Experimental ROV Design using Blue Robotics Components

What are you working on .... Show off your Rov's Projects here.
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 been almost a month since I last posted and the reason being that I was awaiting the receipt of a tether and interface boards to continue on with the construction of my ROV. Well, I do not have to wait to post anymore as the tether and the interface boards have arrived!

The neutral buoyancy tether cable. and the ROV and Topside interface boards are a beta test versions from Blue Robotics and are not yet available from the Blue Robotics Store. I was fortunate enough to be selected by Rusty to test these beta version components and plan to quickly integrate them into my ROV project and provide Rusty with constructive feedback, if any, as to their functionality. Please remember that I am working with beta components and therefore there may be changes to the final versions depending on the results of the beta testing.

I received 75 meters of the neutral buoyancy tether cable. The construction of the tether is as follows:

The Tether is a high quality tether cable designed specifically for ROVs and other subsea applications. It is neutrally buoyant, has 500+ lb breaking strength, and is embedded with water-blocking fibers to seal any leaks. The tether has a diameter of 7.6mm and is slimmer than the vast majority of comparable ROV tethers.

The tether carries four unshielded twisted pairs (UTP) of 26AWG wire. These pairs are colored and arranged in the same fashion as a Cat5 networking cable including cross-talk resistance. Each pair is individually jacketed inside the cable to maintain reliable properties and minimize interference between each pair of wires.

The core of the cable contains Kevlar strands for strength and Dacron fibers for space filling. Both fibers are impregnated with water-blocking compound to block any leaks caused by nicks or rips in the cable. The high-visibility yellow polyethylene foam jacket resists abrasion and provides neutral buoyancy.

The stiffness of the cable is designed to be flexible enough to give plenty of freedom to your ROV, but stiff enough that it does not become tangled easily.

Here are a couple of pictures of the exterior and interior of the tether cable:

Image

Image

The interface boards provide low-latency video, a serial port connection, and remote power on/off switch for tethers up to 300m length. They can be used with the neutral buoyancy tether or a Cat5+ network cable. The interface boards appear to be of high quality with thick printed circuit base material and extremely legible legends on the board silk screen.

The Tether Interface Board Set is open-source and open-hardware, so the schematics and board files are free to view, modify, and reuse. The electrical schematic and board layout are open-source and the design files will be available to all end users.

I plan to start integrating the tether and the ROV-side Interface Board into my Navigation Controller WTC this weekend and will then give consideration to selecting a topside cabinet for the Topside Interface Board.

Once again, please remember that these are beta test components and could be subject to change in their physical and electrical configurations and specifications before becoming available in the Blue Robotics Store.

More to come.

Regards,
SSN626B/TCIII
a_shorething
Posts: 289
Joined: Sep 10th, 2013, 5:26 pm
Location: New Jersey Shore

Re: Experimental ROV Design using Blue Robotics Components

Post by a_shorething »

This looks really cool! Can't wait to see how it turns out.

A mass-produced, readily available, neutrally buoyant tether would be a huge benefit to this hobby!
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 »

@a_shorething,
Unfortunately this neutral buoyancy tether cable will not be cheap and will probably be inline price wise with OpenROV neutral buoyancy cable per meter.
However, based on the tether specifications, you will probably never have to replace the tether due to either a mechanical or electrical failure.
Regards,
SSN626B/TCIII
NCUWI
Posts: 58
Joined: Nov 25th, 2011, 3:27 am

Re: Experimental ROV Design using Blue Robotics Components

Post by NCUWI »

SSN626B wrote:@a_shorething,
Unfortunately this neutral buoyancy tether cable will not be cheap and will probably be inline price wise with OpenROV neutral buoyancy cable per meter.
However, based on the tether specifications, you will probably never have to replace the tether due to either a mechanical or electrical failure.
Regards,
SSN626B/TCIII
The Blue Robotics tether may not be as cheap as standard, interior grade Cat5e cable, but for what you're getting I think it's a bargain. The 4x twisted pairs, double insulation, and overall construction and strength compares very favorably to other commercially available tethers (such as VideoRay, Seabotix, etc.). Plus I think most ROV builders will find the 4 twisted pair / Cat5e design to offer many times more options than OpenROV's single twisted pair tether. I spent a lot of time with Rusty offering my feedback on the design and quite honestly I think they've "hit a home run" with this one.
User avatar
olegodo
Posts: 222
Joined: Aug 30th, 2013, 9:47 am
Location: Bergen, Norway

Re: Experimental ROV Design using Blue Robotics Components

Post by olegodo »

Any word on the price yet?
NCUWI
Posts: 58
Joined: Nov 25th, 2011, 3:27 am

Re: Experimental ROV Design using Blue Robotics Components

Post by NCUWI »

olegodo wrote:Any word on the price yet?
Based on my discussions with Rusty I think the price will be very competitive, but I'm not a liberty to discuss specifics until after the product has been launched. Be sure to follow Blue Robotic's Facebook page as that's one of the places they post new product announcements: https://www.facebook.com/bluerobotics/
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,

I have attached the ROV end cable penetrator to the neutral buoyancy Tether as shown in the picture below. Since the Tether is 75 meters long I stripped approximately one foot of insulation off of the ROV end of the tether to give me a sufficient length of twisted pairs for connections within the Navigation Controller WTC.
Image
Cable Penetrator on ROV end of Neutral Buoyancy Tether

Since the Tether cable will eventually be wound around a cable drum that will include slip rings, I will hold off making any permanent connections to the Topside end of Tether cable.

The path forward now will be to electrically connect the Topside Interface Board to the ROV-side Interface Board through the Tether cable and then attempt to communicate with the ROV-side BBBMINI Navigation Controller (http://diydrones.com/group/bbbmini) from the Topside laptop running QGC. To that end I have fabricated a bi-directional level shifter to convert the 5 vdc serial output of the ROV-Side Interface Board to the 3.3 vdc input of the BBBMINI telemetry connection. The level shifter is a Sparkfun standard bi-directional level shifter available here: https://www.sparkfun.com/products/12009. There is no need for a Topside level shifter as the communication between the laptop and the Topside Interface Board is done through a USB interface.

Once the Topside QGC has been setup to work with a gamepad controller we will attempt to communicate with the ROV-side BBBMINI running an alpha version of ArduSub.

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,

My friend, Linus Penzlien, and I have been busy porting the ArduSub firmware over to the BBBMINI and have been achieving a few successes so far.

We are presently using the latest version of Debian (2016-02-16) recommend by Mirko on the BBBMINI, QGC version 2.9.4 for the Topside Control, and the latest daily build of ArduSub for the ROV-side Control.

We have calibrated the BBBMINI's accelerometers and compass and are presently in the process of calibrating the radio using a gamepad input (Xbox Controller). We would have been much farther along by now, but we had a problem where the accelerometers on the BBBMINI were not calibrating according to QGC even though there were accelerometer offsets and calibration values in the QGC parameter list. The reason for the calibration failure was due to the fact that QGC had two INS units enabled while my BBBMINI presently only has one INS (MPU-9250). Once that error was corrected QGC indicated that the accelerometer calibration was successful as was the compass calibration.

I have also setup a Topside to ROV-side test bench on which I have mounted the Blue Robotics Topside and ROV-side Interface Boards and connected their Tether interfaces with a short piece of CAT5e LAN cable. I have successfully used QGC to communicate with the BBBMINI, running the ArduSub vectored thruster configuration firmware, through the Topside to ROV-side Interfaces and a 5 vdc to 3.3 vdc level shifter connecting the output of the ROV-side Interface serial port to the BBBMINI telemetry connection. A picture of the test bench setup can be seen below:

Image

The Topside Interface Board has a USB connection that allows QGC running on either a PC or a laptop to communicate with the Topside Board,
Once the gamepad calibration is complete we can move ahead with testing the functionality of the ArduSub firmware using QGC.
More to come.

Regards,
SSN626B/TCIII
Last edited by SSN626B on Mar 11th, 2016, 1:46 pm, edited 1 time in total.
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 turns out that we had the wrong thruster configuration version of ArduSub loaded on the BBBMINI. Once we corrected that issue, joystick input to QGC from the Xbox 360 game pad appears to be driving the BBBMINI thruster pwm outputs correctly for forward/reverse, yaw, and vertical assent/descent.

I have put together a wire harness that will connect the BBBMINI servo outputs to the Signal Junction Board that distributes the individual pwm signals to each Thruster. I created the wire harness by crimping seven servo female pins to a 7 wire cable to be able to connect the BBBMINI 6 servo pwm outputs plus ground to the BR thruster Signal Junction Board. I then soldered each wire in the cable to its appropriate pad on the Signal Junction Board and will be able to hopefully begin testing the six Thrusters this weekend.

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,

Believe it or not I was able to literally cram the battery tray, complete with the Power Junction Board connected to the Thruster cable penetrator power cables, into the Battery Compartment WTC without breaking or appearing to short any wires in the cables. Also, the bullet connectors appear to be connected nice and snug with their sleeve shrink intact. Now comes the Smoke Test with a charged LiPo battery powering all of the Thrusters at once instead of one at at time.

After I built the Power Junction Board I performed a continuity test of the Board by buzzing the battery positive side of the power cable to the individual thruster positive cables and likewise with the battery negative side of the power cable. I also checked for shorts between the battery positive and negative power cable leads.

As reported a while back in this discussion thread, I then proceeded to power each Thruster individually from a LiPo battery and checked the functionality of the Blue ESC PWM and I2C control signal lines. Each Thruster performed to expectations when powered individually and proved the integrity of each Thruster power and signal cable.

Now comes the Smoke Test. Assuming there are no shorts between the individual Thruster positive and negative power cables there should be no smoke when I apply LiPo battery power to the Power Junction Board. However, being a realist and believing in Murphy's Law, I plan to put the LiPo battery in a flameproof charging bag that will be inside a metal ammo box. Also I will have a foam fire extinguisher at the ready to quench any unexpected smoke and flames.

Other than running the power test as outlined above, I wonder if there is there anything else I can do to ensure that there are no shorts in the individual Thruster power cables prior to powering up? I thought about running an impedance test at the battery cable connector, but I doubt that my DMM has the capacity to charge the input capacitors on each BlueESC's power input line so that is probably not an option.

Regards,
SSN626B/TCIII
Post Reply