Machine learning in planetary rovers: A survey of learning versus classical estimation methods in terramechanics for in situ exploration

Amenosis Jose Ramon Lopez-Arreguin, Sergio Montenegro

Journal of Terramechanics, Volume 97, 2021, Pages 1-17, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.04.005.(https://www.sciencedirect.com/science/article/pii/S0022489821000380)

Abstract: For the design of space missions in the Moon and planets, analysis of mobility in robots is crucial and poor planning has led to abortion of missions in the past. To mitigate the risk of mission failure, improved algorithms relying intrinsically on fusing visual odometry with other sensory inputs are developed for slip detection and navigation. However, these approaches are significantly expensive computationally and difficult to meet for future space exploration robots. Hence, today the central question in the field is how to develop a novel framework for in situ estimation of rover mobility with available space hardware and low-computational demanding terramechanics predictors. Ranging from pure simulations up to experimentally validated studies, this paper surveys dozens of existing methodologies for detection of vehicle motion performance (wheel forces and torques), surface hazards (slip-sinkage) and other parameters (soil strenght constants) using classical terramechanics maps, and compare them with novel approaches introduced by machine learning, allowing to establish future directions of research towards distributed exteroceptive and proprioceptive sensing for visionless exploration in dynamic environments. To avoid making it challenging to collect all relevant studies expeditiously, we propose a global classification of terramechanics according most common practices in the field, allowing to form an structured framework that condense most works in the domain within three estimator categories (direct/forward or inverse terramechanics, and slip estimators). Likewise, from the experiences collected in previous MER (Mars Exploration Rover) missions, five overlooked problems are documented that will need to be addressed in next generation of planetary vehicles, along three research questions and few hypothesis that will pave the road towards future applications of machine learning-based terramechanics.

Keywords: Machine learning; Rovers; Terramechanics; Planetary exploration; 1DOF sensors

The effect of roller pressure and share of plant matter in mulching soil cultivation on its density and water content

Zbigniew Kogut, Leszek Sergiel

Journal of Terramechanics, Volume 97, 2021, Pages 119-131, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.08.001.(https://www.sciencedirect.com/science/article/pii/S0022489821000616)

Abstract: The aim of this study was to assess the impact of the roller load (with cultivating tools) and doses of plant matter (straw and charlock) mixed with soil on the air and humidity conditions of such soil. The innovation of the research consisted in abandoning the use of Kopecky’s cylinders: the bulk density of mulched soil was determined by measuring its mass and volume, which it obtained in vases before and after the roller work. Capillary infiltration was also carried out for soil in vases. Variable research factors characterizing the roller working conditions in the mulching tillage, were: source/type of plant material cut into 10 cm chopped straw, its share in soil, three ranges of soil water content and vertical unit load on the roller. Increasing the straw dose to 30 Mg.ha−1 reduces the bulk density from 1.17 to 0.76 g.cm−3, while increasing the dose of charlock to 60 Mg.ha−1 under these conditions, it reduces the density to 1.03 g.cm−3. At the same time, humidity conditions change: volumetric water content decreases in case of straw from 13.9% to 8.5% and increases in case of charlock to 17.4%. Changes occur also in case of full water capacity.

Keywords: Land rolling; Seedbed compaction; Mixing soil with plant matter; Density and water content of soil with matter

Development and implementation of an IOT based instrumentation system for computing performance of a tractor-implement system

Tarandeep Singh, Aseem Verma, Manjeet Singh

Journal of Terramechanics, Volume 97, 2021, Pages 105-118, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.07.002.+(https://www.sciencedirect.com/science/article/pii/S0022489821000604)

Abstract: A high precision and compact IOT based digital instrumentation setup to measure, display and record various tractor and implement system performance parameters was developed and installed on a 28.3 kW Tractor. The setup was capable of continuous monitoring and wirelessly transmitting tractor-implement performance parameters on a cloud platform such as engine speed, radiator fan speed, fuel consumption, draft, forward speed, lift arm angle, wheel slip, wheel slip, PTO speed, geo-location/position of the tractor, choking of seeds in the implement and vibrations experienced by the implement. For precision measurements, commercial transducers used in the system were calibrated and assessed under both static and dynamic conditions. The average calibration constant for fuel consumption, forward speed, lift arm angle and load cell were 0.00009804 L/pulse, 0.01610306 km/h/pulse, 0.056 mA/degree and 0.2575 mV/kN respectively. The system based on DataTaker DT 85 Data logger connected to a micro-computer through transducers capable of transferring data wirelessly was installed on John Deere 5038 tractor and was tested with a Spatially Modified No-Till Drill in agricultural field with varied implement depth.

Keywords: Instrumentation system; IOT; Data logger; Sensors; Tractor-implement system; Spatially modified no-till drill

A method for predicting the internal motion resistance of rubber-tracked undercarriages, Pt. 3. A research on bending resistance of rubber tracks

Jakub Chołodowski, Piotr A. Dudziński, Michael Ketting

Journal of Terramechanics, Volume 97, 2021, Pages 71-103, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.06.001.(https://www.sciencedirect.com/science/article/pii/S0022489821000549)

Abstract: Optimizing the efficiency of rubber-tracked undercarriages requires models for calculating external and internal motion resistance, including the resistance resulting from bending of rubber tracks. The experiments on the bending resistance of rubber tracks and a new model of this phenomenon are discussed in this article. An empirical model of friction in bearings typically implemented in driving and idler wheels of rubber-tracked undercarriages is also presented. According to the sample computations carried out on the basis of these models, the efficiency of rubber-tracked undercarriages might be improved by minimizing the number and maximizing the diameter of idler wheels. Furthermore, it has been shown that increase in the initial tension and driving force transmitted by rubber tracks does not significantly affect bending resistance of these tracks; however, it results in increased friction in the driving and idler wheels’ bearings. Nevertheless, the higher the driving force transmitted by the rubber tracks, the higher the efficiency of rubber-tracked undercarriages. Consequently, since track systems of vehicles operating at relatively small drawbar pull will manifest exceptionally low efficiency, there is a serious need for optimizing them in terms of energy consumption.

Keywords: Tracked undercarriage; Rubber track; Internal motion resistance; Undercarriage layout optimization; Track bending; Rubber hysteresis

Rolling resistance and sinkage analysis by comparing FEM and experimental data for a grape transporting vehicle

Enrico di Maria, Giulio Reina, Kazuo Ishii, Nicola Ivan Giannoccaro

Journal of Terramechanics, Volume 97, 2021, Pages 59-70, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.06.004.(https://www.sciencedirect.com/science/article/pii/S0022489821000574)

Abstract: In this study a 2D FEM model was developed to analyze ruts formation, rolling resistance, and power loss for a grape transporting cart aimed to replace the use of heavy tractors while harvesting grape. The model was supported by experiments in a vineyard in South Italy. Cone penetration tests were conducted to estimate frictional and cohesive properties in three soil conditions: firm, soft, and wet saturated. A tractor pulled test rig for a single wheel was developed to measure rolling resistance and sinkage, and complete the selection of the soil parameters. Completed the model, the analysis was conducted for a range of different wheel dimensions, and the outputs analyzed through response surfaces. The results showed the different impacts that width and diameter have on ruts formation and rolling resistance for different soil conditions. Wider wheels determined a main reduction of the sinkage, while the width contribution to the rolling resistance was affected by the total soil volume deformed. Larger diameters led to lower rolling resistance, with a higher impact on more deformable soils. Contact stress was compared with the thresholds recommended in the literature to determine the acceptable designs. This analysis represents a tool to select the running gear dimensions.

Keywords: Cone penetration test; Pull test; Resistance coefficient; Rut formation; Response surface; Vineyard

Modelling of off-road wheeled vehicles for real-time dynamic simulation

Albert Peiret, Eric Karpman, László L. Kovács, József Kövecses, Daniel Holz, Marek Teichmann

Journal of Terramechanics, Volume 97, 2021, Pages 45-58, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.04.001.(https://www.sciencedirect.com/science/article/pii/S0022489821000355)

Abstract: Simulation of wheel-ground and vehicle-ground interactions is very important in many applications. Achieving accuracy and efficiency is challenging for both soft and hard terrains. This is not only because of the simulation and numerical challenges, but also due to the questionable nature of the existing terrain models. For example, the most widely used terramechanics model is not a representative constitutive relation for a full range of dynamic conditions and applications, but rather a parametrization of steady state conditions. In general, the selection and development of the proper constitutive model and the parametrization of the ground properties are very challenging. Here, we present a unified framework for general wheel-ground interaction which can be used with different terramechanics models. The framework is based on a complementarity formulation and also uses the concept of kinematic constitutive relations, beside the other known concepts for modelling and parametrizing the soil properties. The framework makes it possible to consider the appropriate modelling of the terrain for a broad range of dynamic behaviours and simulation conditions. We will illustrate the material with several examples for off-road conditions.

Keywords: Wheel-ground interaction; Dynamic models and simulation; Complementarity formulation

Embedded digital display and warning system of velocity ratio and wheel slip for tractor operated active tillage implements

E. Nataraj, Pranay Sarkar, Hifjur Raheman, Ganesh Upadhyay

Journal of Terramechanics, Volume 97, 2021, Pages 35-43, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.06.003.(https://www.sciencedirect.com/science/article/pii/S0022489821000562)

Abstract: A microcontroller-based embedded digital display and warning system was developed for measuring wheel slippage, velocity ratio, PTO torque, and draft requirement of active tillage machinery. The hardware system included magnetic pickup sensor for measuring the engine speed, load cells and amplifiers to measure and amplify the sensing unit signals of the draft, proximity sensors for wheel slip, and PTO torque transducer for measuring the torque requirement. It was provided with buzzers and LEDs to warn the operator, whenever slip and velocity ratio were not in the desired range based on the algorithm, for maximum fuel efficiency and tractive performance. It measured slippage, velocity ratio, torque and draft with a maximum absolute variation of 12.90%, 7.92%, 8.99% and 11.57%, respectively. The developed system can be easily adaptable to any combination of tractor and tillage implements, and guide the operator for better soil tilth with lesser energy input.

Keywords: Wheel slip; Draft; Velocity ratio; PTO torque; Digital display; Warning system

Machine learning in planetary rovers: A survey of learning versus classical estimation methods in terramechanics for in situ exploration

Amenosis Jose Ramon Lopez-Arreguin, Sergio Montenegro

Journal of Terramechanics, Volume 97, 2021, Pages 1-17, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.04.005.(https://www.sciencedirect.com/science/article/pii/S0022489821000380)

Abstract: For the design of space missions in the Moon and planets, analysis of mobility in robots is crucial and poor planning has led to abortion of missions in the past. To mitigate the risk of mission failure, improved algorithms relying intrinsically on fusing visual odometry with other sensory inputs are developed for slip detection and navigation. However, these approaches are significantly expensive computationally and difficult to meet for future space exploration robots. Hence, today the central question in the field is how to develop a novel framework for in situ estimation of rover mobility with available space hardware and low-computational demanding terramechanics predictors. Ranging from pure simulations up to experimentally validated studies, this paper surveys dozens of existing methodologies for detection of vehicle motion performance (wheel forces and torques), surface hazards (slip-sinkage) and other parameters (soil strenght constants) using classical terramechanics maps, and compare them with novel approaches introduced by machine learning, allowing to establish future directions of research towards distributed exteroceptive and proprioceptive sensing for visionless exploration in dynamic environments. To avoid making it challenging to collect all relevant studies expeditiously, we propose a global classification of terramechanics according most common practices in the field, allowing to form an structured framework that condense most works in the domain within three estimator categories (direct/forward or inverse terramechanics, and slip estimators). Likewise, from the experiences collected in previous MER (Mars Exploration Rover) missions, five overlooked problems are documented that will need to be addressed in next generation of planetary vehicles, along three research questions and few hypothesis that will pave the road towards future applications of machine learning-based terramechanics.

Keywords: Machine learning; Rovers; Terramechanics; Planetary exploration; 1DOF sensors

Optimization and numerical investigation of an excavator carrier

Javad Gholami, Masood Ghassabi

Journal of Terramechanics, Volume 97, 2021, Pages 29-34, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.05.002.(https://www.sciencedirect.com/science/article/pii/S0022489821000434)

Abstract: The excavator carrier is a device for moving the excavator. There are many operational benefits in using this carrier to transport excavators safely, easily, and efficiently. An earlier model of this carrier is manufactured and in tests showed that the design needs to be improved. In this paper, a finite element method is used to model and analyze this carrier and optimize the design for better performance. The static and dynamic analysis is done to optimizing carrier design for removing the defect that identified in practical test. The goal of optimization is to increase the carrier's life, increase the safety of transportation, decrease the cost, and finally, commercialize the product. The results show that the carrier's weight is decreased by up to 30%. Also, a holder and lock system in the back of the carrier is designed for increasing the transportation safety and the stiffness of the carrier chassis. The effect of increasing a suspension system is studied, the idea is using leaf spring. The numerical results show that using the suspension system increases the carrier's life by up to 30% while adding a suspension system increases manufacturing costs by up to 10%.

Keywords: Numerical method; Optimization; Excavator carrier; Lock system; Transport; Leaf spring