Hull Crawling Vehicle

[ScottishTom]

Hi All,

I am currently in my 4th year of Product Design Engineering at Edinburgh Napier University in Scotland, for my honours project (dissertation) I was given a project by my summer placement. The project is "The design of a Hull Crawling Vehicle and Production of a Representative working Prototype", the company i worked for during my summer placement was Fugro Subsea Services. Effectively what i want to prototype is a small free flying vehicle capable of moving across the hull of a FPSO (floating production storage and offloading vessel), this vehicle would be scaled up if it works and would be equipped with inspection and cleaning equipment.

I have looked into different methods of keeping the vehicle in constant contact with the hull of the ship, everything from magnets to a reverse hovercraft style using suction however i have decided that one powerful vertical thruster is the best option.

Some of the specifications i plan of having for my vehicle.

Control: Cat 5 tether connected to a Arduino Uno microcontroller, ideally with a game pad style control.
Power: 12v battery topside
Thrusters: DC Brushless motors, total of 5 motors.
Frame: PVC pipe main frame, with polyprop sections on the side of the tracks.
Control Box: Otterbox.


For my prototype I am planning on keeping the ROV fairly compact, max 500mmX500mmX500mm

I have a few questions for the you guys:

1. Firstly I have absolutly no electronic experience just a lot of CAD experience, therefore is setting an "xbox" style controller to control the ROV pretty hard to do?

2. If the ROV is max 20kgs is the following motor suitable for the thrusters that do forwards/reverse/left/right
http://www.giantshark.co.uk/product/172 ... less-motor

3. What size of motor would you think would be suitable to provide enough positive thrust to keep it against the bottom of the hull of the ship?


Any help would be grand, I feel I may have jumped into the deep end with this one. In the uploaded CAD images i'm aware the rear thursters are way to big was more for representation just now.


Best Regards

Tom.

[a_shorething]

Cool idea!

Sorry I can't comment on the hardware side of things here, I'm new to this and I'm a programmer so I see things as software and 'everything else'.

For the controller:

I have a Windows based software program I wrote that will take XBOX360 gamepad inputs and send them to an Arduino through the serial port and I'm working on changing it over to Ethernet communication. It's very smooth and intuitive and allows you to map any of the gamepad buttons to anything you want them to do in the Arduino. It will actually allow multiple (up to 4) users to control different things or share controls, whatever you want.

If you like, send me a PM and I can send you a beta copy of the software.

Requirements:
1 XBOX 360 gamepad (wired or wireless, if it's wireless you need the Wireless USB adapter)
1 laptop with USB inputs
Arduino
You'll need to download some software for the Microsoft XNA framework as well.


Let me know if you're interested. My e-mail is m.r.frye(at)comcast.net (just replace the (at) with the @ sign.

Mike

[ScottishTom]

Mike,
Thanks for the reply, that program sounds like it does exactly what i am looking for. Does it work in the sense that if you rig the analogue sticks to the thrusters different amount of pressure on these means a different thruster speed? As in not simply on/off?
I will definetly get in contact with you soon about it.

Kind Regards
Tom

[a_shorething]

Tom,
Absolutely!

The left and right stick each put out a 0-255 in each of four directions (rather than + and - I just set up the up and down to act as different 'button numbers' to do with it whatever you wish) and the triggers are each 0-255.

The program is small and has no bells and whistles. I call it XBOX pass-through because all it does is map all of the buttons and present them to you on the serial port or over Ethernet.

You will also have the option in the Arduino code of sending signals back to the controllers for vibration in case you want to add some notification to the system that something is going on (low battery, depth alarm, or as I'm using it in my test, for the amount of throttle so the game pad vibrates more as you apply more throttle and less as you let off).

[m_g]

if you havent already, check out the seabotix website, they manufacture hull crawlers

http://www.seabotix.com/products/lbc.htm

[duncan]

I also hooked up an xbox360 controller to a vb.net program because I didn't realise I could come here and steal ashorethings code. It was good to do and get an understanding of anyway. In fact I used a pre-packaged .dll that made it all really easy anyway so it wasn't much bother

Mine is based on 5 thrusters (with the four horizontal plane thrusters at a 45degree offset to the ROV heading) and sends a string of the percentage power of each thruster (either positive or negative for reverse) to the arduino over TCP/IP. I also put in X/Y offsets to deal with current and whatnot which wouldn't be useful in your situation, though you could use the vertical offset and put it to full to ensure the crawler sticks to the hull at full thrust without needing to hold any buttons down

Link here: https://www.dropbox.com/s/1qlrdfoxc526i ... vSuite.zip

Looks like this just now (work in progress):



I'm also going to connect it up to an Uno (once I get home, at sea just now).

How certain are you a 12vbattery topside will provide enough juice, particularly for 5 thrusters? This isn't my area of expertise so I can't advise.

Your project sounds like it could be somewhat similar to the underwater pipe detectors used on oil pipelines, which you're probably aware of if you've been at Fugro.

Your design looks good, and though I'm not an engineer by a long shot I'd recommend throwing some magnets on there as well as the thruster. Maybe an electromagnet you can enable and disable would be handy too. I guess you'd have to keep it away from any of the electronics though?

[ScottishTom]

Sorry for taking so long to reply to everyone, with the Christmas period and other Uni commitments this was put a bit on the back burner although it is in full force now!

m_g I have already drooled all over my laptop looking at the stuff that seabotix have, their ROV's are absolutely amazing, if mine is a hundredth of one of theirs I will be very happy!

Mike I will get in contact with you shortly about the program, I am still at the stage of making rookie errors and buying the wrong ESC's (they didn't have a reverse function). Seems living in Britain we don't quite have the same resources for buying R/C boat and submarine components.

The Digit ROV Suite looks ideal, my project aims to create a hull crawling vehicle therefore creating my own programs is not as important. I have had almost all my components 3D printed now, motors are bought just need to get my head around the wiring of it. I have no idea if a 12v battery will be enough to be honest, just fingers crossed it will, all the motors are fairly small because they are brushless outrunner motors for model aircraft.

I have already worked on a hull crawler that uses magnets and wasn't overly impressed hence the use of vertical thrusters.

Ill please see below my update CAD drawings.

Hull Crawling Vehicle Assembly 2.jpg (433.54 KiB) Viewed 6587 times

Cheers for all the input again guys, still very very new to all this!


Tom

[profesorul]

HI @ScottishTom

What program did You used to draw these?.

MARIUS

[ScottishTom]

@profesorul

It was all drawn and rendered using Autodesk Inventor 2013.

[ScottishTom]

Bit of an update,


Finished my writing part of the my dissertation just finishing up my HCV (Hull Crawling Vehicle).

I have finally got to grasps with my electronics as well, I have ditched the Xbox idea as it is far to complicated for me, having had zero electronics experience before this it was a bit ambitious doing a ROV anyway let alone with all the parts I wanted to put on it. Unfortunately due to my inexperience the HCV is no longer free flying, it is only going to be capable of crawling mode, I was a bit of a dissapointment but I have struggled enough getting one brushless motor to spin let alone 3 of them and program it. I have a tamiya dual motor gearbox for powering the tracks, a brushless outrunner motor for keeping it in contact with the boat, which has a Turnigy 60A Marine ESC controlled via Arduino. The Uni only have power supply's going to 10A and my motor can draw 40A, although at 10A it is almost lifting off the table its so powerful.

It is now controlled via a single joystick topside, with an umbilical that consists of 2 seperate power cables, the USB cable to arduino and 5 small gauge wires that are the joystick control.

I was wondering if anyone had any idea of how to waterproof my connections into the box? I have gone for some cheapo "lock and Lock" food boxes as the ROV will not be going more than a 2 meters in depth. I was thinking of potting all of the wires into a single 20mm hose and then using a "gland" for waterproofing the entrance into the control box. The waterproofing of the drive shafts of the gearbox was yet another difficult part, but have done with rotary shaft oil seals and a hand turned housing.

Within the next 3 weeks I will have a full working model and fingers crossed have tested it.


Any advice, pointers, ideas are always appreciated.

Tom