A.R. Reece

Bio: A.R. Reece is an academic researcher from Newcastle University. The author has contributed to research in topics: Electronic differential & Axle. The author has an hindex of 6, co-authored 8 publications receiving 713 citations.

The calculation of passive soil resistance

Abstract: A method is presented for the rapid calculation of passive pressure, giving values very close to those obtained by rigorous application of plasticity theory. The method will predict the soil resistance of a plane wide structure extending at least up to the soil surface having any rake angle lying between 5° and 170°. The soil is assumed to be a rigid-plastic Coulomb material having cohesion and self-weight and any angle of internal friction between 0 and 45°. The soil interface properties of tangential adhesion and friction are accounted for, as is any value of uniform vertical surcharge pressure acting on the horizontal soil surface. The method uses dimensionless passive coefficients which are substituted into a basic additive equation. These coefficients are obtained by interpolation between values read from a set of charts. These charts are based on data obtained from computer programs using Sokolovski's method. The resistance coefficients are shown to be functions of the soil numbers c/yz and q/yz and...

Advances in characterization of soil structure

Abstract: Soil structure is defined as “the spatial heterogeneity of the different components or properties of soil” Aspects of soil structure which are important for plant development, soil water balance and soil workability are reviewed briefly The different types of soil structure which occur on different size scales are placed in a hierarchical order Different mechanisms give rise to the different hierarchical orders Similarly, different physical/chemical/biological processes are involved in the stabilization of the different hierarchical orders A number of methods for measuring soil structure are described Preference is given to methods involving direct observation of structural features by scanning electron microscopy and by optical scanning of impregnated sections and fracture surfaces These need to be supported by assessments of the stabilities of compound particles in water and of the mechanical strengths of compound particles as a function of water content “Good” soil structure is described as one where all the hierarchical orders are well-developed and stable The greatest lack of knowledge appears to be in the 2–100 μm size range which is too large to have been studied by colloid chemists and too small to be visible to the naked eye It is suggested that more observations of soil structure should be made in this size range, as it may hold many important clues on how to manage soil structure in the field

Online terrain parameter estimation for wheeled mobile robots with application to planetary rovers

Abstract: Future planetary exploration missions will require wheeled mobile robots ("rovers") to traverse very rough terrain with limited human supervision. Wheel-terrain interaction plays a critical role in rough-terrain mobility. In this paper, an online estimation method that identifies key terrain parameters using on-board robot sensors is presented. These parameters can be used for traversability prediction or in a traction control algorithm to improve robot mobility and to plan safe action plans for autonomous systems. Terrain parameters are also valuable indicators of planetary surface soil composition. The algorithm relies on a simplified form of classical terramechanics equations and uses a linear-least squares method to compute terrain parameters in real time. Simulation and experimental results show that the terrain estimation algorithm can accurately and efficiently identify key terrain parameters for various soil types.

Terramechanics-based model for steering maneuver of planetary exploration rovers on loose soil

Abstract: This paper presents analytical models to investigate the steering maneuvers of planetary exploration rovers on loose soil. The models are based on wheel-soil interaction mechanics, or terramechanics, with which the traction and disturbance forces of a wheel are evaluated for various slip conditions. These traction forces are decomposed into the longitudinal and lateral directions of the wheel. The latter component, termed the side force has a major influence in characterizing the steering maneuvers of the rover. In this paper, the wheel-soil mechanics models are developed with particular attention to the side force and the validity of the model is confirmed by using a single-wheel test bed. The motion profile of the entire rover is numerically evaluated by incorporating the wheel-soil models into an articulated multibody model that describes the motion dynamics of the vehicle’s body and chassis. Steering maneuvers are investigated under different steering angles by using a four-wheel rover test bed on simulated lunar soil regolith simulant. The experimental results are compared with the simulation results using the corresponding model parameters. The proposed wheel-and-vehicle model demonstrates better accuracy in predicting steering maneuvers as compared to the conventional kinematics-based model. ©