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Scale Remote Control Submarine application?


(Bob Martin) #1

Good morning, all!

I was just introduced to the ArduSub project yesterday via a friend that had heard about it, and have been devouring the information on your overview site with a lot of excitement.

I have a small business that offers scale model submarine kits and components (www.rc-submarine.com) and I also offer buildup services for these kits. Historically, control of these craft is accomplished via standard hobby RC gear operating on 75mhz and using hobby transmitters and receivers. Control of the functions of the boat is handled through add-on modules such as pitch controllers, ESC’s, depth controllers, failsafes, etc. which are connected between the receiver and the control units, which are typically pumps, motors and servos.

I’m excited about the possibility of utilizing ArduSub to control these submarine models, as the additional functionality and flexibility is something that this small hobby desperately needs in order to grow and flourish.

Having said all of that, I was hoping to find out if you think that the ArduSub platform would be applicable to this use.

Standard configuration for an RC submarine would see:

Propulsion:

  • Via a single or dual shaft conventional propeller, rear-facing
  • Typically brushed motors, however conversion to brushless is possible and is becoming more commonplace

Pitch control:

  • Via fore and aft dive planes powered by servos
  • In typical setup, rear planes autonomously control the pitch of the model in an effort to keep it level. This can be overridden by the operator in order to pitch the model forward or back during operation.
  • Forward planes dynamically control the depth of the model
  • Forward and aft planes are usually on separate channels, though some users link together for simultaneous operation.

Ballast:

  • via a pump (brushed motor) that empties or fills a ballast tank
  • some systems also use a servo to control an air vent that “blows” ballast or opens a vent valve

Yaw control:
*via rudders that are powered by a servo

Additional functions:

  • peripheral features such as open/close torpedo launch doors (servo), fire torpedo (relay or servo), raise/lower periscopes (motor), lighting (relay), sound (dedicated sound board powered by PPM inputs)

New features not typically seen in this hobby, but that ArduSub may be able to offer: (My wish list)

  • Depth control via pressure sensor manipulation of the ballast system and/or forward dive planes
  • Bottom collision avoidance via depth sounder (in development?)
  • Object collision avoidance via scanning sonar (in development?)
  • Autopilot
  • Information and data relay back to operator during operation (heading, depth, speed, battery condition, etc)

The typical configuration of these submarines is not one that appears to be supported in the standard options that are are outlined in the overview of the ArduSub project, however I don’t think that an alternative setup to match what we need would require much in the way of configuration changes as the system already supports servo and motor outputs. It’s really just switching outputs from motors to servos in most cases (in my amateur opinion, anyway).

So, long story short, is there anyone out there with ArduSub experience that can comment as to the feasibility of using the system to control a scale model submarine rather than an ROV?

Your help is very much appreciated!

Bob Martin
Naples, FL, USA


Towed ROV with ArduSub?
(Jacob) #2

Hello Bob, I’m very happy to see this post. Thank you for the detailed explanation of your situation and questions.

I am the maintainer of the ArduSub project, and I would be happy to help you accomplish your goals with ArduSub.

I have a few questions to begin with:

ArduSub does not support RC transmitter input (and I do not feel inclined to add it, due to it’s limited usefulness in ArduSub applications thus far). Would this be a hard requirement for the project to be useful to you?

Another related question, are you interested in tethering your submarines to provide live video and telemetry to the top?

ArduSub supports control of servos, relays, and brushed/brushless motor controllers, as well as a variety of sensors, and stabilization control. You are correct in your observation that ArduSub does not explicitly support forward-moving craft like submarines and torpedo-style AUVs that use control surfaces for maneuvering. This has been on my wishlist for some time, and it is a feature I want to have. I believe it will be possible to hack around and make it work with minimal modifications to the firmware, or perhaps even without any software changes.

Depth control via pressure sensor manipulation of the ballast system and/or forward dive planes

Sure, should work out of the box I think.

Bottom collision avoidance via depth sounder (in development?)

In development, but working.

Object collision avoidance via scanning sonar (in development?)

This will be a more complicated task that has not been worked on with ArduSub to my knowledge, but yes doable and desirable.

Autopilot Information and data relay back to operator during operation (heading, depth, speed, battery condition, etc)

You will need a tether like the fathom slim:


(Bob Martin) #3

Jacob,

Thank you so much for your quick reply to this topic!

Additional information as per your questions:

There is no requirement to incorporate or support standard hobby radio gear. The only stipulation is easy wireless control of the submarine functions. Now, I haven’t seen any reference to RF hardware, so I’m unsure if your platform is only designed for tethered operation, which would, in hindsight, make sense if your design are primarily oriented around salt-water or deep-water operations. If that is not the case, I would be very interested in getting pointed toward the resources outlining the radio frequencies used and any performance expectations in regard to depth of signal penetration in fresh water. I would also like to know if multiple systems can operate in the same vicinity without causing interference with one another.

While tethered operation for telemetry and video is an option, it would not be a popular choice for RC submarine hobbyists. Typically, these boats will operate in potentially weedy water, and more commonly in conjunction with other surfaced and submerged RC craft.

Telemetry back to the base would be a great feature, even if it only occurred during surfaced operations. Most of the time, these boats operate at “periscope depth”, which would allow an antenna to breach the surface and relay video and telemetry data wirelessly. If the sub were to dive deeper, the loss of that signal would not problematic, particularly if video was being stored on board for later retrieval.

The depth control would be a vital feature and I’m glad that it is developed, or at the very least almost ready.

Bottom-avoidance would be an exceptionally popular feature and I would very much like to know what would need to be done to develop this into a functional aspect of the package.

As a question, what is the approximate footprint of the craft-based hardware? I’m trying to understand what scale of craft this will be feasible for installation in. Our submarines will typically have electronics housed in watertight cylinders ranging from 2" diameter up to 4.25" diameter, with the most common sizes being 2.5" and 3.5" diameter.

Again, thank you for your support. It is greatly appreciated!

Bob


(Anthony White) #4

Hi Bob-
How much penetration do you typically see with 75mhz? Ardusub always uses a tether because depths greater than 3’ are assumed… Putting an rf modem in a unit for surface operations would be easy, and allow telemetry and control- but no video unless you run wifi, which would have lag.

As for size, a pixhawk can be crammed in a 2" tube, but a pi requires 3". Standard for BlueROV2 is 4".


(Bob Martin) #5

75 mhz will typically allow operation to depths of around 30ft (10m) in good, fresh water. That is reduced significantly with mineral or biological impurities. In heavily chlorinated water, such as a swimming pool, this can be reduced to as little as 6ft or even less. Salt water, of course, does not allow good penetration of radio waves at all.

In typical operation, a hobby RC sub will patrol at between 1 and 2ft below the surface at a distance of 30 to 60ft from the operator. Reliable control at depth is, of course, a function of distance from the operator and the depth of the boat.

If there are out of the box RF modules that operate at lower frequencies than 75mhz that do not require HAM licenses, that would be ideal, as the lower the frequency is, the better the transmission through water.

Size of the pixhawk is great, as is the pi board. Even if this product can only be used in larger subs, that would be perfectly okay.

Again, thanks for your help, all!

Bob


(Bob Martin) #6

I’m wondering what the next steps would be in order to begin testing feasibility for this application?

Jacob, you said that implementation with a torpedo-style platform is a feature that you’d like to see and that you feel the ArduSub controller could be hacked to make it work. Is there any way that I could ask you to elaborate? I’ve never used ArduSub before, so I’m diving blind, so to speak.

Another thing I’d be interested in getting some help with would be the requirement for an RF modem for wireless control. Again, this is something that I have no personal experience with (yet).

I realize that everyone contributing here is doing so out of generosity and a desire to grow the hobby, and I very much appreciate any and all help. If there is someone out there that would be willing to guide me through the creation and setup of a prototype, I can look at trying to work out some form of compensation, either with money or product (ever want to have a scale RC submarine!?)

Thank you for all the help thus far! I’m really looking forward to seeing if ArduSub can elevate (dive!?) my hobby to new heights (depths!?) :yum:


(Jacob) #7

Hi @RCSubGuy I’ve been travelling.

We would start by choosing an appropriate motor configuration for a particular vehicle. Can you send a diagram of an example sub and it’s acutators/control surfaces? I can help you further interpret things from there.

Can you show us any examples/links to rf equipment you typically use?


(Bob Martin) #8

Jacob,

Thanks for the reply!

Here is a very standard setup for 95% of scale RC submarines.

Pitch is controlled dynamically via dive planes. Typically, we will have one set forward on the hull and one set aft. The function of the rear planes is primarily to maintain a level keel during operation. They currently utilize a pitch control unit that goes in line between the receiver and the rear plane servo. As the boat pitches forward or back, the planes move to correct the pitch and return the boat to a level keel.

The forward planes are responsible for depth control. We have electronic modules that will monitor water pressure and control the front planes to keep the boat at a specified depth. This can be overridden by the operator via input from the transmitter.

Thrust is attained via either single or dual propellers. In dual-shaft configuration, the spacing between shafts is close enough that the turning moment generated via differential thrust is negligible. Most times these shafts are simply wired together to act as a single thruster, though there are boats that differential thrust will make a positive difference, such as the Russian Oscar and Typhoon class boats.

The main control hardware utilized consists of

  • An RF receiver on 75mhz (typically 6-channel, but up to 10 for peripheral features such as torpedoes)
  • Bow plane servo
  • Stern plane servo
  • Rudder servo
  • Electronic speed control powering either single or dual brushed motors (as I said, we can go brushless as well)
  • Electronic pump controller for the ballast system

I offer conventional RC submarine gear on my website at www.nautilusdrydocks.com. The online shop can show you the typical watertight cylinders we use to house the components, the electronics used to drive it, and the various ballast system configurations.

I hope this helps! Thank you, again, for your assistance in this project.

Bob


(Jacob) #9

Hi again Bob, I’m sorry it’s taken me so long to reply, I’m very busy.

Is the ballast used for depth control at all?

The hard part for now will be fitting RC control into the equation. If you are ok to fit a tether to a model, that will work to sort out the rest of things for the time being. I will work on setting up an output mixer to work with the control surfaces you have pointed out.


(Bob Martin) #10

Jacob,

No problem on the delays. I can definitely relate to having other responsibilities get in the way of hobbies.

Yes, the ballast system can be used for depth control. The experienced operators will want the ability to statically dive, reach a certain depth, and then maintain that depth using the pressure sensor. Beginning operators will flood ballast to the point that the model is slightly positively buoyant and then use forward movement and the dive planes to pull the boat under. This offers a safety margin in case of operator error or mechanical failure.

RC control is a must and a tether is not an option, unfortunately. If we can figure out an RF repeater, we should be in good shape.


(Bob Martin) #11

Good morning, all!

I’m thinking that I can take a stab at working out the repeater if someone can help with the output mixer to allow control via servos versus motors.

I’m really interested in seeing how this might work out in the long run to improve my hobby…

Bob


(Jacob) #12

I saw this yesterday: https://oscarliang.com/betaflight-fc-fpv-simulator/

This is very relevant. I’ve got the hardware here, I can give it a shot and let you know if it works.