PI based ROv utilising..Node.Js..socket.io and HTML5 canvas

Anything to do with the Raspberry Pi
a_shorething
Posts: 289
Joined: Sep 10th, 2013, 5:26 pm
Location: New Jersey Shore

Re: PI based ROv utilising..Node.Js..socket.io and HTML5 can

Post by a_shorething »

perfo wrote:Yep setting a heading or setting an end location are different things.. Just because you maintain a certain degrees of heading then you may not end up at the expected destination as the craft may have been crabbed by the current. I am expecting though that the current won't act on the whole craft at the same time and thus unless it's a prevailing or head on current it will try and rotate the ROV and this should be detectable and correctable. I'm not expecting it to be pin point accurate but as long as I know the direction it was heading when it left the Buoy and the distance from the buoy then I should be able to plot it's rough position on a screen. In any case what I'm trying to achieve is a replacement for a direct joystick connection.
A joystick would be constantly adjusted by the pilot to keep the ROV heading towards something. If that thing is visible then great but if not then it is probably going to be done against the returned compass data. So id being doing the same with the exception of I don't need to constantly adjust the joystick. I just aim the ROV at the object/location (if it's visible) or adjust it so its facing a certain heading and press a button and the on-board controller would look after any adjustments. So if the compass feed back is so vague I have to end up correcting every now and then, I'm no worse off than doing it all manually anyway...so really the accuracy of the sensors don't affect my plan any more than a manually operated one but stand a chance to be a bit better.
I'm not sure I agree with you on that. Have you ever gone scuba diving? When a current is ripping and you're in it, things on the bottom fly by you even though you feel like you're stationary. It's not turning or rolling you like a wave, it's just all moving in one direction. It's just like being on a moving vehicle, after the initial adjustment of starting, you feel like you're sitting still unless there is another adjustment (turn, accell/decel). I'm not sure your system will be more accurate than dead reckoning and in cases where you *think* it's better you sometimes start to trust it more than it should be trusted if you know what I mean.

The giros may be able to compensate for it and maybe it's just a matter of reacting and continually reacting when the current initially starts acting on the ROV, I don't know.

I'm curious to see how this will play out. (and hope you don't think I'm throwing rocks at your design, just playing devil's advocate).
perfo
Posts: 151
Joined: Jan 27th, 2015, 12:05 am

Re: PI based ROv utilising..Node.Js..socket.io and HTML5 can

Post by perfo »

I don't mind rock throwing (as long as they are little ones) :)
healthy debate where folks are willing to state they think an idea is wrong and offer alternatives is where real progress is made... So nope no problems and keep the comments coming.
I have done a fir bit of scuba in the past...
I can see your point. It will be an interesting experiment. The place my ROV is destined for wont have much current any way as its a lake but still an interesting element...

(does anyone else get a load of ads pop up when they access this site ? )
a_shorething
Posts: 289
Joined: Sep 10th, 2013, 5:26 pm
Location: New Jersey Shore

Re: PI based ROv utilising..Node.Js..socket.io and HTML5 can

Post by a_shorething »

Glad you're seeing my comments the way they're meant. I'm still on my first ROV and don't really know what to expect either.

(and I don't get any pop-ups from this site)
perfo
Posts: 151
Joined: Jan 27th, 2015, 12:05 am

Re: PI based ROv utilising..Node.Js..socket.io and HTML5 can

Post by perfo »

just me then with the pop ups. Its only this site though...hmmmm
perfo
Posts: 151
Joined: Jan 27th, 2015, 12:05 am

Re: PI based ROv utilising..Node.Js..socket.io and HTML5 can

Post by perfo »

An ad machine had attached it self to my PC and this site....still all clean again now.

For completeness I've been looking at dead reckoning as well and I don't seem to find any favorable reports for it. Has anyone used this for their ROV and got decent results ?
I've got 3 axis gyro, accelerometer , compass all on board so have the necessary inputs if DR would work.
My final intention is to do my own sonar based positioning thing but that is a long way off on the development time scale at present...
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