First time post - I've never had or been on a boat with an autopilot, so please bare with me. I've been searching the Internet, but I'm not using the right key words so far. If you have a reference link or could suggest a set of key words or if you might take a stab at explaining... I'd really appreciate it.
I've seen pictures of tiller pilots, wheel pilots and on larger boats where it's built-in under the deck. I can fathom how they work in the very simple case of smooth water and a constant boat speed. I assume they simply follow a course and if the boat veers off the course the pilot simple moves the rudder to compensate. I can also see a little more advanced version would know its GPS coordinates and determine the path to a GPS waypoint and steer that course.
I've recently discovered OpenCPN, downloaded and ran some charts for my area on a laptop and then on a RaspPi 4. Then I discovered OpenPlotter and have been reading about OpenPlotter, PyPilot and the required hardware. I thought I had a pretty good handle on the workings until I saw that the MacArthur HAT indicated it had accelerometers and would feed heel and trim to the calculations for the auto pilot. Therefore in the more complicated situations where there are waves coming in from multiple directions and different periods, and further on a sailboat with heel and variable heel with gusts, that the accelerometers would be funneling tons of data to the computer.
In my simplistic mind, I would have thought that the autopilot would simply fix the rudder and as the boat veers going up a wave and then veers in the opposite direction going down the wave, that the average would still basically be on the same direction. That the autopilot would only adjust for trends too far off the desired direction. That it would seem (especially on a sailboat with limited power storage) it would be best to not be constantly driving the piston back and forth for every wave. But... now, I'm guessing, it is desirable (for some reason???) to move the rudder dynamically with every wave.
What I'd like to learn about:
Thank you for any suggestions of where to find my answers or explaining if you are willing to help reduce my ignorance.
I've seen pictures of tiller pilots, wheel pilots and on larger boats where it's built-in under the deck. I can fathom how they work in the very simple case of smooth water and a constant boat speed. I assume they simply follow a course and if the boat veers off the course the pilot simple moves the rudder to compensate. I can also see a little more advanced version would know its GPS coordinates and determine the path to a GPS waypoint and steer that course.
I've recently discovered OpenCPN, downloaded and ran some charts for my area on a laptop and then on a RaspPi 4. Then I discovered OpenPlotter and have been reading about OpenPlotter, PyPilot and the required hardware. I thought I had a pretty good handle on the workings until I saw that the MacArthur HAT indicated it had accelerometers and would feed heel and trim to the calculations for the auto pilot. Therefore in the more complicated situations where there are waves coming in from multiple directions and different periods, and further on a sailboat with heel and variable heel with gusts, that the accelerometers would be funneling tons of data to the computer.
In my simplistic mind, I would have thought that the autopilot would simply fix the rudder and as the boat veers going up a wave and then veers in the opposite direction going down the wave, that the average would still basically be on the same direction. That the autopilot would only adjust for trends too far off the desired direction. That it would seem (especially on a sailboat with limited power storage) it would be best to not be constantly driving the piston back and forth for every wave. But... now, I'm guessing, it is desirable (for some reason???) to move the rudder dynamically with every wave.
What I'd like to learn about:
- What is the desirable response of the rudder to this accelerometer data and why?
- What piece of software is using the accelerometer and determining the rudder angle (OpenCPN, PyPilot, code in MaArthur HAT, code in the tiller pilot)?
- Is it simply using some kind of PID (Proportional–integral–derivative) algorithm or is it using something more AI (Artificial Intelligence) like to predict the sea state and what to do with the rudder?
- In simple AutoPilots like Raymarine St2000 Tiller Pilot, do they do all these calculations internally or do they do some simplistic subset?
- Does PyPilot send NMEA messages to a Tiller Pilot or does it control the motor driver directly?
Thank you for any suggestions of where to find my answers or explaining if you are willing to help reduce my ignorance.