Robot Boat Pioneers

Motivated by the desire for a compact, traditional sailing boat that I could easily chuck in the car and launch with minimal prep, I acquired a second-hand Compass Volantex DG65-class RC yacht.  The previous owner had assembled it from a kit, but never quite finished the rigging.  So, having completed that little task I took it out for a sail using the included 2-channel RC transmitter.  This test sail verified it behaved nicely on the water and gave me a sense of how it might behave after conversion to robotic control!  The conversion would involve a few stages: Replace the original RC receiver and battery with a DroneLink motherboard, Power module and LiPo battery Rework the electronics bay to accommodate the electronics Replace the stock hatch with a new 3D printed hatch to house the battery and Compass module Integrate a GPS antenna and 915MHz dipole for the RFM69 radio Create a miniature wind vane using an AS5600 magnetic encoder  Overall layout: New Brains...

This post describes the underlying operation of the Sailing algorithm built into the DroneLink platform.  The functionality is spread across a number of logical modules, allowing for flexible usage in different types of devices, for example, motorboats requiring waypoint navigation, but not sailing logic. Waypoint Navigation All our boats (and other mobile robots) require basic waypoint navigation, implemented in the Waypoint module.  The module loads a list of lon/lat coordinates and associated target radii from a CSV stored in the ESP32 flash filesystem (waypoint.csv).  An example CSV and the resulting visualization is shown below for 4 waypoints: The Waypoint module subscribes to t he current lon/lat location,  from the GPS module, and uses this to calculate once the boat has come within the target distance of the current waypoint (10m radius for the first waypoint in the example above).  Once the target radius is reached, the next waypoint from the file w...

  Early in our development process, it became clear a flexible, robust mesh network would be an extremely useful feature of the DroneLink platform.  Two of the primary drivers of this were: Supporting multiple boats on the water at the same time (4 is our current record, plus support equipment) Extending the range of our lake testing beyond 100m from the base station This article outlines the background and operation of our solution, referred to as DroneMesh.  As prior reading, you'll need to understand the concepts in  DroneNode Modules and Loosely Coupled Pub/Sub Messaging . For general background see  Wikipedia Wireless Mesh Network .   Use Cases Planning ahead, we also mapped out the various use cases we were likely to encounter on the way to attempting the actual Microtransat challenge: Short-range (<50 m): Bench testing - all devices located within the vicinity of a single building and/or all within WiFi range of a single router Lake testing: ...

Preface this is a blog about making a keel for a model boat. If you haven't read the post about that it won't make a lot of sense - Link to the original So Close post. So Close needs a high-density low heavy keel to keep it the right way up. Sounds easy to make something heavy, but it also needs to be a streamlined shape and have some means of fixing it to the two bits of sheet metal that it will hang between. Still doesn't sound very hard? Just 3D-print a mould of the shape and fill it with concrete, cast in a few bits of threaded rod and job done? Not quite so easy, So Close needs a 6kg keel, but the density of concrete is approximately 2.4kg/L, so 2.5 litres of concrete. Not a small mould to print, but not impossible if done in a few bits. The problem is when put under water it will displace 2.5 litres so now the concrete only weighs 3.5kg and it's huge. Now, of course, I could keep adding more and more concrete, not a very practical strategy, or pick a more dense su...

So Close needs a way to set its sails. Not a new problem. Model boats have been using pulley servos for years, but they are a bit limited. I want a servo with more travel, more strength and not so expensive.  I had previously experimented with modifying a standard RC servo to make it into a pulley servo. By replacing the potentiometer which senses the position with a 10 turn potentiometer it made the servo turn about 7 times over the full travel, but I found spooling string up was unreliable. Very practical on a real sailboat with sailors that can solve the problem of a snagged line, but on an RC boat a minor tangle can be big trouble. I needed something with fewer points of failure. Abandoning the winch approach, I designed a linear actuator based on a gearhead motor and a 1m length of M6 threaded rod. A square nut runs on the threaded rod inside a square tube. As the rod rotates the nut is moved back and forth in the square tube. The screw thread of the rod has a 1mm pitch so ea...

With the autonomous navigation of a boat proven (see previous blog post ), it's time to prove we can sail an autonomous boat. We chose a sloop rig boat as it's a practical rig that we all understand (see future blog posts about wing sailing). Sticking to the philosophy of rapid iteration and easy construction, I designed a monohull boat around a length of 110 mm soil pipe.  Related posts: Link to So Close keel project Link to So Close actuator project Link to the DroneLink System - Robot Brains article Some stats: length                             2.4m exactly Beam         110mm  Draft 500mm Hight of the rig 1100 mm  Sail area 1 sqm  Actuator           800mm travel home brew linear actuator Keel mass 6 kg Displacement 11kg The boat has a completely round cross-section so has absolutely zero form st...