Along developed riverbanks, physical barriers can help contain flooding and combat erosion. In arid regions, check dams can help retain soil after rainfall and restore damaged landscapes. In construction projects, metal plates can provide support for excavations, retaining walls on slopes, or permanent foundations.
All of these applications can be addressed with the use of sheet piles, elements folded from flat material and driven vertically into the ground to form walls and stabilize soil. Proper soil stabilization is key to sustainable land management in industries such as construction, mining, and agriculture; and land degradation is a driver of climate change and is estimated to cost up to $10 trillion annually worldwide.
With this motivation, a team of roboticists at Harvard’s Wyss Institute for Biologically Inspired Engineering has developed a robot that can autonomously drive interlocking steel sheet piles into soil. The structures it builds could function as retaining walls or check dams for erosion control. Their study will be presented at the upcoming 2019 IEEE International Conference on Robotics and Automation.
Conventional sheet pile driving processes are extremely energy intensive. Only a fraction of the weight of typical heavy machinery is used for applying downward force. The Wyss team’s Romu robot, on the other hand, is able to leverage its own weight to drive sheet piles into the ground. This is possible because each of its four wheels is coupled to a separate linear actuator, which also allows it to adapt to uneven terrain and ensure that piles are driven vertically.
From a raised position, Romu grips a sheet pile and then lowers its chassis, pressing the pile into the soil with the help of an onboard vibratory hammer. By gripping the pile again at a higher position and repeating this process, the robot can drive a pile much taller than its own range of vertical motion. After driving a pile to sufficient depth, Romu advances and installs the next pile such that it interlocks with the previous one, thereby forming a continuous wall. Once it has used all of the piles it carries, it returns to a supply cache to restock.
The study grew out of previous work at the Wyss Institute on teams or swarms of robots for construction applications. In work inspired by mound-building termites, core faculty member and Fred Kavli Professor of Computer Science at the School of Engineering and Applied Sciences (SEAS) Radhika Nagpal and senior research scientist Justin Werfel designed an autonomous robotic construction crew called TERMES, whose members function together to build complex structures from specialized bricks.