Testing specifications

A project log for OSUG: Open-Source Underwater Glider

A versatile autonomous environmental drone using a buoyancy engine

alexwalexw 04/30/2017 at 23:510 Comments

I have produced a table of various specifications that the underwater glider must pass in order to fully function as intended. The specifications listed range from absolutely necessary for the glider to glide (watertight etc.) to requirements that allow it to function as an autonomous data-logging drone (way point navigation and a functioning sensor array)

Some requirements I am will be able to achieve relatively easily (function without external connections etc) but some are beyond my current capabilities (inertial navigation, for instance).

UPDATE: An up-to-date version of this table will be maintained in the dropbox folder.

Specification requirement Details How to achieve this
Motors and movement assemblies The stepper motors should be able to control the
movement assemblies easily
If the motors are incapable of moving, reduce resistance. (One source of high resistance could be poorly meshing gears, which could be fixed by increasing clearance or adding
Functions without external cables The final glider should operate underwater, without
external cables for power or control signals
All electronics should be inside the glider and should run off of lithium ion batteries
Watertight No water should enter the glider whilst operating,
otherwise this will damage electronics and cause the glider to sink
If the glider is not watertight, change the seal dimensions and add sealant to ensure the central compartment is water
Neutrally buoyant The glider should be able to become both positively buoyant and negatively buoyant by being neutrally buoyant when the buoyancy engine is half full Add/remove pewter ballast until the glider is neutrally buoyant when the buoyancy engine is half filled with water
Descends and ascends through water If neutrally buoyant, the glider should descend and ascend through the water if the buoyancy engine is full/empty respectively If the glider does not change depth, look at increasing the capacity of the buoyancy engine so that there is a greater density differential
Responds to gyroscope inputs The glider should be able to maintain a constant angle of attack whilst underwater Test the glider’s response whilst above water, the mass assembly should move to oppose a change in angle of attack, to keep the angle of attack constant whilst gliding.
Moves forwards The glider should be able to dive forwards whilst descending, allowing it to travel between two points The center of mass should maintain a constant angle of attack and the hydrofoils will provide forward thrust
The glider should be capable of turning whilst gliding, so that it can go between waypoints that are not in a line By rotating the central mass assembly, the glider should be capable of turning (albeit with a very large turning radius). Lowering the centre of mass of the mass assembly increases the moment and reduces the turning radius (by increasing roll)
Waypoint navigation The glider should be capable of autonomously navigating between pre-deteremined waypoints By using a GPS module, the glider should be capable of finding location whilst at the surface (GPS signals do not penetrate water). By gliding in the correct direction, the glider will be capable of moving between waypoints
Inertial navigation The glider should know its position whilst underwater Using the gyroscope and accelerometer inputs, the glider should be capable of calculating its position whilst underwater, between GPS readings
Sensor array As the glider will be an autonomous environmental monitoring drone, it should be capable of recording gas levels, pH, temperature, light levels Attach the sensor array and program the microcontroller to record data inputs to non-volatile memory
Data mapping The sensor data should overlay onto a map indicating location of the data By recording location when recording sensor readings, the data can be overlayed onto a map