ROV SONAR

[Zaibach]

Hmmm all this talk about using ultrasonic cleaner transducers makes me wonder how viable it might be to harvest the transducer out of one of those $9-20 halloween/desktop/pet foggers that uses an ultrasonic transducer. Heck some of the models they sell in the petshops come in 5+ transducer arrays.

Course no clue what sort of "surprise electronics" are probably epoxied into the cases or how easily or of it its even possible that they might be converted into a useful sensor. Seems they operate ~1.6-2Mhz range again not totally sure how much of that is because of the baked in electronics vs piezo element themselves. Not really sure if they would even pack enough power to be useful tho might work for hobby applications.

they seem cheap enough and certainly readily available, Oh well just musing.

[rossrov]

Thanks Zaibach. I never considered and was never really aware of those fogger things. Acoustic cameras use similar frequency to obtain high detail, but their elements are quite tiny. Not to say there isn't some potential there though!

cameras: http://icesjms.oxfordjournals.org/conte ... 8.full.pdf

[rossrov]

Rotary Actuator. Ordered a stepper motor and driver a while back and now have them wired to the EtherTen and have some test code running. The housing will be pressure-compensated and I'm keen to see how the stepper and other bits go in mineral oil. In addition to the stepper, the housing contains a rotary joint for the transducer or other signals, and a home position sensor. No oil until all electronics and code working properly for both Sonar and actuator parts. The very same actuator could be used for other things on an ROV or other underwater device. With gearing or a worm drive would work as a manipulator servo for example. Stepper is bipolar type and uses a driver from Pololu.

sonar actuator.jpg (73.19 KiB) Viewed 3879 times

sonar actuator assembled.jpg (41.52 KiB) Viewed 3879 times

I made this crude "indexing head" to drill the magnet holes for a mag coupled thruster a while ago. Good to be able to use it for something else.

indexing head.jpg (208.69 KiB) Viewed 3879 times

[rossrov]

Earlier this week I managed to do some limited in-water testing of my Sonar project. The actuator housing is now oil-filled pressure-compensated and as yet the oil has not upset functioning of the stepper motor, opto home sensor or rotary joint. The GUI is now written in Processing rather than using HTML5 and the browser, and communications is based on code from an Arduino IDE Ethernet example. The GUI will also be sending commands to the ROV's motors, in addition to setting the sonar display range, azimuth segment width/scan speed and display gain as it is doing now.

Video production is of the usual standard , including a finger obscuring part of the scene....That aside, I was able to define 3 prominent echoes, clockwise, one from the end of an adjacent pontoon say 18-20 metres away, and two from concrete pilings 25 and 18 metres away. All the noise in the centre of the screen is wave clutter and/or reflections from the bottom - low tide at the time with probably not much more than a metre of water, and was quite windy. When I get the Sonar mounted on the revised ROV, more testing can be done but in deeper water. Next step after that might be to narrow the vertical beamwidth of the transducer.

[kenl]

Hey Ross, great to see you making progress again, do you plan to overlay range rings on your GUI?

[rossrov]

Cheers Ken. Yes, eventually. Easy enough to do the range rings but needed to get it into the water to do a calibration first. Now that you mention it, I forgot to measure how many pixels out the echoes were

[a_shorething]

That is very cool! Can't wait to see how it works on your ROV.

[rossrov]

Thanks a_shorething - good to see you on the forum again. I was planning on mounting the test rig shown in the video on my boat until I had developed a satisfactory ROV platform, and try to detect some Dugongs or Bull Sharks, both of which are common around here. I think now though it will be simpler in the long term to go direct to an ROV mounted unit. Doing this means getting the Fish-Finder circuit board, the Arduino, stepper motor drive, Ethernet switch and a battery into a housing. I don't really want to make a new circuit board but it will be tricky cutting the microcontroller/display section away from the part of the board I want to keep, which will be small enough to fit in a reasonable-sized housing. The Arduino would replace the transmit oscillator and gain functions of the existing micro - much better.

The housing and positioner/transducer unit could be adapted to suitable ROVs, so for now I have re-arranged all the components of the old ROV onto a rough barge-like test bed that I can use for testing Sonar, thrusters and different thruster configurations, other hardware, software... Maybe one day I'll have a good tether and streamlined ROV