Mapping The Depths With An Autonomous Solar Boat

Ever look out at a pond, stream, or river, and wonder how deep it is? For large bodies of water that are considered navigable, it’s easy enough to pull up a chart and find out. But what if there’s no public data for the area you’re interested in?

Well, you could spend all day on a little boat taking depth readings and making your own chart, but if you’re anything like [Clay] you could build a solar-powered autonomous robot to do it for you. He’s been working on the boat, which he calls Gumption Trap, for the better part of a year now. If we had to guess, we’d say the experience of designing and building it has ended up being a bit more interesting to him than the actual depth of the water — but that’s fine by us.

The design of the boat is surprisingly economical, as far as marine designs go. Two capped four-inch PVC pipes are used as pontoons, and 3D printed brackets attach those to an aluminum extrusion frame that holds the electronics and solar panel high above the water. This arrangement provides an exceptionally stable platform that would be all but impossible to flip under normal circumstances.

Around the back of the craft, there’s a pair of massive 3D printed thrusters, complete with some remarkably chunky printed propellers. The lack of rudders keeps things simple, with differential thrust between the two motors enough to keep the Gumption pointed in the right direction.

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Supercon 2022: All Aboard The SS MAPR With Sherry Chen

How do you figure out what is in a moving body of water over a mile wide? For those in charge of assessing the water quality of the Delaware river, this is a real problem. Collecting the data required to evaluate the water quality was expensive and time-consuming, taking over six years. Even then, the data was relatively sparse, with just a few water quality stations and only one surface sample for every six miles of river.

Sherry Chen, Quinn Wu, Vanessa Howell, Eunice Lee, Mia Mansour, and Frank Fan teamed up to create a solution, and the SS MAPR was the result. At Hackaday Supercon 2022, Sherry outlined the mission, why it was necessary, and their journey toward an autonomous robot boat. What follows is a fantastic guide and story of a massive project coming together. There are plans, evaluations, and tests for each component.

Sherry and the team first started by defining what was needed. It needed to be cheap, easy to use, and able to sample from various depths in a well-confined bounding box. It needed to run for four hours, be operated by a single person, and take ten samples across a 1-mile (2 km) section of the river. Some of the commercial solutions were evaluated, but they found none of them met the requirements, even ignoring their high costs. They selected a multi-hull style boat with off-the-shelf pontoons for stability and cost reasons.
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Robotic Boat Rides High On PVC Pipe Pontoons

If you want to build your own rover, there’s plenty of cheap RC trucks out there that will provide a serviceable chassis to work with. Looking to go airborne with a custom drone? Thanks to the immense popularity of first-person view (FPV) flying, you’ll find a nearly infinite variety of affordable fixed wing and quadcopter platforms out there to chose from. But when it comes to robotic watercraft, the turn-key options aren’t nearly as plentiful; the toys are all too small, and the commercial options are priced for entities that have an R&D budget to burn. For amateur aquatic explorers, creativity is the name of the game.

Take for example this impressive vessel built by [wesgood]. With a 3D printed electronics enclosure mounted to a pair of pontoons made of cheap 4-inch PVC pipe available from the hardware store, it provides a stable platform without breaking the bank. Commercial jet drive units built into the printed tail caps for the pipes provide propulsion, and allow the craft to be steered through differential thrust. Without rudders or exposed propellers, this design is particularly well-suited for operating in shallow waters.

A removable electronics tray allows for easy access.

Perched high above the water, the electronics box contains a Raspberry Pi 2, BU353 USB GPS receiver, and a Arduino Mega 2560 paired with a custom PCB that offers up convenient ports to connect a dual-channel Cytron 3 amp motor driver and Adafruit BNO055 9-DOF IMU. Power is provided by two 6,000 mAh LiPo batteries mounted low in the pontoons, and a matching pair of Adafruit current/voltage sensors are used to keep track of the energy budget. A small USB WiFi dongle with an external antenna plugged into the Pi offers up a WiFi network that [wesgood] can connect to with an iPad for control.

If the control software for the craft looks particularly well-polished, it’s probably because [wesgood] just so happens to be a professional developer with a focus on mobile applications. While we’re a bit skeptical of using WiFi for a critical long-distance link, we can’t deny that the iPad allows for a very slick interface. In addition to showing the status of the craft’s various systems, it lets the user either take manual control or place waypoints for autonomous navigation — although it sounds like that last feature is only partially implemented right now.

We love this design, and are eager to see more as the project develops. Recently [wesgood] experimented with payloads that can be suspended from the bottom of the electronics box, specifically a sonar module for performing bathymetric observations. There’s considerable interest in crowd sourced depth maps for inland waterways, and a robotic craft that can reliably chart these areas autonomously is certainly a step up from having to collect the data manually.

Open Source Autopilot For Cheap Trolling Motors

Quiet electric trolling motors are great for gliding into your favorite fishing spot but require constant correction if wind and water currents are at play. As an alternative to expensive commercial GPS-guided trolling motors, [AlexAsplund] created Vanchor, an open source system for adding autopilot to a cheap trolling motor.

To autonomously control an off-the-shelf trolling motor, [Alex] designed a 3D printed steering unit powered by a stepper motor to attach to the original transom mount over the motor’s vertical shaft. A collar screwed to the shaft locks the motor into the steering unit when the motor is lowered. The main controller is a Raspberry Pi, which hosts a WiFi hotspot and web server for control and configuration using a smartphone. Using navigation data from an e-compass sensor and a marine GPS chart plotter, it can hold position, travel in a specified direction, or follow a defined route. [Alex] is also planning to add the option of using a GPS module instead of a commercial plotter.

For an estimated total of $300, including the motor, this seems like a viable alternative to commercial systems. Of course, it might be possible to add even more features by integrating the open source ArduRover autopilot, as we’ve seen [rctestflight] do on multiple autonomous vessels. You can also build your own open source chart plotter using OpenCPN, which rivals commercial offerings.

Solar Powered Autonomous Tugboat For Rescuing Autonomous Vessels

[rctestflight] has built several autonomous boats, and with missions becoming longer and more challenging, he bought an inflatable kayak to serve as a dedicated rescue vessel. Instead of relying on outdated manual paddling, he built an autonomous solar-powered tugboat.

Towing test with kayak
♪ “Rum, treasure, ArduRover, Pixhawk 4 and so much solar, break of dawn till the day is over, the ship will surely go…” ♪

The tugboat uses a pair of molded fiberglass hulls in a catamaran configuration. The wide platform allows a pair of 100W solar panels to be mounted on top. It was [rctestflight]’s first time molding anything out of fiberglass, so there was quite a bit of trial and error going on. The mold was 3D printed in sections, aligned with dowel pins, and glued together. After the epoxy had cured, the mold halves could be split apart for easier removal of the hull.

As with most of [rctestflights] autonomous vehicles, control is handled by a Pixhawk 4 running ArduPilot/ArduRover. A pair of 76 mm brass propellers powered by brushless motors provide propulsion and differential steering. The motors get power from six LiFePO4 batteries, which charge from the solar panels via MPPT charge controllers. The hulls are covered with plywood decks with removable hatches and inspection windows. After a bit of tuning, he took the boat for a few test runs, the longest being 5.1 km with himself in tow in the kayak. At less than 5 km/h (3 mph) it’s no speedboat, but certainly looks like a relaxing ride. Many of [rctestflight]’s previous vessels were airboats to avoid getting underwater propellers tangled in weeds. It was less of an issue this time since he could just haul the tugboat close to the kayak and clear the propellers.

[rctestflights] are always entertaining and educational to watch, and this one certainly sets the standard for sea-shanty soundtracks at 13:32 in part two.

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Autonomous Boat For Awesome Video Hyperlapses

With the ever-increasing capabilities of smart phones, action cameras, and hand-held gimbals, the battle for the best shots is intensifying daily on platforms like YouTube and Instagram. Hyperlapse sequences are one of the popular weapons in the armoury, and [Daniel Riley] aka [rctestflight] realised that his autonomous boat could be an awesome hyperlapse platform.

This is the third version of his autonomous boat, with version 1 suffering from seaweed assaults and version 2 almost sleeping with the fishes. The new version is a flat bottomed craft was built almost completely from pink insulation foam, making it stable and unsinkable. It uses the same electronics and air boat propulsion as version 2, with addition of a GoPro mounted in smart phone gimbal to film the hyper lapses. It has a tendency to push the bow into the water at full throttle, due to the high mounted motors, but was corrected by adding a foam bulge beneath the bow, at the cost of some efficiency.

Getting the gimbal settings tuned to create hyperlapses without panning jumps turned out to be the most difficult part. On calm water the boat is stable enough to fool the IMU into believing that it’s is not turning, so the gimbal controller uses the motor encoders to keep position, which don’t allow it to absorb all the small heading corrections the boat is constantly making. Things improved after turning off the encoder integration, but it would still occasionally bump against the edges of the dead band inside which the gimbal does not turn with the boat. In the end [Daniel] settled for slowly panning the gimbal to the left, while plotting a path with carefully calculated left turns to keep the boat itself out of the shot. While not perfect, the sequences still beautifully captured the night time scenery of Lake Union, Seattle. Getting it to this level cost many hours of midnight testing, since [Daniel] was doing his best to avoid other boat traffic, and we believe it paid off.

We look forward to his next videos, including an update on his solar plane. Continue reading “Autonomous Boat For Awesome Video Hyperlapses”

Autonomous Air Boat Vs Lake Washington

Autonomous vehicles make a regular appearance around here, as does [Daniel Riley] aka [rctestflight]. His fascination with building long-endurance autonomous vehicles continues, and this time he built an autonomous air boat.

This craft incorporates a lot of the lessons learnt from his autonomous boat that used a plastic food container. One of the biggest issues was the submerged propellers kept getting tangled in weeds. This led [Daniel] to move his props above water, sacrificing some efficiency for reliability, and turning it into an air boat. The boat itself is catamaran design with separate 3D printed hulls connected by carbon fibre tubes. As with the tupperware boat, autonomous control is done by the open source Ardupilot software.

During testing [Daniel] had another run in with his old arch-nemesis, seaweed. It turns out the sharp vertical bow is a nice edge for weeds to hook on to, create drag, and screw up the craft’s control. [Daniel]’s workaround involved moving the big batteries to the rear, causing the bows lift almost completely out of the water.

With a long endurance in mind right from the start of the project, [Daniel] put it to the test with a 13 km mission on Lake Washington very early one morning. For most of the mission the boat was completely on its own, with [Daniel] stopping at various points along the lake shore to check on its progress. Everything went smoothly until 10 km into the mission when the telemetry showed it slowing down and angling off course, after which is started going in circles. Lucky for Daniel he was offered a kayak by a lakeside resident, and he managed to recover the half sunken vessel. He suspects the cause of the failure was a slowly leaking hull. [Daniel] is already working on the next version, and were looking forward to seeing what he comes up with. Check out the video after the break. Continue reading “Autonomous Air Boat Vs Lake Washington”