It has been two years since I have touched this project. However, it has lingered in the back of my mind ever since. The significant issues with the previous design were positioning accuracy, skier safety and propulsion. Two of these hurdles were due to over optimising cost in the prototyping stage, which I now realise was a mistake. With lessons learned the new prototype is being built without cost optimisation. I think we can accept that a robotic course will be more expensive than an anchored course.

The new design is drastically different. The shape is entirely spherical with pod thrusters mounted inside the sphere. The sphere itself will be cast out of silicone to reduce injuries. Currently, the sphere is 3D printed for prototyping purposes. Amazingly, it is waterproof. The positioning will be handled using RTK GPS, a major step up from our GPS only system. As a result, positioning accuracy should be around 10 cm, which is probably what you can expect for a tethered course. With the added computation load of the RTK system, every buoy will be controlled using a raspberry pi zero. Consequently, this means ten Linux systems are floating in the water while you are skiing. Finally, we are able to reduce the system to ten buoys by directing the boat using a heads-up display.

Below are some pictures detailing the progress thus far.

Concept drawing

CAD drawing using Fusion 360

3D Printing the design

Adding some pod thrusters. Using normal brushless outrunner motors. Currently using 4 motors, will most probably use 2 in the final design to save cost.

Adding motor drivers and power distribution. Here things start to deviate from the CAD model. Nevertheless, this is a prototype and the main goal is to test the propulsion and station keeping.

PCB boards for RTK GPS, telemetry and breakout pins for the PWM pins. These boards are basically a hat for the raspberry pi.

In the next post, I will report back on the first propulsion test.

 

Last year I started building an intelligent ski-course, which was basically a set of buoy drones that would swim to there positions in a public river to form a ski course. This would then allow tons of interesting possibilities such as easy setup and effortlessly changing the shape of the course. Most of the project is documented on hackaday.io. As I am a very eager slalom skier in dire need of a course I would very much like to finish this project. However, I find myself without time working on finishing my PhD. I will one day restart my efforts, if anyone is interested in developing the project from where I left it, you are more that welcome, just keep me in the loop.

The state of the project:

1. Most of the code has been written.
2. The electronics for the buoy and base station has been mostly finalized
3. 3D printed parts needs to be revised
4. Propulsion system needs to be tested