We developed a buoyancy control device for an underwater robot designed at the STRIDe Lab. The robot walks on the sea floor, swims through open water and jumps to clear obstacles such as rocks or coral. Its current weight improves grip and balance while walking, but causes it to sink too quickly during swimming and jumping, limiting its ability to perform each locomotion mode effectively.
To address this, we designed a syringe-like device that moves water in and out of a sealed tube, thereby varying the volumes of air and water inside. When the piston expels water, the device retains more air, reducing the robot’s effective weight in water. When the piston draws water in, the robot becomes negatively buoyant and sinks. Because the device attaches directly to the robot, we had to mount it near the robot’s center of mass to preserve its original movement and balance, while also ensuring it could attach and detach easily for access to internal components.
We delivered a removable buoyancy control device rated for harsh underwater environments, including resistance to high pressure, temperature changes and corrosion from both fresh and saltwater during deep-ocean operation. The device enables the robot to switch between walking, swimming and jumping in a controlled and repeatable way, bringing it one step closer to fully autonomous ocean exploration.
