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The capability to smooth down the road imperfections affects both the comfort and the road holding of the vehicle. Improving comfort means, basically, limiting the vertical acceleration fluctuations of the vehicle body and hence of passengers. Improving road holding means, among other things, limiting the fluctuations of the vertical force that each tire exchanges with the road. In this chapter suitable models for improving the comfort and/or the road holding of the vehicle are developed. Quite interestingly, it is shown that a well tuned vehicle should have proportional damping, although it appears that this aspect is not commonly taken into account in traditional vehicle dynamics. The benefits of inerter in a Formula car are also discussed in detail.

The topic of reducing structural vibrations in the case of flexible carbodies of railway vehicles has been intensively studied, but it is still an active research topic thanks to the importance of the perspective of improving the ride comfort. However, no study has been identified in the specialty literature to feature the contribution of the vibration structural modes upon the vibration behaviour of the railway vehicle carbody. The structural vibration modes of the flexible carbodies are particularly complex, however, the first vertical bending mode holds great significance in terms of the ride comfort. This paper analyses the influence of the first vertical bending mode on the vibration behaviour in three reference points of the railway vehicle carbody in correlation with the carbody flexibility, the vehicle velocity and the suspension damping. This study relies on comparisons between the results of the numerical simulations obtained for a ‘flexible carbody’ type model of the vehicle and the ones obtained for a ‘rigid carbody’ type model. The first part of this study analyses the characteristics of the vertical vibrations behaviour of the flexible carbody based on the dynamic response of the vehicle and expressed as the acceleration power spectral density. In the second part, the influence of the vertical bending on the vertical vibrations level of the carbody is analysed using the root mean square of the vertical acceleration.

O objetivo deste trabalho foi obter o Índice de Irregularidade Internacional (IRI) de pavimentos sobre pontes utilizando smartphones, estes equipados com acelerômetros, possibilitando a aquisição de dados de aceleração e a determinação da irregularidade através de procedimentos numéricos, consistindo na dupla integral dos dados de aceleração vertical. Foram realizadas medições em três pontes, por meio de um veículo percorrendo as mesmas, equipado com dois telefones móveis diferentes com taxa de aquisição de 100 Hz. Um dos dispositivos foi disposto no interior do veículo e outro na bandeja do sistema de suspensão. Utilizou-se outra abordagem, o Método de Nível e Mira, para a calibração da medição do tipo resposta nas pontes. As conclusões mostram uma boa convergência entre os métodos apresentados para obtenção de perfis de superfície de pontes, demostrando bom indício do uso dos smartphones como método alternativo simples e econômico, revelando fácil operação e boa produtividade.

Acceleration of a vehicle is composed of three components: longitudinal, lateral, and vertical acceleration. Longitudinal and lateral accelerations have been frequently considered as components for investigating driving behaviour, with the aim of improving road safety. But in particular situations during the motion of the vehicle, also vertical acceleration is relevant. In this paper, the authors want to demonstrate that vertical acceleration is also a relevant parameter to be considered in terms of road safety. The authors focus on the difference registered by considering only lateral and longitudinal acceleration and by considering also vertical acceleration in the analysis of driving behaviour through real tests on the road. All the parameters were registered through a global positioning system (GPS) device and a tri-axial accelerometer, which allow the geo-referenced kinematic parameters of the vehicle to be detected. For this purpose, over 110 tests covering about 600 kilometers were completed. All the experimental surveys were conducted in a good weather condition, under dry road pavement conditions, on weekdays, during day time and out-of-peak hours, in order to have no influence from the traffic flow. Each path was repeatedly run by the driver in order to collect the instantaneous speed and acceleration along the pattern. During the tests, about 40,000 instantaneous values of vehicle position have been registered. The survey interested a segment of the Italian National road n.107 (S.S. 107), in Southern Italy. The authors found that by considering vertical together with longitudinal and lateral accelerations, a higher number of unsafe driving conditions can be identified. More specifically, the proposed methodology allows 20% extra of dangerous driving conditions to be registered. For this reason, the authors retain that also vertical acceleration should be considered in the definition of the safety domain, because it determines the intensity of the exchange forces between the tires and road pavement, and in some cases, it leads to a loss of friction. Definitively, the authors retain that vertical acceleration is not only useful as indicator of comfort on board, but it has an important role also in terms of road safety.

A raised crossing (RC), as an alternate to the current form of level crossings to minimise risks of wheel-rail contact failure under frontal collision of trains onto stuck trucks, has been recently formulated by the authors (Engineering Failure Analysis, 80 (2017) 403–415) to mitigate the severity of accidents at road-rail crossings. The aim of the present paper is to assess the effectiveness of the profile of the RC to minimise the risk of speeding through and minimise the peak vertical acceleration of the passing road vehicle below the threshold level for discomfort and safety of its occupants. For this purpose, a simplified two-dimensional multibody dynamic simulation modelling method has been formulated and validated using a detailed three-dimensional industry standard model. The validated model has then been used to optimise the geometric profile of the RC by minimising the peak vertical accelerations of the occupants below the safety threshold of 0.7 g. It is shown that the optimised profile of the RC increases the peak acceleration with the increase in speed of travel of the road vehicles whilst the LC does the opposite. This finding confirms that the RC has the potential to reduce the risk of speeding, which is vital to the safety of the train and road vehicles at rail – road crossings.

One of the criteria adopted by the Word Bank with the aim of defining the economic level of a country is represented by the condition of the road pavements. To ensure adequate road pavement quality, road authorities should be continuously monitoring and repair the detected anomalies. To fast solve problems associated with poor quality of road surface such as comfort or safety, the presence of distress must be detected quickly. The high-performance pavement distress detection, such as those base on the image processing or on the laser scanning, is very expensive and does not allow to the road administration to conduct the appropriate monitoring campaigns. To solve these problems, the paper describes the pave box methodology, an innovative and immediately operational distress detection approach based on the exploitation of data collected by the black boxes located inside the vehicles that routinely pass on the road network. Data processing and the algorithms used in the post-processing evaluation of the vertical acceleration were compared with existing visual surveys procedures such as PCI. Two different indices have been proposed to detect and classify both the local damages and the global condition of the entire road. Pave box provides a robust evaluation of the pavement condition that allows to detect all the severe distress and not less than 70% of the minor damages on the pavement surface. The proposal is characterized by low time and cost consumption and it represents an effective tool for road authorities.

In marine environments, ships are bound to be disturbed by several external factors, which can cause stochastic fluctuations and strong nonlinearity in the ship motion. Predicting ship motion is pivotal to ensuring ship safety and providing early warning of risks. This report proposes a real-time ship vertical acceleration prediction algorithm based on the long short-term memory (LSTM) and gated recurrent units (GRU) models of a recurrent neural network. The vertical acceleration time history data at the bow, middle, and stern of a large-scale ship model were obtained by performing a self-propulsion test at sea, and the original data were pre-processed by resampling and normalisation via Python. The prediction results revealed that the proposed algorithm could accurately predict the acceleration time history data of the large-scale ship model, and the root mean square error between the predicted and real values was no greater than 0.1. The optimised multivariate time series prediction program could reduce the calculation time by approximately 55% compared to that of a univariate time series prediction program, and the run time of the GRU model was better than that of the LSTM model.

Many haptic devices are currently being developed for human upper limbs. There are various types of force feedback devices for upper limbs, such as desktop and wearable type. However, the lower limbs absorb most of the force when standing or walking. Therefore, to render the sensation of force to the lower limbs, a device worn like a shoe to enable users to walk and have a wide range of movement and a device that provides a dropping sensation have been developed. However, both wide-area movement and a dropping sensation could not be combined in one device. Therefore, the authors propose the concept of a lower limb force feedback device that allows the user to wear it like a shoe and provides the sensation of dropping while enabling wide-area movement. In addition, as the first stage of device development, the authors evaluated the human sensation of dropping. Consequently, it was found that a relatively high sensation of dropping can be provided to a human even with an acceleration smaller than the gravitational acceleration in real space. Thus, the lower limb force feedback device to be developed in the future will allow the user to experience the sensation of dropping by using an acceleration smaller than the gravitational acceleration in real space.

Technological evolution impacts several industries, including automotive. The combination of software with advancements in sensory capabilities results in new Advanced Driver Assistance System (ADAS). The pervasiveness of smartphones and their sensory capabilities makes them an solid platform for the development of ADAS. Our work is motivated by concerns on the reliability of data acquired from such devices for developing ADAS. We performed a number of controlled experiments to understand which factors impact the collection of accelerometer data with smartphones. We conclude that the quality of data acquired is not significantly affected by using different smartphones, car mounts, rates of sampling, or vehicles for the purpose of developing ADAS. Our results indicate that smartphone sensors can be used to develop ADAS., Research sponsored by the Portugal Incentive System for Research and TechnologicalDevelopment. Project in co-promotion no. 002797/2015 (INNOVCAR 2015-2018).

Growing interest in zero emission transport modes, such as cycling, is currently generating motivation to construct new cycle paths. However, transportation planners and managers cannot always rely on practical methods for allocating the resources (often limited) needed for inventories and assessing cycling infrastructures. The aim of this study is to develop a method for classifying cycle paths in terms of roughness and general conditions of the pavement surface. Inventory data and information regarding the infrastructure conditions were collected on-site using video recordings taken by an action camera directly mounted on a bicycle. Georeferenced vertical acceleration data were collected using a smartphone. Acceleration data of three different pavement surfaces (asphalt, concrete and concrete bricks) were registered. The results showed the lowest acceleration values for concrete pavement and the highest values for interlocking concrete pavement. The proposed method can be a practical and efficient approach to evaluate cycling infrastructures in terms of pavement condition.

In the structural health monitoring for railway crossings, identifying the condition stages of the crossing elements is an important step for the crossing condition assessment. This paper presents the condition stages identification procedure using the multi-body system method. This study is carried out on the 1:9 crossings that are most commonly used in the Dutch railway and suffering a lot from damages. By introducing different types of damage into the vehicle-crossing model and compare the dynamic responses with the measurement results, the condition stages of the monitored crossing can be identified. The simulation results show that the development of vertical irregularity and clip damage are clearly reflected on the change of wheel-rail contact force and the rail vertical acceleration. The findings of this study can be further applied in the structural health monitoring (SHM) system for railway crossings developed by TU Delft.

A SWATH ships is one of the attractive variants for solving the problem of providing high seaworthiness at small sizes. At the same time, the question of estimating the size limits of such platform takes place, at which the SWATH vessel will have an advantage not only in seaworthiness, but also in the efficiency of the tasks assigned to it. To carry out such an analysis, several variants of a SWATH platform were studied, and their navigability and operational qualities were analyzed. The following indicators were used as the main indicators: vertical acceleration of gravity, indicator of comfort MSI, slamming probability. For each of the variants of the platform with a small waterline area, the characteristics of navigability and operational qualities were taken. As a result of research, the authors created two variants of SWATH type platform. For each of the variants of the platform with a small waterline area, the characteristics of seaworthiness and operational qualities were received, as well as the constructive safety calculation.

The development of a methodology that enables the optimization of passive suspension system parameters, providing a group of optimal solutions, could be an excellent approach to obtain a fast improvement tool during the design of suspension systems. Thus, this paper proposes a methodology for the multi-objective optimization of the passive suspension system of a full-car model travelling in a random road profile. For this purpose, a numerical-computational routine is developed, which integrates the NSGA-II with the vertical dynamic analysis, in the time domain, of an eight degrees-of-freedom vehicle model with a seat. Three objective functions, which take into account passenger comfort and safety, are considered. The proposed methodology provides a Pareto-optimal front, which consists of a set of non-dominated solutions that minimize the three objective functions. Comparing the results of the dynamic analyses of the vehicle model with optimized and non-optimized suspension systems, it was verified that the optimization allowed a reduction of up to 21.14% of the weighted RMS value of the driver seat vertical acceleration, a parameter directly related to comfort, while maintaining or improving the trade-off with safety. The Pareto-optimal front has proven to be an excellent support tool to aid the designer in the determination of the parameters that best fit the suspension system to produce the desired dynamic behavior in vehicles. Thus, the proposed optimization methodology can be recommended as an effective tool for the optimal design of passive suspension system parameters. Finally, this work shows that the design of suspension parameters can be done taking into account passenger comfort and safety at same time.

Accurate soil mapping is critical for a highly-automated agricultural vehicle to successfully accomplish important tasks including seeding, ploughing, fertilising and controlled traffic, with limited human supervision, ensuring at the same time high safety standards. In this research, a multi-sensor ground mapping and characterisation approach is proposed, whereby data coming from heterogeneous but complementary sensors, mounted on-board an unmanned rover, are combined to generate a multi-layer map of the environment and specifically of the supporting ground. The sensor suite comprises both exteroceptive and proprioceptive devices. Exteroceptive sensors include a stereo camera, a visible and near infrared camera and a thermal imager. Proprioceptive data consist of the vertical acceleration of the vehicle sprung mass as acquired by an inertial measurement unit. The paper details the steps for the integration of the different sensor data into a unique multi-layer map and discusses a set of exteroceptive and proprioceptive features for soil characterisation and change detection. Experimental results obtained with an all-terrain vehicle operating on different ground surfaces are presented. It is shown that the proposed technologies could be potentially used to develop all-terrain self-driving systems in agriculture. In addition, multi-modal soil maps could be useful to feed farm management systems that would present to the user various soil layers incorporating colour, geometric, spectral and mechanical properties.

This study investigated generation of random road surface profile by Matlab software based on international standard ISO 8608 and applying this random road surface profile to evaluate motion comfort effect on passenger traveling by sleeper coach. The comfort indicator is determined by Root Mean Square (RMS) vertical acceleration indicator determined according to evaluation of ISO 2631-1 criteria. Evaluation model of sleeper coach is full car model, the model has eight degrees of freedom. The solve method is digital method with Matlab application software to appraise result. The results are shown the level of comfort at all different position of sleeper seat.

The trimaran has excellent navigation and high-speed performance. Fast ferries and transportation vessels have adopted the multi-hull design. However, when the trimaran navigates under high speed, the heave and pitch motions need to be restraint. The vertical acceleration will cause severe seasickness of passengers, and can lead to short-term mechanical failure which bring a threat to the structural safety of the ship. T-foil is an effective appendage to improve the seakeeping performance of trimaran. This paper focuses on its motion reduction performance on a fore-outrigger trimaran. Three different ship models are used in the towing tank experiments, including a bare hull, a hull with non-controlled T-foil, and a hull with an active controlled T-foil. The heave, pitch and acceleration responses of the trimaran in waves are measured in the towing tank. Through the comparison among the different experimental conditions, the efficacies of the non-controlled and controlled T-foil are reported and discussed.

The paper analyzes the effects of vibrations on allowable vibration exposure time in intercity bus users for the criterion of reduced comfort according to the ISO 2631/1985 standard. The analysis was carried out using a validated spatial oscillatory model of 65 degrees of freedom (DOF) built in the ADAMS/View module of the MSC.ADAMS package. Simulation results revealed that passengers on the bus front and rear overhang have very short allowed exposure time. In order to extend the exposure time, by using Design of Experiments (DOE) analysis, new oscillatory parameters for passengers' seats are proposed. With new oscillatory parameters, the exposure time is significantly extended for the assistant driver and passengers on the front and rear bus overhang. For the passenger on the last row seat, power spectral density of weighted vertical acceleration is of lower intensities even at frequencies above 4 Hz. Relevance to industry: Bus users (passengers and drivers) are exposed to harmful effects of vibrations. Vibrations influence comfort, work ability, and if increasingly intense can affect human health. Allowable vibration exposure time referring to oscillatory comfort has a particular importance for intercity bus' passengers when traveling longer distances. Vibration time could be extended by proper selection of seat oscillatory parameters. Results of such an analysis can significantly help bus manufacturers and designers in order to improve ride comfort for bus' passengers.

SAE Mini Baja competitions require efforts in developing a reliable vehicle project that enables their teams to manage time and resources wisely. Vehicle simulations are one the best ways to deal with these conditions and prevent failure during a test. This work outlines the methodology that was carried out for validating the multibody dynamics model of a Mini Baja vehicle through vertical acceleration data acquisition. The data was acquired with the vehicle in different sets of obstacles, based on those seen in previously held competitions. Simulation was done through ADAMS/Car, with the vehicle’s multibody model being simulated in different three-dimensional roads, counterpart to those where data acquisition took place. Simulation data, when compared to acquired acceleration signals for most of the obstacles, exhibited equivalence. Additional data computation revealed that the spectra in the frequency domain presented most severe loads concentrated between 0 and 20 Hz, incoming mostly from road unevenness. Gathering such data, by the presented approach can assist future analyses and guide the Baja Team in defining an improved project by predicting its dynamic behavior. http://dx.doi.org/10.18226/23185279.v6iss1p29

Inertial measurement units (IMUs) have been extensively used to detect gait events. Various methods have been proposed for detecting initial contact (IC) and toe-off (TO) using IMUs affixed at various anatomical locations. However, the accuracy of such methods has yet to be compared. This study evaluated the accuracy of three common methods used for detecting gait events during jogging and running: (1) S-method, in which IC is identified as the instant of peak foot-resultant acceleration and TO is identified when the acceleration exceeds a threshold of 2g in the region of interest; (2) M-method, in which IC and TO are defined as the minimum before the positive peak shank vertical acceleration and the minimum in the region of interest, respectively; and (3) L-method, in which IC is indicated by the instant of peak pelvis anteroposterior acceleration and TO is identified by the maximum in the region of interest. The performance of the IMU-based methods in detecting IC and TO and estimating stance time (ST) were tested on 11 participants at jogging and running speeds against a reference provided by a force-platform method. The S-method was the most accurate for IC detection (overall mean absolute difference (MAD): 4.7 ± 4.1 ms). The M-method was the most accurate for TO detection (overall MAD: 7.0 ± 3.5 ms). A combination of M- and S-methods, called the MS-method, was the most accurate for ST estimation (overall MAD: 9.0 ± 3.9 ms). Thus, the MS-method is recommended for ST estimation; however, this method requires four IMUs for bilateral estimation.

In this paper, vertical motion (heave, roll, and pitch) state estimation and control simulation are performed by using the LQG approach. Cummins’ equation is used to represent the mathematical model of 3DOF ship motions. A passenger ship in irregular bow quartering waves at the Froude number of 0.45 is considered during the simulations. Two pairs of foils which are located on the bow side of the passenger ship are used as actuators. First, the results of the uncontrolled simulation case are presented to show the reliability of the mathematical model. Then, all states are estimated by measuring only velocity signals based on LQE design. Finally, the LQG approach is applied to mitigate the vertical motions and accelerations by taking feedbacks from only easy-measurable velocity signals. LQG results are compared with LQR results as well. Results showed that the implemented LQG approach reduced the bow motions and accelerations up to approximately 40%.

Slab arching is one of the most common damages of the slab track system in Chinese high-speed railway, which causes the instability of the track structure, changes the wheel-rail dynamic characteristics, and even affects the safety. Therefore, to prevent the occurrence of the above problems, the first important step is to detect the slab arching in advance. There have been some detection methods for slab arching, but it is difficult to detect the arching under different degrees, especially for the arching in the early stage. Aiming at the current situation, this paper proposed an arching detection method based on the dynamic responses of the car body. Integrated the analytical mode decomposition and continuous wavelet transform, the arching-induced characteristics in the car body vertical acceleration data, calculated by the vehicle-track finite element model, were found. After that, the measured data from different inspection areas were used for arching detection based on the discovered characteristics. The results showed that the amplitude of the component of the wavelength from 4 m to 6 m of the car body vertical acceleration could be used for slab arching detection. The method has good adaptability to different arching degrees. In practice, the proposed method can be used to detect slab arching, thus guide scientific maintenance.

The movement of the vehicle is mainly determined by the processes that occur at the interaction between the tread and the tire. Knowledge of the tire behavior under the effect of external loads is very important to study the dynamics of the vehicle, and the operating behavior of the tire in movement affects the reliability, the comfort of the occupants, as well as the economy of the motor vehicles and tread wear. Force and the power losses occurring at the contact patch between the tire and the road is very difficult to detect experimentally. This paper aims to estimate the necessary power need to overcoming the rolling resistance forces of a passenger car for different loads and constant tire pressure using the simulation program IPG CarMaker. The chosen vehicle is one with rear-wheel drive, and the chosen route is a route with cones. The computer simulation was done for the car’s curb weight and the for the total weight of the car. The measurement was made on the right rear wheel of the car. The car accelerates uniformly up to a constant speed of 80 km/h at the entrance in the cone zone. The car has performed slaloms through offset cones. The paper follows the influence of the vertical acceleration on the power required to overcoming the rolling resistance force for the two cases of vehicle load and the vehicle speed influence on the power required to overcoming the rolling resistance force.

When a road and rail intersect, a level crossing (LC) is a cheaper alternative to over or under pass infrastructure. Australia currently has approximately 20,000 LCs; annually 37 deaths on average occur mainly as a result of the road vehicles failing to obey warning signals. In this research, it is hypothesised that the current design of LC does not deter the road vehicle drivers from accelerating through the crossing, whilst a raised crossing consisting of ramps and recesses to house the rails would. This hypothesis is proved as valid through a multi-body dynamic simulation modelling method applied to a road vehicle passing through a raised crossing at various speeds. The efficacy of the raised crossing is demonstrated through numerical examples that show increase in the speed of the road vehicle reduces the vertical acceleration of the driver cabin in a LC whilst the same increases the raised crossing. Where the road vehicles fail to stop and subsequently impact a running train laterally or being impacted by a train longitudinally, the derailed wheelsets impact the sides of the recesses in the raised crossing and thereby mitigating the adverse effects of the crash. This paper summarises the train-vehicle collision induced derailment process and presents the maximum impact force time series obtained from various simulations. Finally, structural design options for the raised crossing to resist the impact forces have been explored using an explicit finite element modelling.

Zero fatalities in road transport and overall traffic safety is one of the most important common goals of the society, industry and academia. To achieve this goal, various researches in different fields, from the analysis of the materials and designs to the development of autonomous ground vehicles, are being done. Respectively, vehicle suspension and shock absorbers are essential elements, which significantly contribute to the oscillations of sprung and unsprung masses, also to the handling and braking characteristics of a vehicle, i.e. they affect the safety of the vehicle. Due to this reason, in this work, an experimental research on the condition of the shock absorbers of light vehicles, when applying the original research methodology, is presented. The performed experimental research is based on two stages. Firstly, the condition of the shock absorbers of the researched vehicles was determined by using a shock absorber test stand. Secondly, equipment was installed in the test vehicles, which measures the vertical acceleration values of the vehicle body, when it drives over an obstacle at low velocities. Based on the performed analysis of the experimental results, vertical acceleration values of the sprung masses of vehicles were indicated, which allows to simply and effectively evaluate the condition of the vehicle shock absorber, without a complex investigation of the shock absorber.

Vehicle suspension system is an important part to minimize the vibration of the vehicle caused by road unevenness. Ideal conditions would be difficult to obtain, especially in rural areas with uneven road conditions. Analysis of passive suspension system in this study is expected to explain the level of comfort in riding Rural Multipurpose Vehicles. Full car modelling with 1 DOF riders used in this study, simulated using numerical simulation software. Excitation roads used in the form of a sinusoidal wave with an amplitude of 0.05 m and a wavelength of 0.5 m. Analysis carried out on the comfort of the vertical acceleration response received driver’s head. Based on the simulation results showed that by using a constant speed between 20-40 km / h, the vehicle will be comfortable driving for more than 2.5 hours., Sistem suspensi kendaraan merupakan bagian penting untuk meminimalisasi getaran pada kendaraan yang diakibatkan ketidak rataan jalan. Kondisi ideal tentunya akan sulit didapatkan, apalagi di daerah pedesaan dengan kondisi jalan yang tidak rata. Analisa sistem suspensi pasif pada penelitian ini diharapkan dapat menjelaskan tingkat kenyamanan dalam mengendarai Kendaraan Multiguna Pedesaan. Pemodelan full car dengan 1 DOF pengendara yang digunakan pada penelitian ini, disimulasikan menggunakan software simulasi numerik. Eksitasi jalan yang digunakan berupa gelombang sinusoidal dengan amplitudo 0,05 m dan panjang gelombang 0,5 m. Analisa kenyamanan dilakukan pada respon percepatan vertikal yang diterima kepala pengendara. Berdasarkan hasil simulasi didapatkan bahwa pada dengan menggunakan kecepatan konstan antara 20 – 40 km/jam, kendaraan akan nyaman dikendarai selama lebih dari 2,5 jam.

While it is well known that the gap between twin-box decks is a key design variable that impacts the onset flutter velocity of a bridge, further research is required to ascertain how modifications in several bridge design variables affect other aeroelastic responses. This paper utilizes aero-structural optimization techniques for the design of long-span bridges with short gap twin-box decks considering simultaneously structural, flutter and buffeting constraints. The optimization helps to reduce the material volume of the structure while maintaining all the performance and safety requirements below the imposed thresholds. It has been found that the geometry of the individual box cross-section is an important feature for the control of the buffeting response, particularly the vertical acceleration. On the other hand, flutter and torsional buffeting constraints require designs with larger gap distance and alternative box geometries, leading to a trade-off between conflicting design demands. Hence, depending on the expected wind load conditions and the specific requirements of a particular project, an optimum aero-structural bridge design with a particular deck shape can be identified. The framework presented in this study is an effective tool to achieve sustainable and safe bridge designs that seeks a most efficient balance between all the design constraints.

Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.

For developing countries like Timor-Leste, regular road surface monitoring is a major challenge not only for maintaining road quality but also for national plan of road network construction. In Timor-Leste nearly 50% of roads are still unpaved. For this reason, an automated system is required to do a survey of paved and unpaved roads. In this study, we present a new approach for the use of smartphones sensor to classify paved and unpaved roads, and anomaly detection. Although, the most remarkable factor to differentiate paved and unpaved road is based on amplitude of the vertical acceleration, each vehicle has a different type of suspension system. Therefore, we used high-dimensional features and state-of-the-art machine learning techniques to make the system robust for differences of vehicle and also smartphone type. This study divided into two stages such as paved and unpaved road classification and road anomaly detection such as pothole and bump. For paved and unpaved road classification, we tried to use the SVM, HMM and ResNet and compared the performance of these models. Of all comparison, the ResNet was the best choice in this study, because it outperformed the SVM and HMM on the all performance evaluation criteria. Furthermore, the KNN and DTW are applied for anomaly detection on the paved road. The KNN-DTW are also compared to the other machine learning techniques like SVM and classical KNN using same criteria. As a result of the comparison, the KNN-DTW and SVM performed better than classical KNN.

Flight turbulence is a non-ignorable risk during flying, and its timely detection and prediction are greatly important for avoiding safety accidents. Currently, flight turbulences are detected simply by the measured vertical acceleration value, or reported by the pilots after a flight. All these means or criteria are relatively not substantial, either persuasive or scientific enough. In particular, the turbulence data reported traditionally is far from sufficient for analyzing this kind of events in depth. On the other hand, the QAR data collected, which is characterized by completeness, high accuracy, real-time and fine-grained time-series, can provide a much better data source for flight safety studies. With it, flight turbulences could be detected in real-time via the random forest method. Results show that the detection model can effectively identify flight turbulence within an acceptable tolerance. The different degrees of attribute importance reveal the spatio-temporal aggregations of flight turbulences. This will provide pilots with warning of flight turbulence in real-time to reduce flight risk. In addition, this study also provides important references for flight routing and schedule planning.

This article proposes a new adaptive control algorithm for active suspension systems of passenger cars. It combines a proportional–integral–derivative controller for suspension deflection together with a sliding mode reference conditioning outer loop that uses the vertical acceleration of the car body as a complementary source of control. The proposed approach is software-based and allows setting up limit values to critical variables, such as the vertical acceleration, which can be directly tuned by the system designer to range from the original proportional–integral–derivative response to other ones with tighter control on the constrained variable. A longitudinal half-car system subject to irregular excitation from a road surface is used for assessment. The proposed proportional–integral–derivative with sliding mode reference conditioning is compared to the same proportional–integral–derivative controller without the outer conditioning loop, as well as with a passive suspension system. International standards on overall vibration magnitudes are used to quantify the differences obtained in this assessment. Results obtained from the proposed control system show better performance and handle trade-offs, improving the ride comfort without adversely affecting the road holding of the car. Fil: León-Vargas, Fabian. Universidad Antonio Nariño; Colombia Fil: Garelli, Fabricio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Zapateiro, Mauricio. Edma Innova; España

The paper describes an algorithm to detect wheel flat defects by measuring the vertical acceleration on the axle-box. The algorithm operates in the time domain and it is suitable to define an index to discover the presence of wheel flats at the early stage and to estimate the severity of the problem. In order to verify the algorithm both numerical simulations and experimental tests have been performed on a freight vehicle. The results show that the wheel flat index proposed in this work is able to detect small flats and to estimate its severity. The algorithm has been integrated on a monitoring system for onboard application and it has been developed in order to be able to run on a light hardware architecture.

Monitoring the status of infrastructural networks along their service life is fundamental to ensure a safe and good service quality. Due to the length and extension of infrastructures, it is fundamental to develop effective and low cost approaches that can allow a continuous monitoring. In this paper, an assessment method based on the ride comfort evaluation inside vehicles according to ISO 2631 (i.e. frequency weighted acceleration) was developed and tested on an Italian railway. In particular, the frequency weighted acceleration was calculated along the whole trip between two consecutive stops. In order to identify and localize the most critical areas along the traveling path, the vertical frequency weighted acceleration was also calculated for sub-sections of fixed lengths (i.e. 10 m) and then mapped on geographic information systems (GIS). In this way, it is also possible to determine, for example considering a railway infrastructure, whether the eventual discomfort may be due to localized irregularities or due to the passage on worn switches. Once proper threshold limit values are defined, early interventions can be planned in order to restore adequate comfort and safety levels. To test the proposed procedure, it was applied to a surface metropolitan railway characterized by an automatic guide, which granted the chance of evaluating the repeatability of the present approach. During the in-situ measurements, an inertial measurement unit (IMU) integrated together with a GPS receiver was used.

Recently there is a worldwide trend to transform the heavy troops into more agile and deployable forces. These forces are based on light armored multi-wheeled combat vehicles which are demanding several challenging requirements. Furthermore, the design of suspension system of these vehicles is complex and should provide several conflicting issues such as higher mobility and cornering stability whilst maintaining a sufficient ride comfort for the crew. This paper presents a comprehensive investigation of the ride response of a typical combat vehicle in pitch-bounce plan under the effect of random road excitation. A set of mathematical passive suspension models for the vehicle with different configurations including two-axle, three-axle and four-axle are derived. The numerical simulation is carried out through the MATLAB/SIMULINK environment which aids the future development of controllable suspension systems. The ride responses of the vehicle is obtained and analyzed considering the vibration isolation, suspension deflection, and road-holding. The results show an improvement in the responses of vehicle body vertical acceleration, pitch acceleration anddynamic tire load using four-axle vehicle configuration over three-axle and two-axle ones.

In previous Footbridge Conferences, the focus of researchers has been on the representation of pedestrian actions (vertical and lateral) to design footbridges, on the proposal of methodologies for the analysis in service of these structures and on the description of the serviceability response of particular footbridges. Nonetheless, none of these research works have been focused on the magnitude of the serviceability response of footbridges according to its structural type. This paper characterises the response of footbridges with stayed cables as main structural type. Based on a compiled dataset of cable-stayed footbridges (developed for this research work), the paper presents the geometrical and structural characteristics of a footbridge that can be regarded as representative of this structural type. Considering the best methodologies available for the assessment of its response in vertical and lateral direction, the paper describes the magnitude of the serviceability performance of this bridge under a wide range of pedestrian scenarios. This description familiarises designers at early stages of their design with the order of magnitude of the serviceability response of cable-stayed footbridges with an arrangement similar to that commonly used for this structural type.

Pilots’ operation performance is closely correlated with flight safety, particularly in the final landing phase. The main purpose of this study is to develop a flight landing operation performance evaluation system based on flight data and a risk evaluation model. In this model, 3 flight parameters, including landing touchdown distance, vertical acceleration, and pitch angle of each flight, were used to objectively evaluate the performance of flight landing operations. The system is expected to be used to evaluate, analyze, and pre-alarm the performance of the landing operation of the pilot after the flight task, to provide practical technical support for airlines to monitor and control landing risk, and to provide a more accurate and objective basis for an airline’s performance rewards and punishments.

The evaluation of speed loss is the most important studies in the optimal ship routing. However, the mode of speed loss during rough sea voyages is complicated because of the involvement of the human factor. A speed loss analysis is conducted to improve the accuracy of evaluation of measured data extracted from actual marine conditions. First, the conventional criteria to judge the deliberate speed reduction is summarized with the conventional ship maneuvering techniques. Second, a nationwide questionnaire for marine engineers implemented for engine safety during rough sea voyages is detailed. Third, these conventional criteria are validated by analyzing the collated data on accelerations, ship motions, navigation, and engine parameters. The limiting value of vertical acceleration agrees with that obtained via practical measurements. On the contrary, the limiting values of lateral acceleration, roll motions, probabilities of deck wetness, and slamming do not agree with that obtained via measurements. The probabilities of deck wetness, slamming, and propeller racing start to increase at approximately the same instant where the deliberate speed reduction occurs. Some relations between the deck and engine parameters detailed in this paper were found to be highly correlated. Finally, the results of the analysis were used to model simpler estimations.

In this paper, based on the acceleration signal acquired by a single triaxial acceleration sensor worn at the bottom of the finger, an algorithm for recognizing the daily movement behavior of the human body is proposed. The algorithm converts the three-axis acceleration into the resultant acceleration, horizontal acceleration and vertical acceleration, and extracts the features from them. The 37 features are sorted by the F-score as a measure of the importance of the feature, and a subset of features that meet the application requirements is found. Model training is performed on the feature subset using multi-class SVM to obtain the final classification model. Experiments show that the model has high recognition accuracy and the accuracy can reach 93.17%.

The article proposes a phenomenological model of a passenger car. The model includes the biomechanical model of human bodies in the sitting position of Muksian and Nash acting as passengers, while the driver’s weight has been reduced to the concentrated weight of the loading seat. The research carried out in this study consisted of passing the vehicle through a transverse obstacle along the so-called speed bump. Vehicle passes through the threshold at three different speeds: 10km/h, 20km/h, and 30km/h. The purpose of the conducted experiments was to initially estimate the values of accelerations acting especially on the passenger at selected driving speeds. On the basis of conducted tests, it was possible to verify the numerical model of the vehicle overcoming the obstacle on the road. This approach allows the use of the proposed model to verify the forces and accelerations affecting the passenger, specified before any selected specific biomechanical model of the human person, for example, a model of pregnant women in this configuration allows us to estimate the forces and accelerations acting on the embryo while overcoming some obstacles on the road.

This paper presents ride comfort and driving stability performances of electronic control suspension (ECS) equipped with controllable electrorheological (ER) damper and appropriate control strategy. In order to achieve this goal, a cylindrical type ER damper which is applicable to Macpherson strut type suspension of a mid-sized passenger vehicle is designed and manufactured on the basis of the required damping force level of an existing passenger vehicle. After experimentally evaluating the field-dependent damping force and dynamic characteristics of the controllable ER damper, ECS consisting of sprung mass, spring, tire and controller is established in order to investigate the ride comfort and driving stability performances. On the basis of the governing equation of motion of the suspension system, five control strategies (soft, hard, comfort, sports and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in both time and frequency domains under various road conditions. In addition, a comparative work is undertaken to investigate inherent control characteristics of each control strategy.

The feasibility of a preview control is examined for tracked vehicle’s suspension systems to improve the performance of tracked vehicle systems. Numerical results are compared with LQ, robust H∞, reference model tracking and hybrid preview control methods. The ride quality analysis is performed based on the vertical acceleration at the driver’s position. On the simulations, it is proven that the hybrid preview controller is the most efficient and practical method.

The center of gravity of a moving train differs time to time due to variety of number of passengers on board. There can be significant difference of 3D-locations of the center of gravity on the same train between at rush hour time and at off peak one. It is essential to detect the location for preventing rollover accidents of trains on which the critical speed of rollover for them depends. In this respect, this paper applies the innovative new theory of detecting 3D-locations of the center of gravity of a moving object for trains, which was invented by the second author of this paper and abbreviated as D3DCG(1). D3DCG was created by the concept of motion dynamics of a ship floating on water. This paper assumes that similar condition can occur while a train is moving straight at constant speed. Based on this assumption, the authors measured the vertical acceleration and the roll rate of moving trains, which were to be applied to D3DCG for trains, and were successfully able to detect 3D-locations of the center of gravity on trains by D3DCG.

This paper presents experimental studies from the road profile measurements by employing accelerometers and international roughness index - IRI assessment tools and practical guidelines with respect to measured acceleration data processing in terms of digital filter design and conversion of vertical acceleration data into displacement data. In addition, it shows comparative analysis of measurements with accelerometers and Rod & Level (Leica TS 06 Plus), and gives some recommendations how to process measured data.

A flight path generation algorithm was developed to calculate control inceptor commands required for a rotorcraft in complex aerobatic maneuvers. This algorithm was used to compare the performance of a conventional and compound rotorcraft in dynamic simulations and to assess performance of a dynamic inversion control law. A non-linear dynamic inversion (NLDI) based controller was developed for the conventional rotorcraft (H-60) and a compound variant. The inner loop of the H-60 NLDI controller regulates bank angle, pitch attitude, vertical speed, and yaw rate, while the outer loop commands airspeed. The inner loop of the compound H-60 NLDI controller regulates bank angle, pitch attitude, and yaw rate, while the outer loop commands longitudinal and vertical acceleration. Redundant controls on the compound rotorcraft are scheduled with airspeed and load factor to minimize power in sustained maneuvers and enhance quickness in transient flight regimes. Three aerobatic maneuvers for both the H-60 and compound H-60 are examined in simulation: Pitch-Back Turn (PBT), Combat Ascent Turn (CAT), and Combat Descent Turn (CDT). This study seeks to illustrate the following: the development and testing of tools to generate aerobatic maneuver commands to use for non-piloted simulations, the assessment of NLDI controller performance in tracking commands, and the development of an appropriate methodology for comparing the performance of a compound and conventional rotorcraft in complex maneuvers.

The Atwood machine is a simple device used for centuries to demonstrate the Newton's second law. It consists of two supports containing different masses joined by a string. Here, we propose an experiment in which a smartphone is fixed to one support. With the aid of the built-in accelerometer of the smartphone the vertical acceleration is registered. By redistributing the masses of the supports, a linear relationship between the mass difference and the vertical acceleration is obtained. In this experiment, the use of a smartphone contributes to enhance a classical demonstration., Comment: 5 pages, 5 figures

Liza Plus Fitness or health Apple (iOS V.4.0 or later) €5.99 Liza Plus is an easy-to-use application designed to conduct four common1 ,2 neuromuscular fitness tests and exercises on athletic and non-athletic populations. By using an iPhone accelerometer, Liza calculates the power and speed during exercise by measuring the vertical acceleration of the mass lifted by the subject in opposition to gravity. Liza filters the acquired accelerometer information and processes it to obtain the speed (cm/s); then Liza calculates the power (W) and other output data based on the load lifted in the specific exercise performed, similar to a linear encoder (Power=Force×Velocity, where Force=m (load lifted)×a). Users can measure performance during a workout session using a barbell (half squat, bench press) or body-weight exercises (countermovement jump (CMJ) or squat jump (SJ)) (figure 1). The free version ( Liza Lite ) allows one to perform only jump tests (CMJ and SJ). At the end of each test, the user can read …