Forget Propellers, Embrace Tentacle-based Locomotion

April 9, 2025 by Donald Papp 25 Comments

Underwater robots face many challenges, not least of which is how to move around. ZodiAq is a prototype underwater soft robot (link is to research paper) that takes an unusual approach to this problem: multiple flexible appendages. The result is a pretty unconventional-looking device that can not only get around effectively, but can do so without disturbing marine life.

ZodiAq sports a soft flexible appendage from each of its twelve faces, but they aren’t articulated like you might think. Despite this, the device can crawl and swim.

With movement inspired by bacterial flagella, ZodiAq moves in an unusual but highly controllable way.

Each soft appendage is connected to a motor, which rotates the attached appendage. This low-frequency but high-torque rotation, combined with the fact that each appendage has a 45° bend to it, has each acting as a rotor. Rotation of the appendages acts on the surrounding fluid, generating thrust. When used together in the right way, these appendages allow the unit to move in a perfectly controllable manner.

This locomotion method is directly inspired by the swimming gait of bacterial flagella, which the paper mentions are regarded as the only example of a biological “wheel”.

How fast can it go? The prototype covers a distance of two body lengths every fifteen seconds. True, it’s no speed demon compared to a propeller, but it doesn’t disturb marine life or environments as it moves around. This method of movement has a lot going for it. It’s adaptable and doesn’t use all twelve appendages at once; so there’s redundancy built in. If some get damaged or go missing, it can still move, just slower.

ZodiAq‘s design strikes us as a very accessible concept, should any aspiring marine robot hackers wish to give it a shot. We’ve seen other highly innovative and beautiful underwater designs as well, like body-length undulating fins and articulated soft arms.

We do notice that since it lacks a “front” — it might be a challenge to decide how to mount something like a camera. If you have any ideas, share them in the comments.

The Yamato 1, a sleek grey ship that looks vaguely like a computer mouse or Star Trek shuttlecraft. It has an enclosed cockpit up front with black windows and blue trim. It is sitting on land in front of a red tower at a museum in Tokyo.

Navy Program PUMPs Up Hopes For Magnetic Propulsion

June 5, 2023 by Navarre Bartz 43 Comments

The “caterpillar drive” in The Hunt for Red October allowed the sub to travel virtually undetected through the ocean, but real examples of magnetohydrodynamic drives (MHDs) are rare. The US Navy’s recently announced Principles of Undersea Magnetohydrodynamic Pumps (PUMP) intends to jump-start the technology for a new era.

Dating back to the 1960s, research on MHDs has been stymied by lower efficiencies when compared with driving a propeller from the same power source. In 1992 the Japanese Yamato-1 prototype, pictured at the top of the page, was able to hit a blistering 6.6 knots (that’s 12 kph or 7.4 mph for you landlubbers) with a 4 Tesla liquid helium-cooled MHD. Recent advances courtesy of fusion research have resulted in magnets capable of generating fields up to 20 Telsa, which should provide a considerable performance boost.

The new PUMP program will endeavor to find solutions for more robust electrode materials that can survive the high currents, magnetic fields, and seawater in a marine environment. If successful, ships using the technology would be both sneakier and more environmentally friendly. While you just missed the Proposers Day, there is more information about getting involved in the project here.

A pinwheel sits in an aquarium to simulate an offshore wind turbine. Bubbles come up from the "seabed" to encircle it to demonstrate a bubble curtain with an image of a sound waveform overlaid with the video to show the sound confined to the area within the bubble curtain.

Keeping The Noise Down Under The Sea

May 23, 2023 by Navarre Bartz 13 Comments

Since sound is the primary sense used by most ocean life, disruptions to the natural noise levels in the ocean from human activities can be particularly problematic for marine life. [DW Planet A] has a video describing some of the ways we can mitigate these disruptions to our friends under the sea.

Being noisy neighbors isn’t just a problem for whales but for everything down to the plankton at the base of the food web. Underwater construction like offshore wind installations get flak for being noisy, but technologies like bubble curtains can reduce noise output by up to 90% to the surrounding waters while still getting those nice low carbon energy benefits that prevent further ocean acidification and warming. Continue reading “Keeping The Noise Down Under The Sea” →

Multi-Channel Battery Monitor Aces First Sea Trial

January 20, 2021 by Tom Nardi 4 Comments

A little over a a year ago, we covered an impressive battery monitor that [Timo Birnschein] was designing for his boat. With dedicated batteries for starting the engines, cranking over the generator, and providing power to lights and other amenities, the device had to keep tabs on several banks of cells to make sure no onboard systems were dipping into the danger zone. While it was still a work in progress, it seemed things were progressing along quickly.

But we know how it is. Sometimes a project unexpectedly goes from having your full attention to winning an all-expense-paid trip to the back burner. In this case, [Timo] only recently put the necessary finishing touches on his monitor and got it installed on the boat. Recent log entries on the project’s Hackaday.io page detail some of the changes made since the last time we checked in, and describe the successful first test of the system on the water.

Certainly the biggest issue that was preventing [Timo] from actually using the monitor previously was the lack of an enclosure and mounting system for it. He’s now addressed those points with his 3D printer, and in the write-up provides a few tips on shipboard ergonomics when it comes to mounting a display you’ll need to see from different angles.

The printed enclosure also allowed for the addition of some niceties like an integrated 7805 voltage regulator to provide a solid 5 V to the electronics, as well as a loud piezo beeper that will alert him to problems even when he can’t see the screen.

Under the hood he’s also made some notable software improvements. With the help of a newer and faster TFT display library, he’s created a more modern user interface complete with a color coded rolling graph to show voltages changes over time. There’s still a good chunk of screen real estate available, so he’s currently brainstorming other visualizations or functions to implement. The software isn’t using the onboard NRF24 radio yet, though with code space quickly running out on the Arduino Nano, there’s some concern about getting it implemented.

As we said the first time we covered this project, you don’t need to have a boat to learn a little something from the work [Timo] has put into his monitoring system. Whether you’re tracking battery voltages or temperatures reported by your BLE thermometers, a centralized dashboard that can collect and visualize that data is a handy thing to have.

Lathe And 3D Printer Help Repair Buried Buttons

February 3, 2020 by Tom Nardi 24 Comments

Usually corroded buttons on a piece of electronic equipment wouldn’t be that big a deal to repair, but as [Haris Andrianakis] recently found out, things can get a little tricky when they are sealed inside a device meant to operate in a marine environment. Figuring out how to get into the case to clean the buttons up is only half the battle, when you’re done you still need to close it back well enough that the elements can’t get in.

The device in question is a tachometer intended for a Yamaha outboard motor, and the buttons are sealed between the guage’s face and the compartment in the rear that holds the electronics. Pulling the guts out of the back was no problem, but that didn’t get [Haris] any closer to the defective buttons. In light of the cylindrical design of the gauge, he decided to liberate the front panel from the rest of the unit with his lathe.

Removing the face was a delicate operation, to put it mildly. The first challenge was getting the device mounted securely in the chuck, but then the cutting had to be done very carefully so as not to damage the housing. Once he cut through the side far enough to get the face off, the actual repair of the buttons was fairly straightforward. But how to get it back together?

After a few missteps, [Haris] finally found a solution that have him the results he was looking for. He 3D printed a ring that fit the front of the gauge tightly, hot glued it into place, and used it as a mould to pour in black epoxy resin. Once the epoxy had cured, the mould was cut off and the gauge went back on the lathe so he could trim away the excess. He had to do some hand sanding and filing to smooth out the bezel, but overall the end result looks very close to factory.

We get it, there’s a lot to consider when you add a lathe to your workshop. But hacks like these are wonderful reminders of how many tricks these versatile machines are really capable of.

Continue reading “Lathe And 3D Printer Help Repair Buried Buttons” →

An Open Source Boating Autopilot With Some Custom Tweaks

December 17, 2019 by Lewin Day 11 Comments

Piloting a boat is all well and good, but can get dull when you’d rather be reclining on the deck with a cold beverage in hand. For [Timo Birnschein], this simply wouldn’t do. He began to gather parts to put together an autopilot to keep his boat on the straight and narrow.

The build is based around OpenPlotter, which uses a battery of marine-ready software to handle routing charts, autopiloting, and providing a compass heading for navigation. Naturally, it all runs on a Raspberry Pi. In combination with PyPilot, it can be used to let the vessel drive itself around a series of waypoints, allowing you to soak up the atmosphere on the water without having to constantly steer the craft.

[Timo] ran into some issues, however, with the hardware side of things. Existing implementations for motor control to drive the rudder weren’t quite cutting it, so the system was reworked to run with a robust H-bridge and some fresh Arduino code. This was combined with a custom rudder sensor built with a potentiometer and some 3D printed gears. Future work aims to double up the rudder sensors for redundancy, something we should all consider at times.

Overall, the system is starting to come together, and [Timo]’s enjoying letting his boat think for itself. He notes that it’s very important to keep an eye on the boat while operating in this condition, lest it veer off course – many a boat has been lost this way. We’re always supporters of a mature attitude towards autonomous vehicle operations!

Traffic Updates On The Seven Seas: Open Source Chart Plotter Using A Raspberry Pi

November 4, 2019 by Danie Conradie 7 Comments

As the Raspberry Pi in its various forms continues to flow into the wild by the thousands, it’s interesting to see its user base expand outside beyond the hacker communities. One group of people who’ve also started taking a liking to it is sailing enthusiasts. [James Conger] is one such sailor, and he built his own AIS enabled chart plotter for a fraction of the price of comparable commercial units.

AIS transponders in the Mediterranean. VesselFinder

Automatic Identification System (AIS) is a GPS tracking system that uses transponders to transmit a ship’s position data to other ships or receiver stations in an area. This is used for collision avoidance and by authorities (and hobbyists) to keep an eye on shipping traffic, and allow for stricken vessels to be found easily. [James]’ DIY chart plotter overlays the received AIS data over marine charts on a nice big display. A Raspberry Pi 3B+, AIS Receiver Hat, USB GPS dongle and a makes up the core of the system. The entire setup cost about $350. The Pi runs OpenCPN, an open source chart plotter and navigation software package that [John] says is rivals most commercial software. As most Pi users will know the SD card is often a weak link, so it’s probably worth having a backup SD card with all the software already installed just in case it fails during a voyage.

We’ve seen AIS receiver stations built using the RTL-SDR, as well as a number of projects around the AIS equivalent in aviation, ADS-B. Check out [John]’s video after the break. Continue reading “Traffic Updates On The Seven Seas: Open Source Chart Plotter Using A Raspberry Pi” →