Version 2.4

A project log for Open-Source Shallow Water Glider

With support from Fisheries and Oceans Canada as a part of a co-op work term

seth-fleming-alhoSeth Fleming-Alho 06/05/2023 at 17:060 Comments

Work has resumed on the glider!

Having discovered a hydraulic pump option that can be acquired from hobby stores here we have returned to the 4inch tube design keeping cost and portability in mind. This pump is supposedly capable of reaching depths far past the crush point of our blue robotics acrylic hull but has yet to be rigorously pressure tested. The limit for depth on the glider at the moment its theoretically 40-50 meters of seawater, this is because we are still using the same valves as the previous iteration. Finding couplings to connect the 4mmOD 2.5mmID tubing for the pump to the 1/4" tubing and threads of the valve and bulkhead penetrators has been an ongoing struggle and it is likely a rework of the plumbing is in order. Once completed the hydraulic pump has the advantage of not only higher pressure but also keeping seawater out of the ballast engine by only using mineral oil which is a safer alternative to actual hydraulic fluid. Requiring not only an internal ballast but an external ballast means we have designed and external nosecone to contain the bladder and protect the altimeter. Water testing of various 3d printer materials is ongoing to see which will work best, our current iteration is a mix of PETG (internal) and ABS (external). We have stuck with using lifting bags to act as our ballast "tanks".

The entire structure inside the glider has been redesigned. Only containing an Arduino mega (and a 1500MKR in the future for cellular communication) the rear cell compartment has been simplified. The pitch engine had to undergo large changes because under the transportation of dangerous goods acts it is illegal to manufacture and transport your own batteries. To work around this restriction the power pack had to be assembled in such a way that all of the individual 18650 lithium cells being used are separate and not welded together. The roll engine now also include bearings to promote a smoother rotation and remove the need for anti-friction tape. The ballast engine underwent a rework to house the bladder along with the new hydraulic pump and ESC to control it. As mentioned above the plumbing needs some better connectors and that is being worked on.

The glider now has the custom circuit board installed and while the individual modules are testing well the current converter to bring the 12V of the battery pack to the 5V for the logic of the circuit is unable to deliver adequate current and will be replaced with a 12V to 5V buck converter from a car.

The 9DOF board has been installed and works (mostly). The compass seems to not be very reliable, this could be due to poor calibration or external interference. More testing is required but we may be required to purchase a better compass module. However even with the poor accuracy the glider does now have navigation! Using an onboard GPS and the compass it can take a coordinate input and determine a heading and bearing and should theoretically be able to make it to the coordinate.