1.41 m/s2. All the six operators had shown moderate to higher health risk but this may vary since both intensity and durations of exposure frequently change during the operators’ employment. Vibration signals from a mono-axial accelerometer (z′) placed on the cabin floor was captured in addition to three channel vibration data (x, y and z) of a seat pad accelerometer placed on the vehicle seat. Transmissibility analysis of vibration signals from cabin floor to seat surface showed that the three pneumatic seats resonated in the range of 1.6–2.5 Hz in the z axis. There was significant attenuation of vibration energy ranging from 37% to 63% at 4 Hz which is important in the context of spinal injuries. The seat effective amplitude transmissibility values (%) in the resonating frequencies ranged from 119% to 173%. Interestingly, the conventional seats resonated at 4–5 Hz and the corresponding seat effective amplitude transmissibility (%) values were varying from 128% to 163%. This resonance at 4 Hz is in sharp contrast with the behaviour of pneumatic seats. It is recommended that vibration transmissibility should be considered as a major design parameter for mining vehicle seats.

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.