Article

“Wheels vs. tracks”–A fundamental evaluation from the traction perspective

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Abstract

The issue of wheeled vehicles vs. tracked vehicles for off-road operations has been a subject of debate for a long period of time. Recent interest in the development of vehicles for the rapid deployment of armed forces has given a new impetus to this debate. While a number of experimental studies in comparing the performances of specific wheeled vehicles with those of tracked vehicles under selected operating environments have been performed, it appears that relatively little fundamental analysis on this subject has been published in the open literature, including the Journal of Terramechanics. This paper is aimed at evaluating the tractive performance of wheeled and tracked vehicles from the standpoint of the mechanics of vehicle–terrain interaction. The differences between a tire and a track in generating thrust are elucidated. The basic factors that affect the gross traction of wheeled and tracked vehicles are identified. A general comparison of the thrust developed by a multi-axle wheeled vehicle with that of a tracked vehicle is made, based on certain simplifying assumptions. As the interaction between an off-road vehicle and unprepared terrain is very complex, to compare the performance of a wheeled vehicle with that of a tracked vehicle realistically, comprehensive computer simulation models are required. Two computer simulation models, one for wheeled vehicles, known as NWVPM, and the other for tracked vehicles, known as NTVPM, are described. As an example of the applications of these two computer simulation models, the mobility of an 8 × 8 wheeled vehicle, similar to a light armoured vehicle (LAV), is compared with that of a tracked vehicle, similar to an armoured personnel carrier (APC). It is hoped that this study will illustrate the fundamental factors that limit the traction of wheeled vehicles in comparison with that of tracked vehicles, hence contributing to a better understanding of the issue of wheels vs. tracks.

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... Commonly used methods of sands simulation are finite element method (FEM) and discrete element method (DEM). The widely-used FEM depends on the continuous soil model based on the theory of Mohr-Coulomb, Duncan, Bekker, et al. [2] [3] , which all hypothesize soil as a continuous medium in advance [4] . Actually, soil will be deeply rutted by the shearing of operating wheels, especially in case of high slip along with the soil rupturing and splashing in a discontinuous state [5] , which is more apparent on the condition of large off-road wheels with various lugs. ...
... (a) Mechanical model of DEM (b) Contacting condition of particles While there is any normal contact and overlap u between particles, shown in Figure 3(b), normal contact force Fn will be immediately produced and calculated in Equation (1). At that time, any tangentially relative displacement v will cause the tangential contact force Fs due to Equation (2). On account of the slip, there will be relative slipping between the two contiguous particles, when the tangential contact force Fs no longer increases by its displacement, just as Equation (3): ...
... Figure 7(b) & (c) indicate that both total tractive force and moment of torque the wheel received from sands rapidly increase at the very beginning of slip. The slopes gradually decrease as the slip increases, which match Bekker's semi-empirically theoretical model widely accepted already [2] . However, the difference from the Bekker's model is that those slopes of the simulation in this paper increase again when slip reaching up to a high ratio of 60%-80%. ...
... The robot has three tracks which operate independently and are mounted on three modules which are oriented at 120° to each other. The tracks provide for greater surface traction compared to wheels [2]. The tracks are pushed onto the inner wall of the pipe by passive springs which help in maintaining the contact with the pipe during vertical climb and while turning in bends. ...
... The design intent for the Modular Pipe Climber was to build a robot that is simpler in design with less moving parts, which is easier to build and implement compared to the currently existing pipe climbers. The Modular Pipe Climber has tracks instead of wheels, which provide a greater surface for contact and in return greater traction [2]. The robot has three modules which are separated by 120° and connected with the center chassis by four shafts each, with each shaft equipped with a spring which keeps the robot pressed against the inner wall of a pipe during vertical climb and when turning in bends. ...
... The higher the VCI, or ground pressure, the less mobile the platform becomes. In other paper in Wong et al (2004) [2] the comparison between tracks and wheels for different soil type (and different shear deformation parameter of the terrain value) for the behavior platforms type is highlighted. Previous articles and studies have concluded that wheeled vehicles are intrinsicallymore reliable than tracked vehicles and, therefore, require less maintenance and supply support (spare parts). ...
... The higher the VCI, or ground pressure, the less mobile the platform becomes. In other paper in Wong et al (2004) [2] the comparison between tracks and wheels for different soil type (and different shear deformation parameter of the terrain value) for the behavior platforms type is highlighted. Previous articles and studies have concluded that wheeled vehicles are intrinsicallymore reliable than tracked vehicles and, therefore, require less maintenance and supply support (spare parts). ...
Conference Paper
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In the present paper a system to transform a wheeled excavator in a tracked excavator and vice versa will be disclosed. The system permit the commutation of operation mode of the excavator for the achievement of the best travel condition in off road and in road. The goal is to have very flexible machine, which has the ability of a wheeled excavator and a tracked excavator as well. An important issue is to keep a machine in high efficiency in different condition, from the off road to in road. In this paper the possibility to have the optimal performance in different soil condition and with different type of advancing mode will be shown. The tracked type machine is a good solution for raw terrain condition or in off road situation. However the wheeled type machine is better for long travel in road and doesn't cause the asphalt deterioration. In this work a mechanical solution will considered based on a 16 ton excavator size. After that the method for the commutation from wheeled to tracked excavator and vice versa will be shown, explaining the basic principles of the connections between the prototype parts. Finally a Mathematical Comparison Between three solutions, Wheeled, Tracked and Switchable Excavator will be undertaken on a Standard Mission Profile analyzing the performances of Travel Time and Energy Consumption.
... The robot has three tracks which operate independently and are mounted on three modules which are oriented at 120° to each other. The tracks provide for greater surface traction compared to wheels [2]. The tracks are pushed onto the inner wall of the pipe by passive springs which help in maintaining the contact with the pipe during vertical climb and while turning in bends. ...
... The design intent for the Modular Pipe Climber was to build a robot that is simpler in design with less moving parts, which is easier to build and implement compared to the currently existing pipe climbers. The Modular Pipe Climber has tracks instead of wheels, which provide a greater surface for contact and in return greater traction [2]. The robot has three modules which are separated by 120° and connected with the center chassis by four shafts each, with each shaft equipped with a spring which keeps the robot pressed against the inner wall of a pipe during vertical climb and when turning in bends. ...
Preprint
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This paper discusses the design and implementation of the Modular Pipe Climber inside ASTM D1785 - 15e1 standard pipes [1]. The robot has three tracks which operate independently and are mounted on three modules which are oriented at 120{\deg} to each other. The tracks provide for greater surface traction compared to wheels [2]. The tracks are pushed onto the inner wall of the pipe by passive springs which help in maintaining the contact with the pipe during vertical climb and while turning in bends. The modules have the provision to compress asymmetrically, which helps the robot to take turns in bends in all directions. The motor torque required by the robot and the desired spring stiffness are calculated at quasistatic and static equilibriums when the pipe climber is in a vertical climb. The springs were further simulated and analyzed in ADAMS MSC. The prototype built based on these obtained values was experimented on, in complex pipe networks. Differential speed is employed when turning in bends to improve the efficiency and reduce the stresses experienced by the robot.
... Tracks have many advantages over the wheel and leg types for stair climbing. Tracked mobile robots have a very large ground contact area [1] that provides improved traction and stability along with ease of control and continuous drive. These robots are having the capability to climb up stairs, overcome obstacles and ground adaptability can provide help in search and rescue operations, hazardous situations, terrorist activity and military explorations. ...
Conference Paper
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o design and develop a robot for climbingup the stairs as well as for urban search and rescue missions in buildings and cities, it is often necessary to place flipper or swing arms to get better grip of stairs. Stair climber robot should be quick and agile at the same time be able to deal with rough terrain. This paper presents the mechanical structure of stair climber robot with hardware composition and force analysis using classical mechanics method. To find out the effectiveness of the dynamical model the results from the model is compared with simulation and experiments (4) (PDF) Analytical Approach for Force Stability Analysis of Stair Climber iNaCoMM2015-129 Analytical Approach for Force Stability Analysis of Stair Climber. Available from: https://www.researchgate.net/publication/330011534_Analytical_Approach_for_Force_Stability_Analysis_of_Stair_Climber_iNaCoMM2015-129_Analytical_Approach_for_Force_Stability_Analysis_of_Stair_Climber [accessed Jan 03 2019].
... In addition, various researchers [2,3,6,7] have proposed empirical equations for ground contact pressure and static sinkage based on the results of bevameter pressure-sinkage experiments performed on various types of ground. Wong and Huang [8] and Baek et al. [9] used these equations to calculate the static sinkage of off-road tracked vehicles under various ground and vehicle conditions, which were applied to assess motion resistance. ...
Article
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When an off-road tracked vehicle travels, shearing action and ground sinkage occur on the soil–track interface, severely affecting the tractive performance of the vehicle. Notably, ground sinkage, which is induced by the vehicle’s weight (static sinkage) and longitudinal forces in the direction of travel producing slip (slip sinkage), develops motion resistance, directly restricting the tracked vehicle’s performance. Thus, it is critical to consider both static sinkage and slip sinkage to assess the tractive performance of a tracked vehicle. In this research, model track experiments were conducted to investigate slip sinkage. The experimental results showed that the slip sinkage increased as the slip ratio increased, but the rate of increase decreased. The slip sinkage was found to increase as the density of the ground decreased and imposed vertical load increased. The experimental results were used to calculate normalized slip sinkage, and an empirical equation for slip sinkage in terms of slip ratio was developed. This equation will allow vehicle operators to predict the slip sinkage and associated motion resistance for given soil and vehicle conditions.
... Improved grip between soil and lugs, improved floatation and the potential for reducing ground pressure are among the advantages of tracks (Wong, 2001). Wong and Huang (2006) compared the traction performance of tracks and tyres. They concluded that the traction of wheeled vehicles, in general, cannot match with that of comparable tracked vehicles due to the shorter contact length of tyres compared to the tracks. ...
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The pneumatic wheels of a walking tractor were replaced with rubber track system to improve draught. Performance was evaluated in agricultural soils and compared with that when fitted with wheels. Tests were carried out in sandy clay loam soil with cone index (CI) varying from 250 to 1000 kPa for both the tractors. Data of motion resistance, pull and slip were acquired using different sensors and data acquisition system. For CI of 250, 500 and 1000 kPa, the observed motion resistance values for tracks were found to be 1012, 775 and 620 N, respectively, which represent 18.75%, 14.36% and 11.5% of the weight of the tested walking tractor and 935, 675 and 530 N for the wheeled walking tractor which represents 17.32%, 12.5% and 9.8% of its weight, respectively. Rubber tracked walking tractor developed greater drawbar pull than the wheeled one in all soil conditions. The drawbar pull developed with tracks is 115.2%, 75.9% and 62.4% more than that developed by comparable walking tractor fitted with standard wheels, respectively in soils with CI 250, 500 and 1000 kPa. Tractive efficiency (TE) of walking tractors fitted with rubber tracks was higher in all soil conditions. Also, tracks reached peak TE at higher net traction ratio (NTR) and maintained higher TE for a wider range of NTR. Wheels reached maximum TE at lower values of NTR, which drops off at higher NTR values. The results indicate a significant improvement in the tractive ability of walking tractor.
... The traction properties also depend on parameters of the tyres (SCHREIBER & KUTZBACH, 2008; DABROWSKI ET AL., 2006) especially on the inflation pressure (NORÉUS & TRIGELL, 2008). In case of frictional soil the traction force primarily depends on normal load while in case of cohesive soil the traction force primarily depends on the overall size of the contact area (WONG & HUANG, 2006). Šmerda & Čupera (2010) claim that reduction of the inflation pressure from 180 to 65 kPa causes increase of the traction coefficient from 0.66 to 0.74. ...
Conference Paper
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The paper deals with comparison of three types of tractor tyres with same proportions 600/65 R38 from the producer Mitas (IF and VF tyres and PneuTrac prototypes). The tyres are made from different blends and have different structure which allows operation at lower inflation pressure. The comparison is based on tyre footprints, specific pressure and traction properties of the tyres. The inflation pressure was determined according to values recommended by the producer for a given load (3650 kg). The inflation pressure was 160 kPa for IF tyres, 100 kPa for VF tyres and 60 kPa for prototype tyres PneuTrac. The dependence of the slip on the tractive force was measured in order to compare the traction properties. Results show that the prototype tyres PneuTrac with the inflation pressure 60 kPa made the largest footprints and had the most favourable traction properties.
... Relative to the other forms of locomotion, wheeled/tracked systems are the simplest configurations to implement and easiest to control. They are highly effective over flat, firm ground however they often perform poorly over soft, uneven or broken terrain (Wong and Huang 2006). Tracked vehicles tend to possess improved terrain adaptability over wheeled vehicles, however they use more energy, produce more ground deformation, are noisy and their high stiffness is prone to induce vibrations. ...
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Domestic and human-centered environments pose many practical challenges for service robots, especially those that must perform a diverse range of tasks. Existing robot morphologies have typically failed to incorporate the physical practicality and terrain adaptability needed to achieve high behavioral diversity in these spaces, as the most suitable configurations for certain tasks/behaviors are often highly unsuitable for others. This paper presents the development of a novel wheeled robot morphology that has been designed to possess the physical characteristics necessary to exploit human-centered environments, while also attaining the terrain adaptability to perform demanding locomotive tasks such as crevice crossing and step climbing. The design of a demonstrator embodiment is presented and discussed. Through simulation and real-world testing, the effectiveness of the prototype is evaluated. Finally, several design insights and lessons learned are discussed.
... This kind of robots is ideal for working in tasks under rough terrains. Among the applications tracked robots can achieve are urban reconnaissance, forestry, mining, agriculture, rescue mission scenarios, autonomous planetary explorations [23][24][25]. ...
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Nowadays, there are several meta-heuristics algorithms which offer solutions for multi-variate optimization problems. These algorithms use a population of candidate solutions which explore the search space, where the leadership plays a big role in the exploration-exploitation equilibrium. In this work, we propose to use a Germinal Center Optimization algorithm (GCO) which implements temporal leadership through modeling a non-uniform competitive-based distribution for particle selection. GCO is used to find an optimal set of parameters for a neural inverse optimal control applied to all-terrain tracked robot. In the Neural Inverse Optimal Control (NIOC) scheme, a neural identifier, based on Recurrent High Orden Neural Network (RHONN) trained with an extended kalman filter algorithm, is used to obtain a model of the system, then, a control law is design using such model with the inverse optimal control approach. The RHONN identifier is developed without knowledge of the plant model or its parameters, on the other hand, the inverse optimal control is designed for tracking velocity references. Applicability of the proposed scheme is illustrated using simulations results as well as real-time experimental results with an all-terrain tracked robot.
... Moreover, with the rapid advance in computer technology and computational techniques in decades, the computer-aided methods have become feasible to simulate the interaction between running gear and soil. 9 JY Wong and W Huang 15 have compared the tractive performances of wheeled and tracked vehicles based on the mechanics of vehicle-terrain interaction. For evaluating the thrust, two computer simulation models, one for wheeled vehicles which is known as Nepean Wheeled Vehicle Performance Model, and the other for tracked vehicles which is known as Nepean Tracked Vehicle Performance Model, were established. ...
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The objective of this study is to clarify the differences of tractive performances generated by the sandy loam-grouser system and the clay soil-grouser system. The tractive performances of the grouser/track shoes are widely researched by previous researchers. However, it is essential to illustrate the influences of the soil properties on the tractive performances of the grouser shoe. Sandy loam and clay soil were used as the test soils for investigating soil parameters in this study. Moisture contents of soil were from 7.5% to 27%, dry basis. Parameters of sandy loam were obtained through direct shear tests, penetration tests, bulk density, and moisture content measurements in laboratory. The grouser shoe was made of steel. Based on the prediction result of tractive performances, the clay soil will always be performed better than the sandy loam no matter which dimension was chosen for single grouser shoe. Based on the experimental results, the grouser height of the track should be 5 cm in order to provide enough traction force, if a tracked vehicle is operated on the environment of either clay soil or sandy loam.
... Multiple passes of wheels increases soil strength and decreases the motion resistance simultaneously (Aksenov, 1989;Bekker, 1969;Letoshnev, 1929;Garbari, 1949;Ul'yanov, 1969;Brixius, 1987). The considerable effect of multi-pass on vehicle tractive efficiency, in many initial researches, is not considered for equations suggested for tractive performance analysis and are included only in traditional experimental and analytic methods (Bekker, 1969;Wong, 2008;Wong and Huang, 2006). Later the multi-pass effect is included to predict the vehicle-soil interaction using wheels and tracks (Lyasko, 2010;Gheshlaghi et al., 2020). ...
Article
This paper studies the energy dissipated during experimental and simulated procedures for the pressure-sinkage and shear-strength test. These tests are performed using a clayey-loam soil and modelled as smoothed-particle hydrodynamics (SPH) technique in Visual Environment’s Pam-Crash software. The hydrodynamic elastic plastic material is used to define the equation of state for the clayey-loam soil. The soil is modelled at five different levels of compaction to represent multi-pass of a tyre over soil. The soil calibration is performed using the pressure-sinkage and direct shear-strength test and validated using experimental data from a soil bin facility. The energy dissipation is calculated using the soil sinkage values at every pass of wheel. Finally, the results of experimental and simulation dissipation energy are discussed and the effect of the tyre multi-pass on dissipated energy is investigated and presented. This research will further continue to model an agricultural FEA tyre over the clayey-loam soil to compute tyre performance and interaction characteristics.
... In the field of tracked vehicles like excavators or compost turners, the driving behavior, especially the slack between the ground and the chain itself, is well described [17]. However, until now, no non-military research regarding autonomous tracked vehicle is available considering the characteristic behavior of the vehicle itself in detail. ...
Conference Paper
In the most common method of commercial composting, bio-waste is stacked into triangle-shaped windrows. As oxygen is needed for the composting process, the windrows need to be turned repeatedly by compost turners with spiked drums. The biogenic material has to be turned at low speeds and during the turning process, the drivers are exposed to water vapor, gases and high temperatures. Due to these unpleasant working conditions, operators of large composting plants often have difficulty in finding personnel. Therefore, autonomous compost turners would be a great benefit for operators of composting plants. A prerequisite for an autonomous compost turner is a robust and reliable positioning algorithm which is capable of providing continuous and precise position, velocity and attitude information of the compost turner in real-time. This paper presents a positioning module for tracked compost turners. It gives an overview on the system design and evaluates which sensors can be used for positioning of compost turners based on tests in the environment of a real composting site. Based on the preliminary sensor tests, a set of suitable navigation sensors is selected. The selected sensors include a GNSS dual-antenna array, a stereo camera, a MEMS IMU and encoders. The images recorded by the stereo camera are fused with a precise 3D map. Within this paper, a federated loosely coupled extended Kalman filter is developed to fuse the result of the stereo-image and model matching with GNSS, INS and odometer measurements. The primary innovation lies in the sensor selection and sensor fusion specifically tailored to compost turners. A novel approach, which fuses GNSS, INS, odometer, stereo images and a 3D map, is presented.
... The other is plastic soil, such as loose sand, dry soil,and other disturbed ground soil, the shear stress-strain curve of this kind of soil has no peak of protrusion, and it always changes smoothly. The shear models describing plastic soils are: Janosi shear model, hyperbolic shear model, pure exponential shear model, etc. [1][2][3][4][5]. For the plastic shear properties of deformable ground soil, there is no hump in the shear stress-strain curve, so the Janosi shear model is adopted [3]to describe the shear properties of ground soil at low shear rates, as follows: ...
Article
Full-text available
The classical ground soil shear mechanics model is difficult to predict the maneuverability of vehicles under high-speed driving conditions. The shear mechanical properties of soil under dynamic loading are the key factor to research on the ground attachment characteristics of vehicles under high-speed driving conditions. The relationship between the shear properties of the ground soil and the loading rate was analyzed by numerical simulation method. Based on the Janosi shear model of the ground soil, the loading rate and shear rate were supplemented to establish the applicable driving conditions for high-speed and heavy-duty vehicles. The ground soil shearing characteristics model provides a theoretical basis for researching on the vehicle's driving maneuverability under high-speed driving conditions.
... Tracked or wheeled skid-steer locomotion is chosen for many robotic vehicles due to its mechanical robustness, and high maneuverability and traction [1]. Field applications include agriculture [2], military [3], inspection of nuclear facilities [4], planetary investigation [5], volcano exploration [6] and search and rescue [7]. ...
... where r = wheel radius; and X c ¼ π=4 − φ 0 =2. Based on previous research (Wong and Huang 2006), because the soil is subjected to local shear failure due to the influence of grousers, a reduced value shall be used instead, as described in Eq. (9) ...
Article
This paper introduces a testbed developed from a perspective of soil mechanics that not only focused on wheel design and optimization but also considered the elimination of the boundary effect caused by a soil bin. Using this testbed, a series of experimental investigations were performed by changing the wheel rotational velocity, vertical load, and towed load. Tracks were generated at a regular spacing as the wheel lugs enter and exit the soil periodically. It has been found that there is a relationship between the track length and wheel slip ratio regardless of different mechanical properties of soil. The wheel rotational velocity has little effect on the driving torque and sinkage. The towed load affects the driving torque more than the sinkage. However, the vertical load effects on the driving torque and sinkage are similar. The current models used for parameter estimations may not be appropriate for Tongji-1 lunar soil simulant, which has a relatively high internal friction angle according to the experimental results. But the internal friction angle and cohesion can still be estimated with proper selection of shear deformation modulus.
... Another terminology given in literature is percentage no-go terrain [7]. It is a measure of immobile terrain and can be directly related to the ground pressure [20]. ...
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There has been increasing interest in improving the mobility of ground vehicles. The interest is greater in predicting the mobility for military vehicles. In this paper, authors review various definitions of mobility. Based on this review, a new definition of mobility called fuzzy mobility is given. An algorithm for fuzzy mobility assessment is described with the help of fuzzy rules. The simulation is carried out and its implementation, testing, and validation strategies are discussed.
... The UCP comprises a tracked vehicle for operations on the shoreface profiling. This versatile locomotion can operate over diverse terrains, generating low ground pressure, and preventing it from sinking into soft ground, such as loose sandy terrains [25,26,27]. ...
Article
An underwater caterpillar vehicle has been designed and developed to profile along the beach and shoreface. This prototype is employed for zones that are unsuitable to study through bathymetry or manual measurements. The system consists of a metallic structure propelled by two caterpillar tracks. An electronic accelerometer and a GPS receiver measure the profile data. These components provide the seabed slope and the traveled distance along a path. The data are recorded locally and transmitted to a host computer with a radio modem, conforming a wireless duplex link, which is also used for controlling the vehicle and reporting the status. The profiler system has been tested in several zones in the Pacific Coast of the Baja California Peninsula, Mexico and the results were compared with an Electronic Total Station. Based on the obtained results, the underwater caterpillar system evinces to be a reliable profiler option.
... The study of modern publications in the field of interaction of the propulsion unit of forest tracked vehicles with soil shows that statistical models are most often used [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. ...
... Integrating the distributed normal and shear stress under a wheel on deformable terrains to acquire the wheel-soil interaction force and torque is always utilized by scholars (Gao et al., 2013;Yoshida and Hamano, 2002;Wong and Reece, 1967a,b;Meirion-Griffith andSpenko, 2013, 2011;Ishigami et al., 2007a,b;Ding et al., 2015;Nagatani et al., 2009;Wong and Huang, 2006;Irani et al., 2011). That is to say the distributed stress is the basis of wheel-soil interaction modeling. ...
Article
Wheeled mobile robots are often used on high risk rough terrain. Sandy terrains are widely distributed and tough to traverse. To successfully deploy a robot in sandy environment, wheel-terrain interaction mechanics in skid should be considered. The normal and shear stress is the basis of wheel-soil interaction modeling, but the normal stress in the rear region on the contact surface is computed through symmetry in classical terramechanics equations. To calculate that directly, a new reference of wheel sinkage is proposed. Based on the new reference, both the wheel sinakge and the normal stress can be given using a quadratic equation as the function of wheel-soil contact angle. Moreover, the normal stress can be expressed as a linear function of the wheel sinkage by introducing a constant coefficient named as sand stiffness in this paper. The linearity is demonstrated by the experimental data obtained using two wheels and on two types of sands. The sand stiffness can be estimated with high accuracy and it decreases with the increase of skid ratio due to the skid-sinkage phenomenon, but increases with the increase of vertical load. Furthermore, the sand stiffness can be utilized directly to compare the stiffness of various sandy terrains.
... The main advantage of a tracked robot is that it can be used to navigate in rough terrains. 1,2 The thrust developed by a wheeled vehicle will generally be lower than that developed by a comparable tracked vehicle; 1 this is why these kinds of vehicles are used in a variety of applications where terrain conditions are difficult or unpredictable: urban reconnaissance, forestry, mining, agriculture, rescue mission scenarios, autonomous planetary explorations, to name but a few. 2,3 Besides, tracked robots offer some other advantages, such as follows: ...
Article
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This work presents the implementation in real-time of a neural identifier based on a recurrent high-order neural network which is trained with an extended Kalman filter–based training algorithm and an inverse optimal control applied to a tracked robot. The recurrent high-order neural network identifier is developed without the knowledge of the plant model or its parameters; on the other hand, the inverse optimal control is designed for tracking velocity references. This article includes simulation and real-time results, both using MATLAB®, and also the experimental tests use a modified HD2® Treaded ATR Tank Robot Platform with wireless communication.
... Therefore, the study of off-road wheels in terramechanics has attracted more attention from researchers in recent years (Asnani et al., 2009). The widely used method to research the trac-tive performance of a single wheel is the soil bin test, which was proposed by Bekker MG and advanced in theory by Bekker (1960), Janosi and Eiler (1968), Wong and Reece (1967), Wong and Huang (2006). However, limited to the size and cost of this equipment, soil bins are always shaped in a rectangle to simulate the straight driving condition of an off-road wheel. ...
Article
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This paper presents a numerical analysis on steering performance including tractive parameters and lug effects. To explore the difference between the turning and straight conditions of steering, a numerical sand model for steering is designed and appropriately established by the discrete element method on the basis of triaxial tests. From the point of mean values and variation, steering traction tests are conducted to analyze the tractive parameters including sinkage, torque and drawbar pull and the lug effects resulting from type, intersection and central angle. Analysis indicates that steering motion has less influence on the sinkage and torque. When the slip ratio exceeds 20%, the steering drawbar pull becomes increasingly smaller than in the straight condition, and the increase of steering radius contributes to a decline in mean values and a rise in variation. The lug effect of central angle is less influenced by the steering motion, but the lug intersection is able to significantly increase the steering drawbar pull along with the variation reduced. However, the lug inclination reduces the steering drawbar pull along with the variation raised in different degrees.
... They achieve the highest speeds on flat surfaces. Their downside, however, is their poor ability to operate in difficult terrain, with some of them being vitiated by a significant turning radius [5]. Currently, research on improving their mobility in difficult terrain is being conducted. ...
Article
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This article deals with the design and testing of mobile robots equipped with drive systems based on omnidirectional tracks. These are new mobile systems that combine the advantages of a typical track drive with the advantages of systems equipped with omnidirectional Mecanum wheels. The omnidirectional tracks allow the robot to move in any direction without having to change the orientation of its body. The mobile robot market (automated construction machinery, mobile handle robots, mobile platforms, etc.) constantly calls for improvements in the manoeuvrability of vehicles. Omnidirectional drive technology can meet such requirements. The main aim of the work is to create a mobile robot that is capable of omnidirectional movement over different terrains, and also to conduct an experimental study of the robot’s operation. The paper presents the construction and principles of operation of a small robot equipped with omnidirectional tracks. The robot’s construction and control system, and also a prototype made with FDM technology, are described. The trajectory parameters of the robot’s operation along the main and transverse axes were measured on a test stand equipped with a vision-based measurement system. The results of the experimental research became the basis for the development and experimental verification of a static method of correcting deviations in movement trajectory.
... The wheeled driving system has advantages over the tracked driving system; such as low running resistance, little noise, and good maneuverability [1]- [2]. Additionally, the wheeled driving system can be steered by turning the steering wheels, such that shear damage due to differential steering is avoided [3]. ...
Article
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A six-wheel driving system with a variable wheelbase is proposed to improve the passing ability of unmanned vehicles. As the first step, the effect of the wheelbase variation on the axle load distribution is analyzed. Next, the relationship between the wheelbase variation and rolling resistance is obtained by numerical calculation combined with the theory of terramechanics, and it shows that the traction performance of the vehicle can be optimized by adjusting the wheelbase. Considering the deformation of tires and soil, the mechanism of the effect of the change in wheelbase on the ability of the vehicle to overcome an obstacle and cross a trench is studied, and a variable-wheelbase strategy for a vehicle overcoming an obstacle and crossing a trench is then proposed on the basis of theoretical calculations. Finally, the rationality of the variable-wheelbase strategy is verified in simulation experiments.
... Multiple passes of wheels increases soil strength and decreases the motion resistance simultaneously (Aksenov, 1989;Bekker, 1969;Letoshnev, 1929;Garbari, 1949;Ul'yanov, 1969;Brixius, 1987). The considerable effect of multi-pass on vehicle tractive efficiency, in many initial researches, is not considered for equations suggested for tractive performance analysis and are included only in traditional experimental and analytic methods (Bekker, 1969;Wong, 2008;Wong and Huang, 2006). Later the multi-pass effect is included to predict the vehicle-soil interaction using wheels and tracks (Lyasko, 2010;Gheshlaghi et al., 2020). ...
Article
This paper studies the energy dissipated during experimental and simulated procedures for the pressure-sinkage and shear-strength test. These tests are performed using a clayey-loam soil and modelled as smoothed-particle hydrodynamics (SPH) technique in Visual Environment’s Pam-Crash software. The hydrodynamic elastic plastic material is used to define the equation of state for the clayey-loam soil. The soil is modelled at five different levels of compaction to represent multi-pass of a tyre over soil. The soil calibration is performed using the pressure-sinkage and direct shear-strength test and validated using experimental data from a soil bin facility. The energy dissipation is calculated using the soil sinkage values at every pass of wheel. Finally, the results of experimental and simulation dissipation energy are discussed and the effect of the tyre multi-pass on dissipated energy is investigated and presented. This research will further continue to model an agricultural FEA tyre over the clayey-loam soil to compute tyre performance and interaction characteristics.
Article
Due to the high rolling rate of a regular crawler paddy harvester and the absence of mature first season harvester products of ratooning rice, combined with the planting mode and harvest requirements of ratooning rice, a triangular crawler ratooning rice harvester is specifically designed. The structure and steering principle of the triangular crawler chassis are described. The hydraulic system is simulated and analyzed by AMESim2020 (Guangzhou, China) to verify the rationality of its design; RecurDynV9R4 (Guangzhou, China) is used to simulate and analyze the field straight/turning situation of differential steering chassis and rear-axle steering chassis. The results show that the rear axle steering chassis has a smaller turning radius and lower rolling loss rate and the change of track tension is more stable during steering. The field test is conducted to verify the reliability of the simulation results. The field test shows that the rolling loss rate of the rear axle steering chassis is reduced by 27.9% compared with the differential steering chassis. The machine’s operating speed is 2.8 km/h, the minimum turning radius is 780 mm, and the straight rolling rate is 26.8%. The operating performance is stable, and the operational process is smooth. Compared with the existing conventional harvester, the linear rolling rate of the first harvest of ratooning rice is reduced by 26.1%, and the test results are consistent with the RecurDyn simulation results. The results are reliable, providing a reference for the theoretical research of the chassis of the later ratoon rice harvester.
Article
The electromechanical coupling performance of crawler machinery is investigated. A dynamic equation of electromechanical coupling of crawler machinery is established under multi-typical working conditions. The variation in performance of electromechanical parameters during unstable operations over time is analyzed using the virtual prototype and electromechanical coupling model of crawler machinery. The correctness of the electromechanical coupling model is confirmed by comparing the theoretical analysis, virtual prototype simulation, and physical prototype results. This study provides accurate and valuable theoretical methods and fundamental knowledge to analyze the electromechanical and road driving performance as well as to develop and design a crawler machinery.
Article
This study analyzes resistances to sinking, steering bulldozer, steering friction, running, climbing, inertia, and wind and considered the offsetting effects of instantaneous center of speed and center of mass based on the sinkage method proposed by Bekker. The purpose of the analysis is to show the calculation method for the driving power of crawlers under different working conditions. The influence of several performance factors were analyzed to calculate the steering performance of a dumping machine with heavy double crawler. The performance factors include steering radius, offset mass, width-to-length ratio, crawler width wider than the interior and lateral, caterpillar gauge in crawler drive, drive power, and steering torque friction. These factors are involved in driving wheels at a crawler speed of 3.33 RPM. The law of operation for heavy crawlers under different working conditions is obtained by performing a real vehicle test. The results of this test are compared with the theoretical calculations to verify correctness. Such a test provides important theoretical basis for theoretical modeling and for analyzing the performance of large crawlers running on soft ground.
Article
As the soil traction of the track system consisting of a track plate and protruded grousers is generally higher than that of a comparable wheel system, underwater tracked vehicles are the favored platforms for heavy-weight remotely operated vehicles (ROVs). When an underwater tracked vehicle moves on the seafloor, the track system laterally transmits an engine torque to the soil-track interface, resulting in slip displacement and an associated soil thrust acting as a traction force. Therefore, to evaluate the mobility of underwater tracked vehicle, it is critical to evaluate the soil thrust of the track system based on the soil-track interaction. Unlike the soil thrust of sandy soils, a reliable soil thrust assessment method accounting for the failure mechanism of clayey soil has yet to be developed in spite of its significance. An experimental study on the mechanism of the soil thrust of clayey soil was thus performed. Model track experiments were conducted on a model track system with clayey soil. Based on the experiment results, the mechanism of the soil thrust of clayey soil was investigated and was compared with the mechanism of soil thrust derived from the previous soil thrust assessment methods using sandy soil. Particular attention was given to the development of a new soil thrust prediction model for the track system on clayey soil using the limit equilibrium analysis technique.
Chapter
Elloboat is a tracked vehicle for launching and beaching of small boats and watercrafts, capable of operating in a wide range of operative conditions, here including rescue applications. This paper presents the vehicle architecture and discusses the main design issues. The effects of track dimensions on terrain compaction, bulldozing resistances and, consequently, on track sinkage are analyzed by means of the Bekker model. Obviously, track dimensions also influence the vehicle mass and size, leading to a complex engineering problem. Since vehicle speed and acceleration are limited, stability during locomotion can be assessed using a quasi-static approach, computing the longitudinal and lateral tipping angles for a given vehicle configuration and payload position, and imposing a proper limit to their minimum. Stability analysis can be exploited not only in the design phase, but also for the real-time evaluation of the actual margin of stability, so as to help the operator in the vehicle path/speed planning.
Article
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The investigation “autonomous navigation for tracked compost turners” (ANTON) aims to automate composting machines by means of satellite-based navigation technologies. In the course of this project, a navigation module and a control module for a driverless, electrically driven, tracked compost turner will be developed and tested. A fundamental task during the process of composting is turning the biogenic material with machines. Currently, this is conducted and monitored by an operator inside the driver’s cab of a diesel-driven compost turner or conventional loader. Due to low driving speeds of compost turners (approx. 50 to 300 m/h), high ambient temperatures, released gases, and bad smell during compost turning, the operator is exposed to very unpleasant conditions. Further on, the currently used diesel engines do not meet the expectations of the customers regarding sustainability and green technologies which is the reason why the focus is on electric powered system. The primary innovation is determining a precise and robust position of a slowly moving vehicle like the compost turner under the so far non-tested surrounding conditions. For the vehicle’s motion control, a control structure shall be established and evaluated with the help of the method “Software in the Loop” (SiL). For that matter, the controller software is directly coupled with a multibody simulation model, which describes the driving characteristics of the tracked vehicle. The main goal of the investigation is to develop a prototype of a compost turner which can fulfill the required task “turning windrows” autonomous. Further on the developers expect a minimum of initial start-up time because a significant number of crucial tests for the controller are already done within the SiL system. This approach will decrease the cost of the investigation significantly. Within this article, the authors will mainly elaborate on the interdisciplinary system simulation and its coupling using functional mock-up interfaces, which outlines the base ot SiL method. The system simulation will cover the coupling of a signal flow-oriented simulation to simulate the control structure, a multibody simulation, which simulates the mechanics of the compost turner’s tracks and a discrete element method (DEM) simulation, which simulates the force feedback of the turning of the biogenic material.
Article
This research is spearhead for longitudinal slippage of robot platform wheels traversing on solid balls based uneven terrain. For this purpose, effects of solid ball diameter (0.0127–0.0508 m) accompanying with tire inflation pressure (20.68–55.16 kPa) and platform forward speed (0.17–0.50 m/s) on the slippage were practically quantified. Robotic experiments were executed in controlled test bed prepared by solid ceramic balls. Tentative data collected from the experiments indicate that the wheels experienced low (<30%), moderate (30–60%) and high slippage (>60%) under effects of independent variables. Results demonstrated that the increasing effect of the dominant variable of solid ball diameter on the slippage was 3.6 and 2.6 times greater than that of platform forward speed and tire inflation pressure, respectively. Meanwhile, the increasing linear effect of tire inflation pressure on the slippage was prevailed (1.4 times) than the decreasing linear effect of platform forward speed. Hence, to minimize the slippage as well as power loss of the platform traversing on each solid ball diameter, adjustment of tire inflation pressure should be enumerated as first priority. Overall, analytical results obtained in this research lead to open a new prospection for comprehending the slippage trends of off-road wheeled robots traversing on an uneven terrain composed of solid balls. Practicability of this type of the robots is remark in various industrial robotic operations, especially for process towers and reactors of oil, gas, petrochemical, and chemical industries. Hence, quantitative and qualitative information of this research are a rich source for relevant industrial investigators and experts who involved in this realm.
Article
The information of terrain is highly valuable as the accuracy of decision maker depends on input data for taking the correct decision. For planning of any successful off-road movement, the terrain information plays the vital role. This paper describes the state of art of off-road trafficability leading from the contributing factors, Instruments for measurements and trafficability mapping techniques in chronological order. In modern times, the number & type of tracked or wheeled vehicles, has increased many times, therefore off-road trafficability for operation planning became a complex task to handle. The accuracy and reliability of measurements involved in trafficability will play a major role for any successful operation. Off-road trafficability shows the capacity of soil required for vehicular movement. Remolding Cone Index (RCI) indicates the soil's capability for off-road movement. In this study, the area was divided in equal small grids for ease of computation of RCI. Geospatial technology provides the platform to determine the locations of observation points as well as the extrapolation of information of inaccessible area using geospatial tools and techniques. RCI values were computed for each grid and also measured with cone penetrometer in the field. R² value for observation values was determined for different soils present in the area to check the accuracy of measurements and then based on observed value and computed value, R squared (coefficient of determination) values (0.7754 and 0.4867) were evaluated for both study areas to get the idea about relevance, reliability and accuracy. Residual RCI (RRCI), difference of computed & observed was also analyzed for different soils for different moisture conditions. Based on thisanalysis, a modified equation was developed for different type of soils present in the study area. This development will pave the way to compute the RCI accurately, which will be used to assess the off-road trafficability of other areas in similar manner. Therefore, this study is useful to assess the regional variation of soil behavior towards trafficability based on modified equation.
Chapter
The use of robotic solutions for sustainability is critical to reduce pollution and waste of materials during the manufacturing processes, and it can significantly reduce the amount of energy employed compared with traditional methods. This paper presents two case studies in the development of mobile robotic solutions used to increase the manufacturing sustainability by avoiding waste of materials and physical stress for the operators. Both mobile robots can improve the manufacturing performance by reducing costs and time with special attention to the environment and to the safety.
Article
The National Robotics Engineering Center has conceived a novel system that is able to reconfigure from a track to a wheel while in motion. The purpose of this device is to combine the benefits of wheels and tracks to provide performance optimization on a variety of terrain. The first stage of development resulted in two benchtop prototypes: one to test a transition from rotating hub to rotating tread and another to test a constantly-oriented shape transition from circle to triangle. This paper documents the testing of these devices including current draw, temperature change, and braking characteristics. Through experimentation with the first testbed, desired speed was shown to be consistent within +/−6% when transitioning between wheel and track modes at an approximated ground speed between 5 and 35 km/h while transitioning in 5 to 60 seconds. Testing on the second system identified asymmetry in testbed construction and showed consistent loading patterns throughout a 42 mm-change in sprocket position between wheel and track mode while transitioning between 10 and 50 mm/s. The evaluation of these testbeds informed the design of the next process of the reconfigurable wheel-track project, which resulted in a larger prototype capable of propelling a small ground vehicle.
Article
Inevitable interaction between soil and pneumatic tires of an off road vehicle in a rectilinear motion leads to experience of energy dissipation. Rolling resistance force and longitudinal slip of wheels are responsible for the energy dissipation inside wheel-soil interface. Attention of current study is paid to methodically elucidate the energy dissipation by wheels of front wheel assist tractor for the period of plowing works. To achieve this goal, the energy dissipation dependency on draft force requirement of plow implement as well as tractor drive mode (rear wheel drive (RWD) and front wheel-assisted drive (FWAD)) was quantitatively ascertained. Results disclosed that the energy dissipation ascended in domain of 3.18-17.66 and 3.14-21.04 MJ/ha for the RWD and FWAD mode, respectively, as the draft force requirement proliferated from 3.85 to 23.04 kN. Whilst, energy expenditure for plowing works ranged from 12.45 to 74.85 MJ/ha. It means that the energy dissipation was approximately equal to quarter of energy expenditure for plowing works. When the draft force requirement augmented, portion of the energy dissipation caused by the slip of the wheels raised in range of 12.15-82.51% and thereby, that of rolling resistance force of the wheels dropped in range of 87.85-17.49%. Hence, to reduce the energy dissipation, for both drive modes at the higher draft force requirement, activation of slip control system for preservation of the slip of the wheels in a particular range is sufficient enough. For both drive modes at the lower draft force requirement, not only activation of the system, but also decrement of rolling resistance force of the wheels by overinflating the tires must be prescribed. In case of the FWAD mode, overinflating the tires must be accomplished based on generation of driving lead of front wheels in allowable range.
Article
In this paper, the autonomous navigation of six-crawler machine is studied, and a visual tracking control method based on machine vision for fuzzy proportional–integral–derivative control of six-crawler machine is proposed. The steering principle of the six-crawler machine and the matching relationship between the steering angle and the speed of each crawler are introduced, and the control system is described in detail. Besides, the mathematical model for the unsteady steering is introduced to analyze the influence of deflection angle on the steering trajectory of the six-crawler machine. The image processing algorithm is programmed by LabVIEW software. After the image is fitted by graying, binary, filtering, edge detection, and least square method, the navigation line-fitting curve is obtained. The fuzzy proportional–integral–derivative control algorithm is programmed in the control system to control the six-crawler machine to drive along the navigation line. In order to obtain reasonable control parameters, a virtual prototype model of a six-crawler machine is established. In the CoLink module, the control algorithm of a six-crawler machine is established, and the co-simulation is carried out. By analyzing the simulation results, the control parameters of the fuzzy proportional–integral–derivative controller of the six-crawler machine are established. In order to verify the control effect of the visual tracking control system of the six-crawler machine, a physical prototype of the six-crawler machine is constructed and tested. The results show that the visual tracking control system of the six-crawler machine can complete the preset functions.
Article
Off-road trafficability is one of the most important factors during military operations. Primarily, there are four factors like landuse, soil type, slope and moisture, which are responsible for predicting off-road trafficability. In the present study, multi-level approach leading from landform, land use to terrain factors was used to assess the obstacle induced towards the cross country movement of tracked and wheeled vehicle separately. The information of land use, landform and slope was gathered from space based sensors, while for soil and moisture information, the field samples analysis along with ancillary information was also used other than space based sensors. The main aim of this study is to make the rule based assessment of terrain in categorization of off-road trafficability in four categories of movement like good, restricted, restricted with engineering measures and difficult. This will improve the speedy assessment of off-road trafficability of inaccessible terrain in the many countries around the world.
Article
The traction force of a tracked unmanned ground vehicle (UGV) depends on the soil thrust generated by the shearing action on the soil-track interface. In the development of soil thrust, because the continuous-track system consists of a number of single-track systems connected to each other, interference occurs between the adjacent single-track systems through the surrounding soil. Thus, the total soil thrust of the continuous-track system is not equal to the sum of the soil thrust of each single-track system, and the interference effect needs to be carefully considered. In this study, model track tests were conducted on model single-, double-, and triple-track systems according to relative density of soil and shape ratio (i.e., the length of the track plate to grouser depth). The test results indicated that the interference effect reduced soil thrust due to the overlapping shear zones between adjoining single-track systems. The loss of soil thrust increased as the relative density of the soil increased and the shape ratio decreased. Based on these findings, a soil thrust multiplier that can be utilized to assess the soil thrust of a continuous-track system was developed.
Article
The comparative analysis of the known researches and approaches to the assessment of all-wheel drive vehicles terrain crossing capacity in the conditions of moving on snow-covered bearing surfaces (BS) is carried out. The analysis shows that domestic approaches are based on traditional USSR principles that are different from those adopted in NATO countries in terms of indicators and evaluation criteria. In addition, an analysis of the geographical conditions and road and climatic zones of Ukraine regarding application of wheeled military automotive equipment (MAE) allows to confirm that much of the territory of Ukraine in winter is absolutely snow-covered. Under such conditions, when considering the perspective parameters of wheeled MAE for assessing terrain crossing capacity under snow covered traffic conditions, it is necessary to take into account this factor. Snow is a special kind of BS for military automotive equipment with two-order physical-mechanical variations and corresponding transitions from running to cohesive type of BS. Therefore, mobility and performance of wheeled MAE has some unique characteristics and terminology. Wheeled MAE movement on snow-covered surfaces is related to the thickness of the snow cover and depends on the depth of the formed track, which is a function of snow compaction and shear strength in response to vehicle loads. Besides, the basic empirical dependences of the motor resistance forces and tire coupling with the BS are significantly different from those applied for soil and sand BSs. The comparative analysis provided may be the basis for the formation of a national regulatory framework for assessing terrain crossing capacity of wheeled MAE, taking into account the requirements for compatibility of domestic approaches with those adopted in NATO countries.
Chapter
Heavy drawbar work on cultivated soil is the most critical aspect for agricultural tractors after the impairment of efficiency resulting from wheel slippage. To investigate this aspect with specific reference to cultivated soils, the data of 100 tractors of varying engine power and weight were processed to obtain a regression equation as the starting point to analyze driveline efficiency, power loss due to rolling resistance, and wheel slippage. To fit the results to soil conditions, four tractors of different mass fitted with agricultural tires of varying size and pressure settings were tested in field conditions to correlate drawbar force with wheel slippage. The algorithm obtained was introduced in the regression equation with the aim to obtain simplified algorithm for the assessment of the optimal wheel-slip value during drawbar works that enables optimal fuel consumption with minimum tractor efficiency impairment. According to the results, in case of heavy drawbar work, keeping the wheel slippage below 10% and running the tractor at low forward speeds results in greater tractor efficiency. This underlines the importance of the motion resistance of tires on the agricultural soil and the role that the proper evaluation of the drawbar force of tires plays, even at low levels of wheel slippage.
Article
Soil thrust acts as a reaction force that enables an off-road tracked vehicle to overcome motion resistance and move the vehicle forward. Thus, the estimation of soil thrust for a track system has great importance in the design and path planning of off-road tracked vehicles. In this study, we first present analytical solutions for the soil thrust of clayey ground by performing an upper-bound limit analysis, as a basis for the assessment of the tractive performance of off-road tracked vehicles. Two different failure modes (block and triangular wedge) are possible on a soil-track interface, and the resultant soil thrust is determined as an upper-bound solution for the most critical failure according to the principle of least action modes (i.e., the least-upper-bound solution). Based on the upper-bound solutions, parametric studies were conducted to explore the effects of the shear strength of clayey ground, geometry of a track system, and the weight of the vehicle on soil thrust. For practical use, this study also offers a soil thrust design chart for a single-track system.
Article
This study aims to provide a method to increase the mobility capabilities of wheeled military vehicles such as off-road trench and obstacle crossing by designing a preview control strategy based on model predictive control (MPC). The study is divided into three parts. The first part aims to create a vehicle dynamics model with active suspension and a co-simulation environment involving MATLAB ® and MSC ADAMS/Car™. In the second part, the level of achievable improvement in the vehicle’s operational abilities is investigated. Here, it is aimed to develop a controller and optimize vehicle ride height and attitude for improving mobility operations. Measured road data is used to improve the controller performance and create an obstacle crossing algorithm. Finally, a comparison of simulation results for different land operation scenarios is given for both uncontrolled and controlled systems based on which improvement levels are determined.
Article
This study aimed to investigate the applicability of the 1g similitude law to the physical modeling of soil-track interaction. Model track experiments were performed using four physically modeled soil-track systems with different geometric scale factors, under three different relative densities of the model ground. Based on the modeling of the model technique, the results of the physical models were compared in terms of the largest physical model scale. The soil-track interaction behaviors showed similar tendencies on the whole, but slight differences were also observed depending on the geometric scale factor. Such differences, however, were not significant compared to the differences in relation to other soil-structure interaction problems. Moreover, considering that the shearing action on the soil-track interface is a large replica of the shearing process in the direct shear tests of the soil, the differences among the physical models were attributed to the specimen size effect observed in the direct shear test of the soil, rather than to the similitude relationships. Therefore, it can be concluded that the 1g similitude law can be applied to the assessment of the soil-track interaction behavior, provided that the mechanical boundary restraint of the shearing action on the soil-track interface is properly accounted for.
Thesis
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A peculiarity of AWD off-road vehicles is that their behaviour depends not only on the total power, provided by the engine, but also on its distribution among the drive axles/wheels. In turn, this distribution is largely regulated by the drivetrain layout and its torque distribution devices. At the output of the drivetrain system, the torque is constrained by the interaction between the wheels and the soft soil. For off-road automotive applications, the design of drivetrain systems has usually been largely dominated by the mobility requirements. With the growing demand to have a multi-purpose on/off road vehicle with improved manoeuvrability over deformable soil, particularly at higher speed, the challenges confronting vehicle designers have become more complex. The thesis presents a novel integrated numerical approach to assess the dynamic behaviour ‎of all-wheel-drive vehicles whilst operating over deformable soil terrain. A full ‎drivetrain system including all aspects of rotational inertial dynamics, friction, damping and stiffness properties ‎is integrated within a fourteen-degrees-of-freedom vehicle model. For off-road simulations, the terra-mechanical ‎phenomena between tyres and deformable soils has also been taken into account. The integration of all modules resulted in a fairly complex generic model which is implemented in the MATLAB/Simulink/SimDriveline environment. In addition to the conventional mechanical torque distribution devices, particular attention has been paid to the modelling of various visco-lock devices, including the viscous couplings ‎of shafts and visco-lock limited-slip differentials. In the present work, these devices are ‎represented by fully parameterised physical models which capture the torque transmission mechanism ‎represented by various thermodynamic, hydrodynamic, structural and mechanical modules. The characteristics ‎of these devices can easily be altered so that comparisons can be made between different types. In addition, the ‎influence of a wide range operating conditions, vehicle design parameters and tyre characteristics can also be ‎made over various deformable soils. Both viscous shear and self-torque amplification (hump) have been ‎considered. In order to validate the proposed modules of visco-lock devices, a test rig is devised. The results of the experimental work conform to those obtained from the numerical models. A number of simulation studies, during longitudinal and cornering manoeuvres, are conducted to investigate the contribution of significant parameters. In addition, the influences of different drivetrain arrangements are presented. The obtained results delineated that both traction and cornering response of AWD off-road vehicles are highly affected by the way driving ‎torque is distributed between axles/wheels. ‎Also, It was demonstrated that, by appropriate selection of silicone fluid rheological properties, vehicle behaviour can be tuned in a simulation environment, avoiding time consuming and costly experimental procedures.
Article
Full-text available
An analytical framework for predicting the ground pressure distribution and tractive performance of tracked vehicles is presented. It takes into account all major design parameters of the vehicle as well as the pressure—sinkage and shearing characteristics and the response to repetitive loading of the terrain. The subsequent substantiation of the analytical method by means of full-scale tests made with an instrumented vehicle is described. A comparison between the theoretical prediction and test results is made and it is found that there is a fairly close agreement between them. This paper includes three sections: (i) an analytical method for predicting the normal pressure distribution; (ii) an analytical method for predicting the shear stress distribution and tractive performance; (iii) experimental substantiation of the analytical framework by means of full-scale tests. The analytical framework presented is suitable for evaluating the effects of vehicle design parameters and terrain conditions on the performance of tracked vehicles with relatively short track pitch designed for high speed operation and for comparing the tractive performance of different tracked vehicle designs.
Article
This paper describes the results of a study of the effects of articulation joint configuration, suspension characteristics, location of the centre of gravity and initial track tension on the mobility of a two-unit, articulated tracked vehicle. The study was carried out using a comprehensive computer simulation model known as NTVPM-86. The results show that suspension characteristics, location of the centre of gravity and initial track tension have noticeable effects on the mobility of articulated tracked vehicles over marginal terrain, while the articulation joint angle has a less significant influence on vehicle performance. Locking the articulation joint between the two units of an articulated tracked vehicle usually causes a degradation of tractive performance. The approach to the optimization of the design of articulated tracked vehicles is demonstrated. It is shown that the simulation model NTVPM-86 can play a significant role in the optimization of articulated tracked vehicle design or in the evaluation of vehicle candidates for a given mission and environment.
Article
This paper describes the results of an investigation into the effects of the characteristics of the suspension system, initial track tension, vehicle weight and location of the centre of gravity on the tractive performance of tracked vehicles over unprepared terrain. The investigation was carried out using a newly developed computer simulation model NTVPM-86. The results show that the suspension characteristics, initial track tension and vehicle weight have noticeable effects on the mobility of tracked vehicles over marginal terrain, while the location of the centre of gravity, within the normal range, has a less significant influence on the tractive performance. It is demonstrated that the simulation model NTVPM-86 can play a significant role in the optimization of tracked vehicle design or in the evaluation of vehicle candidates for a given mission and environment.
Article
In the past decade, a computer aided method for design evaluation of high-speed tracked vehicles with flexible tracks (or tracks with relatively short track pitch commonly in use in tracked transport vehicles and military vehicles) has been developed. It has been successfully used in assisting vehicle manufacturers in the development of new products and governmental agencies in the selection of vehicle candidates. For low-speed tracked vehicles commonly in use in agriculture, construction and logging, rigid tracks with relatively long track pitch are employed to achieve a more uniform ground pressure distribution. To assist manufacturers of this type of vehicle to expedite the development of new products in a cost effective manner, a computer aided method for design evaluation of tracked vehicles with rigid links has recently been developed. It treats the track as a system of interconnected rigid links and takes into account the characteristics of the interaction between track links and deformable terrain. The basic features of the method have been verified by field test data. The method can be an extremely useful tool for the engineer to optimize vehicle design and for the procurement manager to select appropriate vehicle candidates to meet specific operating requirements.
Article
This paper describes the applications of a computer aided method known as RTVPM to the selection and optimization of the basic design parameters of track systems with rigid links, commonly in use in agricultural and industrial vehicles. It is found that the ratio of roadwheel spacing to track pitch is a significant parameter that affects the tractive performance, particularly on soft terrain. For a given track system configuration and roadwheel spacing, it is important to select an appropriate track pitch to ensure good tractive performance on the one hand and minimal vehicle speed fluctuation on the other. It is also shown that the initial track tension has a considerable effect on tractive performance when the ratio of roadwheel spacing to track pitch is high and that its effect decreases with the decrease of the roadwheel spacing to track pitch ratio. The effect on tractive performance of the ratio of roadwheel spacing to track pitch becomes less significant with the increase of soil strength. It is demonstrated that by selecting the appropriate ratio of roadwheel spacing to track pitch, initial track tension, location of the centre of gravity and other design parameters, an optimum track system configuration for a given operating environment can be evolved.
Article
This paper demonstrates the applications of a computer aided method (CAM) to the parametric study of tracked vehicles with rigid links, commonly in use in agriculture, construction and logging. The results of the study show that the track pitch, number of road-wheels, initial track tension and location of the centre of gravity have a noticeable effect on tractive performance over soft terrain. It is also found that by careful selection of a combination of design parameters, vehicle performance can be significantly improved. It is shown that the computer aided method can play a significant role in design optimization of tracked vehicles with rigid links and in the evaluation of vehicle candidates for a given mission and environment.
Introduction to terrain-vehicle systems. Michigan: University of Michigan Press
  • Mg Bekker
Bekker MG. Introduction to terrain-vehicle systems. Michigan: University of Michigan Press; 1969.