Operation

This page describes operation of the PowerTroll with the steer10 operational software installed and configured as described elsewhere.

Calibration

Before you start using your PowerTroll in earnest you need to calibrate the compass(s). This is necessary because the geomagnetic characteristics at your location are different from those at mine. The procedure to calibrate the compasses depends on what compass arrangement you installed. There are three choices:

  1. You installed only a Devantech horizontal compass (or wish to calibrate that compass independent of your installed vertical compass).
    1. With the PowerTroll installed in your boat and connected to the Electro-Steer switches but not powered on or connected to the Electro-Steer relays, move switches #3 and #4 to the on position (toward the large blue connecters).  These switches are called 'JustCalibrate' and 'Just2D' respectively. Leave the PowerTroll case open so you can observe the LED's.
    2. Plug the PowerTroll into the 12v source. You should observe the red led blink 5 times.
    3. Start the boat in slow circles (either direction). The boat should take at least 30 seconds to go all the way around.
    4. Observing a real compass, each time you reach N, S, E, or W press one Electro-Steer button (either) for a moment. Go around at least twice, so that you have pressed a button at least twice for each of N, S, E, and W. When this is complete press both Electro-Steer buttons at the same time for a moment. You should observe the green led blink 5 times.
    5. Unplug the PowerTroll from the 12v source. Move switches #3 and #4 back to the off position (away from the large blue connecters).

  2. You installed only a Mindsensor horizontal compass (or wish to calibrate that compass independent of your installed vertical compass).
    1. With the PowerTroll installed in your boat and connected to the Electro-Steer switches but not powered on or connected to the Electro-Steer relays, move switches #3 and #4 to the on position (toward the large blue connecters).  Leave the PowerTroll case open so you can observe the LED's.
    2. Plug the PowerTroll into the 12v source. You should observe the red led blink 5 times.
    3. Start the boat in slow circles (either direction). The boat should take at least 30 seconds to go all the way around.
    4. Unlike the Devantech compass, the Mindsensor does not require you to indicate direction. Simply do a few slow circles. When this is complete press both Electro-Steer buttons at the same time for a moment. You should observe the green led blink 5 times.
    5. Unplug the PowerTroll from the 12v source. Move switches #3 and #4 back to the off position (away from the large blue connecters).

  3. You installed both a horizontal and vertical compass with associated FPU and accelerometer. Note that if desired you may perform one of the above procedures to standalone calibrate your horizontal compass but that is not necessary for this tilt compensated calibration to be effective.
    1. With the PowerTroll installed in your boat and connected to the Electro-Steer switches but not powered on or connected to the Electro-Steer relays, move switch #4 to the off position (away from the large blue connecters) and move switch #3 to the on position (toward the large blue connecters).  Leave the PowerTroll case open so you can observe the LED's.
    2. Plug the PowerTroll into the 12v source. You should observe the red led blink 5 times.
    3. Start the boat in slow circles (either direction). The boat should take at least 30 seconds to go all the way around.
    4. Simply do a few slow circles. When this is complete press both Electro-Steer buttons at the same time for a moment. You should observe the green led blink 5 times.
    5. Unplug the PowerTroll from the 12v source. Move switch #3 to the off position (away from the large blue connecters).

How to Use it

When the Controller is off it is effectively out of the circuit so the Electro-Steer switches work exactly like they would if the autopilot was not installed. To wit: Press one of the wired remote control buttons and the outboard is steered one direction (while the button is down); Press the other button and it is steered the other way. With both switches unpressed the outboard stays in it's last position. Operation with both switches depressed is undefined.

When the Controller is on the Controller reads the Electro-Steer switches and controls the Electro-Steer relays.

A manual control mode is provided (default at power on) that simulates power off control, in this mode the switches directly change the positioning of the outboard. To wit: Press one of the wired remote control buttons and the outboard is steered one direction; Press the other button and it is steered the other way. With both switches unpressed the outboard stays in it's last position. Depressing both switches at once causes the controller to switch from manual mode to automatic mode with the current heading the desired heading. The controller acknowledges this mode change by a double 'rattle' of the Electro-Steer Relays - sounds like 'ticka-ticka, ticka-ticka'.

The automatic control mode enables the Controller to use the compass to control the Electro-Steer to maintain the desired heading; in this mode the switches change the desired heading and the Controller steers to that new heading and then holds that heading. Switch operation is as follows: Press one of the wired remote control buttons and the desired heading is changed to port by 10 degrees per second; Press the other button and the desired heading is changed to starboard by 10 degrees per second. With both switches unpressed the desired heading stays the same. Depressing both switches at once causes the controller to switch from automatic mode back to manual mode. The controller acknowledges this mode change by a single 'rattle' of the Electro-Steer Relays - sounds like 'ticka-ticka'.


Tuning PID constants

Boats vary enormously in how they respond to the helm. A long deep-V hull with little canvas to catch the wind probably has so much directional stability that something like PowerTroll is unnecessary. Contrast that with an inflatable, round, flat bottom life raft - can you imagine trying to make that go any particular direction? Most boats fall between these extremes, often because their cabins or canvas acts like a sail and let the wind push them every which way.

PowerTroll uses a PID algorithm to keep on heading, and this algorithm is effected by tuning constants you can change to improve how PowerTroll works with your boat. PID is short for "proportional", "integral", and "derivative".

Some pre-tuning is done when you assemble your PowerTroll.  That will probably result in a condition I'd call 'barely tuned'. As over time you observe the way your PowerTroll steers your boat you will probably want to make further adjustments. That is done using the wireless remote or the p2test9 and p2test10 programs as described on the EEProm page.

Before getting into that let's think about how you try to manually hold a heading with respect to wind direction:

Going downwind, or on a downwind quarter, is easy. On many boats you can find a 'sweet spot' that will hold a heading for long periods. You can run the trolling motor as slow as you like.

A crosswind or somewhat upwind quarter is harder. You must have enough power to turn that far up into the wind. But sometimes you can still find a sweet spot, balancing the wind with the trolling motor power and the helm turning up into it. If you need to troll more slowly than engine power allows you can use a sea anchor to reduce you speed through the water without reducing steering efficiency.

Going more or less straight into the wind is much more difficult. There is no sweet spot to find. You must have enough power to not only turn directly into the wind, but to do so briskly. Holding the heading involves achieving the heading then having the wind blow you across it the other way, so you have to turn back, achieve the heading from that direction, and then have the wind blow you across it the other way. And so on. A sea anchor is very useful in this case not only because it reduces what would be too fast a troll, but because it will tend to stabilize the heading swings.

A 'barely tuned' PowerTroll [one using the default settings] can usually handle the downwind quarter pretty acceptably. It should find the sweet spot within a few minutes. It will work on a crosswind heading but may swing quite a bit, and may not ever find a sweet spot. It may not work going straight into the wind, especially without a sea anchor

A 'well tuned' PowerTroll can handle both the downwind quarter and crosswind situation well. It should find the sweet spot within a few minutes and subsequently make only occasional minor corrections. It will work straight into the wind but some swings may be large if no sea anchor is used - but even with those large swings heading maintenance should be sufficient to keep you lines from getting tangled. Realistically you would want a sea anchor if only to control your speed!

How do you get the PowerTroll tuned?

First you need to establish the power level you are tuning to - how effective will the helm be. On a day with the wind as brisk as you think you'd like to fish in, find a trolling motor power level that is able to briskly turn the boat all the way up into the wind when the electro-steer is fully deflected to port, and to starboard. If this power level results in an unacceptably fast trolling speed you should experiment with a sea anchor to ensure you can get the speed you seek with the power setting. 

Use this speed for all further tuning. If you decided you would use a sea anchor while fishing you should use it while tuning.

Start with PID_I at 100, PID_D at 0, and PID_P at 5.

Begin by tuning PID_P. PID_P influences how much helm to apply based on how far off heading. PID_P dominates when you are far off heading.

In manual mode establish a heading straight into the wind, then go to autosteer. The boat should start swinging back and forth over you heading. Use a compass to observe and record the size and duration of the swings. Your recorded data may look something like this:

Increase the value of PID_P by 5 and repeat the above procedure. This time you data might look like

Continue increasing the value of PID_P and recording what happens. Each time the size of the swings should decrease, and the time between swings should also decrease. But at some point the change will no longer decrease the swings (or it might even make them bigger). When that happens back off the the prior value..

Now tune PID_D. PID_D works counter to PID_P to apply helm slowing down swing. PID_D dominates when you are nearly on heading, so as you are swinging back to heading and getting close to it PID_D applies helm the other way to slow the swing so you stop at the right place instead of overshooting.

Start with PID_D at 1 As before in manual mode establish a heading straight into the wind, then go to autosteer. The boat should start swinging back and forth over you heading. Use a compass to observe and record the size and duration of the swings. Your recorded data may look something like this:

Increase the value of PID_D by 1 (a little goes a long way!) and repeat the above procedure.

Continue increasing the value of PID_D and recording what happens. At some point you will stop seeing symmetric swings back and forth over the desired heading and instead see small swings before you get to the heading or after. That's the time to stop. Your final result might look like

Or, enhancing the chart a bit

Your controller should now be well tuned to these conditions. When the wind dies down you would reduce power to keep trolling speed and this is exactly the change the would be necessary to keep the powertroll tuned. And the same applies going crosswind or downwind.

If you want to troll a little faster you could decrease PID_P slightly; to troll a little slower you could increase PID_P slightly. Usually this is not necessary as the powertroll still works even if not completely tuned.

Are these optimal settings? Probably not. But I'm interested in fishing - not messing with the controller - and this simple technique results in settings that keep the boat going reasonably straight most of the time.

 

Sea Anchor for Trolling

Sea anchor's don't have to be real involved. I use an extra 5 gallon paint bucket on a rope attached to the stern. Cheap, easy to deploy, easy to retrieve, extra storage when I'm not using it as a sea anchor!

 


What can go wrong?


Copyright © Mike Noel, 2005, 2006; 2007 last updated 5/20/2007