Blue Robotics/OpenROV 2.8 Hybrid ROV


#1

I have been working on a three thruster ROV configuration that combines a BR BlueROV1 chassis1 (no thrusters or WTC) and three T100 Thrusters with an OpenROV 2.8 Developer’s Controller Kit1, WTC, End Caps and IMU/Compass/Depth Module.
The only limitation of this hybrid ROV is the fact that the OpenROV Controller is not designed to handle the maximum current required by the BR T100 Thrusters. Therefore the ROV cannot be run at its full thrust, but close enough for my kind of work.
I have completed assembling the BR ROV chassis and have added the three T100 Thrusters. To be able to mount the center vertical Thruster I flipped the chassis center plate upside down putting the 4" diameter WTC on the bottom of the chassis instead of the top. The WTC will hold the two 5,000 mah 9.6 v NMHi batteries.
On the top side of the chassis center plate I built a platform that looks like the letter “H”. I have two vertical plates separated by two 1/4 inch diameter stainless steel rods which are used to support the vertical Thruster.
Since the bottom portion of the chassis is not tall enough to clear the 4 inch diameter WTC, I have added 1/2 thick HDPE extenders to the bottom of the chassis.
To mount the OpenROV WTC I have built a cradle that attaches to the front of the ROV. I will provide pictures of the WTC Cradle as soon as I have it completed.
Regards,
TCIII AVD




OpenROV 2.8 Developer's Controller Kit
Thrusters / Motors
What brand of brushless motors?
OpenROV as Sport Fishing Aid
Two controller boards
Any one located around central mid west US
Gettings Started build ROV
Unable to connect to ROV 2.8 after IMU installation
Learning from others mistakes
Newb ROVer - School me on making my first!
#2

It is looking good! Glad your making progress!


#3

I completed the OpenROV WTC Cradle today.

The WTC locks into a permanent transverse bar on the bottom of the Cradle. The top transverse bar, being removable, is held in place with a stainless steel 4-40 machine screw at each end so that the WTC can be installed and removed from the Cradle with a minimum of effort.
The back support of the Cradle has two holes for M5 stainless steel metric screws that mate with stainless steel “T” nuts in the slotted transverse bar at the front of the ROV Chassis.
Tomorrow I will disassemble the Chassis in order to slide the “T” nuts into the slotted bar and to reposition one of the front facing transverse rods that presently interferes with the Cradle assembly. I will then shoot a couple of pictures of the Cradle installed in the front of the ROV Chassis.
Regards,
TCIII AVD






#4

I completed the installation of the WTC Cradle into the front of the ROV Chassis and relocated one of the transverse rods that was interfering with the bottom of the Cradle.
Regards,
TCIII AVD




#5

Great pictures! Love seeing the progress of the vehicle!


#6

Thanks Brian. I will keep them coming as I progress with the ROV build.
Regards,
TCIII AVD


#7

This is really cool!


ZORROV-IV build
#8

Hi Zack,
Thanks for the kudos, much appreciated.
Unfortunately, this is not an inexpensive ROV to build due to the fact that just the three BR short cable Thrusters alone are $315 plus shipping which is quite a bit more than the three OpenROV brushless motors plus the three propellers.
I was able to purchase just the BlueROV1 chassis for around $245 plus shipping. So you can see that the price counting only just the chassis and the thrusters is already at $560.
The OpenROV 2.8 Developer’s Controller Kit plus the WTC, End Caps and the Controller Assembly acrylic chassis components add another $572 plus shipping and I still have to purchase the battery WTC (around $156 plus shipping) and the two NMHi 5000 mah 9.6vdc batteries ($48/battery).
Regards,
TCIII AVD


#9

Hi All,
I would like to report that I have successfully built and tested an OpenROV IMU/Compass/Depth Sensor Module for my hybrid ROV.
I have received the NMHi 9.6 vdc 4500 mah batteries to power the Controller and have therefore been able to determine the correct length of the 4 in diameter battery WTC in relation to the length of the batteries. So I will now order a BR WTC of the appropriate length along with O ring flanges, end caps, cable penetrator fittings and pressure relief valve.
In the meantime I will determine the appropriate Controller cable harness routing and construct a mount for IMU/Compass/Depth Sensor Module.
Regards,
TCIII AVD


NEW PRODUCT- External Light Cube
#10

Hi All,
I have received the BR custom length (9.5 in) 4 in diameter WTC along with two 6 mm cable penetrators, one pressure relief valve, and two blank cable penetrators which will be used to block off two of the unused cable penetrator holes in the front End Cap Plate.
I have potted a two conductor 16 gauge power cable into each of the two 6 mm cable penetrators. The external end of each power cable will connect to one of the two battery wire pairs in the OpenROV wire harness. The internal end of each power cable will connect to one of the two NiMH 9.6 vdc 4500 mah batteries that will reside in the battery WTC.
I will continue to route the OpenROV wire harness to the BR Thrusters, battery cables, external lights,and IMU/Compass/Depth Sensor Module.
I have also vacuum tested a second set of OpenROV WTC End Caps and was able to sustain a 540 mm Hg vacuum for more than two hours.
More to come.
Regards,
TCIII AVD


#11

Very Nice build!

I love blue robotics products, they seam very good!
Hope to use them when i’ll build my second ROV (at least the thrusters.)

Concerning the current limitation, you could use the thrusters at their full potential by just replacing the 3 esc :wink:

nick


#12

@ncx94,
Thanks for the kudos, much appreciated.
I have spent a fair amount of time reviewing the OpenROV 2.8 Controller Board electrical schematics and unfortunately have found that the Controller ESCs are not necessarily the limiting factor concerning maximum current draw.
The 2.8 Controller has two low dropout reverse polarity protection diodes, one each on each of the battery inputs on the Controller Board. These diodes are rated at 10 amps continuous and 16 amps peak for brief periods. Therefore the maximum continuous current that can be provided by the Controller Board is 20 amps.
The maximum current that can be consumed by the Blue Robotics T100 Thruster is 13 amps where as the maximum current that can be consumed by the OpenROV Thruster brushless motor is around 7 amps. Therefore a worst case current consumption for the T100 Thrusters could be close to 40 amps which is double the continuous current that can be provided by the Controller Board and that does not take into consideration the current being consumed by the BBB, the Arduino 2560 and associated components.
Therefore replacing the original ESCs with higher current ESCs is not going to solve the issue of the 20 amp continuous current limitation.
I have asked several members who have been using the T100 Thrusters with their OpenROV Controllers as to how they have been limiting the current consumption of the T100 Thruster, but I have yet to hear back from them. I suspect that they have set the Thrust parameter to a value of less than 4 to keep from overloading the Controller Board.
Regards,
TCIII AVD


#13

Well, sorry i didn’t explained it all.

If i remember well, current to power the esc is cut as long as the usb port on the ground side isn’t connected right?

So I think you could try something:

Connect a 50amps relay to the original power source of the esc, which would connect a different circuit directly from the battery to power the new esc. Then obviously connect the signal/ground of the esc to their original placement

Doing this, you keep the power cut feature of openROV which is good, but allow a much greater current to flow through the escs/thrusters. Don’t know if that makes sense, if not i’ll try to explain it better.

Nick


#14

@ncx94,
Thank you for your insights, however providing a higher current path for the T100 Thrusters in parallel with the two existing battery connections will bypass the Controller Board current sensing measurement capabilities which will result in the loss of accurate battery usage and remaining bottom time.
Regards,
TCIII AVD


#15

Hi,

Yeah sure I had forgotten that point… I just looked a little bit at the datasheet of the powerboard.
Current mesurement sensor is given for 12.5A…(digikey 620-1370-1-ND)
I didn’t look the datasheet for it, but maybe another current sensor with the same kind of output could be used (with minor tweeks in the code) so you could do a small pcb integrating the relay, sensor and bypass the original sensor…

But that might be a lot of work for a small result. It could then be sold on the shop as an option for the Developper Kit?

Nick


#16

Hi TCIII:

I’m glad to hear that you’re studying the design of the 2.8 Controller Board, with an eye towards using it in other products. As you’ve found out, it’s really optimized for driving thrusters that peak out at about 7 amps or so. If you go much beyond this, pretty much everything starts to stress out- the current sensing on the battery and ESC channels, the blocking diodes, the DB-25 connector, even the traces on the PC board itself.

That being said, the situation involving T100 thrusters is not quite as dire as you wrote about. IIRC the current draw plots provided by Blue Robotics are for operation at 12V, and if you run them at 9.6V the peak current will be proportionally less- maybe 10 Amps or so? I’m sure Rusty can give you more information on that. I think you’ll be OK driving 3 T100 thrusters with a 9.6V battery bus as long as you’re careful not to use full power on multiple thrusters for anything more that brief bursts.

For folks who are puzzling over why there are solder pads for 20A ESCs on the controller board, that’s done for supply chain management. When we designed the board, the Afro 12A ESCs were in short supply, so the board was made to accept either 12A or 20A ESCs. The ESCs are not really the limiting factor here. Switching to 20A ESCs would marginally lower power dissipation within the ROV, but it’s probably not worth the effort.

Hope that helps.

-W


#17

Hi Walt,
Thanks for the insights and the analysis of the current handling capabilities of the 2.8 Controller Board in relation to the BR T100 Thruster.
As I have stated before, I plan on powering the 2.8 Controller Board with 9.6 vdc NiMH batteries so, as you have indicated, the current draw of the BR Thruster will be less than when it is operated on 12 vdc and I will keep the Thrust parameter at 4 or less.
Regards,
TCIII AVC


#18

Hi All,
I have completed the routing of the Controller Board 2.8 wire harness in relation to the physical locations of the three Thrusters, the IMU/Compass/Depth Sensor Module, the Battery WTC and the two External Light Cubes that I purchased recently.
I will now make the necessary solder connections between the three Thrusters, the IMU/Compass/Depth Sensor Module, the Battery WTC and the two External Light Cubes. I still need to build support platforms for the IMU/Compass/Depth Sensor Module and the External Light Cubes. I have selected the locations for the IMU/Compass/Depth Sensor Module and the External Light Cubes supports and have routed their wire harness wires appropriately.
Upon completion of the soldering I will waterproof all of the exposed solder connections and unused wire ends.
Below are a series of pictures of my wire routing work in progress:


ROV Head on View showing the Controller Board WTC & the front of the Battery WTC

ROV Head on shot showing the routing of the Controller Board Wire Harness to the two horizontal Thrusters

Head on shot showing the Vertical Thruster cable in relation to the Wire Harness Vertical Thruster ESC wires

Head on Rear View shot of the Battery WTC power cables and the Controller Board Battery Cables and the Tether Cable wires

Head on shot of the Vertical Thruster wire routing on the Vertical Thruster Support.
The routing of the Vertical Thruster wires allows the longitudinal movement of the Vertical Thruster on its support rails without putting undue strain on the Thruster wiring.
More to come.
Regards,
TCIII AVD


#19

Good Job :slight_smile:
Looks really nice !


#20

@ncx94,
Thanks for the kudos, much appreciated.
I will be updating my build log today now that the wife has returned with the family camera from her road trip.:grin:
Regards,
TCIII AVD