Energy Efficient Depth Control for Underwater Devices Using Soft and Hard Actuators

A Proton Exchange Membrane (PEM) fuel cell enabled buoyancy control device (BCD) is developed to address the challenge of depth control in underwater devices by compensating for buoyancy changes during underwater manipulations. The BCD splits distilled water into hydrogen and oxygen gases, increasing the volume of balloons attached to it, providing a permanent change in buoyancy of the device, and reducing the need for motors to run constantly. Results indicate that energy savings can reach up to 85% in comparison with experiments that use DC motors only. Additionally, the response is smoother and device stability is increased when DC motors are not running. Experimental results show the trajectory profiles when the BCD is active and passive, respectively. Furthermore, the PEM electrolyzers can be used as fuel cells to charge a battery or run another mechanical device after the operation, resulting in around 28% energy savings.