An Autonomous Digging Vehicle

Abstract

This project is intended to develop a self-guided digging vehicle for various applications. Hence, the main focus for this vehicle is to have the ability to dig through loose soils. This project has focused on key digging technologies such as the use of shape memory alloys (SMAs) to motor power, precision motors to power conical and helical augers and biological movements as observed in “fossorial” creatures. Initially SMAs were selected as the source of motion to drive an auger to move the vehicle through the soil; whereas precision motors have become more promising for this purpose and became the second phase of this project. It was observed that SMAs of a feasible geometry could not produce the torque required to move the vehicle. Small SMAs have a low energy conversion efficiency (less than 5%) and cannot handle large loads. Large SMAs can handle larger loads, however these seem to experience shape “amnesia” at an increased rate (with currents over 10 A), when compared with standard SMAs. The use of an electric motor offers long lasting capabilities and when used with currents of around 15 A can produce the torque needed to bury itself sufficiently with customized augers. The third phase of this project looks at researching digging creatures and their movements to move through the earth. To scale down the amount of creatures involved in the research, an initial criterion of being “fossorial” was established. Upon selection of the creatures to be researched, specific questions were created to maximize the time researching each creature and not researching useless information. A weighting system was established ranking the following criteria deemed important for a digging vehicle: speed, power, depth, material substance, mechanical complexity, geographic range and size of organism. This ranking consisted of a scale of 1-5, with a score of one being harmful and a score of 5 being important. Three scenarios were then created, giving each of the seven metrics different percentages based on the importance of each: Scenario 1, small body (= 30 cm; 12 in) at low depths (= 152 cm; 60 in); scenario 2, small body (= 30 cm; 12 in) at medium depths (152 cm; 60 in – 610 cm; 240 in) and scenario 3, medium body (30 cm; 12 in – 91 cm; 36 in) at deep depths (= 610 cm; 240 in). Each creature was then given a final score and compared to each other, with the highest score from each scenario receiving the chance to be selected for further modeling. Although more information is needed for all the creatures to identify an animal most worthy of modeling, the available information indicates that the Townsend mole is the creature worthy of being selected.