During my Junior year of University, I worked as a research assistant in Dr. Daltorio's Biologically Inspired Robotics Lab, working on the ARPA-E sponsored GOPHURRS robotic worm project. The robotic worm is intended to burrow through the ground using a drill head, and use its segments to install underground utilities such as conduit.

I led a subteam assigned to the actuator design and preliminary testing for the drill head. The technical requirements were quite demanding due to the high torque required to drill a large-diameter hole in soil, the limited physical space, and the thermal constraints that come from sand and soil's insulating properties.  

Process

Initially the team was looking towards electric actuation due to the lab's familiarity with electric actuators. We did preliminary research and were not able to find COTS electric actuators that met the torque and thermal requirements simultaneously, and did initial design and Thermal FEA for solutions like gear reducers and fluid cooling.

Through research into similar earth-boring systems, I identified that hydraulics may be more feasible at this scale. I did first-principles based calculations around torque, efficiency, and the heat capacity and transfer rates of various cooling methods.

After I proposed hydraulic actuation, I worked with the lab to create a test bench that could prove out the concept. I spec’d components, created CAD, and made hydraulic diagrams and system interconnect diagrams.

There were several rounds of design iteration based on feedback from those in the lab as well as industry professionals in hydraulics; I implemented feedback to simplify the design, develop safe installation and operating procedures, and communicated with my subteam throughout the process. 

Our solution to prove out the concept was to take a cart and COTS HPU and integrate them with a solenoid valve, oil pressure and temperature transducer, pressure gauge, and COTS hydraulic motor with displacement sized to produce the correct torque and RPM. 

Results