Coupled nonlinear controller for vehicle trajectory tracking in a deformable soil: Application to a four-wheeled mobile agricultural robot

Rania Majdoubi, Lhoussaine Masmoudi, Abderrahmane Elharif

Journal of Terramechanics, Volume 110, 2023, Pages 47-68, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.08.001.(https://www.sciencedirect.com/science/article/pii/S0022489823000666)

Abstract: In this paper, the coupled longitudinal and lateral control of the mobile agricultural robot “Agri-Eco-Robot’’ is addressed. As a first step, the Newton's law is used to develop the dynamical modeling of the mobile agricultural robot. The wheel-ground contact is modeled using the Terramechanics law called Extended-Bekker. The validation of the developed vehicle model was then conducted using an automotive simulator. The developed vehicle model is then used to derive the coupled control laws for the lateral and the longitudinal vehicle dynamics. The proposed controller is realized using two overlapping controllers, the first is dealing with coupled control of longitudinal and lateral dynamics to command the traction, and the second is the controller that minimize slipping, both are developed using the Lyapunov's theory. This controller is compared with the dynamics where the slip ratio is not controlled according to two scenarios in which one is the heigh velocity and the other is low velocity, this control law is validated using an automotive simulator applied to the mobile robot ‘Agri-Eco-Robot’. The result of this control law shows the necessity of the slipping control when navigating in a rough environment such as agricultural fields, assuming a low-speed command to ensure system stability.

Keywords: Combined controller; Mobile agricultural robots; Navigation in a rough environment; Dynamic model; Terramechanics law; Trajectory control law; Traction; Slip ratio; Lyapunov's control; Heigh velocity; Low velocity

Optimization of grouser shape ratio for coastal terrain driving device using discrete element method

Ji-Tae Kim, Hyuek-Jin Choi, Jae-Won Oh, Young-Jun Park

Journal of Terramechanics, Volume 110, 2023, Pages 27-37, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.07.004.\(https://www.sciencedirect.com/science/article/pii/S0022489823000575)

Abstract: Using the discrete element method (DEM), this study derived the optimal shape ratio of a grouser driving in a coastal terrain. To develop a DEM model that considers the properties of the coastal terrain, experiments were performed on the physical and mechanical properties of the terrain, and parameters of the DEM model were calibrated using the experimental results. In addition, a terramechanical experiment was performed to validate the DEM model, for which parameters were calibrated. Furthermore, simulations were performed on the change in thrust according to the existence or nonexistence of the grouser and the change in thrust and sinkage according to the shape ratio using the validated DEM model. Consequently, the track with grouser generated a larger thrust than that without the grouser. Thus, the optimal shape ratio range of coastal terrain was derived using the DEM model, considering the mechanical properties of the terrain.

Keywords: Discrete element method (DEM); Coastal terrain; Terramechanics; Grouser optimization; Driving performance

Development of a tire testing machine for evaluating the performance of tractor tires based on the soil compaction

Siwakorn Phakdee, Chakrit Suvanjumrat

Journal of Terramechanics, Volume 110, 2023, Pages 13-25, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.07.002.(https://www.sciencedirect.com/science/article/pii/S0022489823000551)

Abstract: Soil compaction, which is more effective than soil shear owing to the weight of tractor tires, reduces sugarcane cultivation. Instead of a field study, a single-wheel tester is more suitable for studying the tractor tire tracks on a soil bin in a laboratory. However, the soil compaction measurement is time consuming and analyzes the bulk density only at the sampling point of the track. In this study, a tire-testing machine (TTM) was developed to evaluate tractor tire performance based on soil compaction. A 3D scanner was employed to model the tractor tire track on a sandy clay loam soil, which is suitable for sugarcane planting in Thailand. Mathematical models for soil bulk density prediction were proposed and used to transform the 3D footprint model into a 3D color contour of the soil bulk density. The soil compaction effect of tractor tires at three different tread depths was evaluated. It was found that deeper treads caused higher soil bulk density than shallow treads. Static tires induce greater soil bulk density than rolling tires. This novel TTM with measurement techniques is a novel method for evaluating the tire-soil compaction in crop fields. It can also guide farmers to purchase suitable agricultural tires.

Keywords: Soil Bulk Density; Soil Compaction; Three-Dimensional Scanning; Tractor Tires

Machine learning approach for predicting soil penetration resistance under different moisture conditions

Anis Elaoud, Hanen Ben Hassen, Rim Jalel, Nahla Ben Salah, Afif Masmoudi, Atef Masmoudi

Journal of Terramechanics, Volume 110, 2023, Pages 39-45, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.08.002.(https://www.sciencedirect.com/science/article/pii/S0022489823000678)

Abstract: The investigation and evaluation of the phenomenon of soil compaction after the passage of repetitive equipment (Tractor, cultivator..) is considered as a preventive solution to preserve agricultural soils against degradation and maintain sustainable agriculture. In reality, there is currently no reliable method for predicting the primary causes of soil compaction, particularly in moist soils. This study applicates Artificial Neural Network (ANN) modeling to make a resistance penetration prediction. Resistance penetration (Rp) test data acquired from measured experimental values are used to train the models. The learning score coefficient (0.96), the RMSE (0.51) and MAE (0.39) show that the forecasts from the ANN models coincide with the measured field data. It is concluded that the developed ANN models would be used effectively to make predictions that are more accurate on the soil state compaction in different moisture conditions. This work will help the farmers to optimize the machine use and hence to enhance production and improve yields with minimal costs.

Keywords: Soil resistance; Moisture; Artificial Neural Network; Modeling

A tractor hydraulic assisted embedded microprocessor-based penetrometer for soil compaction measurement

Kumari Nisha, Ganesh Upadhyay, Naresh, Bharat Patel, Swapnil Choudhary, Vijaya Rani

Journal of Terramechanics, Volume 110, 2023, Pages 1-12, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.07.003.(https://www.sciencedirect.com/science/article/pii/S0022489823000563)

Abstract: Measurement of soil compaction in terms of penetration resistance using a hand penetrometer requires more time and effort. A tractor hydraulic-assisted embedded microprocessor-based penetrometer was developed to make the results easy to monitor and decrease human error. The developed penetrometer consisted of a driving system for pushing the penetrometer probe into the soil at a desired speed, a sensor unit (load cell and ultrasonic sensor) for measuring the force required to push the probe and the depth of penetration, and a data logging system. The embedded system of the penetrometer comprised various components: Arduino Uno microcontroller, I2C, WiFi module, and HX711 amplifier. The system was able to measure a soil penetration resistance of 5000 kPa up to a depth of 500 mm. A WiFi module helped to transmit the data to an Android mobile application. The acquired data also include date/time parameters along with latitude and longitude locations picked up from the GPS of the mobile. Its performance was assessed based on sensor characteristics such as accuracy, sensitivity, non-linearity, and non-repeatability. The average and maximum absolute variations in the cone index values measured with developed system and a hand-held digital penetrometer were observed to be 22.50% and 27.88%, respectively.

Keywords: Soil compaction; Penetration resistance; Ultrasonic sensor; Microcontroller; Sensor characteristic

The effect of integrating a bio-inspired convex structure with a low-surface energy polymer on soil adhesion and friction

Abouelnadar El Salem, Guozhong Zhang, Hongchang Wang, Haytham M. Salem, Mohamed A.I. Abdalla, Ahmed A. Ghazy

Journal of Terramechanics, Volume 109, 2023, Pages 93-100, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.06.003.(https://www.sciencedirect.com/science/article/pii/S0022489823000526)

Abstract: The capacity of soil-burrowing animals to move freely in sticky soil is a motivational trait for developing soil-engaging tools with high operational efficiency. Meanwhile, outstanding hydrophobicity, chemical stability, and corrosion resistance make ultra-high molecular weight polyethylene (UHMW-PE) a potential option for reducing soil adhesion. This study looked into the viability of combining a domed surface inspired by the micro-convex structure of the dung beetle skin with the UHMW-PE as a surface coating to reduce sliding resistance. The sliding resistances of three plates (a flat plate of carbon steel, a flat plate of UHMW-PE, and a domed plate of UHMW-PE) were assessed under varied operating and soil conditions. In each treatment, the tested plate was dragged for 0.7 m of the soil bin length, and the sliding resistance was recorded using the distributed stress and strain test and analysis system (DH3820 N). The results revealed that in all treatments, the sliding resistance of the UHMW-PE domed plate was significantly lower than that of the flat steel plate. Furthermore, the UHMW-PE domed plate outperformed the other tested plates in reducing sliding resistance in more moist and sticky soils, paving the way for the development of highly practical and effective soil-engaging tools.

Keywords: Soil adhesion; External friction coefficient; Ultra-high molecular weight polyethylene; Bio-inspired surface

Review of modeling and validation techniques for tire-deformable soil interactions

Varsha S Swamy, Rashna Pandit, Alba Yerro, Corina Sandu, Denise M. Rizzo, Katherine Sebeck, David Gorsich

Journal of Terramechanics, Volume 109, 2023, Pages 73-92, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.05.007.(https://www.sciencedirect.com/science/article/pii/S0022489823000411)

Abstract: The mobility of vehicles in off-road environments is critical for many applications. Predicting the tire-soil interaction is a challenge, especially in non-linear deformable terrain. This paper presents an overview of the bibliographic references on tires–deformable soil interactions after the 2000's, identifying the gaps in the literature. The capabilities and challenges of different modeling frameworks used for mobility (i.e., empirical, semi-empirical, and physics-based) are discussed; special emphasis is given to continuum-based frameworks. A summary of terrain material models used to approximate the behavior of coarse and fine-grained soils is provided with practices used to characterize such materials. A review of tire models for deformable soil navigation and the tire-soil interfaces is provided. Strategies to validate all these models are presented. Finally, the application of these studies for assessing the sensitivity concerning input parameters (e.g., velocity, inflation pressure, and normal load), multi-pass, multi-layered soils, wet soils, and fully integrated multi-body vehicle models are discussed. The final contribution of this review paper is a summary table that synthesizes the extensive bibliographic review. Overall, this work highlights a lack of physics-based trafficability studies in wet and plastic deformable soils. Moreover, studies on contact adhesion, stone picking, multipass, and cornering also need improvement.

Keywords: Terrain mobility; Terramechanics; Deformable soil modeling; Tire-terrain interaction; Soil numerical simulation

Construction of a soil clod recognition bench-scale experiment for discrete element method modeling of tilling phenomena

Shuto Ishii, Isami Suto, Hiroaki Tabe, Kota Aono, Moju Zhao, Yoshifumi Ueshige, Kohei Matsushita, Takashi Iritani, Tadayuki Hanamoto, Masayuki Nakao, Keisuke Nagato

Journal of Terramechanics, Volume 109, 2023, Pages 63-71, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.06.004.(https://www.sciencedirect.com/science/article/pii/S0022489823000538)

Abstract: Rotary claws are used to break soil into small pieces and plow the soil flat. In this study, rotary claw development in tiller machines was evaluated using both equipment and the discrete element method (DEM). However, evaluation through equipment is imprecise and time consuming. Although DEM is an effective method for modeling the movement of granular materials, it requires numerous parameters to ensure accuracy, which must be determined through experimental evaluation and comparison. To resolve this concern, an image processing method was developed that leverages point cloud data obtained from a depth camera to capture changes in soil shape, distribution, and soil clod size before and after tilling. The effect of soil moisture content and claw rotation speed on soil clod formation and decomposition was evaluated. The experimental results show that the location, number, and soil clod size vary with soil moisture content and claw rotation speed. The results were compared with the DEM simulation to reconcile differences and confirm the feasibility of the proposed method. The model experiment system for soil clods and the image processing method facilitates a quantitative comparison between experimental and DEM simulated soil dispersal, which accelerates the search for DEM parameters to reproduce the tilling.

Keywords: Discrete Element Method (DEM); Recognition of Soil Clods; Tillage claw; Moisture Content Ratio; Rotation Speed

Experimental investigation of factors affecting the characterisation of soil strength properties using a Bevameter in-situ plate sinkage and shear test apparatus

Ray Kruger, P. Schalk Els, Herman A. Hamersma

Journal of Terramechanics, Volume 109, 2023, Pages 45-62, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2023.06.002.(https://www.sciencedirect.com/science/article/pii/S0022489823000514)

Abstract: The Bekker-Wong soil-wheel interaction model has been widely adopted in the terramechanics field. This model requires the soil to be characterised using a Bevameter, which entails performing in situ plate sinkage and shear stress tests. Bevameter soil characterisation is not a standardised test procedure, and the test setup may influence the identified soil model parameters. This study investigates the influence of the following five factors for partially saturated sandy soil: I) soil preparation method on pressure-sinkage, II) soil preparation method on shear stress, III) torsional vs. translational shear mechanism, IV) shear contact area, and V) the influence of shear velocity. The results indicate that the influence of soil preparation on pressure-sinkage response is substantial, exhibiting an order-of-magnitude difference. The influence of soil preparation on shear tests is notable, but less significant. The shear mechanism, shear contact area and shear velocity exhibited a maximum absolute shear stress difference of 18%, 20% and 10%, respectively. Moreover, depending on the test setup configuration and data processing decisions, the estimated internal soil friction angles ranged from 16.5 to 37.5° for the same soil. The findings are expected to have significant implications for the prediction of vehicle drawbar pull using the Bekker-Wong model.

Keywords: Bevameter; Pressure-sinkage; Soil shear strength; Shear mechanism; Shear contact area; Linear shear; Torsional shear