Abstract-only

0178 / Model To Estimate The Force Exerted On The Sphere Rolling On The Sandy Road

Takeshi Fukumoto, Ken Yamamoto, Makoto Katsura, and Hiroaki Katsuragi Keywords: getting stuck; terramechanics model; fundamental research Abstract: The importance of the rover for exploring the planetary surface is recently increasing. It is important to move off-road (e.g. regolith) ground safely without getting stuck. To do that, it is necessary to predict the force exerted on the tire while moving on an off-road environment. The traditional terramechanics model has been widely used to predict the force since a half-century ago by many researchers. However, there are some drawbacks to that model. There are many parameters (~10) to predict the force and it takes a lot of time and effort to determine the reasonable parameter values. We would like to establish a way of predicting the force easily. This research aims to develop a semi-empirical model to predict the force with few parameters based on the traditional terramachanics model. In this work, we carried out a simplified experiment to obtain the relation between soil and tire. Here, we experimentally investigated the dynamics of the spheres (without driving force and their radius is 6.4 mm) rolling up a sandy slope (consisting of 0.8 mm glass beads). We systematically varied the density of the sphere (0.93, 1.4, 2.6, 3.9, and 7.8 g/cm3), the slope angle (from 0 to 20 deg), and the initial velocity (0.2-0.7 m/s). As a result, the dynamics of the sphere show a constant deceleration in both translational and rolling motions. We assume there are 2 forces (normal force and tangential force) exerted on the sphere at one point with these constant acceleration. The ratio between normal force and tangential force is constant, and the point angle is about 0.4 times the angle of the sinking depth. This relationship suggests that we can compute the forces exerted on the object (sphere, tire) with the relations we obtain from this research.

0376 / Improvement Of Formulations Of Clegg Impact Hammer And Rammsonde Penetrometer For Use In Compacted Snow

Mohit Shenvi, Corina Sandu, and Costin Untaroiu Keywords: compacted snow; Clegg Impact Hammer; Cone penetrometer; penetration resistance; sinkage Abstract: From the terramechanics viewpoint, assessing sinkage and penetration resistance in a deformable terrain is crucial for on-site terrain characterization. Existing devices often encounter limitations when characterizing compacted snow, as documented in the literature. The Clegg impact hammer and the Russian snow penetrometer (utilizing the Rammsonde principle) are extensively employed tools for gauging the penetration resistance of compacted snow. Despite the widespread use of the Clegg impact hammer, there are relatively few studies, primarily conducted by CRREL, focusing on its application in snowy conditions. This study aims to propose enhancements to classical literature formulations of two devices that have been used in compacted snow conditions to evaluate snow characteristics. One such device viz. the Clegg impact hammer has outputs correlated to the evaluation of sinkage and Young’s modulus. Modifications to the classical methodologies have been proposed in this work. The in-house device yielded consistent measurements even when the CTI gauge exhibited variations on a commercial test track used for winter tire evaluations. In this case, formulations have been developed that contribute to a more analytical assessment of the resistance pressure. Additionally, these formulations may aid in evaluating the compacted zone forming in front of the cone as it penetrates deeper into the terrain. The comparison results offer insights into the potential variation in calculating these parameters, with a subsequent discussion of the findings from a physics-based perspective. Future work in this field could entail evaluating the resistance pressure across various terrain types to validate the proposed hypotheses or offer correction factors based on field testing results.

0677 / Adaptive Particle Refinement In Terramechanical Dem Simulation

Markus Pogulis and Martin Servin Keywords: Discrete Element Method; Particle Scaling; Adaptive particle refinement; Computational efficiency; Granular Material Abstract: DEM is computationally intensive for granular dynamics simulation, leading to a need for efficient strategies. This study explores using local particle refinement, scaling particle size based on expected spatial resolution needs, inspired by adaptive mesh refinement in FEM. Finer particles are used where intense interaction occurs, and coarser particles further away. We hypothesize this method can maintain good accuracy while reducing particle count and computational effort. Fine particles are used on the soil bed's top, with coarser particles at greater depth, creating a particle size gradient. By adjusting the gradient we introduce a “scaling aggressiveness”, allowing control over the trade-off between efficiency and accuracy. We use triaxial tests to verify that the method is scale invariant. Pressure-sinkage and shear-displacement tests are then used to evaluate the method's effectiveness and accuracy in terramechanics applications. All beds were compared to a reference bed with homogenous particle size, where the mean static sinkage was 1.25 mm for a 50 kPa load. The dynamic sinkage was 73 mm for the full simulation time. For quasi-2d simulations, mild scaling aggressiveness reduced the particle count by 2-4 times with relative error up to 4% for dynamic sinkage (11% for static sinkage). For medium aggressiveness, 4-6 times reduction with relative error of 4% (19% static). For highest aggressiveness, 6-8 times reduction with relative error of 7% (29% static). The internal friction proved to be very resistant to gradient changes, with errors within 1%. When extending the model to full 3D, we estimate up to a reduction in particle count of up to a factor 25.

0815 / Using Simulation To Characterize Rassor Excavation In Lunar Environments

Luning Bakke, Zhenhao Zhou, Alexandra Kissel, Ruochun Zhang, and Dan Negrut Keywords: Off-road mobility modeling; Robotic system; Excavation; Discrete Element Method (DEM); Terramechanics Abstract: We describe modeling and simulation approaches used to investigate the operation of NASA’s Regolith Advanced Surface Systems Operations Robot (RASSOR) excavator while operating in lunar gravitational environments. With a total mass of 66 kg, RASSOR is equipped with four wheels and two arms, each of the latter connected with a rotating bucket drum for soil excavation. The design compensates for the low mass and low gravitational pull by digging using two counter-rotating bucket drums. The rover can raise its drums when transporting the soil, and it unloads the material by reversing the drum's rotation at destination. We simulate digging operations at two levels of fidelity using Project Chrono, an open-source multi-physics simulation platform that provides terramechanics modeling, robot modeling, sensor models, and a ROS2 autonomy stack for synthesizing RASSOR’s autonomy in simulation. We discuss two terrain modeling techniques – the Continuum Representation Method (CRM) and the Discrete Element Method (DEM). CRM employs the μ(I)-rheology model for describing the elasto-plastic behavior of the granular material, with the partial differential equations for the mass, momentum, and Cauchy rate of change spatially-discretized via the Smoothed Particle Hydrodynamics (SPH) method. The interaction between the implement and terrain is captured using Boundary Conditions Enforcement (BCE) markers. Unlike CRM, DEM represents the terrain discretely, by describing frictional contact forces at particle level. In this study, we compare the CRM and DEM results in terms of accuracy and time to solution.

1169 / (Cancelled) Cold-Weather Performance Analysis On The Us Army’S Polaris Alpha Side-By-Side

Clifford Witte and Michael Parker Keywords: Lightweight Tactical All Terrain Vehicle; LTATV; Cold Regions; Arctic Mobility; Snow Mobility; Off-road mobility Abstract: The US Army recently updated its fleet of light tactical vehicles with an upgraded version of the Polaris MRZR, named the MRZR Alpha. The Polaris MRZR Alpha has substantially different characteristics in overall dimensions, drivetrain, suspension, electronics, and so on over the older model. Therefore, the Polaris Alpha has significantly different driving dynamics from the older model. The Army Corps of Engineers Cold Regions Research & Engineering Lab (USACE-CRREL) has previously identified and tested this new vehicle for its potential mobility in artic conditions. For artic conditions, the vehicle can be equipped with tracks and an artic cab enclosure kit. CRREL owns two older MRZR D4 and two newer MRZR Alphas and has substantial test data for both vehicles. This research includes field test data from USACE CRREL engineers on various types of snow surfaces and transition season soils and provides engineering feedback on the positives and negatives of the changed systems, and qualitative feedback from US Soldiers. The goal of this project is to characterize the vehicle on wheels and tracks on cold weather surfaces, as well as provide early insight into systems on the vehicle requiring improvement, as well as illuminate key successes and failures in comparison to the older MRZR D4.

1499 / Development Of Evaluation Technology For Tire Traveling Performance On Soft Soil Of Lunar Surface

Kei Tsuchiya, Kon Seiji, Masahiro Katayama, Tomoya Arai, and Shingo Ozaki Keywords: Wheel Test Bed; Terra mechanics; Lunar Vehicles; Mobility Abstract: Bridgestone Corporation is taking on the challenge of developing tires for lunar vehicles. In this development, evaluating the tire traveling performance on the soft soil of the lunar surface is important because it is nearly impossible to conduct pre-testing using actual tires under actual conditions. Therefore, we are developing both experimental and simulation technologies for performance evaluation. In this presentation, we will explain two testing devices developed by Bridgestone Corporation for evaluating the performance, including examples of measurement results. The first device is an indoor installation type that uses scaled-down model tires. The device incorporates special features to simulate various traveling conditions such as constant slip ration mode, cornering, and climbing. The second device is an outdoor testing type that allows for testing with tires equivalent in size to those used on lunar vehicles. This device is portable and can be taken to various testing sites. Additionally, while conducting outdoor tests, it can reproduce steady-state traveling conditions which are important for accurate evaluations of tire traveling performance. Furthermore, in this presentation, we will briefly introduce the evaluation technology that combines experiments and simulation using the extended terramechanics model proposed by the Ozaki Laboratory at Division of System Research, Faculty of Engineering, Yokohama National University, with whom we are conducting joint research.

2520 / Efficient Tire-Terrain Interaction Modelling: Effect Of Flexibility On Traction

Mahdi Maleki and Jozsef Kovecses Keywords: Tire Dynamics; Flexible Tires; Tire-Terrain Interaction Abstract: The analysis of tire dynamics is essential in the simulation of vehicle behaviours. The forces exerted on a tire depend on the tire and terrain interaction, and the tire structure directly influences this interaction. Complex models with a high number of degrees of freedom, such as lumped parameter models or finite element models, are typically required to represent tire flexibility appropriately. These models, however, can lead to high computational costs that can be a significant challenge for real-time simulation. In this work, we developed a reduced model for the flexible tire that can represent the effects of tire flexibility with low computational costs in the simulation. By calculating the effective stiffness of a flexible tire model (base model) and augmenting it with a model representing the rigid body motion of the wheel, we could represent the flexibility of the tire more efficiently. The tire deformation affects the tire contact patch size, influencing the traction forces acting on the tire. By having the effective stiffness at hand, we are able to calculate the contact patch size at each instant of time. The traction forces acting on the wheel depend on the size of the contact patch since a larger contact patch would be capable of carrying more tangential load. In order to observe the effect of the contact patch size on the traction forces, we scaled the friction coefficient based on the size of the contact patch. This way, we could take the effect of tire deformation on traction forces into account. Our simulations show efficient real-time performance while maintaining accuracy. By integrating effective stiffness and adjusting friction, we effectively capture tire dynamics, making them a practical solution for diverse vehicle simulation applications.

2800 / Granular Flow In Reduced Gravity: Analysis And Insights From Centrifuge Experiments At The International Space Station

Genya Ishigami, Shingo Ozaki, Masatsugu Otsuki, Hideaki Miyamoto, Koji Wada, Masataku Sutoh, Takao Maeda, and Taizo Kobayashi Keywords: Granular media; Low gravity experiments; Discrete element method Abstract: Gravity-dependent characteristics of regolith, fine-grained granular media covering extraterrestrial surfaces, are essential for reliable design and feasible operation of space probes. Parabolic flight or drop tower facilities for simulating reduced gravity experiments on Earth can only perform short test durations and a limited number of tests with less quality artificial gravity. A numerical simulation requires an accurate interaction model of space probe and regolith. Further, the model parameters must be carefully identified for verification and validation. Therefore, the experimental dataset of granular media under stable reduced gravity is essential for solving the abovementioned issues. We performed a granular flow experiment under varied artificial gravity generated by a centrifuge on the International Space Station. An hourglass-shaped apparatus containing granular media was used to observe the granular flow in high-quality, long-term, and stable gravity conditions. We also performed a numerical simulation that calculates the granular flow in both artificial and natural gravity environments. The simulation verifies that the granular flow at the hourglass’s orifice in artificial gravity is equivalent to natural gravity. The mass flow rate of the granular media measured from the experiment follows a well-known physics-based law, while some deviations are found in low- and micro-gravity conditions. The deviation implies that the bulk density of the granular media decreases as the gravity decreases. This finding provides a useful insight that improved simulation of space probes in reduced gravity can be realized by reducing the bulk density of the granular media, resulting in reliable design and analysis of the space probes.

3071 / Study On Applicability Of Extended Terramechanics Model To Various Traveling Modes Of Wheels

Tomoya Arai, Kei Tsuchiya, Seiji Kon, Masahiro Katayama, and Shingo Ozaki Keywords: Simulation; terramechanics model; ground deformation; wheel-soil interaction; braking Abstract: To promote lunar and planetary exploration missions, the development and operation of exploration rovers is essential. However, it is difficult to evaluate prototypes of wheels and vehicles under environments corresponding to extraterrestrial gravity and atmosphere conditions. Therefore, systematic evaluation of vehicle traveling characteristics using a numerical simulation is required. Under these circumstances, an extended terramechanics model based on cellular automaton that considers terrain surface deformation was proposed by Yokohama National University group, and its validity was confirmed through comparison with the results of traveling experiments using a rigid wheel. In this study, we propose a model that can handle various traveling modes to improve the versatility of numerical analysis simulations that implement extended terramechanics theory. First, we conduct single-wheel experiments using a rigid wheels and obtain data for model verification of both straight traveling and braking. Then, we extend the extended terramechanics model by implementing braking logic, etc., and establish a simulation model for a single rigid wheel using the commercial software package Simscape. In addition, systematic simulations are performed under forced-slip condition in which the angular velocity is fixed, while the translational velocity is varied. Here, the wheel specification and traveling conditions are the same as those of the experiment equipment. Finally, we demonstrate the effectiveness of the proposed model by comparing it with the results of experiment under various conditions.

3304 / Development Of An Unmanned Exploration Robot For Lunar Surface Geotechnical Investigation

Taizo Kobayashi, Atsushi Kakogawa, Shinichi Ito, Masafumi Nakagawa, Takeshi Tsuji, Shingo Ozaki, Satoshi Matsumura, Akihiko Kondo, Masanori Takigawa, Keitaro Kitamura, Takahito Hiramatsu, Hisatoshi Sano, Takeshi Yoneoka, Junichiro Odaka, Kenji Hosobori, Taichi Ikenaga, and Ryu Taniguchi Keywords: Lunar regolith; Geotechnical investigation; Three-dimensional surveying; Active seismic exploration; Radioisotope density gage; Bevameter Abstract: The lunar surface is covered by a thick layer of soil known as regolith, which remains largely unexplored from a soil mechanics perspective. Additionally, significant uncertainties exist in geology and topography, posing risks to the safety and efficiency of lunar surface operations. Effective geotechnical risk assessment and management are essential for the safe planning and execution of lunar activities. To address these challenges, we are developing an unmanned exploration robot, named the Robotic Geotechnical Investigation System (RGIS), aimed at gathering critical data on the lunar surface. The RGIS is equipped with four key components: (1) a positioning and surveying system for detailed micro-topography measurements, (2) an active seismic survey system to investigate subsurface stratigraphy and bulk density distribution, (3) a radio isotope density meter for precise soil density measurement, and (4) a plate loading and shear testing system to evaluate the deformation and strength characteristics of lunar regolith. Data collected by the RGIS will enable the construction of a three-dimensional geological and geotechnical map of the lunar surface. This map will aid in predicting the behavior of exploration vehicles, construction robots, and designing earthworks such as excavation, filling, leveling, and module/structure installation. This presentation offers a comprehensive overview and outlines the current development status of RGIS.

3352 / Sph Modelling To Understand Wheel Locomotion In Uneven Terrain

Z Lei Keywords: SPH; Wheel-soil interaction; Robot locomotion Abstract: We use Smooth Particle Hydrodynamics to model the interaction of small wheel robots with uneven, soft, terrain. The SPH modelling approach is validated against experimental results before we test numerically the interaction of wheel passes on terrain of various inclinations, from flat to steep angles of up to 35 degrees. We show the dependency of sinkage, translational velocity, and wheel size for different input wheel torques (angular velocities). The mapped parameters allow the creation of non-dimensional groups that can be applied to other situations not included in the original modelling. An independent verification of these proposed similarity laws are checked against SPH results.

3456 / Tire-Soil Interactions For Large Deformation Problems

Diana Jimenez, Siamak Arbatani, Jozsef Kövecses, and Marek Teichman Keywords: RANCF; tire-terrain interaction; tire modeling; soil modeling Abstract: This work explores the simulation of tire-soil interactions in the multi-body system framework by using the rational absolute nodal coordinate formulation (RANCF). This method accurately represents large deformations and rotations while representing rigid body motion exactly. This approach is suitable for potential real-time simulations of off-road vehicle dynamics. More specifically, RANCF elements make it possible to model initially deformed geometries with relatively few degrees of freedom and higher fidelity than their ANCF counterparts. This study employs a first-order time-stepping integration scheme that treats the internal elastic forces of the RANCF elements as relaxed quadratic constraints approximated by Gaussian quadrature points along the elements. The quadrature approximation leads to a set of stabilizing implicit damping forces that are incorporated into a stabilized semi-implicit Euler integration scheme. This method exhibits excellent stability even for large timesteps, allows for stiff elastic forces, and does not artificially dampen rigid body modes. A penalty-based approach using signed distance fields handles collisions or contacts between the tire and terrain elements. The signed distance field efficiently represents the element's deformed surface geometry for collision detection. Normal and tangential contact forces can then be distributed over the collided surface regions to resolve penetrations and sliding constraints. An iterative process resolves only the penetrations requiring positive contact forces, avoiding artificial deformations from correlated grid points. The results of this work showcase the potential of the proposed RANCF modeling method for computationally efficient simulations of tire-terrain interactions.

4021 / Ecological Performance In The Wltc Test Of A Diesel-Hydrogen Dual-Fuel Ci Engine

Dawid Tatarynow, Rafał Longwic, Jarosław Pytka, Michał Kuszneruk, and Przemysław Sander Keywords: Hydrogen; compression-ignition engine; dual fuel injection; WLTC; alternative fuel Abstract: Even though regulations in the European Union talk about banning the registration of combustion cars after 2035, yet no such regulations have been introduced in other parts of the globe. The rapidly changing economic and political situation creates many complications for business including the automotive sector. Tests were carried out on a CI engine with a common rail injection system and an additional hydrogen system. Hydrogen was injected sequentially into the intake manifold with an injector opening time of 3 ms at a pressure of 0.115 MPa. The energy and ecological parameters of the engine installed in the Fiat Qubo were recorded in a mapped WLTC test on a MAHA chassis dynamometer. The effect of adding hydrogen on the above-mentioned parameters was analyses in relation to the use of diesel fuel alone. The use of hydrogen for co-firing with diesel can contribute to extending the life of current compression-ignition engines.

4046 / Study On Mobility And Strategy Of Mars Rover With Faulty-Driven Wheel

Zhicheng Jia, Jingfu Jin, Xinju Dong, Yingchun Qi, Meng Zou, and Lianbin He Keywords: Mars Rover; Faulty-Driven Wheel; Mobility; Emergency Control Strategy Abstract: Due to the particularity of planetary exploration mission, the Mars rover cannot be recovery and repaired in time when it fails like a conventional field robot. The failure of its core components such as wheels may directly lead to the interruption of detection tasks and even the loss of its own mobility. In this study, the motion state and model of the Mars rover with faulty-driven wheel are analyzed, and an emergency movement mode based on active suspension wheel lifting driving and faulty wheel dragging driving is established. In order to restore the hidden danger scene on the ground and accumulate experience in advance, the mobility test was carried out using the Zhurong Mars rover prototype based on the simulated Martian terrain. The test results show that the mobility of the Mars rover under the two emergency mobility modes is reduced. The average driving power of active suspension wheel lifting driving increases by about 30.1 %, the average current increases by about 24.8 %, the sinkage is larger and the terrain adaptability becomes weaker. The average driving power of faulty wheel dragging driving is increased by about 167.6 %, the average current is increased by about 112.6 %, the bulldozing resistance is larger and the heading deflection occurs. To maintain the subsequent basic detection capability of the Mars rover, this study concludes by summarizing and proposing an emergency control system that integrates fault movement mode switching strategy and intermittent heading correction. These test results on ground can provide valuable reference for Mars rover operators and related researchers, and help them take timely and effective measures when facing similar accidents.

4375 / Development Of A Multi-Legged Robot Capable Of Ground Stiffness Detection

Tomoya Nishiyama, Tatsuki Honjo, Yugo Hosizawa, Ryota Hayashi, Koji Yoshida, and Tetsuya Kinugasa Keywords: Multi-Legged Robot; i-CentiPot; Ground Stiffness Detection Abstract: Centipedes move by generating retrograde waves in their legs in an antiphase pattern left and right, and they increase their stride by undulating their trunk as their speed increases. On branches, they move with the legs on both sides in phase, stretching and contracting their trunk. Furthermore, they can swim by relaxing their legs and undulating their trunk on the water, demonstrating high mobility in various environments. The changes in gait adapted to the environment shown by such animals are interesting and provide essential clues for realizing vehicles that can move in multiple environments. Terramechanics focuses on propulsion mechanisms on terrain, especially on soft terrain. Understanding the movement strategies animals adopt in various environments and how they achieve their gait patterns are significant in ground vehicles. Hence, the objective of this study is to analyze the gait of centipedes on sand and to develop a prototype multi-legged robot, which is designed to emulate the observed gait. First, it was confirmed that centipedes change to a gait with legs moving in phase on both sides on the sand. It was also confirmed that, whereas the swing phase is longer than the propulsive phase on rigid terrain, the opposite is true on sand, with a longer propulsive phase. Next, to realize a robot that can recognize the ground stiffness and alter its gait accordingly, a system was introduced that has a bending sensor in the flexible legs and can actively rotate each leg. Finally, it was clarified that the flexibility and rotational angle of the legs recognize the terrain stiffness.

4695 / An Image Analysis Method For Obtaining Wheel Performance Of Rover Using Wheel Tread Traces Remained On Lunar Simulant Soil

Yujin Lim and Viet D. Le Keywords: Rover wheel; image analysis; lunar soil; wheel tread; pattern recognition; machine learnining Abstract: An image analysis procedure was proposed and adapted in this study to obtain rover wheel performance by analyzing wheel tread images remained on the surface of lunar simulant soil. Wheel-soil interaction is usually simulated by using Bevameter test results and adapting sinkage model such as Bekker’s and Wong and Reece methods. However, the pressure-sinkage models obtained from the Bevameter test do not clearly provide in-detail information about sinkage and slip of the wheel when a rover runs on loose and fine dry soil. The wheel tread images captured by a camera mounted on the single wheel tracking device were analyzed successfully by using a specific pattern recognition procedure that is composed of Gabor wavelet filter, Principal Component Analysis (PCA), and Support Vector Machine (SVM). Next, We do successfully develop a required scheme of machined learning that was used to obtain an improved calculated torque of the wheel that is required for the next movement of the rover running on lunar terrain.

4998 / Dynamical Modeling Of The Power Hop Phenomenon In An Agricultural Tractor With Front Axle Suspension

Masahisa Watanabe, Keisuke Kazama, and Kenshi Sakai Keywords: Agricultural tractor; Power hop; Axle suspension; Nonlinear dynamics Abstract: Power hop refers to the coupled oscillation of vertical, longitudinal, and pitch motions observed when four-wheel-drive tractors tow moderate to high draft loads on dry soils or operate on slippery roads or slopes. The severe vibrations resulting from power hop reduce operational precision, ride comfort, and tractor stability, while also increasing soil compaction and damage to operators and tractor body. Unlike forced oscillations, power hop is a self-excited oscillation caused by the nonlinear dynamics of agricultural tractors, including stick-slip and impact dynamics. Our previous paper investigated how these nonlinear elements contribute to the power hop phenomenon in farm operations. In this study, we explore the efficacy of front axle suspension in mitigating the occurrence of power hop and its associated vibrations. Although front axle suspension is generally employed to improve ride comfort during tractor operation at higher speeds, its efficacy on power hop have not been investigated thus far. We newly developed a power hop model for an agricultural tractor equipped with front axle suspension and conducted numerical simulations varying model parameters of the developed model. Our results demonstrate that front axle suspension can effectively suppress power hop even under load and soil conditions that would induce power hop in a tractor without such suspension. However, we also observed occurrences of power hop in front axle suspension tractors under more severe conditions including higher draft loads and drier soils.

6277 / Comparison Of The Energy Performance Of A Diesel Engine Fueled By Alternative Fuels Along With The Addition Of Hydrogen

Michał Kuszneruk, Rafał Longwic, Jarosław Pytka, Dawid Tatarynow, and Sławomir Tarkowski Keywords: hydrogen; diesel engine; dual fuel injection; alternative fuels; emission standards Abstract: A review of the literature shows that the use of hydrogen improves the energy performance of an internal combustion engine. These properties are of interest in the context of improving the combustion processes of vegetable oils. Tests were carried out on a 1.3 Multijet compression-ignition engine built in a Fiat Qubo, which was fuelled with four different mixtures: diesel with hydrogen, diesel with LPG, rapeseed oil with 10% n-hexane solution, rapeseed oil with 10% n-hexane solution and hydrogen. The diesel engine, with a common-rail injection system, was adapted to run on various liquid fuels and an additional gaseous fuel supply system. While running on the MAHA chassis dynamometer, power and torque measurements were taken. The injection control parameters were also recorded each time. The results of the tests were synthesised in the context of the influence of the alternative fuel used on the injection control and the energy parameters achieved.

6865 / Extended Terramechanics Model Considering Ground Surface Deformation And Its Application To Wheel Traveling Analysis

Shingo Ozaki, Tomoya Arai, and Mai Shimizu Keywords: Wheel; Ground deformation; Trafficability; Simulation; Cellular automaton Abstract: Based on the pioneering work by Bekker, Wong, and Reece, terramechanics models have been used to evaluate the traveling performance of off-road vehicles of a wide range of scales, from small robots to mining dump trucks. Recently, it has also been used to study the performance of lunar and planetary exploration rovers. Meanwhile, multi-body dynamics analysis implementing the terramechanics model is a typical method to study the performance of off-road vehicles on soft ground. This approach can be a powerful tool not only for evaluating the overall vehicle behavior, but also for evaluating safe work plans. The quality of a multi-body dynamics analysis of an off-road vehicle depends on the terramechanics model that describes the interaction between the driving parts and the ground. In this study, the effectiveness of an extended terramechanics model (xTerramechanics model) is demonstrated, which considers soil deformation actions based on cellular automata, for the evaluation of traveling performance of a rigid wheel. First, the results of single-wheel traveling analysis are compared with experimental results under the forced-slip condition, and it is shown that drawbar-pull and sinkage are represented with good accuracy. We then apply the xTerramechanics model under the self-propelled traveling condition at a constant towing load and slope climbing. The model successfully reproduced the well-known “difference in traveling performance depending on traveling conditions.”

7116 / Dem-Sph Analysis For Interaction Mechanics Of Tracked Vehicle On Wet Sand

Hiroki Yanagawa and Genya Ishigami Keywords: Soil deformation; Tracked vehicle; Construction robots; moist sand Abstract: Tracked vehicles are extensively employed in unstructured environments, traversing on uneven and deformable terrains. The mobility facilitated by the track unit which is composed of interconnected metal plates, is pivotal for enhancing vehicle mobility and safety. In the context of construction machinery, there is a paramount need for stable traversability across sand imbued with moisture. Despite this, the existing research on evaluating tracked vehicle performance in wet sand conditions is significantly limited in contrast to the extensive research conducted on dry sand. This study aims to develop a DEM-SPH-based simulation methodology for assessing tracked vehicle traversability on water-laden soil. The DEM, or Distinct Element Method, is a proven technique for soil-machinery interaction analysis, but it inaccurately represents water-infused sand dynamics. Incorporating the Smoothed Particle Hydrodynamics (SPH) addresses these difficulties, allowing it to improve the simulation accuracy of moist soil behavior. Our approach involves calibrating and validating DEM-SPH parameters through cone penetration tests across various soil moisture levels and resistance force variations. Subsequent cross-validation of the calibration was performed by examining the deposition angles of differently moistened sand in a cylindrical container. By calibrating DEM-SPH parameters, our simulations of track unit vehicles on moist sand considering various slip ratios of the track provide insights into the complex dynamics of vehicle-soil interactions. This research highlights the potential of DEM-SPH in delivering precise analyses of tracked vehicle performance on moist sand.

7555 / Practical Applications Of Hybrid Terramechanics Model Using Machine Learning

Eric Karpman, Jozsef Kovecses, and Marek Teichmann Keywords: Terramechanics; Machine Learning; Hybrid Modelling Abstract: Real-time wheel-soil models in terramechanics primarily rely on traditional semi-empirical terramechanics models as a foundation. Because of the steady-state assumption that these models are formulated with, their accuracy can suffer in dynamic simulations. Methods such as the Finite Element Method (FEM) and the Discrete Element Method (DEM) can capture transient effects that traditional semi-empirical models cannot, but their computational cost is prohibitive for real-time applications. Using a machine-learning (ML) approach in combination with the semi-empirical models, the authors have previously shown that it is possible to create a hybrid model that can run in real time while capturing transient wheel-soil behaviour. This was achieved by generating training data in the form of DEM simulations and using the resulting forces to compute the difference between the force prediction of the semi-empirical and DEM models. A neural network was trained to predict the difference between these forces. This work builds off the authors’ previous work to expand the scope of this modelling approach so that it can be used in a wider range of practical applications. This is achieved by studying the ideal network input and output parameters and creating DEM simulation scenarios that result in high quality training data. Notably, the idea of having the neural network predict a force per unit width of the wheel is explored as strategy for saving computational resources and creating neural networks that work for a wider range of problems. Detailed description of the creation of training data and network training procedure as well as various examples of the trained network implemented as part of a hybrid wheel-soil model in real-time dynamic simulations will be presented.

8330 / Semi-Empirical Terramechanics Model For Variable Terrain Height In 3D

Eric Karpman, Wing Hang Ho, Jozsef Kovecses, and Marek Teichmann Keywords: Terramechanics; Rough Terrain; Semi-empirical Abstract: When employing semi-empirical terramechanics models, dynamic simulations typically rely on the assumption that all terrain, even rough terrain, can be approximated as a plane in any given simulation time step. This assumption is made necessary by the fact that traditional semi-empirical terramechanics models are formulated to compute wheel-soil interaction forces for a wheel travelling over a flat plane, and adapting these models to compute the reaction forces for a wheel travelling on a sloped plane is straightforward. In many cases, approximating the contact between a wheel and a complex terrain mesh as contact between a wheel and a sloped plane - whose normal direction is determined by the terrain nodes that intersect with the collision geometry of the wheel - can give a reasonable approximation for the contact forces. However, there are conceivable scenarios where important terrain features, such as gaps in the wheel-terrain contact patch, can be overlooked when using this approach. The authors have previously proposed an alternative method for adapting the traditional semi-empirical models for rough terrain without the need to simplify the contact problem to a wheel on a sloped plane. This is accomplished by treating the terrain as a height field and integrating the contact stresses along the wheel's rim by computing the sinkage at each point along the rim based on the un-deformed height field height at that position in space rather than based on the wheel's position relative to an approximate contact plane. In this work, the previous 2-D implementation of the proposed approach is extended to three dimensions to illustrate how it can be used in full-scale dynamic simulations.

8506 / Introduction Of Hourglass Mission To Investigate Characteristics Of Granular Materials In Low Gravity Environment

Masatsugu Otsuki, Shingo Ozaki, Genya Ishigami, Takao Maeda, Masataku Sutoh, and Taizo Kobayashi Keywords: Hourglass; Low gravity; Granular materials; Dynamics; Regolith; Spacecraft design Abstract: The Hourglass mission has been conducted to investigate the gravitational dependence of basic parameters for reproduction of behavior of granular materials such as regolith and ground sand, and to obtain information that contributes to future spacecraft design. In the Hourglass mission, the behaviors of regolith and ground sand in an arbitrary gravity environment are observed with an artificial gravity generator included in the Cell Biology Experiment Facility (CBEF) in the Kibo module of the International Space Station (ISS). The purpose of this mission is to investigate the effect of low gravity on the properties of granular materials. An hourglass-type container and a measuring-cylinder-type container including particles such as simulated regolith of planets and ground sand are packed into a sealed metal box mounted on the artificial gravity generator. The behavior of particles is observed with an optical camera while the containers are periodically flipped under arbitrary low gravity. Eight kinds of specimens are employed for the target samples, and dynamic behavior and sedimentation state (bulk density, angle of repose, etc.) of these granular materials are evaluated. Hourglass mission would have the contribution of understanding of the celestial growth process, provision of basic data for the construction of terramechanics on celestial bodies, optimization of design for future landers, exploration rovers, automatic construction machines on the lunar surface and manned pressurized rover for lunar exploration, and the appeal of the value and ability of Kibo artificial gravity environment. This presentation outlines the Hourglass mission, from start-up to development, and provides application examples of the results obtained.

8861 / An Efficient And High-Fidelity Track Model For Dynamic Simulation Of Off-Road Tracked Vehicles

Oz Ben-Yosef and Dror Rubinstein Keywords: track model; drawbar pull; multi-body model; track high-fidelity; track efficient Abstract: A high-fidelity simulation model of tracked vehicles is required for proper prediction of the mobility of tracked vehicles traveling over soft soils. The vehicle components can be modelled using standard tools of multi-body programs. A track model was developed and successfully worked together with Altair's MotionSolve multi-body program. The model based on classic soil mechanics equations. The grousers, which are a significant part of many types of track-links, are taking into the account. The plasticity and viscosity properties of the soil are considered in the model. Verification tests were conducted in an agricultural field in the Jezreel Valley. The tests were run over soils with varying mechanical prop-erties, achieved through irrigation and tillage. The chosen test vehicle was an M113 armoured carrier. Several drawbar pull loads were applied on each soil condition. Reasonable correlation between the tests and simulation results were achieved. However, this model is not efficient and require consumption of large amount of CPU time. On the other hand, the more efficient models are based on simplifying assumptions with lack of accuracy. This work proposes a method for creating an efficient high-fidelity model. This can be implemented by representing the interaction between the track and the ground according to the previous work. The solution for the track-links will be done independently to the solu-tion of the entire vehicle. The solution of the track link will be obtained through a solver that will be developed for this purpose. The solution of the entire vehicle will be done by the solver of the multibody program (Altair MotionSolve). Good correlation between the efficient model and the previous model were achieved.

9688 / Evaluation Of The Dynamic Sinkage And Its Effect On The Compaction Force Prediction Of Off-Road Vehicles

Yang Jiao, Jozsef Kovecses, and Marek Teichmann Keywords: slip-sinkage; off-road vehicle; discrete element method; symbolic regression Abstract: In off-road wheel/tracked vehicle operations, shearing and compaction actions of- ten occur simultaneously, with both contributing to the total sinkage of the vehicle. The sinkage induced by the vehicle’s compaction is typically referred to as static sinkage. This type of sinkage can be accurately quantified using pressure-sinkage relations such as the Bekker equation or the Wong and Reece equation. The sinkage resulting from the shearing behavior of the wheel and track is referred to as slip-sinkage (or dynamic sinkage in some literature). Compared with the first part, the slip sinkage is usually neglected in simulation. However, neglecting slip-sinkage can lead to inaccuracies in predicting motion resistance and traction, both of which are closely tied to vehicle performance. In past literature, slip sinkage has typically been calculated based on the slip ratio and static sinkage. In this research, the Discrete Element Method (DEM) virtual experiments were conducted to investigate the physical causes of wheel slip sinkage and identify the main contributing factors. The experimental results demonstrated that, in steady-state conditions, slip-sinkage increased with higher slip ratios, while also being influenced by the shear velocity of the wheel. In transient states, the primary contributor appears to be shear displacement rather than the slip ratio. The DEM virtual experimental results were utilized to develop an empirical equation for calculating slip sinkage, incorporating shear displacement, shear velocity, and slip ratio through symbolic regression. The normal force calculation based on the pressure sinkage equation was also modified to better accommodate slip-sinkage, thus improving the accuracy and stability of the simulation.