1.) The Hull

Having switched out the syringe ballast engine for the pump design we are considering a larger enclosure tube. We realized while looking for an adequate pump that most 12V pumps are just slightly over 4Inches in diameter and would hence not fit in the tube. Switching to a 6inch enclose would allow for a much wider range of pumps to be considered, most of which are far more powerful than what is currently inside the glider.

The 4" acrylic tube was used because it was part of the original design. 4" acrylic is great for prototyping since you can see what is going on inside, however, it is no longer available from Bulerobotics, was difficult to source, and was one of the most expensive parts of the project. In addition, it was very difficult to source a pump that would fit inside a 4 inch tube. Increasing the size of the tube to 6" should give enough room for a larger variety of pump options.

All parts for 6" enclosures are available from Bluerobotics (https://bluerobotics.com/product-category/watertight-enclosures/6-series/), however, the longest length available is 11.75"/298mm. Longer tube could be sourced elsewhere and doesn't need to be clear or acrylic. Options could include aluminum, PVC, etc.

2.) STL files

Increasing the size of the enclose will mean an overhaul of the printed files. Opportunities will be taken to increase battery capacity, install a larger pump and change the circuit rack design to either copy or use the prefabricated model from Blue ROV  (along these lines https://bluerobotics.com/store/watertight-enclosures/locking-series/wte4-etray-r1/). The prefabricated circuit rack will only be viable if the glider design keeps the 4Inch tubing.

Currently the different sections of the glider are connected with wood for ease of prototyping however this will be replaced with long metal standoffs https://bluerobotics.com/store/rov/bluerov2-components-spares/standoff-m3x0-5-212-mf/.

3.) Cable connectors

The prototype wiring definitely needs some wire clean-up and ideally all connectors will be either soldered together or connected with clip-in connectors. These connectors will be introduced into the PCB design.

4.) Replacing the IMU.

Currently the glider operates off of a MPU-6050, this is unfortunately only a 6-DOF chip and for reliable navigation during the dead reckoning dives we require a 9-DOF chip. Testing has begun on the https://bc-robotics.com/shop/9-dof-sensor-stick/ to see if it satisfies our requirements.

5.) More Sensors

With and Arduino interfacing with sensors is incredibly easy and with a few open slots in the bulkhead it would be good to find sensors important to oceanographic work that could be easily installed.

6.) Ballast Volume Measurement

The whole ballast engine design is a pretty crude prototype, pretty good for the first version and a huge improvement over the syringe design. The big thing we need to figure out is how to measure whether the ballast is all the way in or all the way out and ideally some way of measuring/estimating the volume between those two extremes. Limit switches, pressure sensors, and the flex sensor (https://bc-robotics.com/shop/short-flexbend-sensor/) are a few options we discussed, but we should be open to other options including a different interior reservoir that would allow better measurement 

7.) Remove raspberry pi

The pi and its separate power supply exist solely for being able to wirelessly reprogram the Arduino during the testing phase. It will no longer be necessary once the design and code are finalized. This will save room and reduce power consumption.

8.) Bladder

Ideally an internal and external bladder should be used. Unfortunately we were unable to source a fitting during this phase of the project that allowed tubing to be attached to both sides of the end-cap. Running the ballast engine with normal seawater will run the chance of the tubing or penetrators becoming clogged. Having an internal and external bladder filled with oil would be able to run without any risk of foreign materials getting sucked in.

9.) navigation, communication, and piloting interface

The glider currently has a simple interface where a single command 'dive' can be sent over a long range radio and the glider follows a pre-programed series of events to do a single dive.

Future improvements to communications could include: adding a cellular communications so the glider could be monitored remotely and ideally could receive commands. Having the glider send back data over radio or cellular, especially location