Search Results

Abstract Three suspension structures including the parallel vertical suspension (PVS), the horizontal parallel suspension (HPS), and the negative stiffness element added into suspension (NSES) of the driver’s seat are proposed to improve the driver’s ride comfort of off-road vehicles. Based on the dynamic models of the PVS, HPS, and NSES established and simulated under the same random excitations of the cab floor, the effect of the design parameters of the proposed models is analyzed, and the design parameters are then optimized to evaluate their isolation performance. The indexes of the root-mean-square (r.m.s) accelerations of the vertical seat direction, pitching seat angle, and rolling seat angle are used as the objective functions. The study results indicate that the dynamic parameters of the PVS, HPS, and NSES greatly affect the driver’s ride comfort while their geometrical dimensions insignificantly affect the driver’s ride comfort.

Abstract Articulated vehicles form an important part of our society for the transport of goods. Compared to rigid trucks, tractor-trailer combinations can transport huge quantities of load without increasing the axle load. The fifth wheel (FW) acts as a bridge between the tractor and trailer, which can be moved within the range to achieve rated front and rear axle loads. When the FW is moved front, it adversely affects the cab dynamics and cab suspension forces. Compared to the cab pitch and roll, yaw motion increases drastically. The current study tries to address this issue by providing reaction rod links in the rear cab suspension. In this study, a 4×2 tractor with a three-axle semitrailer is considered by keeping the FW at its frontmost position, which is the worst-case scenario for a cab. Three different cases of reaction rod arrangement and its influence on cab dynamics are studied in comparison with a model without reaction rods.

Abstract This research examined tractor operators’ daily vibration exposure A(8) with different input riding parameters, i.e., average speed (m/s) (2.78, 3.89, 5.0), body mass (BM) (kg/m2) (35.3, 32.6, 25.4), and different terrain types (brick, farm, and tar roads). To arrange the systematic sequence of experiments, Taguchi’s L9 orthogonal array has been selected for this study. The signal-to-noise ratio (SNR) is calculated to analyze the overall influence of input parameters over the output parameters. In this study, it is found that A(8) responses exceeded the recommended action value among all the tractor operators according to ISO 2631-1 (1997). The average speeds and various terrain conditions were shown to be the most influential significant variables (p ≤ 0.05), with percentage contributions of 53.71% and 11.53%, respectively.

Abstract The riding-comfort of high-speed trains affects the travel experience of passengers, and the lightweight design technology of the carbody increases the flexible vibration and reduces passenger comfort. To this end, a vertical dynamics model of railway vehicles is established to demonstrate the potential of using passive inerter-based suspensions to reduce the flexible vibration of the carbody and improve riding-comfort. According to the characteristics of the inerter component, an appropriate inerter-based suspension is applied to the railway vehicle to reduce low-frequency resonance. The sum of the comfort indexes of the three reference points of the carbody is optimized as the objective function to improve the passenger comfort of the whole vehicle. The results reveal that the inerter-based suspension applied to the primary or secondary suspension has different effects on vehicle vibration.

Abstract Under the influence of the interactions between the vibratory drum/wheel and deformable terrains, the ride comfort of the soil compactors is greatly affected. Therefore, the isolation systems of the cab and driver’s seat of the soil compactors have been researched and developed to improve ride comfort. Based on the existing research results, this study provides an overview of the development of the isolation systems of the cab and driver’s seat of the soil compactors. The research result shows that the cab isolations used by the semi-active hydraulic mounts (SHM) or semi-active hydraulic-pneumatic mounts (SHPM) can greatly improve the driver’s ride comfort and control the cab shaking, whereas the driver’s seat suspension embedded by the negative stiffness structure (NSS) strongly improves the driver’s ride comfort.

Abstract The human body models consisting of bone, soft tissue, and skin were created based on the latest anthropometry data. The mechanical modeling of vehicle seat cover was studied, as well as the simulation of human-seat interface pressure. As a case study, the seat finite element (FE) model was established using the real-vehicle seat geometric data considering the condition with and without seat cover. The seat and body were assembled to conduct the simulation of human-seat interface pressure. By comparing the simulative result with those of the test, the accuracy of the simulation and the important role of cover material in body pressure simulation were validated. The result also showed that the cover material could not be ignored in the simulation of human-seat interface pressure.

Abstract For commercial vehicles, the parameter design and optimization of the cab suspension system are very important to ride comfort. Taking the vibration problem of a commercial vehicle as the starting point, the road load spectrum is tested and analyzed according to the user’s working scenarios, and the multibody dynamics model of the cab suspension system including actuator is established. The displacement drives of the system are obtained by the virtual load iteration method. The influence of boundary frequency to noise signals and drives standard deviation is analyzed, which is used in system identification. The method based on design of experiment is used to carry out joint experimental design and obtain the exploration space, and the cubic polynomial fitting is carried out to build a surrogate response surface model with high prediction accuracy.

Abstract The objective of the present article is to design a nonlinear passive suspension system for an automobile subjected to random road excitation which generates a performance as close to a fully active suspension system as possible. Linear Quadratic Regulator (LQR) control is used to synthesize an active suspension system. The control forces corresponding to the nonlinear passive suspension and the active suspension are equated, and the parameters are optimized as the performance error between the two systems is reduced. The nonlinear equations of motion are reduced to equivalent linear equations, where the system states are a function of the vehicle response statistics, by using the equivalent linearization method. The performance of the optimized nonlinear model and the linear model are compared with the performance of the LQR control active suspension system. The nonlinear model performs better than the linear system with chosen parameters.

Abstract Aiming at the problems of insufficient perception and adaptability of vehicle-mounted drilling rig control system to complex formation and unsatisfactory drilling efficiency, an adaptive drilling weight on bit (WOB) control system of the vehicle-mounted drilling rig is designed in this article. Based on the real-time monitoring of drilling parameters obtained by various sensors, the lithology of drilling formation is identified by particle swarm optimization-support vector machine (PSO-SVM), the corresponding high-efficiency WOB is matched according to the differences in rock properties of different formations, and the valve port size of electrohydraulic proportional overflow valve is controlled by fuzzy proportional-integral-derivative (PID) to adjust the feed force of the feed cylinder so that the WOB of the drilling rig can change adaptively with the formation, and the rock-breaking efficiency of the drilling rig can be improved.

Abstract The optimal negative stiffness structures and the hydraulic mounts used to replace the driver’s seat traditional suspension system and cab’s traditional rubber mounts of the soil compactors are proposed to enhance the driver’s ride quality and control the cab shaking. A nonlinear dynamic model with 7 degrees of freedom of the vehicle is established to analyze the ride quality under various operating conditions of the vehicle moving and working on off-road terrains. The root mean square values of the driver’s seat displacement, driver’s seat acceleration, and cab pitch’s acceleration are chosen as the objective functions. The investigation results show that both the optimal negative stiffness structures and the hydraulic mounts used on the driver’s seat suspension and cab isolation system greatly improve the driver’s ride quality and control the cab shaking under all the different operating conditions of the vehicle.

Abstract Letter from the Special Issue Editors

Abstract Vehicle aerodynamics has been the subject of extensive research, with a heavy emphasis on the vehicle. Heavy vehicles, such as trucks and buses, have undergone aerodynamic studies in recent years to reduce drag and improve fuel economy [1]. In this study, the distribution of air conditioning in the cabin of a passenger bus was investigated by discussing the factors that influence in attaining the desired thermal comfort values such as temperature distribution, relative humidity ratios, and air velocities inside the bus. The research was conducted on three different cases. In this study, different types of air-conditioning (AC) outlets—linear grills, slots diffusers, and gaspers—were used, and the effect of each outlet on temperature distribution, air velocities, and relative humidity ratios within the bus was investigated. In all three cases, the inlet air velocity was set to 0.8 m/s, and the return air was combined in the middle of the bus.

Abstract The vibration transmissibility and ride comfort for the human body elements are the important evaluation parameters while traveling in a passenger’s vehicle because both directly influence the occupant’s health and effectiveness of working. These parameters also examine the sensitivity of the human body to vehicle vibrations, which is an important area of research and investigations these days. The present work analyzes the effects of road disturbances on the vehicle and human biodynamic subject vibrations. A nine degrees of freedom (9 DoF) three-wheeled coupled vertical-lateral vehicle dynamic model and eleven degrees of freedom (11 DoF) biodynamic model are formulated and integrated. The vibration transmissibility and ride comfort based on the International Organization for Standardization (ISO) and ISO 2631 standards are investigated for the different segments of a human subject in a seated posture.

Abstract The civil aircraft nosewheel is clamped, lifted, and retained through the pick-up and holding system of the towbarless towing vehicle (TLTV), and the aircraft may be moved from the parking position to an adjacent one, the taxiway, a maintenance hangar, a location near the active runway, or conversely only with the power of the TLTV. The TLTV interfacing with the nose-landing gear of civil transport aircraft for the long-distance towing operations at a high speed could be defined as a towbarless aircraft taxiing system (TLATS). The dynamic loads induced by the system vibration may cause damage or reduce the certified safe-life limit of the nose-landing gear or the TLTV when the towing speed increases up to 40 km/h during the towing operations due to the maximum ramp weight of a heavy aircraft.

Abstract Based on the dynamics theory and the negative stiffness structure (NSS), the optimal design of the driver’s seat suspension system of the cab or vehicle equipped with the NSS is proposed to enhance the driver’s ride comfort and health. To design the seat suspension system using the NSS, the dynamic models of the seat suspension system and the NSS are established to calculate the vibration equations. The influence of the geometrical and dynamic parameters of the NSS and the different operating conditions of the vehicle on the driver’s ride comfort are analyzed, respectively. Three indexes of the reduction of the root-mean-square displacement (xRMSs ), the weighted root-mean-square acceleration (aRMSs ) of the driver’s seat, and the seat effective amplitude transmissibility (SEAT) of the seat suspension system are selected to evaluate the NSS efficiency.

Abstract A tandem axle suspension is an important system to the ride comfort and vehicle stability of and road damage experience from commercial vehicles. This article introduces an investigation into the use of a controlled active tandem axle suspension, which for the first time enables more effective control using two fuzzy logic controllers (FLC). The proposed controllers compute the actuator forces based on system outputs: displacements, velocities, and accelerations of movable parts of tandem axle suspension as inputs to the controllers, in order to achieve better ride comfort and vehicle stability and extend the lifetime of road surface than the conventional passive suspension. A mathematical model of a six-degree-of-freedom (6-DOF) tandem axle suspension system is derived and simulated using Matlab/Simulink software.

Abstract To further reduce fuel consumption and CO2 emissions of heavy-duty vehicles, recovering waste heat from the engine’s exhaust gases is a promising method. By means of an Organic Rankine Cycle (ORC), the thermal energy of the exhaust gases is converted into useable energy to support the powertrain. The integration of such a waste heat recovery (WHR) system into the powertrain as well as the transient operation presents several challenges: The interactions between the WHR system and the powertrain have to be analyzed, and their effect on fuel consumption has to be quantified in order to provide reliable fuel-saving potentials. In this article, a co-simulation model that couples the cooling system, the combustion engine, the vehicle’s longitudinal dynamics including the control system, and the WHR system is presented.

Abstract Articulated vehicles contribute to the major portions of cargo transport through roads. Fifth wheel (FW) is an important component in these vehicles, which acts as the bridge between tractor and trailer and is often used as a parameter to adjust the axle loads. Ride and comfort studies linked to FW position exist. However, its influence on durability is often not considered seriously. In this article, three different FW positions placed at 200 mm, 400 mm, and 600 mm in front of the rear axle are studied virtually on a 4×2 tractor with three-axle semitrailer combination. To assess the risk associated with FW movement, acceleration-based pseudo-relative damage, power spectral density (PSD), and level crossing plots are analyzed for each FW position. Further, fatigue analysis is done on the cab structural components to understand the durability. Outcome shows that the FW position has an influence in determining the cab dynamics and durability of the components to a great extent.

Abstract The present article analyzes the influence of the track and rail vehicle vibrations on the biodynamic human subject. A mathematical model of 47 degrees of freedom (DoF) human body-vehicle-track vibratory system is formulated for the analysis of ride behavior of the vehicle and human body system. The human body, vehicle, and track system are assigned 7 DoF, 37 DoF, and 3 DoF, respectively, and the system is formulated using Newton’s method. Stationary random irregularities of the track are accounted for in the analysis, represented by the power spectral density (PSD) function, and are used as an input to the system. The ride comfort of the rail vehicle is examined based on the International Organization of Standardization (ISO) comfort specifications. The biodynamic human subject, vehicle, and track system are evaluated independently and integrated to examine the response of one system due to the excitation of another.

Abstract Hybrid Electric Vehicles (HEVs) achieve better fuel economy than conventional vehicles by utilizing two different power sources: an internal combustion engine and an electrical motor. The power distribution between these two components must be controlled using some algorithm, be it rule based, optimization based, or reinforcement learning based. In the design of such control algorithms, it is important to evaluate the impact that variations of certain design parameters will have on the system performance, in this case, fuel economy. Traditional methods of sensitivity analysis have been applied to various power flow control algorithms to determine their robustness to the variations of HEV design parameters. This article presents a sensitivity analysis of three power flow control algorithms: twin delayed deep deterministic policy gradient (TD3), deep deterministic policy gradient (DDPG), and adaptive equivalent consumption minimization strategy (A-ECMS).