Search Results (14)

Load rating, using nominated rating vehicles by individual road authorities, is described in the Australian standard for bridge assessment, AS 5100.7, for all load effects, including shear. The load rating can be used to indicate the strength condition of bridges and to determine load posting for weak bridges. Thus, the information is useful for managing vehicle movements. However, for road authorities to accurately assess requested movements for a heavy vehicle with a prime mover and a platform trailer, additional information is required. This paper describes an approach employing a nonlinear search technique to determine the maximum allowable cartage loads of vehicles for various number of trailer axles up to that of a nominated load rating vehicle to ensure shear adequacy. A vehicle–bridge system has been analyzed considering a two-span bridge girder subject to a nominated rating vehicle. The calculated scaling factors for trailer loads corresponding to the total number of axles in the vehicle are presented. A platform table can then be created to assess the requested permits. The approach ensures full compliance with Modified Compression Field Theory (MCFT) as the section shear strength used for load rating is consistent with the load effects of the rating vehicle for the vehicle–bridge system under assessment. Full article

Articulated heavy vehicles exhibit poor lateral stability, which may lead to unstable motion modes, e.g., trailer-sway and jackknifing, causing severe accidents. Varying relevant vehicle parameters improves the static stability but degrades the dynamic stability. The past studies focused either on the static or dynamic stability alone. However, little attention has been paid to exploring the trade-off between the static and dynamic stabilities. To gain design insights for active safety systems for AHVs, this article studies this trade-off systematically. To this end, a systematic method is proposed to conduct the linear stability and trade-off analysis. To implement and demonstrate the proposed method, a linear three-degrees-of-freedom yaw-plane model is generated to represent a tractor/semi-trailer. A trade-off analysis is conducted considering two tractor rear-axle configurations and three trailer payload arrangements. In each case, simulation is performed in both steady-state and transient testing maneuvers. To validate the linear stability analysis based on the linear yaw-plane model, two nonlinear TruckSim models are introduced, and the corresponding simulation is conducted. Insightful understanding of the trade-off is gained through analyzing the simulation results, and the linear stability analysis will provide valuable guidelines for the design and development of active safety systems for AHVs. Full article

This paper introduces a two-tier feedback control law for the path tracking of a mobile robot equipped with N on-axle trailers. Initially, through a recursive design process, the curvature-tracking challenge is converted into stabilizing the joint angles at predefined reference values. This design approach is straightforward and can be easily extended to configurations with multiple trailers. Using input-to-state stability analysis, we demonstrate the asymptotic stability of the closed-loop system, which is structured in cascade form. Furthermore, we reformulate the path-tracking problem as a curvature-planning challenge and propose an algorithm to determine the desired curvature for the tail trailer. The simulation results validate the effectiveness of this novel algorithm in truck-trailer systems. Full article

Road transport plays an important role in the transport of goods and people and is important for the national economy. Damage usually excludes the means of transport from operation, which causes disruption of supply chains. One such damage is the failure of the suspension system of the vehicle or trailer, which usually occurs when the vehicle is heavily loaded. Such a defective system has been analyzed in this publication. Mathematical apparatus and finite element method (FEM) numerical simulations were used. A dangerous axle cross-section in terms of load was indicated and the maximum stresses in this area were calculated for two types of roads. On highways, the stress at the critical point was 199 MPa, and on uneven roads it increased to 304 MPa, which is comparable to the yield point. It was found that the second form of vibration may cause stresses in the damage area, but the excitation frequency would have to be quite high. The probability of such a load and failure event occurring is low under operating conditions. Full article

The performance of agricultural tires varies with the characteristics of both the terrain and the tractors on which they are mounted, which differently affect the rolling resistance, the traction capacity, and the slip. To reduce the variability of test conditions, CREA developed an original mobile test (MTB) bench which consists of a dynamometric single axle trailer pulled by a tractor and can be used both in traction performance tests (driving wheels) and in rolling resistance tests (driven wheels). A control system alternatively operates the adjustment of traction force or slip, so that each test is performed maintaining constant the desired values. The MTB underwent tests under different conditions (type of surface, pre-set values of force of traction and slip) aimed at verifying its accuracy and reliability. In a final test, two pairs of identical new tires were simultaneously mounted on the MTB and on the rear axle of the 2WD tractor that pulled it, to discover information on the different interactions occurring, under the same traction conditions, between the soil surface and each pair of tires, with reference to the relationship between the slips and the load transfers observed on the MTB and on the tractor rear axle. The results evidenced the capability of the MTB to guarantee repeatable test conditions, including field conditions, allowing comparison among the performance of different tires. Full article

The variety of wood loads and their parameters (humidity, density, assortment) are often the cause of the increased total weight of the vehicle (GVW). With significant GVW exceeding, forest roads are exposed to high-tonnage vehicles, which results in vehicle axle loads above the accepted design parameters for the pavement. The purpose of this study was to investigate the real axle loads of round wood transport vehicles arising from the gross vehicle weight (GVW) of the transport set in different seasons of the year and depending on the type of transport set and the type of wood assortments. Measurements of axle loads for round wood truck transport sets were carried out on the sites of three large wood industry companies from the north of Poland, which process different types of wood. The load on the individual axles of the high tonnage truck units was measured using model DINI ARGEO WWSD portable truck scales with a 3590M309 weighing terminal with 0.01 t graduation. In total, measurements were taken for 904 round wood deliveries made by different transport sets: a truck and trailer set with 473 deliveries, including 344 deliveries by six-axle sets, a truck, and semi-trailer with 334 deliveries, where 193 were made by six-axle sets. The lowest axle load for all the sets occurred on axle one in the range of average values 7.07–7.86 t with a spread of results from 4.49 to 10.20 t. The highest average axle loads of 9.15–12.43 t was found on the axle for all the observed transport sets, where a maximum value of 14.52 t was also found. There were statistically significant differences in the values of the loads on individual axles depending on the type of truck set and type of wood assortment. Comparative analysis by the Kruskal–Wallis test of all axle load results depending on the vehicle types and number of axles, showed statistically significant differences. When analyzing the axle loads in five-axle sets with respect to the delivery date, statistically significant differences were found for all the axles. These differences occurred mainly for measurements performed in the summer and other seasons, the most visible of which were on the second and third axle. The loads of transported wood (assortments) also influenced the resulting axle loads, which was confirmed by statistical analysis. For most axles, there are differences in the axle loads for sets with MS (medium-size, industrial wood) deliveries and other assortments. Additionally, on axles 4–5, there are differences between Ls (large-size) deliveries and other deliveries (multiple mean rank test). In the case of TS transport sets, there is no big difference between the axle loads, only in the case of short assortment Ms where the second and third axles have higher average axle loads of just over 10 t. In the truck and trailer combinations (TT), the highest average axle loads are on the fourth and fifth axle in the range 8.5–12.0 t, with lower values for shorter 3.7 m and Ms grades. The distribution of the total gross vehicle weight of the set is, on average, 58–60% to the truck (three axles) and 40–42% to the trailer/semi-trailer (two axles) in five-axle sets and in six-axle sets, the truck and trailer/semi-trailer (three axles). Full article

This paper deals with the design and operational evaluation of a timber tractor-trailer unit with a hybrid trailer drive. The source of electrical energy for the two induction motors driving the front wheels of the tandem trailer axle is a battery, which is recharged by an induction machine operating as a generator during periods of a lower demand for power from the tractor diesel engine. An electric drive was designed for the defined working cycle of the tractor-trailer unit, and its loading characteristics were tested in the laboratory. The parameters measured on the field tests during timber forwarding were battery voltage and power, and the energy balance. Three adjustment levels of the potentiometer controlling the trailer hybrid drive (50, 75 and 100%) were tested at three different forwarding distances of 100, 500 and 1000 m. Additionally, any slippage of the prime mover wheels and trailer was measured. The maximum peak power taken from the battery was ca. 33 kW during the field tests, whilst the drive was able to deliver a peak output of up to 72 kW for 10 s and permanently up to ca. 50 kW. Even in harsh terrain conditions, the electric drive assisted the combustion engine only when the loaded tractor-trailer unit was travelling uphill. The hybrid drive operation was sustainable for the whole working shift, without the need for recharging when the potentiometer was set to 50%. This appropriate setting of the potentiometer controlling the trailer’s hybrid drive reduced the slipping of the driven wheels of the tractor-trailer unit whilst travelling uphill. Full article

The air suspension system has become more and more popular in heavy vehicles and buses to improve ride comfort and road holding. This paper focuses on the evaluation of the dynamic load reduction at all axles of a semi-trailer with an air suspension system, in comparison with the one using a leaf spring suspension system on variable speed and road types. First, a full vertical dynamic model is proposed for a tractor semi-trailer (full model) with two types of suspension systems (leaf spring and air spring) for three axles at the semi-trailer, while the tractor’s axles use leaf spring suspension systems. The air suspension systems are built based on the GENSYS model; meanwhile, the remaining structural parameters are considered equally. The full model has been validated by experimental results, and closely follows the dynamical characteristics of the real tractor semi-trailer, with the percent error of the highest value being 6.23% and Pearson correlation coefficient being higher than 0.8, corresponding to different speeds. The survey results showed that the semi-trailer with the air suspension system can reduce the dynamic load of the entire field of speed from 20 to 100 km/h, given random road types from A to F according to the ISO 8608:2016 standard. The dynamic load coefficient (DLC) with the semi-trailer using the air spring suspension system can be reduced on average from 14.8% to 29.3%, in comparison with the semi-trailer using the leaf spring suspension system. Full article

This work investigates the fuel energy and emission reductions possible with the hybridization of a Class 8 tractor-trailer. The truck tractor has two drive axles: one powered by an internal-combustion-engine-based powertrain (CP) and the other powered by an electric powertrain (EP) consisting of an electric drive system supplied by a battery pack, resulting in a through-the-road hybrid. The EP has two modes of operation depending on the direction of power flow: motoring/battery discharging and generating/battery recharging. Switched optimal control is used to select between the two modes of EP operation, and a recently developed distributed switched optimal control is applied. The control is distributed between the CP, the EP, and the vehicle motion operation components. Control-oriented, component-specific power flow models are set forth to describe the dynamics and algebraic relationships. Four different tractor-trailers are simulated: the original CP and three hybrids with engine sizes of 15 L, 11 L, and 7 L. Simulations are performed over a short test cycle and two regulatory driving cycles to compare the fuel use, total energy, and emissions. Results show that the hybrids have reduced fuel use, total energy, and emissions compared to the original CP; the reductions and reference velocity tracking error increases as the engine size is decreased. Particularly, fuel use is reduced by at least $4.1$% under a charge sustaining operation and by $9.8$% when the battery energy can be restored with an off-board charger at the end of the cycle. Full article

This study is an examination into the feasibility of a quasi-static approach to evaluating the reaction forces that impact tires. This information could lend valuable insight into efforts to limit overturning and side-slip accidents of vehicles exposed to strong side winds. The performance of the quasi-static approach was evaluated by comparing the calculated tire forces with those created using TruckSim, which is a dynamic vehicle analysis software. Governing equations were formulated for two types of vehicles that are susceptible to the force of wind, vans, and trailers, by considering a force equilibrium, a compatibility condition, and several assumptions. The quasi-static approach for trailers is a novel expansion of the conventional approach to a two-axle vehicle. Proposed enhancements to the quasi-static approach reflect the additional rolling moment of a trailer. The curvature and the cant of a curved road were accounted for via centrifugal forces. Both uniform and turbulent wind conditions were considered in questioning the feasibility of this novel approach. Full article

Longitudinal-connected air suspension has been proven to have desirable dynamic load-sharing performances for multi-axle heavy vehicles. However, optimization approaches towards the improvement of comprehensive vehicle performance through the geometric design of longitudinal-connected air suspension have been considerably lacking. To address this, based on a 5-degrees-of-freedom nonlinear model of a three-axle semi-trailer with longitudinal air suspension, taking the changes of driving conditions (road roughness, speed, and load) into account, a height control strategy of the longitudinal-connected air suspension was proposed. Then, in view of the height of the air spring under various driving conditions, the support vector regression method was employed to fit the relationship models between the performance indices and the driving conditions, as well as the suspension geometric parameters (inside diameters of the air line and the connectors). Finally, to tackle the uncertainties of driving conditions in the optimization of suspension geometric parameters, a double-loop multi-objective particle swarm optimization algorithm (DL-MOPSO) was put forward based on the interval uncertainty theory. The simulation results indicate that compared with the longitudinal-connected air suspension using two traditional geometric parameters, the optimization ratios for dynamic load sharing coefficient and root-mean-square acceleration at various spring heights are between −1.04% and 20.75%, and 1.44% and 35.1%, respectively. Therefore, based on the signals measured from the suspension height sensors, through integrated control of inflation/deflation valves of air suspensions, as well as the valves’ inside connectors and air lines, the proposed DL-MOPSO algorithm can improve the comprehensive driving performance of the longitudinal-connected three-axle semi-trailer effectively, and in response to changes in driving conditions. Full article

Research to date on Dynamic Amplification Factors (DAFs) caused by traffic loading, mostly focused on simply supported bridges, is extended here to multiple-span continuous bridges. Emphasis is placed upon assessing the DAF of hogging bending moments, which has not been sufficiently addressed in the literature. Vehicle-bridge interaction simulations are employed to analyze the response of a finite element discretized beam subjected to the crossing of two vehicle types: a 2-axle-truck and a 5-axle truck-trailer. Road irregularities are randomly generated for two ISO roughness classes. Noticeable differences appear between DAF of mid-span moment in a simply supported beam, and DAFs of the mid-span sagging moment and of the hogging moment over the internal support in a continuous multiple-span beam. Although the critical location of the maximum static moment over the internal support may indicate that DAF of hogging moment would have to be relatively small, this paper provides evidence that this is not always the case, and that DAFs of hogging moments can be as significant as DAF of sagging moments. Full article

The frame structure of the trailer may influence both the traction and the tractor-trailer stability, especially along sloped paths. The aim of this research was to analyze a trailer overturning and the strains on the connected tractors (wheeled, or crawled) during log transportation (loose or tied) along a hillside. Two two-axle trailers were used: tandem and turntable steering. Three types of measurements were carried out during the field tests: (i) the detachment from the ground of the rear upstream wheels (or crawler); (ii) the transversal and longitudinal strains occurring when the trailer overturned (and released the hooking system of the tractor); (iii) the lateral deviation of the rear wheels (or crawler) of the tractor. The study highlighted that the two-axle trailer with turntable steering combined with the crawl tractor gave better results in terms of safety during trailer overturning. In addition, independent of the type of trailer, a tied load was found to be more dangerous than a load restrained only by steel struts, because when overturning, the load forms a single unit with the trailer mass which increases the strains. Full article

Driving vehicles with one or more passive trailers has difficulties in both forward and backward motion due to inter-unit collisions, jackknife, and lack of visibility. Consequently, advanced driver assistance systems (ADAS) for multi-trailer combinations can be beneficial to accident avoidance as well as to driver comfort. The ADAS proposed in this paper aims to prevent unsafe steering commands by means of a haptic handwheel. Furthermore, when driving in reverse, the steering-wheel and pedals can be used as if the vehicle was driven from the back of the last trailer with visual aid from a rear-view camera. This solution, which can be implemented in drive-by-wire vehicles with hitch angle sensors, profits from two methods previously developed by the authors: safe steering by applying a curvature limitation to the leading unit, and a virtual tractor concept for backward motion that includes the complex case of set-point propagation through on-axle hitches. The paper addresses system requirements and provides implementation details to tele-operate two different off- and on-axle combinations of a tracked mobile robot pulling and pushing two dissimilar trailers. Full article