Diving problems


#1

Hi, I`m Korean Student.^^

I made Rov like my profile photo.

Waterproof problem was solved.

But.. I have another Problem..

Diving do not...

Thrust Part work well. Of course BLDC Motor is working Well

What`s the problem?

Do I made a center of buoyancy?


#2

Diving means Not going Underwater... just floating on the water like boat..


#3

Try adding small weights, anything you can attach to the threaded stainless steel rods. You want the ROV to be as close to neutrally buoyant (but slightly positively buoyant).

Are you using the same ESCs that we listed on the Bill of Materials? Can you go in reverse? Does the vertical thruster power down?


#4

Thank for yout answer!^^

I use ESCs which is attached QuadCopter that i have.

Is it Specific ESCs?

in that case i should change ESCs,^^

I thought its function is same.^^

And.. motor is specific?


#5

thruster direction is right.

water is springing up like a fountain

And i think vertical thruster power is weak.


#6

esc for quadcopter/planes wont work, they dont have reverse. you need a car or boat esc with reverse.

motors should also have low KV, but this is common for quadcopters aswell. the openrov kit has 800kv motors.


#7

I bought ESCs^^

Is there no problem that i use Quadcopter motor?

this is motor spec:

FlyCam 925
Dimentions: 28x30mm
Rating: 925kv
Battery Config: 3 Lipo Cells, 4 Lipo Cells(MultiCopter Only)
Shaft: 3.175mm
Weight: 54gr (with Prop Adapter)
Standard Current: 6-12A
Max Current: 22A

I have one more Question.

why needed ESC`s Reverse function??

I think forward is Necessary to go Into the water(it means diving^^)

But if the motor turn off, ROV is Automatically rised on the water due to buoyancy?


#8

the motor should work fine, but you should probably have a bit smaller propeller than standard to get more efficient drive, with that high KV you could get alot of amps going with a 3inch propeller.

regarding reverse: you can drive it without reverse, but im not sure how the openrov cape arms the esc's. because an forward/reverse esc must be armed at center point(1.5ms pulse ie midle stick on rc controller) while a airplane/quadcopter esc need to have a pulse at 1ms(stick at bottom on rc controller) to arm.

i would say that there will be alot easier to controll the ROV with reverse and it would take less time to rise to surface and maneuver under the water than to only use the positive bouyancy. with positive boyancy(it rises to surface on its own) you must use more power to keep the rov submerged than if you would make the rov neutral bouyant.

how are you controlling the? do you have the beaglebone cape from openrov?


#9

i use micro controller (cortex-m3)

communication is serial ( Uart(wired) ).

motor is controlled by PWM signal.

i`m wondering that rc controller can communicate with ROV into the water?


#10

ah, then things start to make more sense ;-)

with rc controller you mean a normal stick radio? i've read somewhere(probably on rcgroups) that radios in the Mhz area work a few meters under water. 2.4Ghz radios do not.


the best is to use tether to controll a rov, then you also have something to pull your rov up with, incase something fails.


#11

that`s good idea!! ;-)

tether that you indicate means Ethernet change to 2 twist line using EBS-10BASET-ST?

and i am wondering that you use just 2 lines(tether) to control ROV and to view the Image?

Is EBS-10BASET-ST working just connection each other without any setting?

and Where can i buy beaglebone cape you use?

that`s lots of Question.^^


#12

the definition of a tether is mearly a form of cable you use to connect with the rov, tethers can be anything from a twisted pair as on the openrov, to kevlar reinforced cables with fiber optic lines and power lines.

On the openrov setup you can use the EBS adapter to run a 10mbit ethernet line(on just 1pair(2wires)) to have both controll and videoimage from the rov with the beaglebone+cape installed in the rov.

you can also do the same with 2pairs(4wires) without the EBS adapters.

the beaglebone cape is not available yet, i'm not sure when it will be available either(i'm waiting for it aswell)


here is a link to a video where they show the cape: http://openrov.com/profiles/blogs/report-on-the-final-tests-on-the-beaglebone-capes


#13

Do I have to use fiber optic?

normal line is impossible?


ESC electronically, can change the direction of motor?

generally line1 and line3 is changed by hand.

and motor direction change

this ESC is Special?


when diving,The direction of the wind & Current is up? or down?

i think 'up', By law of action and reaction.

Current is up, ROV is Down. is that right?


#14

no you dont need to use any fiber optics, it was just an example. you use what fits your project the best.

with the EBS adapter you use a normal twisted pair cable.

since you have quadcopter esc, you need to change the wires to change the direction.

wind/current up = ROV down. youre thinking correctly.


#15

Aha! I understand!

1.5ms is midpoint.

More than 1.5ms is Forward

Less than 1.5ms is Reverse

Right?

Thank you for your interest! :)


#16

correct! but you will need an boat or car esc _with_ reverse function.