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A multistage adaptive lateral deformation tracked robot was designed to improve the passing ability of field robots. The designed robot can change its width under the combined action of space barrier constraint and internal stored elastic potential energy. The lateral sliding friction affected by grouser parameters during lateral deformation is a key factor that determines whether or not the robot can achieve deformation. This study focuses on the track terramechanics and grouser parameter optimization. On the basis of the theory of terramechanics, the interaction of the flexible track lateral movement with the ground model and traction model was established. Taking the requirement of traction as the constraint condition and the minimum lateral sliding resistance as the optimization objective, we used the multitarget optimization algorithm (NSGA-II) to optimize and analyze the grouser parameters. Then, the optimal combination of grouser parameters was obtained. Simulation analysis was carried out on RecurDyn software to complete the simulation verification of the lateral force and traction force under different grouser parameters. The correctness of the theoretical model and the optimization of the grouser parameters was verified through prototype experiments.

A Passivity-Based Adaptive Controller (PBAC) is derived and tested for the integrated Argo J5 Skid Steering Mobile Robot (SSMR) and custom-built landing platform. The twofold aim is to demonstrate landing platform dynamic self-leveling accuracy, coupled with accurate Argo J5 trajectory tracking in rough and uneven terrains. The overall system dynamic model based on Euler-Lagrange and Terramechanics theory is summarized, followed by derivation of the PBAC. Performance is first tested/evaluated in a MATLAB/Simulink environment using actual/experimentally identified Argo J5-landing platform physical parameter values and constraints. Results are, then, verified/validated using the V-REP Simulation Package. Different terrain slope angles, different platform initial angles, and different realistic Argo J5 velocities are used in all studies. It is observed that dynamic self-leveling is achievable for Argo J5 slow velocities and small slope terrain angles. Results also reveal current design limitations that need to be overcome before actual testing.

In an autonomous scientific exploration system, the terrain map generated from mapping process integrates sensing information from multiple aspects and lays the base for decision making processes. With the increasing challenges in planetary exploration, equipping planetary rovers with the principles of terramechanics is becoming more and more common, especially on rough or intricate terrain. However, it is difficult for conventional maps with elevation information only to reflect terrain mechanical properties, which play important roles in terramechanics-based simulation or motion control. This study extracts the dominant parameters in terrain bearing and shearing models, and presents a multi-layered grid map with fundamental geometric and mechanical elements. A corresponding mapping scheme based on dense visual input is designed to reconstruct elevation in the map and predict terrain mechanical parameters of the entire visual field. Experiments are conducted to verify the practicability of the approach proposed in a Mars emulation yard with a rover prototype.

More than 50% of the land on earth is not suitable for wheeled and tracked vehicle, and more than 15% of the world army’s arrival areas urgently need a new walking device with higher passing ability. With the evolution of billions of years, animals can walk on many dangerous and complex terrains, therefore, the legged robot is designed to learn from the foot animals, and it is assumed to behave higher passing ability. However, it has not shown good passing ability in complex unstructured road. Aiming at the soft terrain which is common in the complex terrain, this paper studies the present research around three aspects of the bionic legged robot in soft terrain , including the application of terramechanics in robot, the foot design of legged robot, the dynamic modeling and motion control method. The theory and method introduced in this paper will support the technology development of the legged robot in soft terrain.

This paper proposes a supporting force model of a Push-Pull Locomotion on the rough terrain. Planetary rovers should avoid many obstacles on the planetary surfaces, for instance, rocks, stones, and rough terrain. When planetary rovers become stuck, this typed rover can move by using a large supporting force of the wheel, which is generated by keeping a position of a supporting wheels relative to the ground and move to another position. Recently, planetary rovers need to be controlled autonomously, therefore, the interaction mechanics between supporting wheels and soil need to be investigated. The drawbar pull force of the rotational wheel model has been investigated in the terramechanics field, however, in the Push-Pull Locomotion, the supporting wheels are locked during bulldozing soil. Therefore, the conventional model cannot apply to the supporting wheels. As the initial step, this paper constructs the supporting force model of the locked wheels without considering normal force of a wheel by using the Coulomb and GLEM (Generalized Limit Equilibrium Method) theory. The validity of these models is confirmed by a single wheel bulldozing tests. The experimental results revealed that the proposed model based on the GLEM theory can predict the supporting force of the wheel without a normal force in each wheel size and sinkage.

This paper presents detailed analysis, modeling, and controller design of the Skid Steering Mobile Robot (SSMR) Argo J5 with a custom-built landing platform, which also considers wheel-terrain interaction for control purposes. Terramechanics theory and the Argo J5 kinetics are combined to analyze the wheel-terrain interaction for different types of terrain. A PD controller is, then, designed to demonstrate tracking capabilities of the Argo J5. The main contribution of the modeling approach is adding a vertical load on each wheel to obtain the wheel's entry angle with respect to the terrain. Shear displacement is derived from knowing the point's position on each wheel in 3D space. The Argo J5 model and controller are tested in a MATLAB/Simulink environment by using the real Argo J5 parameter values. Obtained results illustrate Argo J5 velocity, wheel rolling resistance, wheel turning moment resistance, and shear stress on different terrains.

Planetary exploration rovers are expensive, weight constrained, and cannot be serviced once deployed. Here, we explore one way to increase their capabilities while avoiding the cost, mass, and complexity leading to these issues. We propose to re-use the large wheel actuators for trenching and other digging operations, which will enable a range of missions such as sampling deeper layers of soil. We present a new, closed-form model of the soil displaced by an angled, spinning wheel to analyze the trenching potential of a driving strategy and inform the control of the wheel. The model is demonstrated with single wheel experiments under different driving conditions. The model suggests: that a deep trench does not require large tractive efforts; that the shape of the trench can be controlled; and that a rear wheel has a lower risk of entrapment when trenching than a front wheel. Ultimately this model could be used in a nonprehensile manipulation planning or learning algorithm to enable autonomous trenching.

the second part of the present paper focuses on torque control of the optimized wide robotic wheels moving on the soft soil. The SCM method is implemented to numerically simulate the soil-wheel interaction during the dynamic control process. The power consumption, maximum sinkage, lateral forces, effective radius and traction error are the measures which are necessary to investigate the effect of the wheel shape in torque control process. The simulations are classified into pure steering, pure linear motion and complex point tracking to calculate the measures in various situations. The pure steering simulation investigates the effect of the wheel shape on the lateral forces and the sinkage. The effective radius and the distance are investigated through the linear movement. The point tracking simulation considers all measures investigated in a torque control process.

the first part of this paper presents an approach for characterization of the essential terra mechanic and dynamic parameters of the wide robotic wheels moving on soft soil using the soil contact model (SCM) method. This method will be used in a complex optimization algorithm based on the direct search approach to find the optimized shape of the wheels whereby the rovers can properly steer and move. The sinkage of the wheel, the lateral and longitudinal interaction forces, the pressure distribution and some new measures such as effective radius will be investigated as the optimization cost functions to achieve the elite shapes. According to the results of this optimization, the complete spatial dynamics of a four-wheeled rover will be extracted in part II of this paper. Using the optimized wheels, the rover will be empowered to rove on the rough and soft soil or sand. Indeed, the main idea of the part I of this paper is to dynamically optimize the shape of the super wide wheels according to the terra mechanic principles of the wheel-soil interaction.

In recent years, realistic simulation of vehicles on soft terrain has increasingly gained importance due to its use in operator training, mission planning and design. In this work we present a method which is tailored to the requirements of real-time simulation of soft soil in Virtual Reality applications. We combine models from terramechanics and soil mechanics in order to represent the interaction of vehicles and their digging tools with a deformable terrain, allowing us to simulate a broad range of vehicles, including earth moving equipment and planetary rovers on soft ground in real-time. We consider the impact of both wheel -- ground and tool -- ground interactions on the vehicle behavior by creating a fully coupled simulation of the dynamics of the vehicle and its environment. Furthermore we present verification experiments which show that our wheel -- ground interaction method yields realistic results.

Environment recognition is an effective way for a mobile robot to move across rough terrain. In particular, this makes it possible to prevent a tiny mobile robot from getting stuck or turning over. Several studies have been conducted on environment recognition using a laser range finder or camera. However, almost all of these studies focused on obstacle detection or shape recognition, which cannot be used to recognize the surface condition such as slipperiness. The purpose of this work is to design a model for estimating the surface condition using a tiny mobile robot. We set slipperiness as one of the parameters for recognizing the surface condition, which is already used by terramechanics, along with two additional parameters, the hardness and unevenness. We find that a robot can roughly estimate the ground hardness by measuring the current peak of a motor and the unevenness from measuring the robot posture. By recognizing the surface condition, the robot can change the parameters of the controlling motor based on the ground characteristics. This new method for recognizing the surface condition is significant, not only because it fills gaps in the previous research, but also because it does not require any special sensors such as a laser range finder and does not consume a large quantity of energy. Therefore, it achieves a core objective of our environmental monitoring system using multiple mobile robot.

Soft soil covers planetary surfaces, so the wheel of a planetary rover easily slips and gets stuck. In order to prevent increase in the slip and getting stuck, the wheel can have lugs that have a shape of a paddle to improve the wheel force. There have been some studies about the influence of the lugs. However, design method of an effective lug has not been studied well yet. Since terramechanics-based wheel models have been considered with a flat wheel surface, those models based on terramechanics are not applicable to the lugged wheel. In this research, in order to establish the design method of the effective lugs, a lugged wheel model was discussed and proposed regarding the variation of the shear characteristics. The variation of shear characteristics is indicated by a shear deformation modulus. The lugged wheel model is based on the shear deformation modulus varied by the lug design. In this paper, the simulation was performed to verify the validity of the lugged wheel model, and it was confirmed that the model could formulate the performance of the wheel traversability. Moreover, the wheel experimental device was described to understand the traversability of the lugged wheel. The evaluation method of the proposed lugged shear deformation model was also considered.

A great majority of current researches on obstacle negotiation focus on the critical state where CG position get over the obstacle using kinematics model. However, the models assume that the sinkage of the robot can be ignored and do not take into account whether the terrain can provide enough drawbar pull to keep the robot moving. While, when robots running on the soft terrain, the sinkage of the robot is very big that it can be ignore and it is very easy for the robots to slip. In order to solve that problem, this paper focuses on the effects of terrain physical parameters in the process of obstacle negotiation. Based on this point, the interaction models of wheel-terrain and track-terrain are built according to terramechanics. Using these models, two key postures of climbing obstacles are discussed, and the relationship between maximum surmountable obstacle-height and geometry parameters of the robot are obtained. Then maximum draw pull tests of wheel-track model and wheels model are designed to compare experimental results with theoretical results. Finally, experiments on surmounting obstacle performance of tracked robot are carried out, and the results show that our model is more exact than the CG kinematic model.

The wheels of planetary rovers will slip when they climbs up deformable slopes. On the contrary, the wheels will skid in the longitudinal direction in order to generate resistance force to balance the gravity component when a rover moves down the slopes. The wheel-terrain interaction principles of slip versus skid are quite different, but there is little research about the longitudinal skid mechanics and the relationship of it with the slip mechanics. This paper analyzes the problem of longitudinal slip and skid that occur to a wheel on the slopes with the knowledge of terramechanics. The slip and skid mechanics are compared based on experimental results measured by a single wheel testbed. The piece wise linear function is proposed to predict the drawbar pull and resistance moment under both slip and skid conditions. A semi-empirical equation of predicting the skid mechanics according to the slip mechanics is also provided. The models are verified using the experimental data.

An outdoor wheeled mobile robot with foldable wheels and a self-adapting suspension structure are described. The traffic ability and obstacle surmounting performance are analysed based on a terramechanics model. The relationship between the radius of the foldable wheel and the unfolding angle is obtained. The influence of slip on drawbar pull and the driving efficiency at different unfolding angles are calculated, so the influence of the foldable wheel on stability and obstacle surmounting performance do. At last an experiment will be carried out. The experimental results indicate that the mobile robot with foldable wheels has a better obstacle surmounting performance. This will make the robot adapt to the rough terrain better and broaden its application field.

Wheeled in-pipe robots have been widely used in pipelines inspection and exploring because of simple structure, steady performance and consuming less energy. However when wheeled mobile robots run in muddy in-pipe environment they often can't be control to move accurately and continuously mainly because the ground cannot provide adequate adhesion. In order to improve the movement performance of the robot in this environment we establish a model based on terramechanics. With this model further research including motion performance of wheeled in-pipe robots has been conducted in muddy in-pipe environment in this paper. The model of wheel-terrain interaction is established with the finite element software ABAQUS. With this model we analyze what and how the factors which affect the adhesion. The actual experimental results show the model and simulated analysis is useful and helpful to mechanical design and control strategy design for wheeled in-pipe robots.

In this work, a multibody dynamics model of a wheeled mobile robot is developed to characterize the terrain reaction forces in terms of the physical and control parameters of the system. A common strategy for simulating the motion of mobile robots on soft soil is to compute the soil reaction forces using terramechanics models and to solve a forward dynamics problem by considering the soil reactions as a set of forces applied to the system. This intends to provide an accurate computation of the forces involved in the wheel-soil interaction; however, a series of factors such as the sensitivity of reaction forces to soil parameters limits the applicability of the existing terramechanics models in unstructured environments. We propose an alternative approach which does not rely on the soil properties, but at the same time does not intend to provide an exact computation of wheel-soil interaction forces. The main objective of this approach is to estimate the effect of changes in control and design parameters on the performance of the system, using the information provided by the dynamics model of the vehicle. To this end, the reaction forces for the wheel-terrain interaction in the ideal limit case of pure rolling and no penetration are obtained upon the specification of the motion at the contact points, via kinematic constraints. The validity of the analysis results obtained using the proposed paradigm is verified by simulation runs and experiments. The experimental results suggest that this approach is successful in predicting the variation of a set of important performance indicators in terms of the changes in the parameters of the system.

Mars rovers have to this point been almost completely reliant on the solar panel/rechargeable battery combination as a source of power. Curiosity, currently en route, relies on radio isotope decay as its source of electrical power. Given the limited amount of space available for solar panels and that the wattage available from radioisotope decay is limited; power is clearly a critical resource for any rover. The goal of this work is to estimate the energy cost of traversing terrains of various properties. Knowledge of energy costs for terrain traversal will allow for more efficient path planning enabling rovers to have longer periods of activity. Our system accepts grid-based terrain elevation data in the form of a Digital Elevation Model (DEM) along with rover and soil parameters, and uses a newly developed model of the most common rover suspension design (rocker-bogie) along with a terramechanics-based wheel-soil interaction model to build a map of the estimated torque required by each wheel to move the rover to each adjacent terrain square. Future work will involve real world testing and verification of our model.

This paper details a novel pressure-sinkage model for small-diameter, rigid wheels on dilative soils. Pressure-sinkage models are fundamental to the prediction of UGV mobility on deformable terrains. The proposed model builds on previous work in which the flat-plate pressure-sinkage assumption of classical terramechanics was shown to yield diminished accuracy for UGVs with wheels less than 50 cm in diameter. It has been shown that classical pressure-sinkage models can be modified by a diameter dependent term, yielding greatly increased accuracy. Here, an investigation into the effect of wheel width on the diameter-dependent model is detailed. Results from over 250 pressure-sinkage tests on three soils using 85 wheel geometries are summarized. The results of this investigation are used to create a comprehensive pressure-sinkage model for dilative soils that includes wheel width and diameter parameters. The physics of the model are visually validated with X-ray images of sub-surface soil deformation during the wheel indentation process. A comparison between the dilative soil pressure-sinkage model and a previously obtained model for compactive soils is also presented. The pressure-sinkage model presented here can be used to improve the accuracy of the terramechanics framework and UGV mobility predictions.

The performance of wheels operating in loose granular material for the application of planetary vehicles is well researched but little effort has been made to study the soil shearing which governs traction. Net traction measurements and application of energy metrics have been solely relied upon to investigate performance but lack the ability to evaluate or describe soil-wheel interaction leading to thrust and resistances. The complexity of rim and grouser interaction with the ground has also prevented adequate models from being formulated. This work relies on empirical data gathered in attempt to study the effects of rim surface on soil shearing and ultimately how this governs traction. A novel experimentation and analysis technique was developed to enable investigation of terramechanics fundamentals in great detail. This technique, the Shear Interface Imaging Analysis Tool, is utilized to provide visualization and analysis capability of soil motion at and below the wheel-soil interface. Analysis of the resulting displacement field identifies clusters of soil motion and shear interfaces. Complexities in soil flow patterns greatly affect soil structure below the wheel and the resulting tractive capability. Grouser parameter variations, spacing and height, are studied for a rigid wheel. The results of soil shear interface analysis for wheels with grousers are presented. The processes of thrust and resistances are investigated and behavior characterized for grousered wheels.

Applications ranging from planetary exploration to military operations require small unmanned ground vehicles to traverse deformable terrains such as sand or moist earth. Crossing such terrains can be difficult because failure to generate enough traction can result in immobilization and mission failure. Thus, the ability to accurately predict a vehicle's traction on deformable terrain is critical. Traditionally this has been accomplished via terramechanics based on Bekker theory. However, it has been shown that classical terramechanics loses considerable accuracy when applied to vehicles with wheels less than 50cm in diameter. This paper details the development of a modification to the pressure-sinkage relationship used in Bekker theory that explicitly includes a dependence on wheel diameter. The new model is integrated into a numerical simulation that predicts the tractive performance of an experimental unmanned ground vehicle (UGV). Field tests are performed on sandy terrain, and the results validate the simulated predictions. The new model is found to be significantly more accurate than previous models.

In recent years, the rover-based planetary exploration missions have put forward some new challenges to the simulation platforms for rovers. This paper introduces a simulation platform, ROSTDyn (ROver Simulation based on Terramechanics and Dynamics), for planetary rovers developed with C++ programming language on the basis of Vortex software. In this paper, the structure of ROSTDyn is introduced briefly. Key algorithms for developing ROSTDyn are presented in detail, including the computation of the contact-area parameters, the transformation of velocity and force, the balance of the forces, and the integration of the algorithms and the modules. The simulation results verify that the algorithms are right, the integration is effective and the simulation runs stable.

During rover lunar exploration missions (such as China's “Chang'e”), rovers are required to move autonomously on the loose lunar soil. Control methods based on the rigidity hypothesis can hardly be expected to satisfy these requirements practically so wheel-soil interaction mechanics should be taken into account. The currently used integral model based on wheel-soil interaction mechanics, however, is complicated, and it cannot be directly applied to the design of a lunar rover's controller. This paper presents a new simplified method of determining the wheel-soil interaction of lunar rovers by introducing a normal stress factor and the ratio of the forward region to the rear region, based on an analysis of the integral model and lunar soil parameters. As an example, numerical analysis is performed for a lunar rover wheel with a width of 165 mm and a radius of 135 mm. Based on a slip ratio as high as 0.4 and an entrance angle that varies from 10° to 40°, the results show that the maximum errors of the model for the calculation of normal force and drawbar pull force are less than 2%, while the maximum error of resistance torque is approximately 5%. When designing a rover's controller, the relationship between the driving torque of wheel T and the drawbar pull of wheel F DP is T = F DP r according to the rigidity hypothesis, a relationship that contradicts the terramechanics model. The proposed simplified model, which is verified by experiments, provides an important basis for the design of a control algorithm for a lunar rover that takes into account lunar wheel-soil interaction mechanics.

Based on wheel-soil interaction terramechanics, locomotion system configuration of manned lunar rover is analyzed to get better trafficability, maneuverability and terrainability performance by this quantitative and qualitative analysis. The influence of the main parameters of lunar soil, wheel loading and terrain conditions on configuration parameters of the chassis and wheels is discussed. The results of this study could provide methods of conceptual design for manned rover's locomotion system in deformable rough lunar terrain.

In this paper new procedures for the measurement of mobility parameters, such as contact pressure, and an analysis of a low-pressure wheel model on deformable terrain, are presented. Because the lunar surface is covered by regolith which implies an irregular and rough terrain, the rover has difficulty in moving. Therefore a new low-pressure wheel is recommended for high mobility performance and low power consumption with a less complex mechanism. A low-pressure wheel can change its contact shape and pressure distribution to account for terrain. The presented measurement is achieved by a new measurement instrument on the wheel, and we presented analysis model is conducted through analysis of terramechanics mobility dynamics of a low-pressure wheel with normal stress. These procedures are valuable for evaluating the longitudinal velocity of the low-pressure wheel on deformable terrain.

Wheeled exploration robots are prone to slip during locomotion on deformable rough planetary terrain, which leads to loss of velocity and extra consumption of energy. Experimental results show that the power required for driving a wheel is an increasing function of its slip ratio; further, the tractive efficiency decreases rapidly after it reaches a peak value when the slip ratio is between 0.05 and 0.2. In this study, wheel-soil interaction terramechanics, which considers the slip ratio as an important state variable, is applied to analyze the quasi-static equations of a planar robot system. The slip ratios of wheels are controllable, but the degree of freedom is the number of wheels minus 1. A generalized algorithm for distributing the slip ratios of all the wheels of a robot to optimize the energy consumption is presented. Experimental and simulation results show that the “equal slip ratio” is at least a sub-optimal solution for optimizing energy consumption. Further, a more robust control method has been developed; this methods aims to equalize the slip ratios of all the wheels while maintaining a constant body velocity on rough terrains, without solving the values of the slip ratios. This method is verified by controlling a virtual four-wheeled robot using dynamics simulations.

This paper describes the mathematical modeling and the propulsive characteristics of a novel robot driven by Archimedean screw mechanisms, named Screw Drive Rover. For secure locomotion on soft soil, the proposed rover would become one of the good solutions because of its robustness to slipping and getting stuck in the soil. Furthermore, the rover is expected to move in various directions by using the dual screw units. However, the interaction between such screw unit and the surrounding soil is quite complicated and remains undefined. So, this paper attempts to model the tractive effort of the rover on the soil. The mathematical modeling is newly developed based upon terramechanics, addressing soil-vehicle interactive mechanics. Finally, the validity of the proposed model is demonstrated by simulation analyses.

This paper expounds the relevant knowledge of terra mechanics, including the sinkage of wheels, stress model and wheel-soil interaction force. Based on the theoretical background, wheel-soil interaction force is calculated and analyzed numerically. Then establishes the force distribution equations and dynamics simulation model for a bogie-rocker lunar rover. On this basis, simulation method is proposed on loose soil, which is the fundamental simulation condition for further motion control.

This paper presents the Axel robotic rover which has been designed to provide robust and flexible access to extreme extra-planetary terrains. Axel is a lightweight 2-wheeled vehicle that can access steep slopes and negotiate relatively large obstacles due to its actively managed tether and novel wheel design. This paper reviews the Axel system and focuses on its novel paddle wheel characteristics. We show that the paddle design has superior rock climbing ability. We also adapt basic terramechanics principles to estimate the sinkage of paddle wheels on loose sand. Experimental comparisons between the transport efficiency of mountain bike wheels and paddle wheels are summarized. Finally, we present an unfolding wheel prototype which allows Axel to be compacted for efficient transport.

Numerical simulation analysis of the motion of wheeled mobile robots is significant for both their R&D and control phases, especially due to the recent increase in the number of planetary exploration missions. Using the position/orientation of the rover body and all the joint angles as generalized coordinates, the Jacobian matrices and recursive dynamic models are derived. Terramechanics models for calculating the forces and moments that act on the wheel—as a result of the deformable soil—are introduced in consideration of the effect of normal force. A rough terrain modeling method is developed for estimating the wheel-soil interaction area, wheel sinkage, and the terminal coordinate. A simulation program that includes the above techniques is developed using Matlab and SpaceDyn Toolbox. Experimental results from a 4-wheeled mobile robot moving on Toyoura soft sand are used to verify the fidelity of the simulation. A simulation example of a robot moving on a random rough terrain is also presented.

The Bekker Theory of Locomotion has long been the leading applied theory when it comes to calculating and predicting soil-tyre interaction for terrestrial wheeled and tracked vehicles. Whilst the theory is applicable for terrestrial systems, there is no evidence to suggest it also applies under water. Furthermore, the complications of measuring the required soil parameters in marine substratum makes it difficult to apply. This paper explores the slip-based approach to the Bekker theorem and suggests an experiment designed to validate this theorem for underwater applications.

A critical component of remote terrestrial and planetary exploration is understanding how terrain properties affect rover mobility. Bekker theory has long been used successfully in this regard for the analysis of large vehicles. In recent years, the semi-empirical formulae contained within Bekker theory have also been applied to small UGVs. Bekker himself noted, however, that his formulae offer significantly less accurate predictions for vehicles with wheel diameters and normal loading lower than 50 cm and 45 N, respectively. This has been shown to lead to errors in the prediction of tractive performance. The results of this paper show that Bekker theory yields under-estimates of small wheel sinkage and resistances. The consequences of such errors are severe, as they could potentially lead to unexpected rover immobilization. With increasing numbers of small UGVs being used in planetary, research and military roles, it is crucial to investigate the source of these errors. This paper details an empirical approach to characterizing small vehicle wheel sinkage and its impact on vehicle-terrain models.

Identifying planetary soil parameters is not only an important scientific goal, but also necessary for exploration rover to optimize its control strategy and realize high-fidelity simulation. An improved wheel-soil interaction mechanics model is introduced, and it is then simplified by linearizing the normal stress and shearing stress to derive closed-form analytical equations. Eight unknown soil parameters are divided into three groups. The highly complicated coupled equations, each of which includes all the unknown soil parameters, are then decoupled. Each decoupled equation contains one or two groups of soil parameters, making it feasible to make a step-by-step identification of all the unknown parameters that characterize the soil. Wheel-soil interaction experiments were performed for six kinds of wheels with different dimensions and wheel lugs on simulated planetary soil. Soil parameters are identified with the measured data to validate the method, which are then used to predict wheel-soil interaction forces and torque, with a less than 10% margin of error. The improved model, decoupled analytical model, and soil-characterizing method can play important roles in the development of both the planetary exploration rovers and the terrestrial vehicles.

The wheel slip ratio is an important state variable in terramechanics research and the control of planetary rovers. Definitions of the slip ratio for a wheel with lugs and methods of estimating it for all wheels onboard have seldom been attempted. This paper presents several definitions for the slip ratio of a lugged wheel, which can be interconverted by altering the shearing radius. Equations for calculating the longitudinal velocity and slip ratio of a wheel moving on rough terrain are deduced from the horizontal speed of the wheel's axle. Wheel-soil interaction experiments were performed for two types of wheels with different radii and lugs of different heights. The drawbar pull, torque, and wheel sinkage were measured using sensors. These data confirmed the effectiveness of the proposed slip ratio definition methods. Furthermore, two slip ratio estimation methods are proposed and verified: a visual information-based method by analyzing the lug traces marked on the terrain with high precision, and a terramechanics-based method in which the equations for the vertical load and torque are solved to estimate the slip ratios of all wheels.

The wheels of planetary rovers that are used in space explorations sometimes slip or lose contact with the ground while traversing a sandy terrain. In order to estimate the behavior of these rovers moving on loose soil, it is very important to accurately estimate the drawbar pull of their wheels. Some wheel-soil interaction models based on terramechanics have been proposed for the estimation of the normal stress distribution and drawbar pull of such rovers. However, our experimental results (normal stress distributions are directly measured using a pressure sensor array, which is attached to the wheels of a rover) show that the distribution range of normal stress for small wheeled rovers obtained using the proposed method is considerably smaller than that obtained by using conventional method. Consequently, the drawbar pull estimated using conventional methods is inaccurate. Therefore, in this study, the normal stress distribution is directly measured using pressure sensors in order to estimate drawbar pull accurately. From the data obtained using the sensors, a soil parameter, which is generally very difficult to measure, is estimated. Then, the drawbar pull is estimated using this parameter. The drawbar pull estimated by using the proposed method is more accurate than that estimated using conventional methods. In this study, we propose a new method for the estimation of drawbar pull and also validate this method.

As terrain provides the only and powerful thrust to a mobile robot, design with consideration to terrain is most important, particularly for the robot in sandlot or the soft soiled environment. A trade-off design based Terramechanics about a reconfigurable mobile robot is proposed based on Multi-Objective Optimization (MOO) with respect to Terramechanics. A novel analytic projection method is proposed to build the model of stability, mass of robot and the drive torque respectively with non-linear characteristics. A minimum-maximum method is also applied to obtain the optimal configurations parameters for design synthesis.

The virtual prototype model for fast simulation analysis of the complete integrated sea trial system for deep ocean mining is built up based on single-body model of the seafloor tracked miner and discrete element model of the pipeline system. Dynamic simulation analysis is performed and investigated taking into account the interactions between each subsystem and corresponding complex ocean environment. Both for the tracked miner and the pipeline system, two different modeling and simulation methods are considered and compared with regard to computational efficiency and solution accuracy. Focusing mainly on the integrity and rapidity of the dynamic simulation of the total mining system, the seafloor miner is preferred to be modeled as a single-body with 6 degrees of freedom, which allows real-time simulation, while the interaction model between the miner and seafloor soft cohesive soil is built based on the theory of terramechanics and with consideration of seafloor soil special mechanical characteristics. The pipeline subsystem including the lifting pipe, pumps, the buffer and the flexible hose is chosen to be built as 3-D discrete element model which is divided into rigid elements linked by flexible connectors, and external forces such as the hydrodynamic forces due to the maritime sea current, the buoyancy forces acting at discrete locations on the flexible hose are considered. The simulation analysis results are obtained and discussed, which in a way can reflect the actual working conditions and provide useful guidance and reference for the practical deep ocean mining system design and operation.

On-line prediction of unmanned ground vehicle (UGV) behaviour during interactions with terrain is essential for autonomous and safe operations of skid-steering UGVs. This paper presents a fast and accurate algorithm for a new interaction model to predict performance of a UGV running on a particular terrain. By approximating nonlinear relations involved in the interaction between the vehicle and terrain, a closed form of the interaction model is obtained to enable on-line computation. The minimum absolute error criteria are applied to secure accuracy for the proposed method. The development is compared with the other models in terms of both computation speed and accuracy.

For mobile robots driving across soft soils, such as sand, loose dirt, or snow, it is critical that the dynamic effects occurring at the wheel-terrain interface be taken into account. One of the most prevalent of these effects is wheel sinkage. Wheels can sink in soft soils to depths sufficient to prohibit further motion, leading to danger of entrapment with consequent mission failure. This paper presents an algorithm for visual estimation of wheel sinkage in deformable terrain. We call it the Visual Sinkage Estimation (VSE) method. It assumes the presence of a monocular camera mounted on the wheel assembly, with a field of view containing the wheel–terrain interface. An artificial pattern, composed of concentric circumferences equally spaced apart on a white background, is attached to the wheel side in order to determine the contact angle with the terrain, following an edge detection strategy. The paper also introduces an analytical model for wheel sinkage in soft, deformable terrain based on terramechanics. In order to validate the VSE module, several tests were, first, performed on a single-wheel test bed, under different operating conditions including non-flat terrains, variable lighting conditions, and terrain with and without rocks. Successively, the effectiveness of the proposed approach in real context was proved, employing an all-terrain rover traveling on a sandy beach.

Virtual simulation is of great importance for both the research and development phase and the tele-operation phase of a lunar rover. The role and state-of-the-art of rover's simulation is introduced in the beginning. Comprehensive high-fidelity/high-speed virtual simulation system for lunar rover is designed in accordance with the developing trend. Key technologies such as terramechanics and recursive dynamics are discussed and related work that have been done in RCMAC of Harbin Institute of Technology are presented. The system can be switched between high-fidelity simulation and high-speed precision simulation to be used in both phases of a lunar rover.