Bio-Inspired Manta Ray Robots

Sketching up designs for the AUV frame I keep getting drawn towards doing a bio-inspired design. As part of that design arc I have started looking at what other people have done with bio-inspired underwater drones. Two of the inspirations I keep getting drawn back to are the whale shark and the manta ray. So I was really excited to find this. Researchers created a tiny manta-ray inspired swimming robot.

Posting it here so everyone on the project can see it, but even if you don’t look at any of the other AUV stuff this work is awesome and I highly recommend looking at it.

On a larger scale, back in 2012 the Bio-Inspired Engineering Research Laboratory (BIER Lab) ( put together an interesting ROV ray based robot.

This video is worth watching. It does have that TV show puffery, but it makes up for it. The video shows how they used x-rays of cartilage of the rays as inspiration. It also shows their mechanical actuator for driving the fins in more details.

This is probably my favorite stingray inspired robot. Not really bio-inspired, but its still kind of awesome.

Thoughts on Ballast Control

I have wanted projects to play with some of the newer machine learning algorithms for a while, so this year’s holiday hacking project is going to be an autonomous underwater drone (AUV). The plan is to start by designing the ballast system first, as it can be independently tested and as a module.

From what I understand Navy Subs use compressed air, charged during surface stops, to run their ballast systems. Water is driven out of the ballast chamber by opening valves on the bottom of the ballast tank while leaking high-pressure air into the chamber. Similarly water is let into the ballast chamber by opening the valves on both the bottom and the top of the ballast tank, letting air escape out the top while water enters through the valves at the bottom of the tank.

I am thinking of using a similar approach for the first version of the AUV. The main difference is that rather than compressed air, I am going to try using CO2. So something like this – where there are two solenoid valves for air and water venting to a ballast tank, and a third valve and regulator system for letting CO2 into the ballast tank.


So to empty the ballast tank with this system you open the valve to the water, at the bottom of the tank, and then blast in CO2.


For the CO2 side of things version one will use a pressure regulator intended for hooking CO2 tanks to compressed air tools. They are relatively cheap 80-160PSI regulators. For plumbing I am going to use 1/4 inch NPT push to connect fittings and pressure line meant for breaks. The design adds an on off valve to the tank as a safety for when the AUV is being transported. Best guess is $140 for ballast control.

Starting to Interview Again

So I started interviewing for jobs again – and just got back from California. It was a weird trip start to finish.

The capstone for the trip is that I got back late last night from the land of sunshine – and woke this morning to a white world where it has been continuing to quietly snow all day. It is gorgious outside, but oddly melancholy.

So I just started looking for non-consulting work again, and my first interview was for an incubation team at Apple. Really interesting group, and everyone seemed genuinely nice and like someone I could work with. I even found myself having fun during the technical questions. Still over all it was over all a really weird interview.

Last time I interviewed at Apple it ran from 10-6:30 with no breaks or meals. About 2 o’clock someone found out there had been no lunch round and dumped what seemed like half a vending machine of soda and candy on the table with an apology. By the end of the interview I was on a memorable sugar high.

So this time I decided to have oatmeal for breakfast because of its glucose index in order to avoid a repeat performance. I figured it would help keep my blood sugars even for the first few hours. What I did’t factor was that it came served with some sort of type of dried flower petals and bee pollen on the top; for decoration I suppose. It turns out I am mildly allergic to one of those things. So while I genuinely had fun for parts of the interview, most of it was trying to seem calm and collected while trying not to vomit on anyone. I kept finding myself looking at problems for which I knew the answers, and just giving weird answers to weird questions.

I went to visit my friend Ben and Pip afterwards. Pip loaded me up with two day old home made birthday cake, and some of the best whisky I have had in years. It was exactly what the doctor ordered.

It was a huge contrast to the next day. I stopped in at a robotics company for a lunch chat since a friend their knew I was in town and set up a get to know you lunch. After a positive lunch they quickly re-arranged peoples schedule to grill me. After passing the personality lunch test, there was a quick initial hour of coding on a white board to basically prove I was worth their time. After that I got a few hours of talking over how to solve real world problems they were having just hard core engineers who had written and shipped code running their fleet of robots. They were all simple seeming problems at first – but with razor sharp edges in the real world. Every edge case and example used as follow up questions were things they had run into in the real world too. It was tremendous fun. Really made the trip.

The great squirt gun wars…

So if there was ever a clear example of why you need to be careful what you say to kids this has to be it. I was washing my truck with my nephew, and he turns to me and says:

Nephew: “This must be so traumatic for you!”

Me: “What? Why?”

Nephew: “Because you lost your other 12 brothers in the great squirt gun wars when they started using pressure washers.”

Me: “Your weird. How did you come up with that?”

Nephew: “You told me. Last summer. When we were pressure washing the deck.”

I know he did not think I used to have a bunch more brothers – but wow. I definitely need to watch what I tell him.

How to compliment an engineer….

Showing someone a design I came up with today I got the best of all compliments for an engineer:

I am paraphrasing but conversation went something like this:

“Thats weird!”

“So you don’t think it will work?”

“No, it will work, and we should definitely do it, but its just weird!”

And ladies and gentlemen, thats how you compliment an engineer.


A thorough retaliation, served up 25 years later….

I woke up this morning to the following email from my dad.

You said, ‘if you are going to drink whiskey, drink the best you can afford.” So, thank you. I am drinking the best you can afford.

Love Dad

And that is what happens when your dad gets access to your liquor cabinet and you are on the other side of the planet and can not stop the inevitable. It took him 25 years, but his revenge for my teenage raids on his alcohol supply was both thorough and proportionate. Well-played dad.

Swearing when English is not your first language

Working on a particularly nasty engineering problem with a co-worker – I slipped up and swore at the office. I immediately apologized, which brought about a round of confusion followed by a really interesting conversation.

I am working over seas and so although he is fluent, the co-workers in question has english as his second or third language. He made an interesting observation, that for non native speakers swearing gets used in english language popular media so much that it just seems part of the language. There are no levels or apparent filters. So while he understands that we don’t all walk around dropping f-bombs like in the movies or on TV, its totally unclear what the cultural contexts around swearing is. So as a result swearing is just seen as any other part of the language. Which is kind of fascinating given the range of feelings and social constructs that exist around swearing back home.