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Hybrid BR/OpenROV2.8 ROV


(TCIII) #1

Hi All,
Because the ArduSub firmware has been in a constant state of change and it is a PITA to pull the BBBMINI navigation controller out of its WTC, I have also been working on a three thruster ROV configuration that combines a BR BlueROV1 chassis (no thrusters or WTC) and three T100 Thrusters with an OpenROV 2.8 Developer’s Controller Kit, WTC, and IMU/Compass/Depth Module.

The WTC for the batteries will be mounted on the underside of the chassis instead of on top where the Vertical Thruster is now mounted. That is the reason for the HDPE extenders on the bottom of the chassis to get clearance for the 4" dia BR WTC. The OpenROV 2.8 Controller chassis will be mounted in a WTC that will be mounted laterally on the front of the ROV chassis.

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 to it fortunately.
Regards,
TCIII AVD





(Paul) #2

Pretty nifty build.

True, it is a bit of a PITA to open up the housing to update the firmware on my BlueROV2, but for what it’s worth, I’ve not updated mine since building it over a month ago and it worked fine. I’m using the Fathom-S board which I think has had fewer “growing pains” than the Fathom-X which has only recently had video working under Windows. My BlueROV2 's housings are open while I finish a sonar integration and so will have an opportunity to update the firmware to get all the new “goodies” that Rusty and gang have added.


(TCIII) #3

Hi All,

Building the OpenROV WTC Cradle:

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


(TCIII) #4

Hi All,

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


(TCIII) #5

Hi All,
These photos show 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


(TCIII) #6

Hi All,
This last weekend I managed to wire up all three Thrusters to their respective Controller Board ESC wire harness wires using this BR wiring & potting document, fabricated and mounted the IMU Module Bracket on the Vertical Thruster forward vertical Support Plate, and I have mounted and wired up two External Light Cubes to their respective Controller Board wire harness wires. The External Light Cubes are attached with wire ties to the ends of two acrylic arms that extend forward from the ROV chassis side plates.

I have also attached one end of 50 meters of the OpenROV Neutrally Buoyant Tether cable to a hard plastic thimble to provide a strain relief for the tether. The tether is presently just hanging on one of the chassis transverse support rods until I can attach it to a permanent mount on the chassis. I have purchased a stainless steel “Eye” bolt that I will attach to the back of the vertical thruster rear vertical support. The “Eye” bolt will be mounted perpendicular to the vertical support plate and I will use large cable ties to attach the thimble to the “Eye” bolt. The ROV end of the Neutrally Buoyant Tether cable will be attached to the Controller Board wire harness tether wires through a two pin waterproof connector.
The pictures below will give an idea of what I accomplished this last weekend:

Head On view showing mounted External Light Cubes

Side view of External Light Cube mounting on ROV chassis

Horizontal and Vertical Thruster cable to Controller Board Wire Harness wiring and sealing

IMU Module Mount Bracket

Neutrally Buoyant Tether and Tether Thimble Strain Relief
More to come.
Regards,
TCIII AVD


(TCIII) #7

Hi All,
I got the Tether Thimble and waterproof two pin connector installed today. As I stated in yesterday’s post the Thimble is attached to a stainless steel “Eye” bolt that is attached to the back of the Vertical Thruster rear vertical support. The “Eye” bolt can be easily removed from the vertical support plate and the waterproof connector disconnected to allow removal of the Tether for travel. I used large cable ties to attach the Thimble to the “Eye” bolt which keep it from swiveling on and solidly anchored to the “Eye” bolt. I still have to cleanup and secure the waterproof connector and tether wires to the chassis.

The pictures below will give an idea of what I accomplished today:

Head On View of Thimble Mount with Waterproof Connector in the Background

Upper View of Thimble Mounted to “Eye” Bolt with Tie Wraps

Side View of Thimble/Eye Bolt Mounting Scheme

More to come
Regards,
TCIII AVD


(Kevin) #8

@TCIII, looking good and professional. How were you thinking about getting it to sit straight in the water? Buoyancy foam?


(TCIII) #9

Hi Kevin,

The next step, once I get the IMU/Pressure Sensor Module soldered in to the wire harness and mounted to the chassis, will be to put the ROV in our Association’s swimming pool and do a ballasting/buoyancy test to determine what additional weight needs to be added to the ROV chassis.

Regards,

TCIII AVD


(undersearobotics.com) #10

@Tom - Only thing I might recommend is to replace the zip-ties holding the tether/nylon thimble to the eye-bolt with a small, stainless shackle.


(Rusty) #11

Tom, this is looking really cool! Nice work! I’m excited to see this get completed and in the water.

-Rusty


(TCIII) #12

@undersearobotics.com,

Why do you feel that a “small, stainless shackle” is superior to the 1/4 in wide heavy duty zip ties?

@Rusty,

Thanks for the kudos, much appreciated. I am keeping my fingers crossed that I will not have a problem with the buoyancy or the fore and aft trim.

What in the way of ballast/buoyant material did you have to add to the original BlueROV1 to achieve a just slightly awash buoyancy?

On my 6 vectored thruster ROV chassis with two 4 in diameter WTCs, I had to add 5 pounds of ballast to get it to be just slightly awash on the surface. The chassis was made up of HDPE which is almost neutrally buoyant.

Regards,

TCIII AVD


(undersearobotics.com) #13

@Tom - Because:

  1. It can easily be disconnected if necessary
  2. It allows some pivot movement of the tether / thimble
  3. Even smaller stainless steel shackles will have a significantly higher breaking strength than the zip ties

(Rusty) #14

@Tom - The BlueROV1 was designed to be neutrally buoyant in standard configuration, so we didn’t have to add any ballast or buoyancy usually. If anything, a small amount of foam for added buoyancy was helpful.


(TCIII) #15

Hi All,
Two weekends ago I got the IMU/Depth Sensor Module attached to its mount on the front vertical support plate for the Vertical Thruster and the leads solder and sealed to the their respective wires in the wire harness.

<span class=“reimg-zoom”>Zoom in (real dimensions: 4000 x 3000)</span>Image
IMU/Depth Sensor Module viewed from below
<span class=“reimg-zoom”>Zoom in (real dimensions: 4000 x 3000)</span>Image
IMU/Depth Sensor Module viewed from above

Then I attached the 2.8 Controller Board to the ROV wire harness, connected up the Tether to my laptop and then connected up the batteries. After connecting the Topside Adapter’s USB cable to my laptop the OpenROV Cockpit appeared on the laptop display after about a minute or so. I then completed the Guide 5 Finishing Operations Steps 78 - 92 of the OpenROV 2.8 to calibrate the lasers. Since I am using Blue Robotics (BR) T100 Thrusters that cannot be run out of the water for very long, I skipped the Guide 5 Finishing Operation Steps 93 - 95 Motor Direction until I have the ROV chassis in my Association swimming pool. I also verified the operation and calibration of the IMU/Depth Sensor Module using the Forum instruction here.

Moving on to the OpenROV Operators Manual I verified the operation of the OpenROV Cockpit Display using Steps 15 - 25 which includes configuration of the batteries.

At this point I will run ballast and trim tests on the hybrid ROV chassis to ensure that the ROV chassis is just buoyant enough to be slightly awash on the surface and that it is level in the water.

More to come.

Regards,
TCIII AVD


(TCIII) #16

Hi All,
A week ago last Saturday I completed the battery tray for the two NMHi 4500 mah 9.6 vdc batteries that will be housed in the Battery WTC. The battery tray slides into the Battery WTC and is compressed between the two WTC End Caps so it will not slide around. The tray sits in the WTC tube just above the two power cables at the far end of the WTC tube.

Now I am ready to perform ballast/trim testing in my Association’s swimming pool which I hope will occur tomorrow if it does not rain too much. I found that the 2.8 Controller Board weighs around 12 oz so I have 12 oz of lead weights sitting on the ROV Chassis just behind the OROV Controller Board WTC. I decided to to test the watertight integrity of the OROV WTC without the Controller Board in case there is a first time leak issue.

Below are a couple of pictures of the Battery Tray with and without the batteries:
Image
Bare Battery Tray
Image
Batteries on Tray

More to come

Regards,
TCIII AVD


(TCIII) #17

Hi All,

Since the weekend I have been working on ballasting/trimming the Hybrid BR/OROV ROV Chassis. Due to the OROV Controller Board WTC being that the front of the ROV chassis I had to offset its 90 cu inches of buoyancy with a 2 in inside diameter PVC SCH 40 capped pipe that brought the ROV chassis trim to near perfect awash. I found that all I needed was around 4 oz of ballast at the front of the ROV chassis, after the addition of the PVC pipe, to complete the trimming process.

As can be seen in the following pictures, the top of the Vertical Thruster’s impeller is just under the surface when the ROV chassis is ballasted to being just awash. The two 2 oz lead weights can be seen in a plastic bag sitting on the top of the OROV WTC. There are 12 oz of lead weights in the OROV WTC to simulate the weight of the 2.8 Controller Board. And yes, the batteries are in the place in the BR Battery WTC. By the way, my test tank is a 38 gallon storage bin.
Image
ROV Chassis Side View 1
Image
ROV Chassis Side View 2
Image
ROV Chassis Front View
This weekend I plan to install the 2.8 Controller Board in the OROV WTC, hook up the batteries and check out the Controller Board functions including the Thrusters and the IMU/Pressure Sensor Module.

During the functional checkout I found that I needed just 2 oz of lead weight just to the right and slightly below the OROV WTC to bring the chassis to being just awash fore and aft and trim from side to side.

More to come.

Regards,

TCIII AVD


(TCIII) #18

Hi All,

I am pleased to announce that I successfully tested the functionality of my Hybrid ROV yesterday in my 38 gal test fixture. Everything went as expected in relation to thruster, camera, and light functionality. The only thing I had to change was the direction of the two horizontal thrusters. At a thrust setting of 2, the thrusters appear to have plenty of thrust to move the ROV chassis up/down and forwards/backwards to my satisfaction.

I will be taking the ROV to the Association swimming pool for some real testing as soon as I get the tether cable reel completed. I am building a tether reel similar to this one: http://rayhightower.com/blog/2014/09/10/manage-that-openrov-tether/.

More to come.

Regards,
TCIII AVD


(TCIII) #19

Hi All,

Tomorrow is the big day for my BR/OROV Hybrid Three Thruster ROV as I completed my Tether Reel this week and will be checking out the ROV in my Association’s swimming pool. Unfortunately the pool is only five feet deep, but that will allow me to see how well ballasted the ROV is in open water rather than my 38 gal test tank.
A picture of the Tether Reel is below:

More to come.

Regards,
TCIII AVD


(TCIII) #20

Hi All,

I just finished with my Hybrid ROV pool trials and everything went very well. I had to adjust the roll ballast slightly from when it was in the test tank, but that was all I needed to do as far as ballasting went. The OROV Depth Hold function worked well, though I did not try and use the Heading Hold yet.

The BR T100 Thrusters worked well as was to be expected. Though the horizontal thrusters can overwhelm the vertical thruster when in Depth Hold, but the Depth Hold recovers quickly. I really need to hook up the joystick next time so I can have proportional control with the horizontal thrusters and move the Thrust parameter from 2 to 3. I suspect that the new OROV 2.9 Controller Board might be able to handle nearly double the thruster current allowing full thrust from the T100s?

I think that OROV would be smart to allow different thrust ranges for the horizontal and vertical thrusters. Ie: vertical thrust at 3 while the horizontal thrusters are at 2. With a setting of 2 the ROV moves along quite well in MHO. However a setting of 2 does not give enough thrust to the vertical thruster when moving forward.

The OROV neutrally buoyant tether worked great in the pool and easily followed the ROV around without sinking to the bottom as the original twisted pair can do.

Regards,
TCIII AVD