Hope all is well.
I know there is already a thread on Autopilots. But I wanted to start one specifically for smaller auxiliary motors or trolling motors for you fishing types :-)
I'm thinking in the 20HP and under range.
There is an excellent product already on the market for sometime called the TR1 Autopilot that Garmin now sells. Many people I know have been extremely happy with this autopilot.
That being said, I'd like to start a project of building a similar product and get it to be an opensource community developed project. I think a project like this would be fun and provide an opportunity to build something that the opensource community can tweak and use for potentially other projects.
I know there is the Ardupilot, Openpilot and other projects that seem to be geared towards RC based applications; which might work for this. But one of the fundamental challenges with any of these is starting with the hardware and actuators.
The commercially available product, the TR1, uses a hydraulic ram with a stroke of 2". It has a hydraulic pump and of course a flux gate compass and controller. Additionally, it has a sensor attached to the spark plug to read the RPMs of the engine.
Given the cost of the hydraulic components, I'd like to look at using a 12V DC Linear Actuator that is (waterproof) IP65 or higher rating. Such as this http://dcactuators.com/Detail.asp?Pr...302.390_6102TP
Additionally, for position feedback, these Linear Actuators can be ordered with a potentiometer embedded to provide fairly accurate position.
The throttle control can be a servo motor tied to the carburetor linkage (such as used on the Troll Master products).
As far as controllers...well I'm thinking either a Ardunio based board or potentially an ARM processor board with embedded Linux (such as the Beagleboard, Beaglebone http://beagleboard.org/bone
It just depends on what all makes sense from an expandability perspective.
I have a 9.9HP Mercury Bigfoot I'd like to try to build this on.
But first, I'm curious to see if anyone else has tried to do this?
The tiller Autopilots I see out there don't really work well on Aluminum fishing boat type of applications where the 'kicker'/trolling motor is mounted off the stern with tight space (sometimes with a bracket attached to the transom). That is why the TR1 has been so popular. It mounts the hydraulic ram to the actual bracket/swivel point of the engine and a proprietary bracket attached to the lower vibration isolation mounting shroud (above the lower unit).
For example, here is a mount on a Mercury 9.9 Bigfoot 4stroke outboard: https://picasaweb.google.com/lh/phot...eat=directlink
As you can see, the value of having a actuator attached in this location provides several things:
1. You don't have to have a device attached and in the way of the tiller.
2. The actuator stroke (distance from fully retracted to extended) doesn't have to be a long as something attached to the tiller handle.
3. Allows you to easy trim, tilt / raise the motor without having to disconnect a tiller handle based autopilot. The bracket is mounted to the swivel point of the engine and moves up/down with the engine (such as when you trailer the boat and want the motor up or you're running your big (Main) motor(s) and you want the trolling motor up).
With this design, there is indeed some benefits. But just brainstorming here...the hydraulic ram has the support of allowing the user (captain) to manually steer the motor if he deactivates the Autopilot. I believe there is a bypass valve to allow for easy manual steering. If I go with a DC Linear Actuator, the static holding pressure is pretty high and I have not seen any 'cheaper' models that have a clutch system to provide a similar feature. I think you'd have to use pins to remove the Linear actuator when you wanted to steer manually. Not sure how practical this is - or if someone has a workaround for this.
But this is one thing that comes to mind.
Additionally, where this is located, do you think that an IP65 rated actuator will be adequate? Its not going to be submerged in water, but it will get splashed with river/ocean water and of course rain water as its exposed to the elements.
At any rate, I've been at the brainstorming phase of this project.
I want to do this in two phases:
Phase I: Physically mounting and just using a simple rocker switch control to steer port/starboard and a simple PWM control for the throttle.
The reason for this, why work on the autopilot navigation piece before I get the physical mounting, water intrusion concerns, bracket design, etc.etc all figured out.
With phase one, I can spend some time on the water testing general behavior, steering, throttle and make sure that the actuator and the servos purchased are going to work. If they don't then I need to go back to the drawing board and investigate other designs (maybe going back to using a hydraulic
which is going to drive the cost up).
If it does work well, then move on to phase 2.
Phase 2: Incorporate a controller (again either Ardunio or a embedded Linux board) to provide control (such as PWM which can be used to change the speed of the actuator). Also using the serial & general I/O ports, I can add a fluxgate compass, and take NMEA 0183 feeds from the GPS.
Phase 2 would be simple 'stay on heading'.
Phase 3 - take waypoints provided by GPS for full auto nav functions.
Phase 4 - Trolling pattern options (such as zig zag'ing, etc)
Personally, I'd be very happy just to get to phase 1 & phase 2. Phase 3 & 4 would be cool...but as they say, you have to walk before you can run.
So what do you think? Is there anyone out there that has tried this?
Do you think the Linear Actuators will work? Is there another manufacture that provides a better IP67 rated Actuator that is reasonably priced?
I'm leaning towards the Beaglebone because I already have been working on other projects using Beaglebone and it comes with the Angstrom Distribution of Linux which supports perl and python right out of the box. I'm writing other projects in python...so I was thinking that I'd just use Python for all of the control software.
The benefit of using the Beaglebone is expandability and if I wanted to really geek out later, you can easily add a touch screen or other items (heck its got a USB interface and controller built in including an ethernet interface).
Like I said, I'm just in the brainstorming phase of this so if you have any insight; would like to be involved in this too, please let me know.