Method and apparatus for on-line estimation of soil parameters during excavation R. Yousefi Moghaddam, A. Kotchon, M.G. Lipsett ⇑ Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada T6G 2G8 Received 14 September 2011; received in revised form 1 March 2012; accepted 3 May 2012 Available online 7 June 2012 Abstract Time-varying forces from soil–machine interactions cause stresses in the components of earthmoving machinery, which may cause damage to the machine. It is not always possible to know all the characteristics of a soil sample prior to excavation; however, by esti- mating necessary soil parameters, it is possible to predict the soil–machine interaction forces in a practical manner. This article presents the development of a simple apparatus and method for estimating the soil parameters from the cutting force measured by the novel bench-scale excavating tool, validation of the soil model, and comparison with other available techniques. The apparatus used to collect data of soil forces on a tool consists of an instrumented crank-slider mechanism equipped with a thin plate to fragment the soil, which is contained in a sample box. Using the Mohr-Coulomb earth pressure model to predict failure force during the interaction, two methods are used to minimize the error between the predicted and measured failure force, that allows to estimate soil parameters: First, the New- ton–Raphson Method (NRM) is used to minimize the error, which allows estimation of two soil parameters (interface friction angles) on non-cohesive soil samples. Additionally, a new estimation scheme based on the NRM is presented, that uses an auxiliary equation, and allows estimation of up to three soil parameters, including interface friction angles and cohesion. Comparing the results obtained from the presented apparatus, it is confirmed that the friction angles are successfully estimated for two non-cohesive particulate materials. Additionally, it is shown that the new scheme demonstrates smaller error in estimating soil parameters for cohesive and non-cohesive soil samples than previously reported methods. The parameter estimation method is subsequently applied to determine the properties of highly cohesive oil sand, and delivers promising results. Ó 2012 ISTVS. Published by Elsevier Ltd. All rights reserved. Keywords: Soil–tool interaction; Failure force; Soil parameter estimation 1. Introduction Excavation and earthmoving require a high amount of interaction between the excavator and the medium being cut and displaced. The forces of interaction between the machine and the soil depend on the tool geometry, the material, the operating conditions, and the soil characteris- tics (density, degree of compaction, cohesion, friction against the tool, moisture content, etc.) [1]. Soil parameters also play an important role in the traction forces of the machine on the soil during excavation. As the digging material is not always homogenous, there may be considerable variation in soil properties, which will contribute to the soil–tool interaction force. High variable loads can damage structural components and elements of the power transmission when the loads exceed a certain level [2,3]. Having a proper estimate of the soil parameters, it is possible to predict the soil–machine interaction forces in order to avoid such scenarios by changing the digging strategies, depth of cut, or angle of attack of the tool. In this way, knowledge of soil characteristics can inform equipment design, operating practice, and machine control. Numerous research studies have been conducted on parametric and numerical methods for modeling the 0022-4898/$36.00 Ó 2012 ISTVS. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jterra.2012.05.002 ⇑ Corresponding author. Tel.: +1 (780) 492 9494; fax: +1 (780) 492 2020. E-mail addresses: yousefim@ualberta.ca (R. Yousefi Moghaddam), akotchon@ualberta.ca (A. Kotchon), mlipsett@ualberta.ca (M.G. Lip- sett). www.elsevier.com/locate/jterra Available online at www.sciencedirect.com Journal of Terramechanics 49 (2012) 173–181 Journal of Terramechanics