[T200s] Seeking Guidance on Power Optimization for MATE ROV Competition

Blue Robotics Products Thrusters and Motors
1

Hello!

I am a member of a high school underwater robotics team participating in the MATE ROV competition, specifically in the Ranger category. Our Team has bought four T200 Thrusters (two for up/down and two for turning) from this company and we plan to incorporate them into our design for this year’s competition. I am reaching out seeking guidance on power optimization.

We are aiming to utilize a 10-gauge tether for our ROV, and our primary concern is maximizing the power delivered to the thrusters without surpassing the 24 AMP limit for our entire system. I find myself in need of expert advice on how to achieve this delicate balance.

If you could spare some time to share your insights or point us in the right direction, it would be immensely appreciated. Any recommendations or best practices regarding power management, voltage regulation, and efficient thruster control would be particularly valuable.

2

Is this design without a battery and powered from the tether?
You say a 24 amp limit. Is there a voltage limit? 10 gauge is very heavy to drag around. How long is the tether?
Sending higher voltage down the tether and using a switching regulator in the ROV will permit a thinner tether.
Are you limited to how many wires in the tether? How are the control signals being sent?
I took a look at the MATE ROV competition website but could not find the rules. It seemed to imply just buying a ROV kit which means the richest team wins.

3

Good Morning!

First, we are limited to 12 volts and 24 amps. Second, we have had as many as 15 wires running down our tether. Our tether is 50feet long so we do plan to divide the current in multiple wires to avoid the issue of 10 gauge mass.

The question is finding the best wire to acconplish the task that has the pairs needed.

Below is last years’ manual the electrical componnets dont change much so this can give you a little insight on our issue.

Thank you for your response, we look forward to hearing back from you!

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://20693798.fs1.hubspotusercontent-na1.net/hubfs/20693798/2023/2023_EXPLORER_Manual_FINAL_1_17_2023_withcover.pdf&ved=2ahUKEwjJ8Mmwj4WDAxX6mYQIHdkUD-cQFnoECBQQAQ&usg=AOvVaw2v-NB83ECQiN9FBSiJaqsg

4

I’m not going to read the 68 pages. However on page 6 it says you can send 48 volts that must not be converted until it reaches the ROV.
That means the tether only needs 1/4 to 1/3 of the ROV current if the ROV runs on 12 to 16 volts

Specifications are on page 43 for anyone interested. You can use converters. You cannot use batteries. The thruster motors must be sealed.
You should spell this out so we don’t have to go digging for it. I did ask about batteries.

What options have you looked at for thrusters? How many? What thruster configuration do you plan to use? That depends on the task requirements.
I think the tether is the least of you concerns until you define the system and the power it will draw. I don’t think you need #10 wire. Starting with 48 volts you can afford to drop several volts in the tether.
Take a look at CPSdrone – Making Underwater Drones for ideas. They use cheap model airplane brushless motors and flood them which you are not allowed to do unless you seal them… You get to 3D print your own propellers which can work both ways for you. You probably have limited time so the solutions must be simple.

You need to define the requirements a bit more here. What tasks do you have to accomplish? How much mass do you have to move? Do you have to thread an obstacle course?
Have you already defined your power to 12 volts and 24 amps? In that case you only need 6 amps in the tether.
Peter

1 Like
5

Good Morning,

I am very sorry for the confusionq we have a meeting today so i will gather more information from the team and get back with you this afternoon, with more information.

Again, thank you so much for your assistance on this matter, and thank you for the assistance you have given us so far!

I will provide more information as soon as possible, thank you.

Xia

6

I did some rough thruster tests which you may find interesting.
Brushed vs brushless motors - General Discussion - Blue Robotics Community Forums
scroll down to my test setup and be aware that the plastic tub I used would not hold as much water as I wanted. The sides will bulge out and you will need sand bags or a frame to hold the shape.
It uses a lever pressing on a food scale to measure the thrust. Do the math for lever length, etc.
Note that thruster efficiency can differ a lot from what you think. Smaller does not mean a power saving.
I use Cat5 tether with 4 pairs of tinned and stranded wire. Not the cheap non stranded (solid wires).
One pair is used for bi-directional Ethernet (BlueRobotics/Ardusub style) and I am reserving another pair for my custom bi-directional communications to avoid messing with the Pixhawk software. The other two pairs can be paralleled and high voltage sent down. I was planning 200 v DC.
In your case 48 volts. My Cat5 uses #24 awg at 0.027 ohms per foot (x2 = 0.054 ohms per foot for the pair for a total of 2.7 ohms for your 50 ft tether, and half that if you double up a pair. If you don’t need the extra pair it would be roughly an ohm for 3 pairs). 6 amps drops 6 volts from your 48 volts. You will get close to your 24 amps but your average current will be much less. Are you allowed to use a large capacitor? Are super capacitor available at that high a voltage? Just a thought.
1752A Technical Data Sheet (belden.com)

7

I apologize for any confusion. I wasn’t intending for you to read over the entire manual. I also sent you the wrong manual, sorry about that. Our team, Phoenix Robotics, participates in the Ranger class. However, the manual I posted was for last year’s Explorer class. Please keep in mind that this year’s manual has not yet been published. I am sending you last year’s manual as a starting point. Here’s a link to the 2023 Ranger class manual, which includes the electrical specifications along with the specified page numbers.
The technical sections should not change significantly. They have been consistent for many years.

Pages relevant to our discussion include the following: 41, 46, 47, 49, 50, 51, 52, 53, 54.

Blue Robotics has provided our team with five thrusters in all; we desire to use four of them and save one as a spare. Two thrusters will be used for up and down movements, and two more for forward and reverse movements. We will be running a 12 Volt system, we wont know the payloads we will be using until the manual is released but we will most likely have one or two claws that will require a minimum of two servos each unless we chose to implement an elbow.

The tasks we have to complete are not yet fully specified; we should receive the updated manual in sometime toward the end of December, which will serve as a guide while we build our ROV. Here is a summary of the things MATE has sent out as a teaser to the manual.

#1. Trigger” the release of the multi-function node’s recovery float
• Visually determine failed deployment of recovery float
• Pull pin to release recovery float to the surface
• Return the recovery float to the surface, side of the pool
• Connect a recovery line to the bale on the multi-function node for ship recovery
• Manually return the multi-function node to the surface, side of the pool

#2.Deploy SMART cable through waypoints
• Place SMART repeater in the designated area
• Return SMART cable end to surface, side of the pool
• Measure temperature to verify SMART cable sensor readings
• Connect AUV docking station power to SMART cable
o Retrieve the power connector
o Install the power connector

#3.Smart Reefs
• Probiotics 2
o Place probiotic irrigation system in designated location
o Deploy probiotic sprinkler on coral head
o Activate the irrigation system
• Coral Restoration
o Transplant branching coral
o Transplant brain coral
:black_small_square: Autonomously
:black_small_square: Manually
• 3D Coral Modeling
o Create a scaled 3D image of the coral restoration area
:black_small_square: Autonomously
:black_small_square: Manually (CAD)
:black_small_square: Manually (paper) - RANGER/PIONEER only

#4.Tennessee Lakes and Rivers
• Determine location of sturgeon spawning grounds
o Recover an acoustic receiver to retrieve its data
o Determine the location of a potential spawning site
:black_small_square: Create a graph of sturgeon locations from acoustic receiver data
:black_small_square: Determine the potential spawning site
o Determine habitat at potential spawning site
:black_small_square: Place ADCP
:black_small_square: Recover sediment sample

#5.Design and construct an operational profiling float
• Prior to the competition, design and construct an operational vertical profiling float
• Deploy the float into a designated area
• Float communicates with the mission station prior to descending
• Float completes two vertical profiles -
o Vertical profile 1
:black_small_square: Float completes first vertical profile
:black_small_square: Float communicates data to mission station
:black_small_square: Data is graphed as depth over time
o Vertical profile 2
:black_small_square: Float completes second vertical profile
:black_small_square: Float communicates data to mission station
:black_small_square: Data is graphed as depth over time

I hope that the information above will help you better understand what we must complete. Thank you for your patience and all of your help

Xia

8

So your tether can only supply 12 to 14 volts. I suggest you design for minimum power and maximum efficiency and let that dictate what your tether will be.
Keep it simple and get the ROV working. You may find it draws less power than you anticipated.

9

Thank you!