Piecewise model of track sinkage based on underwater cohesive soil

Abstract

The soil resistance force prediction model plays a vital role in estimating trafficability of unmanned tracked vehicles on unknown terrain, especially for river floor soil, a kind of soft soil with high saturation. In order to obtain characteristics of soft soil, a soil test platform was built which track segment sinkage, and shear tests can be performed in river floor soil. Comprehensive analysis of mechanics of track-soil interaction, a new pressure-sinkage empirical model is proposed for soft soil. This piecewise empirical model with two functions relies on two sets of independent parameters to describe the stratification of the underwater soil, including loose layer and dense layer. To evaluate the accuracy of the piecewise empirical model, an underwater tracked vehicle driven by two brushless DC motors was designed and an underwater travel test platform was built, which the vehicle can be operating in the river floor soil. The main external forces enacting on the vehicle, including environmental loads caused by the river floor soil and water, were analyzed in the process of vehicle running at a constant speed, and a soil resistance force prediction model was deduced with the proposed piecewise empirical model. The current of two brushless DC motors is used to estimate the external loads and validate the piecewise empirical model. Test results indicate that the soil resistance force prediction model was effective and feasible.