Experimental ROV Design using Blue Robotics Components

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SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

After having second thoughts about powering the Power Control Board wit a live LiPo battery, I remembered that I have an AC powered 12 amp peak 13.8 vdc battery eliminator, complete with overcurrent and short circuit protection, that I can use to check out the integrity of the Thruster Power cable penetrator cable connections to the Power Junction Board. If all goes well, then I can switch over to the LiPo battery to simulate actual ROV operation.

Good news, there was no smoke and fire when I powered up the 6 Thrusters with the DC battery eliminator power supply which means the bullet connector connections between the Power Junction Board and the Thruster power cables have no shorts or opens.

I then hooked up my trusty servo tester to each Thruster PWM control input and tested each Thruster briefly as to CW and CCW operation and all of the Thrusters were found to be functional.

Now I can setup the Navigation controller and see if I can use the Gamepad along with QGC to command the BBBMINI to drive the Thrusters.

More to come.

Regards,
SSN626B/TCIII
User avatar
KR2_Diving
Posts: 391
Joined: Aug 30th, 2012, 11:43 am
Location: Currently: NW Suburbs of Chicago. Originally: NE Wisconsin

Re: Experimental ROV Design using Blue Robotics Components

Post by KR2_Diving »

SSN626B wrote:After waiting approximately 20 hours I checked the vacuum in the two WTCs and found that it had only dropped 10 mm Hg to 550 mm Hg which to me is indicative of a good watertight WTC based on the previous testing of the individual WTCs. The slight loss of vacuum can be attributed to the vacuum line cutoff valve which I believe is not completely leak proof.
I have been doing some vacuum testing of my own recently, and I was curious... while I understand that degradation in the vacuum signals that there is a leak... at what rate would you say the vacuum leak is "acceptable" for a water dive? I am not planning any extreme depths, maybe 50m max (depends on the price of the BR tether!).

Thoughts? Comments?
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

@KR2_Diving,
Blue Robotics has told me that they have had no vacuum leakage over a 24 hour period after pumping down with an oil vane vacuum pump which is much better than my diaphragm pump.
Using my diaphragm vacuum pump I was able to evacuate either of my two WTCs down to between 560 - 580 mm Hg. After 24 hours the vacuum had risen to between 550 - 570 mm Hg which is a 10 mm Hg loss which I believe is due to leakage in the vacuum cutoff valve between the WTC and the diaphragm vacuum pump.
Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

Linus Penzlien and I have been working with Rusty at Blue Robotics to properly configure the ArduSub firmware to appropriately drive the horizontal and vertical Thrusters in my six thruster configuration depending on the desired ROV motion input from the GCS (QGC) gamepad joystick inputs.

Validation of the BBBMINI six servo outputs, when driven by the GSC gamepad joystick inputs, was accomplished by communicating with the BBBMINI over a UDP LAN connection and using a R/C receiver PWM output tester to verify the servo PWM output values in relation to the expected PWM values.

An example BBBMINI servo output verses expected output Correlation Chart is in an attached pdf file below. It can be seen that the BBBMINI servo outputs verses expected outputs are not correct for Thrusters 1, 3, and 4 for the Forward ROV direction. This discrepancy can be easily corrected using the MOTOR_MOTION parameters in the QGC default parameter list to reverse the BBBMINI servo PWM outputs to achieve the correct Thruster output direction.

Having validated the ArduSub firmware for my six Thruster ROV configuration, I moved on to completing the Navigation Controller Tray that will reside in the Navigation Controller WTC.

The Blue Robotics ROV-side Tether Interface Board and the BBBMINI are attached to a removable sub tray that is attached to the main Navigation Controller Tray. The Signal Junction Board is permanently mounted at the rear of the Navigation Controller Tray and is not attached to the sub tray. See photos below:
Image
Navigation Controller Tray and Signal Junction Board at the rear with the BBBMINI and the ROV-side Tether Interface Board on the Sub Tray

Image
Navigation Controller Tray mocked up in the Navigation Controller WTC

The next step will be to complete the mechanical and electrical installation of the Navigation Controller Tray in the Navigation Controller WTC. This will include connection of the Signal Junction Board individual thruster PWM control signal cables to their respective Thruster Cable Penetrator Control Signal cables, connection of the Tether four twisted pairs to the ROV-side Interface Board, and the connection of the ROV-side power input cable to the Cable Penetrator Power Cable wires coming from the Battery Compartment WTC.

More to come.

Regards,

SSN626B/TCIII AVD
Attachments
Thruster Correlation Chart Forward Motion.pdf
(188.4 KiB) Downloaded 477 times
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,
It has taken about a month to get the baseline ArduSub software working with the BBBMINI. Much of the time was spent debugging the various updates to the software and coping with several changes to the ROV Thruster configuration layout.

Since this ROV is a six Thruster Vectored configuration, Horizontal Thruster #1 is located in the front right corner of the chassis, Horizontal Thruster #2 is located in the front left corner of the chassis, Horizontal Thruster #3 is located in the rear right corner of the chassis, Horizontal Thruster #4 is located in the rear left corner of the chassis, Vertical Thruster #5 is located in the middle of the right chassis side, and Vertical Thruster #6 is located in the middle of the left chassis side. All the Thruster locations are viewed from the top of the ROV chassis.
I am attaching a Thruster layout diagram below.

If you decide to duplicate my BR T100 BlueESC Thruster layout, please note the orientation of the Thrusters in relation to the centerline of the chassis. The "U" shaped protrusion with the two small holes in the top is the front of the Thruster.
Once the Thrusters were mounted in the chassis I used a servo tester to determine the PWM input to the Thrusters that would provide forward thrust and noted it on the Thruster ROV Chassis layout diagram. This came in handy when verifying the servo output PWM values of the BBBMINI for forward/reverse, yaw right/left, and strafe right/left joystick inputs from the Xbox 360 joysticks.

Rusty at BR has provided these instructions http://ardusub.com/ to get the software up and running on your ROV and to use QGC to communicate with your favorite Navigation Controller which in my case is the BBBMINI. I am presently using UDP over my LAN to allow QGC to communicate with the BBBMINI for bench testing purposes. However I have communicated with the BBBMINI using BR's Topside USB Interface to ROV-side serial Interface using BR's Tether.

There are several ROV control functions that should be assigned to the various buttons on the gamepad. I assigned the Arm function to the Start button, the Disarm function to the Back button, the Stable Flight Mode to the B button, the Altitude Hold Flight Mode to the Y button, the Input Gain Increase to the A button, the Input Gain Decrease to the X button, the Trim Roll Right to the right Bump button and the Trim Roll Left to the left Bump button.

The Input Gain buttons can be used to raise or lower the servo output PWM range of each Thruster in 25% increments. I found that I had to increase the Input Gain to 100% to get QGC to be able to calibrate the R/C Radio Channels.

The Trim Roll Right/Left buttons can be used to raise or lower the Trim PWM input to the two Vertical Thrusters when there is no input from the Y axis of the right joystick on gamepad. I found that the input to the two Vertical Thrusters would drift down to ~1300us from a neutral of ~1500us with no input from the Y axis of the right joystick of the gamepad which is used for vertical ascend/descend control. Using the Trim Roll Right/Left buttons I was able to trim the PWM input to the Vertical Thrusters to around ~1500us with no input from the Y axis of the right joystick of the gamepad.

Once the BBBMINI sensors, the gamepad joysticks and the R/C Radio Channels were calibrated per the BR instructions, I verified, using the QGC MavLink Inspector and the Info Viewer, that the BBBMINI PWM servo outputs to each Thruster were correct for forward/reverse, yaw right/left, and strafe right/left joystick inputs from the Xbox 360 joysticks and that the Input Gain, Trim Roll Right/Left, and Flight Mode buttons performed as expected.

The next step will be to test the ROV in my Association's swimming pool using a short Tether.
More to come.
Regards,
SSN626B/TCIII AVD
Attachments
ROV Thruster Layout_20160416.pdf
ROV Thruster Layout
(186.37 KiB) Downloaded 507 times
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,
Not to worry about me completing this Blue Robotics/BBBMINI ROV Project.
It has been very hot in the part of Southern Florida where I live and there have been substantial changes in the ArduSub software that controls the BBBMINI therefore I have concentrated on just performing and verifying the incremental software updates that have occurred since early May of this year. I will begin swimming pool test in my Association's swimming pool once the weather cools down in the Fall.
In the meantime I have been working on a Hybrid ROV using Blue Robotics Chassis/Thrusters/WTCs and an OpenROV 2.8 Controller. That project can be followed here:viewtopic.php?f=18&t=1839
Regards,
SSN626B/TCIII AVD
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

Recently I have decided to replace my home brew HDPE chassis with a BlueROV2 chassis due to the weight of the HDPE chassis. Since both of the ROV chassis support a vectored six thruster configuration replacing the HDPE chassis with the BlueROV2 chassis should be fairly straightforward. Though I will have to pot the Battery Power Distribution Board, which is presently located in the 4 in diameter Battery WTC, because there will be no room for it in the BR 3 in diameter Battery WTC. Actually BR had originally intended for both the Battery Power Distribution Board and the Signal Distribution Board to be potted (encapsulated) and be mounted externally to the Battery and Navigation Controller WTCs.

The BlueROV2 chassis should be here around the end of November which is just about when I will finish up my BR/OROV Hybrid Three Thruster ROV.

More to come.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,
The BlueROV2 chassis components just shipped from BR today so I should have them by a week from today which should be Dec 8th
Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,
This has been a busy week for me since my BlueROV2 chassis components arrived on Dec 7th.
Upon receipt of the chassis components I proceeded to assemble the basic frame which also included the installation of the Battery WTC by following these instructions (http://docs.bluerobotics.com/brov2/assembly/)

Image
BlueROV2 Frame Front View
Image
BlueROV2 Frame Head On

I then tackled the assembly of the Electronics Tray using the same instructions as above, but not before I had actually assembled the Electronics Tray Frame using these instructions (http://docs.bluerobotics.com/etray/).

Image
Electronics Tray Frame

The assembly of the Electronics Tray consists of attaching the RPi, the Pixhawk, the 3DR Power Module, and the Fathom-X Interface to the Electronics Tray Frame and then adding interconnecting cables and BECs.

Image
Electronics Tray Starboard Side
Image
Electronics Tray Port Side
Because I am using the BlueESC thrusters, my Electronics Tray does not include the six thruster ESCs seen in the Port and Starboard Side pictures above.

Tomorrow I plan to move all six BlueESC thrusters from the home brew chassis to the BlueROV2 Frame to see how much excess cable I have to deal with and how the two cables from each thruster will be routed. I have already modified the BlueESC thruster control cables to mate with the Pixhawk Servo Output Bus correctors so my main efforts will be directed towards setting up the BlueESC thruster power cables in order to attach them to the external Power Distribution Board.
More to come.
Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,
On this last Sunday I spent the day moving the six BlueESC Thrusters from the homebrew chassis to the BlueROV2 chassis. It took most of the day as I had to turn each Thruster's ESC/motor Housing180 degrees in its accompanying Nozzle so that the Control/Power Cables pointed towards the bottom of the Frame Thruster/Faring Plates. Then I proceeded to route the Control/Power Cables to the back of the ROV chassis. The Control Cables appear to be long enough to reach the Electronics Tray WTC and have a sufficient amount of slack. The Power Cables appear to be too long and will have to be trimmed back to be able to connect to the outboard Power Distribution Board. Here is a typical Thruster installation on the Frame Thruster/Faring Plates (Note: the ROV chassis is upside down in this picture):
Image
Typical Thruster Installation on a BlueROV2 Chassis

This morning I began the process of deciding where to mount the outboard Power Distribution Board. I finally ended up deciding to mount the Board on an aluminum/ABS plastic fixture that attaches to the back of the Battery WTC End Cap. The fixture uses three of the lower screws that hold the End Cap plate to the End Cap. I plan to degrease the aluminum part of the fixture and paint it with a good grade of marine epoxy paint to help reduce corrosion. Once the power cables are soldered to the Power Distribution Board pads I will coat the exposed solder joints with a sealing resin. A picture of the Power Distribution Board fixture is below:
Image
Power Distribution Board mounted on Aluminum/ABS Plastic Fixture

More to come.
Regards,
626B/TCIII
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