SwapStop

Early Contruction Progress

Saturday, January 18, 2020

It has been a busy few weeks here, as the team has seized the opportunity of the winter break to make some solid progress. First and foremost, the arrival of the t-slot extrude has allowed for assembly of the project's frame. Everything's built perfectly to spec, but we still can't help but be impressed by the sheer scale of this thing.

Assembly of the frame, in its early stages. Assembly of the frame, in its early stages.

In addition, the arrival of drawer slides and v-slot rollers allowed for the construction of the elevating carriage, which we have affectionately named Flyn. Sandwiched between two parallel sheets of aluminium, with drawer slides and limit switches already in place, this hefty piece of equipment will hold the two linear actuators which move the LiPo batteries around. All together, Flyn is predicted to be quite heavy at completion — about 8 kilograms — but this is well within spec, and more importantly, allows the machine to operate seriously fast.

Flyn, assembled and waiting for the intelligent moving bits. Flyn, assembled and waiting for the intelligent moving bits.

There's been progress on the software/electrical front, too! Precise control of the large stepper motors (responsible for actuating Flyn up and down along its vertical rail) now works end-to-end. This includes software control and a hardware setup comprising of the motor, gearbox, motor controller, and power supply. This system moves with an almost unbelievable amount of torque- and there will be two of them, working together, in the final build.

Computer control of the stepper motors.

Lastly (as far as this update is concerned...) computer vision localization is now working! Using a webcam (which will be mounted to the landing platform, facing upwards) we can now precisely track the position and orientation of an AprilTag in 3D space. An AprilTag is similar to a QR code, except it encodes much less data and can therefore be accurately detected from much futher away. One of these tags will be mounted to the underside of each drone, and the resolved position data will be fused with the readings of onboard sensors to achieve a precise position lock, far more accurate and reliable than GPS. This is all the data we will need to attempt a successful landing.

That's it for today! There has been much more progress on many other fronts, of course — machining, wiring, soldering, and coding — but these are the highlights for now. Stay tuned for some exciting updates in Flyn actuation, coming to you very soon.