Design

TideRider uses a novel low-cost buoyancy engine. The engine is passive and bi-stable: it works by leveraging water pressure to collapse a bladder. At the surface the bladder is fully expanded. A propeller will force the vehicle to dive, increasing the ambient water pressure and collapsing the bladder. A few meters below the surface the bladder will have collapsed enough to allow the vehicle to sink without the thruster, and drift to the bottom. The propeller is then used in reverse to bring the vehicles back to the surface and restore the bladder. I implemented this concept by categorizing various bladder types, eventually landing on using a COTs piston and cylinder to act as a virtual bladder.

TideRider can be built from off-the-shelf components and hand tools. It uses cellular connectivity to allow for real time communication on the surface. I designed the vehicle, wrote its control system, and integrated its electrical components. 

Embedded Software

• Architected entire system, including hardware drivers, state logic, mission planning, and communications. This code is still in use today. A few highlights from this code base are below:

• Wrote I2C hardware drivers for EEPROM memory, a RTC, and a register level watchdog driver

• Designed the core state machine, including ensuring reliable operation even during partial system failure though a robust failure detection and correction module

• Developed a waypoint tracker that governed the core state machine, allowing for passive waypoint navigation (see Field Trials and Navigation below)