New ROV - The Mimee

[Tal]

Hey Everyone,

I'm pleased to be finally placing 'The Mimee' (pronounced My-me) in the projects forum for your viewing pleasure I'm really only just starting but want to be able to update my progress as you all are, and share my successes, and failures....

Project Team

First about me. I'm not an engineering graduate, I don't work in any industry related to ROV's, water, or fabrication, and I've never built anything like this before. I'm at somewhat of a disadvantage, but I'm really enjoying all the new information. I have had model making experience, am confident with electronics and computing (although I only have a basic skillset), and generally see my projects to completion. I am comfortable putting both time and money into this project but both resources are meager, so things may progress slowly at times. Sorry if that felt like a job application but I feel it may help when responding/contributing/answering, along the way.

Specifications

Chassis/Frame - Aluminium Sheet (3mm)
Watertight Compartments - PVC
Body - Fibreglass (just a cover, not watertight)

Thrusters - 2 Brushed motors at rear providing fwd/rvs and left/right, 1 Brushless motor - vertical movement
ESC's - for above motors to cover their max amp draw (stalling) (and now forward and reverse on all three)
Power - I'm currently swapping between a couple of 12v 4ah lead acid batteries I picked up 2nd hand (from a scooter). I was going to run them together, giving me 12v8ah but I'm having issues recharging them (but they said they were in good condition....). I've ordered a new 12v7ah lead acid and will see how that goes. I had planned to run it onboard and will test to see how much run time it will give me. I expect to add another giving me 12v14ah, but accept it may only be good for testing in the workshop and I may end up with LiPo....I may have to set up a test bed like Ryan
Command/Control - I've got an Arduino Mega 2560 with a PS/2 controller. I'll probably use an Arduino Uno on land so I can use a Cat5 tether and keep the cost down. This would also allow me to USB back to the laptop for sensor data. I'm hoping to write some Python script that will give me a gui, but haven't really thought too much more about it. It seems too far off in the distance.....I've also got a camera that is used for car reversing (with RCA connection). Its of good quality and I've got it sitting in the shed so I thought it would be ideal. If I need to go and buy something else (webcam), that's fine.
Sensors- Water Temperature, internal temperature, Video. I also want to add voltage remaining, maybe a leak detector, depth gauge, and of course have the option to add all the other fun stuff later. I'm a realist, though, and I think its more important to get the project completed (operational), with realistic parameters, than to aim for something that Nasa would be proud of, and still be writing to you guys about it in 10 years and how I'm about half way done....
Lighting- At this stage, I've got a couple of LED torches i'll hack. Each has about 30 LED's. I was going to pot them and control them with a mosfet. I will give them independant power if required.
Manipulation/Arms/grippers- No plans for any of these yet, because I want to get everything else done first. I see adding an arm as a second project, along with an autopilot feature etc etc.

I'm sure I've missed something, but I can update you all as required. The most obvious areas that require attention are:
*The video data to the surface: I just haven't given any thought to it yet
*Battery Solution: Will have to test the Lead acid battery when it arrives and see what sort of mission time it will give me.
*Watertight Compartments/Shaft Seals: See below

On that last point, its confusing to me why, but I don't want to run my motors in the water. I don't know if its because of the challenge of creating a watertight compartment that has a shaft coming out of it....or some other crazy notion. It's probably got more to do with this project starting as a rc submarine adventure, and turning into an ROV. Remember, I've literally started with no knowledge and done way too much reading....This approach may change in time but I acknowledge that I can run all three of my motors in both fresh, and salt, water. I'm sure more conversation will follow on this.

Lastly, I have always believed that projects require purpose; a mission. So, as I mentioned in my introduction post, my mission is to descend to the bottom of an old flooded quarry (fresh water) to measure how deep it is, and to see if there is a crane on the bottom, a story I've heard many times. Sure, I could use easier methods to determine these facts, but its designed to give the ROV project a purpose, and not a project specifically to determine this information. In my next post, I'll outline my progress to date.

Thanks for reading,

Steve (Tal)

[Tal]

So far, inspired by Ryan (KR2 Diving), I stopped carrying all my bits and pieces in and out of the workshop in a big pile of mess. Oh, its pathetically warm and humid here, and I prefer to do most of the work I can in the air-conditioned house, and not in the kiln like workshop. So, anyway, I re-organised everything into an old drawer and found life much easier. It still looks like a mess but its better than before....

Test Bed 2a.jpg (504.98 KiB) Viewed 7286 times

Hard to see from the photo, but I made some quick motor mounts out of alluminium, so I didn't have to hold the motor's in my hand everytime I needed to test the controller

I've got all three motors working forward and reverse, now, using the PS2 controller. The left stick controls forward and reverse, left and right (left controls the right motor, and visa versa, like a tank). The right stick controls the brushless motor which is ascent, descent. Until I get it all mounted, I won't know if I have enough thrust to actually achieve this.

I worked out ESC values by trial and error but it just didn't seem good enough. It worked, but was eratic. SO, I set up a potentiometer and serial.print to give me the actual values, and am updating the code with these 'accurate' values. I have also done the same with the controller, as it seems that the neutral position is far larger than I imagined. So I spent some time writing out the range of values that constituted the 'centre' position of the PS2 Controller. I still need to update these values into my code as well. It felt like I was going backwards but once I had done it, I felt foolish for not doing it properly the first time. I guess I just didn't understand it well enough at the time.

So my arduino code, at the moment, allows the PS2 controller to move the motors forward, reverse, left, right, and up/down. No other controls (lights, sensors) have been coded yet.

Steve (Tal)

[Tal]

So as we all do, I jump around from one area to the next. I've also started working on the thruster housing. I've put together some PVC fittings and tried to keep the water tight area as small as possible to reduce the water displacement, although if it turns out that I need to add bouyancy, I'll feel a little silly. Did I mention I have started with no knowledge at all

Thrusters 3a.jpg (225.56 KiB) Viewed 7286 times

So the idea was to have the PVC watertight compartment with an alluminium chassis, that slides out, that I could mount the motor to.

Thrusters 4a.jpg (275.94 KiB) Viewed 7286 times

I haven't made any decisions on the power connection, between the chassis, and the inside of the pvc (obviously I'll pot the wires from the outside and have them run to the main watertight compartment with the arduiono inside) but have sorted out some of the shaft assembly and props. I'm waiting on parts too, but will put this in another post.

Thrusters 5a.jpg (155.82 KiB) Viewed 7286 times

Not tightened completely but you get the idea. I haven't started on an o-ring yet, or done any testing on the effectiveness of the unit but will post it when i do.

Steve (Tal)

[Tal]

So I really liked the idea of having something that looked the part as well, although the photo might convince you otherwise. I kind of started backwards, I suppose, with the cover and have worked backwards to design an ROV that'll fit within it. It not exactly how it was meant to be, and if I need to make massive changes, then so be it.

Shell 1a.jpg (133.5 KiB) Viewed 7286 times

I've basically started with paper mache' and then started coating in plaster. I've left it for a couple of months as I realised that i'd probably need to make some changes to the body as the ROV developed. Once I've got the chassis (frame) completed, I'll revisit the body and make any final changes. I intend on fibreglassing it and having it join along the centre, horizontally. It will only be a cover and thus, will be a wet area.

I know it looks a bit rough, but if you squint, and really use your imagination, you might get a very brief glimpse of what I'm striving for

Steve (Tal)

[scubersteve]

Well thanks for the boost Steven!
I'm glad to see your progress so far.
Interesting combination of brushed and brushless motors.
Keep us updated.

[scubersteve]

P.s. what's a Mimee???

[Tal]

Well thanks for the boost Steven!
I'm glad to see your progress so far.
Interesting combination of brushed and brushless motors.
Keep us updated.

Hey Scuba!

The Combination of brushed and brushless was really just an opportunity for me to get to play with a brushless motor, and to be able to experience the differences between the two. I'm relieved to have posted the project and appreciate you taking the time to look over it

'The Mimee' is one of those 'in-house' jokes no one ever understands. See, due to many factors, it was believed I would be only able to have daughters. So when my wife was pregnant with our second child, we'd gone out and got all the pink stuff, called her 'Jemima' and I use to chat with her while she was in the belly. Over the months, she became affectionately known as 'The Mimee' (short for Jemima), and a few months later, she became a he, and 'The Mimee' was no more....until now.

Steve

[KR2_Diving]

Hey Steve!
looking really good! I like the thruster housings! I was planning on a very similar concept for my main body. (Removable frame inside a sealed tube.)

You had mentioned that you were not sure about the video feed... If you are running a CAT5 cable (and not using ethernet to communicate between surface and ROV) you might want to consider getting some video balons. (Like these) These will allow you to use one of the twisted pairs of the Cat5 cable to get your video signal to the surface with minimal loss of quality.

I like the clever name. It is always neat to learn about the story of a name.

Keep up the progress reports!

[Tal]

You had mentioned that you were not sure about the video feed... If you are running a CAT5 cable (and not using ethernet to communicate between surface and ROV) you might want to consider getting some video balons

Thanks heaps Ryan. I hadn't really thought about communication from ROV to surface other than that I needed a tether. It wasn't until I read one of your posts that I looked at my current setup, and realised that I'd need quite a few wires in my tether. I guess I've really been focussing on the small areas I'm working on, rather than looking at the big picture (which is tough for me to do with such limited experience).

Of course, I've since realised that I can run Tx/Rx between two arduino's and that would reduce the mess, and size of the tether. Cat5 seemed a good choice, but I'm not really sure of my alternatives and pro's/con's yet. I'll have to do more reading when I come to this.

The video balun's you linked will be perfect and won't over-complicate things. Now i've just got to decide what to do on the surface, with the video data.....

For another day

Thanks again

[Tal]

Main Body 1a.jpg (136.15 KiB) Viewed 7228 times

So I've got the basics of my housing exterior started. One end is threaded with a cap (no o-ring yet). The other end started with a PVC flange. I've cut out some clear acrylic (3mm) and made a gasket out of an old car tyre tube. I haven't completed assembly but once it's done, I'm hoping to put together a water sensor inside the housing, and conduct some testing.

On the thruster assembly, I've now started the motor mount and will need a couple of holes for cooling.

Please excuse the primitive presentation of the project. I really do have a very simple workshop, at this time, which prevents the type of precision that impresses me about your projects I'm also learning on the job and hope to continue to improve as I go.