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Soil strength testing and collecting soil cores from wetlands is currently a slow, manual process that runs the risk of disturbing and contaminating soil samples. This paper describes a method using an instrumented dart deployed and retrieved by a drone for performing core sample tests in soft soils. The instrumented dart can simultaneously conduct free- fall penetrometer tests. A drone-mounted mechanism enables deploying and reeling in the dart for sample return or for multiple soil strength tests. Tests examine the effect of dart tip diameter and drop height on soil retrieval, and the requisite pull force to retrieve the samples. Further tests examine the dart’s ability to measure soil strength and penetration depth. Hardware trials demonstrate that the drone can repeatedly drop and retrieve a dart, and that the soil can be discretely sampled. 

This paper presents a method for performing free-fall penetrometer tests for soft soils using an instrumented dart deployed by a quadcopter. Tests were performed with three soil types and used to examine the effect of drop height on the penetration depth and the deceleration profile. Further tests analyzed the force required to remove a dart from the soil and the effect of pulling at different speeds and angles. The pull force of a consumer drone was measured, and tests were performed where a drone delivered and removed darts in soil representative of a wetland environment. 

Localization is a key ability for robot navigation and collision avoidance. The advent of technologies such as GPS have led to many improvements in terrestrial navigation. Unfortunately traditional electromagnetic (EM) communications propagate poorly through lossy media such as underwater and underground. Therefore, localization remains a challenging problem in such environments, necessitating other approaches such as acoustics and magnetic induction (MI). This paper investigates estimating the relative location of a pair of MI triaxial coil antennas in air, as a preliminary step to underwater applications. By measuring the voltages induced in the receiving antenna when the transmitting antenna's coils are turned on sequentially, the distance between the antennas can be computed. Then, with knowledge of the current velocities of the antennas, we can apply a particle filter to generate an estimate of the location of the transmitting antenna with respect to the receiving one. The theory is supported by simulations and later verified through a series of experiments.