Off-road Vehicles Research Articles

Research on Global Off-Road Path Planning Based on Improved A* Algorithm

In field driving activities, off-road areas usually lack existing paths that can be directly driven on by ground vehicles, but their surface environments can still satisfy the planning and passage requirements of some off-road vehicles. Additionally, the existing path planning methods face limitations in complex field environments characterized by undulating terrains and diverse land cover types. Therefore, this study introduces an improved A* algorithm and an adapted 3D model of real field scenes is constructed. A velocity curve is fitted in the evaluation function to reflect the comprehensive influences of different slopes and land cover types on the traffic speed, and the algorithm not only takes the shortest distance as the basis for selecting extension nodes but also considers the minimum traffic speed. The 8-neighborhood search method of the traditional A* algorithm is improved to a dynamic 14-neighborhood search method, which effectively reduces the number of turning points encountered along the path. In addition, corner thresholds and slope thresholds are incorporated into the algorithm to ensure the accessibility of path planning, and some curves and steep slopes are excluded, thus improving the usability and safety of the path. Experimental results show that this algorithm can carry out global path planning in complex field environments, and the planned path has better passability and a faster speed than those of the existing approaches. Compared with those of the traditional A* algorithm, the path planning results of the improved algorithm reduce the path length by 23.30%; the number of turning points is decreased by 33.16%; and the travel time is decreased by 38.92%. This approach is conducive to the smooth progress of various off-road activities and has certain guiding significance for ensuring the efficient and safe operations of vehicles in field environments.

Smart whole-body vibration attenuation, cushion for heavy equipment seating: Model and simulation

Off-road mobile machine operators are exposed to whole-body vibration (WBV) which can result in adverse health effects. Seat suspensions are used to reduce WBV exposure, but typical passive seats cannot attenuate frequencies below 1.13 Hz. The proposed device is designed to minimize transmissibility from 0 to 20 Hz because this bandwidth contains the dominant frequency for most off-road vehicles. The semi-active smart device uses bang-bang control and is designed to be installed in place of the seat-pan cushion in OEM passive seats. Modelled as a two degree of freedom system, simulations were performed using a lumped mass model (ωn = 3 Hz; sinusoidal base excitation 0-20 Hz). Using a hexapod robot, a prototype reduced transmissibility compared to a passive OEM seat. The device was up to 5 times more effective than a passive seat in reducing vibration transmissibility. Simulations revealed that operator mass and seat stiffness variations have little effect on device WBV attenuation performance.

Research on hexagonal grid off-road path planning algorithm considering multiple factors

Abstract This article proposes a hexagonal grid off-road path planning algorithm that takes into account multiple factors for the path planning problem of motor vehicles in complex off-road environments. This method first uses a hexagonal grid model to abstract and quantify the terrain factors that affect off-road vehicles. Then, the Analytic Hierarchy Process is used to determine the weight of each factor on the impact of off-road vehicle traffic. Finally, by comprehensively considering the elevation, slope, and surface coverage elements, as well as the search efficiency of the algorithm, the cost function and heuristic function of the A * algorithm are further designed and optimized. The experimental results show that the method proposed in this paper outperforms existing algorithms in terms of pathfinding results and search efficiency, thus verifying the effectiveness and feasibility of the algorithm proposed in this paper.

Impact of the COVID-19 Pandemic on the Incidence, Etiology, Demographics, and Treatment of Craniomaxillofacial Trauma.

To compare the incidence, etiology, demographics, and treatment of craniomaxillofacial (CMF) trauma before, during, and after COVID-19. Retrospective cohort. Eighty-three health care organizations across the United States. The TriNetX Research Network identified 77,977,880 patients during 2017 to 2022. CMF fractures and soft tissue injuries during March to August of each year, aligning with the 2020 pandemic lockdown, were analyzed. In 2020, compared to immediately prepandemic in 2019, there were significant reductions of -17.5% in facial fractures and -19.0% in soft tissue injuries (P < .001). Conversely, in 2021, both injury types increased by +16.7% and +16.3%, respectively, compared to 2020 (P < .001). Changes in injury mechanisms in 2020 included significant decreases in athletic injuries (-57.6%), falls (-16.8%), assaults (-15.5%), motor vehicle collisions (-8.7%), and pedestrian accidents (-6.9%) (P < .01), while off-road vehicle (+48.4%), bicycle (+16.2%), and motorcycle (+8.9%) accidents increased (P < .01). The 10- to 14- and 5- to 9-year-old age groups experienced the most substantial reductions in facial fractures (-39.7% and -29.9%, respectively) and soft tissue injuries (-29.2% and -28.3%, respectively) in 2020 compared to 2019 (P < .001). Operative management of fractures and soft tissue injuries dropped by -20.3% and -12.4%, respectively, in 2020 versus 2019, and then rebounded with +15.8% and +14.6% increases in 2021 compared to 2020 (P < .001). In 2022, compared to prepandemic rates of 2019, there were fewer patients with facial fractures (-2.8%), soft tissue injuries (-4.5%), and operative repairs (-6.9% for fractures, -1.2% for soft tissue injuries) (P < .03). CMF trauma decreased in 2020, with subsequent years showing a rebound to levels slightly below those immediately prior to pandemic onset. Changes in etiology, demographics, and treatment highlight the complex dynamics of traumatic injuries during periods of societal disruption.

Semi-empirical terramechanics modelling of rough terrain represented by a height field

Dynamic simulations of various types of off-road vehicles, from planetary rovers to agricultural equipment, have long relied on well-established semi-empirical terramechanics models. While these models do have drawbacks and reliability issues that have been addressed by numerous works in the decades since the models were first introduced, semi-empirical approaches remain one of the few ways to simulate realistic wheel-soil interaction in real-time. One of their drawbacks is their assumption that the terrain is a flat plane. The models work by integrating normal and shear stresses along the wheel-terrain contact patch. The normal stress at each point along the contact patch is determined using an equation that computes soil pressure based on semi-empirical parameters, the dimensions of the wheel and the sinkage, which is determined based on the distance between the point and the plane that defines the terrain. Other works simplify the rough terrain contact problem by defining an equivalent contact plane at each time step in order to continue to be able to use semi-empirical models - modified to work with slanted planes - to compute the interaction forces. In this work, we propose a new, modified version of the semi-empirical model in which interaction forces for a wheel travelling on rough terrain can be computed without the need to use an equivalent contact plane. To highlight the advantages of our proposed approach, we compare our simulation results to the results of simulations using an existing approach for modelling a wheel travelling over rough terrain using traditional semi-empirical models.

Unlocking the potential of electric and hybrid tractors via sensitivity and techno-economic analysis

The majority of agricultural vehicles in use today still rely on diesel-based propulsion, a major source of air pollution. Electrification is seen as a potential solution for decarbonizing these off-road vehicles but is hampered by higher upfront costs in energy storage and charging infrastructure. To better quantify these barriers, this paper proposes a techno-economic tool that can assist farmers in evaluating the total costs of ownership of electric and hybrid tractors. A pragmatic simulation model of the tractor is developed to predict the annual energy/fuel consumption and NOx emissions, while an economic model estimates the total acquisition, operation, and maintenance costs. For managing the energy in hybrid tractors, a new power split strategy based on model predictive control is developed, allowing the designer to balance energy efficiency and NOx emissions, while taking into account operational constraints of the electric powertrain. Additionally, we propose novel decision maps that allow farmers to quickly identify operating regions (in term of average load and yearly working time) where the deployment of electric/hybrid tractors is economically viable. To account for variability in the tractor’s operational conditions, we conduct both a deterministic sensitivity analysis with multi-parameter variation and a stochastic analysis of the total cost of ownership. The tool is validated with different mission profiles based on data from a California farm. The results show that, compared to diesel powertrains, electric tractors are more cost-effective for light-duty farming activities (engine loads less than 20%). On the other hand, hybrid powertrains are more economical for medium-duty tasks, where engine loads range from 20% to 60%.

Lower and upper bounds for scheduling a real-life assembly problem with precedences and resource constraints

In this work, we consider a real-life scheduling problem involving the production of off-road vehicles using a three-level assembly process, subject to precedence, machines, and resource constraints. This problem shares multiple characteristics with other scheduling problems such as the Parallel Machine Scheduling and Flexible Flow Shop Problems. However, it also comprises less investigated aspects such as a specific job precedence structure resulting in a directed rooted in-tree and a global resource constraint limiting the number of simultaneously active machines. We present a straightforward adaptation of a time-indexed mathematical formulation to the problem and introduce a new lower-bounding procedure. To solve the problem, we propose constructive heuristics based on classical priority rules and adaptations of job sequencing heuristics. We also propose CORE, a specialized approach tailored to leverage the problem structure. All the algorithms are extensively evaluated on two benchmark sets, various shop floor configurations, and eight real-life scenarios. Our results reveal the general effectiveness of job sequencing approaches and demonstrate the overall superiority of CORE.

Optimization study of tail-lateral occupant injury and restraint system for an off-road vehicle ramp rollover

The process of rollover accidents involving specialized vehicles is characterized by intense motion and long duration. Although these accidents are infrequent, they often lead to a high fatality rate. In this study, we utilized LS-Dyna software to simulate the rollover of a vehicle on a side ramp. This simulation aimed to verify the reliability of our model establishment by comparing the vehicle’s motion attitude and center-of-mass acceleration with experimental results. Additionally, we sought to investigate the lateral occupant injuries that occur in the tail section of a certain type of specialized vehicle during a rollover. Initially, we obtained the vehicle’s motion trajectory and the dummy’s motion state through simulation. Subsequently, we extracted the injury response of each part of the dummy. We then simplified the entire vehicle model and made improvements to the occupant restraint system, ultimately designing an enhanced system. Finally, we approximated and replaced the entire vehicle model by establishing an approximation model. We combined this with an optimization algorithm to optimize the occupant restraint system. The simulation results demonstrate that the improved occupant restraint system significantly reduces the axial force on the neck of the occupant and the comprehensive evaluation index of injury. Furthermore, the simulation results for each component fall below the injury limit value specified in the FMVSS208 crash occupant protection standard. Therefore, the improved occupant restraint system proposed in this study effectively mitigates lateral occupant injury during rollover accidents.

Pediatric Off-Road Vehicle Injuries: Side-by-Sides Worse for the Upper Extremity.

Side-by-side (SXS) and all-terrain vehicles (ATVs) are different off-road vehicles (ORVs) but often categorized together in the literature. We hypothesized pediatric upper extremity (UE) fracture patterns and injury severity scores (ISS) differ between ORV types. The authors' home-state trauma repository identified 157 pediatric patients aged 0 to 17 years with UE fractures after ORV accidents during 2011-2021. ORV injuries, fracture type, and procedures were identified using International Classification of Diseases, 9th Revision and 10th Revision coding followed by manual chart review or phone calls. We identified specific ORV type, driver/passenger status, and restraint use to compare differences between fracture characteristics, number of surgeries, and ISS. Groups were compared for differences at P < 0.05 significance. Among 157 ORV injuries, 75 resulted from ATVs (48%), 50 SXSs (32%), and 32 from all other vehicles (20%). Average age was 12 years, and 49% (n = 77) required surgery. SXS injuries had significantly higher open fracture rates (42%, n = 21) compared with ATVs (7%, n = 5) and all other ORV types (16%, n = 5; P < 0.0001). Seventy percent of fractures (n = 35) sustained after SXS accidents required surgery compared with 41% (n = 31) for ATVs and 34% (n = 11) for all other ORV types (P < 0.001). SXS drivers had 71% left-sided injuries, whereas 85% passengers had right-sided injuries (P < 0.0001). Patients younger than 13 years (n = 73) had significantly higher surgery rates (59%) compared with 40% for those 13 years and older (n = 84; P = 0.02). There were no significant differences in mean ± SD ISS between ATV (8 ± 6), SXS (8 ± 6), and other vehicles (7 ± 4; P = 0.34). UE fractures caused by SXS were more likely to be open and require surgery compared with ATVs and other ORVs. SXS drivers were more likely to sustain left-sided injuries, whereas passengers had significantly higher right-sided injuries. Patients younger than 13 years were more likely to require surgery compared with teenagers.

Design, Modeling and Control of a Hardware-in-the-Loop Testbed for Off-Road Vehicles

Abstract This paper presents the design, modeling, and control of a hardware-in-the-loop (HIL) testbed for off-road vehicles. The proposed HIL testbed employs a transient hydrostatic dynamometer to load a diesel engine to emulate any loading cycles of a wheel loader, which is a representative off-road vehicle. A fully validated wheel loader model is used to calculate the engine load, including both the drive and work functions. Besides, Iterative Learning Control (ILC) has been designed for the loading torque tracking of the hydrostatic dynamometer to ensure accurate emulation of real-world operation scenarios. The developed HIL testbed is used to demonstrate more than 26% energy benefits of automated wheel loaders through systematic optimization compared with human-operated wheel loaders. This HIL testbed serves as a robust platform for advancing research and development across various off-road vehicles, including excavators, tractors, and harvesters.

Multibody Dynamics and Terramechanics-based modeling and simulation of Quarter-Car with Suspension

Abstract While tires only compress when acted upon by a load in on-road scenarios, in off-road conditions, on the other hand, the tires not only undergo compression but also sinkage into the ground, in a manner that depends on the terrain. The tire-ground contact, in turn, affects the forces acting on the suspension system. Hence, it is necessary to study the vertical dynamic response of a system in off-road conditions by accounting for the terramechanics phenomenon (tire-terrain interface). The forces acting at the tire and terrain interface in off-road conditions have been studied in terramechanics separately; however, their integration with multibody systems is relatively less explored. In this paper, a multibody dynamic-based modeling and simulation of a quarter car with a linear spring-damper suspension system for off-road vehicles is presented. The generalized external forces are obtained using the Bekker-Wong based soil pressure-sinkage approach for two different kind of multibody systems interacting with sandy loam terrain. This model is integrated with the Tangent Space Ordinary Differential Equations of the quarter car and suspension system and solved using numerical integration techniques. Thus, by accounting for the terramechanics in the multibody system, the technique provides a more realistic response of the system in off-road scenarios.

The emission of off-road vehicles and their reduction options

Abstract The reduction of harmful emissions is a popular topic in both scientific and public circles. Contrary to popular belief, emissions from transport are only a small part of global emissions. As shown in the figure, the average of the EU 27 countries attributes only 15% of emissions from transport. From common perspective, vehicles with internal combustion, including diesel engines, will soon be replaced by alternative drivetrains. However at least at the commercial and off-road transportation, the diesel technology it is not so easy, and also the environmental reasons are questionable. Although the local emissions of electric vehicles are zero, their global emissions are, according to some research, more significant than their counterparts with internal combustion engines. The total electricity produced in the world in 2016 was about 25 PWh, two-thirds of which came from fossil energy carriers, which seriously damages the ecosystem, so it cannot be labelled as green energy.

A Study of the Improved A* Algorithm Incorporating Road Factors for Path Planning in Off-Road Emergency Rescue Scenarios.

To address the problem of ignoring unpaved roads when planning off-road emergency rescue paths, an improved A* algorithm that incorporates road factors is developed to create an off-road emergency rescue path planning model in this study. To reduce the number of search nodes and improve the efficiency of path searches, the current node is classified according to the angle between the line connecting the node and the target point and the due east direction. Additionally, the search direction is determined in real time through an optimization method to improve the path search efficiency. To identify the path with the shortest travel time suitable for emergency rescue in wilderness scenarios, a heuristic function based on the fusion of road factors and a path planning model for off-road emergency rescue is developed, and the characteristics of existing roads are weighted in the process of path searching to bias the selection process toward unpaved roads with high accessibility. The experiments show that the improved A* algorithm significantly reduces the travel time of off-road vehicles and that path selection is enhanced compared to that with the traditional A* algorithm; moreover, the improved A* algorithm reduces the number of nodes by 16.784% and improves the search efficiency by 27.18% compared with the traditional 16-direction search method. The simulation results indicate that the improved algorithm reduces the travel time of off-road vehicles by 21.298% and improves the search efficiency by 93.901% compared to the traditional A* algorithm, thus greatly enhancing off-road path planning.

Sizing and simulation of modular electric off-road vehicle using Scilab Xcos

Abstract As a sustainable transportation alternative, particularly in the realm of off-road vehicles, electric vehicles are rapidly gaining popularity. Despite the limitations that records have imposed including short-lived ranges and low speed as opposed to conventional vehicles, their eco-friendly nature and efficiency renders them to be appealing. The ongoing technological leaps in motor and battery technologies have improved the standing of long-distance electric vehicles, optimizing their performance by tailoring motors and batteries to suit specific regions and driving patterns. This study aims to size the motor and battery components of an off-road modular vehicle using Scilab Xcos, open-source software. The data obtained from the driving data accessed by driving the electric vehicle around 1 km of Dhulikhel is used as input for the simulation. The output of the simulation is used to understand the requirements of the motor and battery specifications. The motor was able to provide a maximum torque of 100 Nm and a nominal power of 10kW with peak power of 25 kW, while the battery was able to provide a battery power of 16kWh. The design went through theoretical validation and was compared against the established experimental data of the vehicle. Altogether, results affirm that the customized model aligns with the vehicle’s performance requirements by delivering adequate power, torque, and energy efficiency.

Combining Optimization and Simulation for Next-Generation Off-Road Vehicle E/E Architectural Design.

The automotive industry, with particular reference to the off-road sector, is facing several challenges, including the integration of Advanced Driver Assistance Systems (ADASs), the introduction of autonomous driving capabilities, and system-specific requirements that are different from the traditional car market. Current vehicular electrical-electronic (E/E) architectures are unable to support the amount of data for new vehicle functionalities, requiring the transition to zonal architectures, new communication standards, and the adoption of Drive-by-Wire technologies. In this work, we propose an automated methodology for next-generation off-road vehicle E/E architectural design. Starting from the regulatory requirements, we use a MILP-based optimizer to find candidate solutions, a discrete event simulator to validate their feasibility, and an ascent-based gradient method to reformulate the constraints for the optimizer in order to converge to the final architectural solution. We evaluate the results in terms of latency, jitter, and network load, as well as provide a Pareto analysis that includes power consumption, cost, and system weight.

Analysis of Non-Road Mobile Machinery Homologation Standards in Relation to Actual Exhaust Emissions

This article presents issues related to the current approval procedures in the group of off-road vehicles. Our research aimed to demonstrate significant differences between actual railway vehicle operation and stationary homologation tests regarding exhaust emissions. The research cycle consisted of analyzing emissions of toxic compounds from exhaust systems under real operating conditions, supplemented by a temporal share analysis based on the denormalized NRTC test upon which the tested object was homologated. Based on the conducted analyses, a significant difference was found between the actual operation of the tested railway vehicle and the stationary homologation test. By interpreting emission intensities within the parameter ranges of the propulsion unit’s operation, key areas with a significant impact on the vehicle’s overall emissions were identified. Based on the obtained results, a critical opinion is expressed regarding current homologation standards for the off-road vehicle group and the necessity for further empirical research in the area of actual operation of the tested vehicle group.

Electrifying Off-Road Vehicles: Is 1000 [Wh/kg] Enough?

Electrifying Off-Road Vehicles: Is 1000 [Wh/kg] Enough?

Mapping off-road tracks and animal paths in protected areas using high-resolution GeoEye-1 panchromatic satellite imagery

ABSTRACT Off-road driving activities are common in many protected areas. This study aimed at applying a curvelet-based approach for the automatic extraction, mapping and separation of off-road tracks and animal paths in Masai Mara National Reserve, Kenya, using high-resolution GeoEye-1 panchromatic satellite imagery (50 cm). A novel hybrid remote sensing-GIS method comprising three main blocks is proposed: (1) extracting the high-contrast curvilinear feature from curvelet magnitudes derived from the finer scale of curvelet coefficient; (2) extracting the low-contrast curvilinear feature from coarser scale curvelets and refine the shape by deformable active contour (Snake), and (3) categorizing the extracted curvilinear feature into vehicle tracks and animal paths by a fuzzy logic inference system. Results from quantification of extraction and categorization performance of the trails were 77.5% for completeness, 89.2% for correctness, and 4.5% for redundancy, with an overall accuracy of 79.5%. Using grid matching, we find a high correlation between off-road vehicle tracks and animal paths in the area (r = 0.75, p < 0.05) indicating co-occurrence of these two types of trails. The proposed approach provides a basis for large-scale mapping and monitoring of off-road tracks and animal paths in the African savanna from space.

The association between county ordinances allowing off-road vehicles on public roads and crash rates

BackgroundLegislative bodies across the country have increasingly allowed off-road vehicles (ORVs) including all-terrain vehicles (ATVs) and utility task vehicles (UTVs) on public roads, an environment for which they are not designed. In 2004, Iowa gave individual counties the discretion to pass ordinances allowing ORVs on public roadways. The objective of this study was to evaluate the relationship between the passage of ORV ordinances and ORV crash rates, especially on public roads.MethodsAn Iowa ORV roadway ordinance database and an Iowa ORV crash database (2002–2018) for all 99 counties were compiled. Crashes for which county location could not be determined were excluded. Utilizing a zero-inflated Poisson model, correcting for background crash frequency trends and population, investigators compared the relative rates of crashes after ordinance passage to time points before ordinance implementation and to counties without such ordinances. Sub-analyses, including that focused on more recent years (2008–2018), were also performed.ResultsForty-five county ORV roadway ordinances went into effect between 2011 and 2018 and 2,347 crashes (69%) met inclusion criteria. Adjusted for year, there was a 58% greater ORV crash rate in counties after passing an ORV roadway ordinance (incidence rate ratio (IRR) 1.58, 95% CI 1.32–1.90). Roadway crashes (n = 834) increased 48% after ordinance passage (IRR 1.48, 95% CI 1.14–1.94). This roadway crash association remained statistically significant when analysis was limited to the years 2008–2018 (IRR 1.39, CI 1.06–1.83, n = 544); to ATV crashes only (IRR 1.70, CI 1.20–2.40, n = 683); and to ATV crashes excluding counties with UTV-only ordinances (IRR 1.74, CI 1.40–2.15, n = 2,011).ConclusionsORV roadway and total crashes increased significantly after implementation of county ordinances allowing ORVs on public roadways and when compared to counties without such ordinances. It is likely that these increased crashes have resulted in more injuries and possibly deaths. Results from this study may help inform policymakers as they consider legislation regarding ORV usage on public roads.

Investigating off-road vehicle lateral stability with integrated chassis control

This study investigates the improvement of off-road vehicle lateral stability by integrated control of active rear steering (ARS) and rear differential braking (RDB) and how the performance of such systems compares on smooth and rough roads. The ARS and RDB controllers comprise a sliding mode controller (SMC) for which critical design choices are the SMC reference model, SMC gain and integration rule. Findings include that the kinematic model reference error is preferred over the phase plane location error on both terrains, the SMC gain is terrain dependent, and the rear axle slip angle is the preferred integration rule over the stability index (SI) on both terrains. The study also found that RDB, and to a lesser degree ARS, tends to improve on the baseline vehicle path-following ability for a double lane change (DLC) manoeuvre on both terrains, but RDB has a larger loss of speed compared to ARS. The Rear axle slip angle was found to be a terrain-dependent tuneable integration rule to combine ARS and RDB, and this resulted in a control system that has the good path-following ability of RDB but the low loss of speed associated with ARS after tuning.