Controlling a Catamaran with RC Radio

[Bluefang]

A friend has a small house boat built on top of a 5m catamaran hull that he wants to electrify with twin motors. One of his major things that he wants is to be able to remote control the house boat so he can sit where ever he wants to navigate it slowly down the river.

Atm the boat will be designed to cruise at a walking pace, one of the things I have been thinking about is to be able to pivot the boat, driving one motor forward and the other in reverse. Does anyone have any suggestions on how to do that with RC radios and controllers? As I was typing this I just thought about tanks, and then realized that the controllers would have separate sticks for each track/motor system. More thinking along the line of a single throttle for power and a slider that toggles the % of throttle that each motor controller sees all the way into negative for reverse. Also will need a normal steering channel for the rudder control.

The pivoting is not really on his wish list but I personally think it would be awesome and incredibly useful.

 

[Drunkskunk]

I can just see it. he's on the roof, getting some sun, in his boat with a drink on the rocks.
He gets up for another drink, but trips on a towel and the remote slips out of his hand and over the side, banging the throttle to full before landing in the water. Your friend stands there helpless as the boat races out of control, and he ends up in the drink with his boat on the rocks.

You could try a Spektrum DSMX or any of the competing 2.4Ghz DSM RC radios.

Your pivoting idea could be done on one stick by channel mixing. Its easy enough for most high end radios to handle this, but wouldn't be very efficient on a cat. the twin hulls don't turn that easy, so a rudder would be better.

 

[Bluefang]

Well no matter what I do he will be having a remote control of some sort I ll just make sure its easy to shut the boat down and return to manual control. He says he can move the boat along with hand paddling.....so worst case I just set it up with some emergency stop switches in easy to reach locations. Great to hear you can channel mix on good quality remotes, will be something to play with. Hopefully I can use HK or Turnigy RC controllers as this will allow him to carry spares easily or get a replacement posted to him.

yeah the efficiency is going to suck when they are running different directions, but this would only ever be used for extreme tight turns and manoeuvring. The boat will have a normal rudder system which will be used 99% of the time. Currently thinking about using a paddle wheel on either side for efficiency and lower maintenance. Its only going to be going <6knots so it should be fairly good. The motor RPMs that will likely be used will be 200rpm or 400rpm.

 

[Bluefang]

This is the kinda theory for the paddle drive.
http://shantyboatliving.com/2012/3357/

In regards to the feathering of the paddle blades, would it be feasible to use a large servo on each blade to hold it vertical for maximum efficiency, each wheel is only expected to output a absolute max of 2kw, so if I hinged the blade fairly close to the tip most of the water force would be on the pin holding the blade rather then the servo which would have plenty of leverage to hold the blade vertical while pushing thru the water? Any suggestions on how to wire the servos up so that they would be self contained with a vertical sensor and only need a power source?

 

[JackB]

You don't need rudders if you have widely spaced motors that can run forward and reverse.
Rudders themselves are inefficient by creating drag.

I designed and built 2.4Ghz R/C controllers for R/C car racing. Can be programmed to do any kind of control.
A programmable controller can add in safety checks, have overrides and different modes, etc,
compared to an off-the-shelf unit.

 

[mauimart]

It just so happens I am working on a similar project on a smaller scale. The catamaran, now turned tri-maran for extra buoyancy, will be used as a research vessel to collect data. It uses two electric tolling motors controlled via RC radio. Currently only the right stick (2 channels) is being used. The signal from the RC receiver is fed into an Arduino where it is mixed to perform the desired function. The Arduino outputs PWM signals to two motor controllers which in turn drive the motors. If the stick is centered forward/aft while moved to the right the left motor will spin forward and the right motor in reverse thereby pivoting the boat to the right. The opposite is true if the stick is moved left. If the stick is advanced forward, both motors will provide forward thrust. If the stick is moved left or right while in the forward position a left or right turn will be commanded proportional to the stick movement. If the stick is advanced aft the boar will reverse. It's very easy to control the boat this way with just one hand. Other mixing configurations are possible such as one stick per motor, forward or reverse on each. With some of the more elaborate RC systems you might be able to program this type of mixing in the radio itself. Our Arduino solution is inexpensive and will work with any generic two channel radio. I will try to upload some pictures of the setup tomorrow. In the mean time here's a video of one of our students piloting it for the first time on its maiden voyage. We will be adding the sensors and data telemetry functions in the near future. If you are interested I can provide the arduino code and a simple schematic.

[youtube]mjW9zdUdXAM[/youtube]

 

[Bluefang]

Not sure if i can get the wheels spaced along way apart, atm its a 5mx3m catamaran and the guy is currently thinking of having the wheels in the middle. Pretty sure i should be able to talk him into putting them on the sides.

Atm as a drive motor i am thinking of using a Mini-monster mounted in the middle of each wheel. Its supper efficient, cheap, fully sealed and big enough to be able to run for ever with out a problem even if i use the outer shell of the drum brake for the mounting points of the wheel. Extending the center shaft for a pivot point for the other side of the wheel. Using a car ESC for each wheel i can keep the RPM way down by using 3s/4S for around 100rpm or bring it up to 6S for 200rpm using the slower speed setting of the mini-monster. Should help with keeping the wheel at >80% efficiency if i can get the wheel up to 2m diameter or similar, will probably only be a foot wide or so as it will not be a high power boat with ~5kw absolute max power.

Still trying to think of ways to feather the paddles properly so they are 100% vertical when going thru the water, it could be done the old mechanical way with a off center spider. This only has the paddles vertical in one spot, just gives the impression that the wheel is ~3x larger and very shallow, ie it still lifts and pushes the water down. Trying to think if it would be possible with a slow moving high power servo and a pendulum swing switch mounted on top of the paddles, if its out of vertical the motor drives until it is, more weight at the bottom of the paddle holds it vertical until its hitting the water then the servo forces it to hold vertical. Pretty sure it will involve alot of extra power and maybe the normal spider method of mechanicaly getting close will be better.

Jackb that sounds like a awesome control, only problem is the guy i am building for is trying to do everything cheap but efficient. So i think i will be lucky to get him to spring for a high quality off the shelf controller let alone a programmable race one. May just try a cheap HK rechargeable controller and see if i can get it to do what i want with a few tweeks. First i have to get him sorted to build the thing first.

 

[Monstarr]

I am working also on a similar project.

But i will use a PS3 dualshock controller with a servoshock module (http://www.servoshock.com)
That module got a whole bunch of programmable IO.

I use the PWM output to a brushed 40A dc motor controller to control the power to the 36 lbs Minn Kota trolling motor.
For steering i will mount a chainsprocket on the trolling motor shaft which is connected by a chain to a PWM controlled continuous motion RC servo motor which i fixate on the trolling motor's mounting bracket.

 

[John in CR]

You might check to see if any newer wheelchair controllers are wireless. Some are using brushless motors, but I don't know about wireless. Otherwise yes, control for an RC tank would be perfect.