Changing design


#1

May be here we could share new ideas about the ROV main body design.

My concept design:

I'd like to share what I have arrived to and would like to know opinions from you.

My starting point is .... This is a research project, hence crazy ideas, may give way to practical solutions.

My concept uses the original ROV electronics and robotics, albeit a few modifications would be required.

The ROV is governed by means of three propellers that allow for 3D motion. But Z axis is served by only 1 prop.

Dual propeller approaches are a solution, but I thought ..... How could I get the same result with only 2 props ?

From another point of view, I wanted to increase the working depth.

The question is .... What if instead of combining props thrust, that thrus is made directional as in bigger ROVS ?

And ... How to achieve this without increasing commanding requirements ? What is the same, using only three commands (3 motors control).

The solution I found is:

2 Motors are fixed to the end caps centers.

The whole electronics are set inside the Tube, supported by a frame that is able to rotate inside that tube by means of a wich-type servo.

When the inernal frame moves, the center of gravity moves as well, but the center of buoyancy does not move, hence, the frame holds its possition (with respect to the world coordinates), while the external tube rotates, and both motors with it, allowing for directional thrust.

That way, the same 2 propellers will work along 3 axis and not only two.

Supported by the main frame, another winch servo allows for camera rotation around a 180º arc.

Hence, only two ESC are required as only two motors are used.

Limited by the components sizes (mostly by the control board), the choice has been an Acrylic tube

OD 177mm; ID 158mm; L= 65mm, with two "submarine hatch covers type" for the end caps, 27mm thick, that allow for a working depth of:


From UnderPressure software, by Deepsea, 397metersFrom ABS rules: 393 meters.

Battery tubes, perhaps only one tube is going to be used, hanging below the main tube.

Three fins have been found to be required, being fixed to the motors mounting. Two of them, fitted at both sides, and a third one, between the proppelers ducts working as tail fin.

Hydrodynamic performance has been sacrificed for the seek of manouverability, camera angular range and depth improvement.

Some pics of the first design stages.

Framing loads.


Control board and fixed framaing. (Two similar frames will be set at each side of the arrangement, with the servos and cam mounting between them).


Virtual recreation.

The gear crown mounting can be substituted by rubber wheels.


All parts have been selected from standard catalogues.

Regards

ION


#2

Unique and compact ROV design concept cant wait to see in operation.


#3

Thanks for your appreciation Mark.

That's only a first approach to the design still under development.

Regards


#4

That's nearly 1300 feet with 1'inch thick acrylic!!!! Talk about research potential!!! I had no idea the acrylic could withstand that kind of depth/pressure. Would it be prudent to fill it with mineral oil or something similar?


#5

Hi Ken:

Depth can be increased in two ways. Changing the building material (The most obvious), or changing design.

I made the choice of a thicker "wall" together with a shorter tube for limiting and delaying buckling.

The whole hydrostatic load is supported by the tube, helped by the end caps, as internal framing must move inside it.

The calculations starting point has been to hold radial distortion under control, and not the collapse condition.

As per ABS and good Marine practice, a 0.8 safety factor has been applied to all calculations, which means, that design parameters would be maintained even at 1.2 x working depth.

For safety reasons and the same Old Good Practice, all calculations have been tested by hand prior to any computation.

If an aluminum internal ring is fitted at each end, working depth could be a lot increased.

Im not for mineral oil filling. It has bad optical conditions, and hence would distort the camera image. At the same time, any little air bubble would ruin the oil compensation effect.

At the same time, as it has been posted here by many users, oil would transmit pressure to electronic components that may not be designed for withstanding external pressure loads.

Regards

Note: ABS stands for American Bureau of Standars.

Albeit Im located at Europe, the ROV project is mostly American, that solved the Rules choice question.


#6

So by shortening the tube, did you have to modify the arrangement of the electronics? Seems that there would be a point at which you would end up having to use a separate tube for electronic components. Also, you mentioned optical properties. How much more image distortion would the thicker wall acrylic impart to the video?

As you probably figured out already, I like to research things thoroughly before I buy parts and build something that won't work like I intend. What you show here is pretty much where I want to go. I'd like to have something capable of carrying a nice complement of sensors and video equipment at depths up to about 300m for marine research and seafloor structure mapping.

The sensors I would like to incorporate include water chemistry (pH, conductivity/salinity), temperature, depth, and chlorophyll (I do realize that chlorophyll will be effectively nil at these depths). I'd also like to incorporate video streaming with telemetry and another camera that records at higher definition for later download. Strobes would be nice too. Am I too ambitious here?


#7

Ion:

Check out this ROV.

-W


#8

Ohhh Walt ¡¡¡

That's almost the same solution Im arriving to. Thousands of thanks for the link :-)

Seems it has been already done :-( But ........ let's try cheaper :-)

A years ago, we had a meeting regarding the design of a transportation device for mining workers at south Patagonia. The problem to solve was providing a way for workers to move under very rough winter conditions.

During the initial brainstorm many ideas were proposed, until our project director stopped us and said ....

Eureka ... You've invented the subway ¡¡

Hi Ken ¡

In this design, all electronics are fitted inside the main tube. BBB, controller, two servos, two ESC and one CAM.

Differences:

There is still spare volume for more sensors.

More volume for the same weight means more flotation= more payload capacity.

About how a thicker wall will affect the video. Some calculations are required, but image distortion will come from three main factors.

1-] Material

2-] Curvature radius. The bigger, the less distortion.

3-] Thickness. The bigger the more distortion-light attenuation as well.

The real solution for big depth devices is most time achieved by providing an internal or external framing for supporting the mechanical loads. A correct framing design allows for withstanding high loads with the less weight.

I've studied the framing solution, using three web frames and three floors that could allow for really deep voyages without increasing weights, but required dimensions badly interfere with the cam. At the same time, a very high building precision is required and mounting procedure becomes complex. All together work against the "Do it yourself" and simplicity concepts that are a key in the ROV project.

Specially floors, would limit the camera angular sweep range, that Im trying to increase.

About the sensors, check the forum, there are some threads related to the topics you are searching for.

Kind regards


#9

Hey there,

Sam from Deep Trekker Inc. here. What you are describing is our design essentially, for which we have a patent. Cool that you thought of it! We think it's pretty great too.

Sam


#10

Interesting that you should post here. Rather coincidental, actually. I am looking at the DTG2 Pro on your website right now.


#11

Why's that? I've been a member for a long time. I think what openROV is doing is great. I also think it's neat how innovation can happen completely independently, and yet still arrive at a similar solution.


#12

That was me asking you on our site if I could be of any assistance too!!

Let me know if you have questions; we are open, and wish to help.


#13

I haven't been here long. I just thought it was a neat coincidence that I was looking at this thread and your site simultaneously and you posted. No harm or insult intended at all.


#14

None taken; the internet is a weird and wonderful place, but a place where google knows too much about our movements!! Coincidence or big brother, I'm not sure, but I am sure that I'm glad to make your acquaintance, Ken! Nice to "meet" you.


#15

WOW!!!! LOL that is cool. Just sent you a chat on your site. I didn't see it before.


#16

Hi Sam:

Glad to read you. Yes, I had no prior knowledge about your design. Once known I stopped developing my own.

By the way, Im quite busy now and have a little time for the OpenRov comunity.

Once again, glad to read you.

Regards Rovers ¡¡


#17

Ah, too bad!! ROVs are amazing. I thought it was really cool that you thought of the design too. The credit for ours goes to my partner, and he has never been able to tell me how on earth he came up with it.

Happy Rovving!!!


#18

Hahahaha.

Fist time Im online at the same time than another OpenRov member ¡¡

Surprised to get such a fast answer ¡¡

Regards