2022-09-20, 08:29 AM
(This post was last modified: 2022-09-20, 08:30 AM by seandepagnier.)
there is another javascript autopilot that uses an old android phone: https://github.com/yOyOeK1/ykpilot
I did not decide to take this path with pypilot:
1) the inertial sensors vary from phone to phone. There are a lot of marginal inertial sensors that dont give as good performance. I am not sure if you can access and read the inertial data directly with the same low latency either, but its probably possible.
2) I did some simple ping tests to an android phone and the latency is ok 95% of the time, but often enough 50ms which is borderline for degrading autopilot performance especially on light or fast boats. I think it can do much worse in theory at times, a lag of 200ms could cause my boat to go at least 5 degrees off course at speed which just means less efficient sailing and more power for the motor to correct. I would consider this likely usable but not desirable. The wifi link has an unreliable nature.
3) This may possible to completely solve, but I am not sure about how to make the critical processes have realtime priority on android.
raspberry pi was available when I started pypilot and cheap enough that the above issues did not seem worth the trouble. In any case, python can run on android so it is potentially viable.
As for battery size, it depends on the boat and so forth. I typically average 3-6 watts on the motor steering in most conditions for the motor, but other boats can consume much much more power to hold course. To power for 24 hours a day even in overcast weather you need to multiply your load (in this case say 12 watts average if you turn the screen off a lot) by 40, so 480 watts of solar would allow a minimal battery size of 200 watt hours to ensure continuous 24 hour operation even in winter in my area. You can get away with much much less solar if you expect some direct sun or better solar conditions and/or a larger battery capacity.
On my boat I have about 250watt hour main battery now, plus up to 300 watt solar (200 normally stored below but panels can be deployed in overcast if needed) I also have a tow generator which can produce 30-40 watts all the time under sail, so there is really not a question of power.
I did not decide to take this path with pypilot:
1) the inertial sensors vary from phone to phone. There are a lot of marginal inertial sensors that dont give as good performance. I am not sure if you can access and read the inertial data directly with the same low latency either, but its probably possible.
2) I did some simple ping tests to an android phone and the latency is ok 95% of the time, but often enough 50ms which is borderline for degrading autopilot performance especially on light or fast boats. I think it can do much worse in theory at times, a lag of 200ms could cause my boat to go at least 5 degrees off course at speed which just means less efficient sailing and more power for the motor to correct. I would consider this likely usable but not desirable. The wifi link has an unreliable nature.
3) This may possible to completely solve, but I am not sure about how to make the critical processes have realtime priority on android.
raspberry pi was available when I started pypilot and cheap enough that the above issues did not seem worth the trouble. In any case, python can run on android so it is potentially viable.
As for battery size, it depends on the boat and so forth. I typically average 3-6 watts on the motor steering in most conditions for the motor, but other boats can consume much much more power to hold course. To power for 24 hours a day even in overcast weather you need to multiply your load (in this case say 12 watts average if you turn the screen off a lot) by 40, so 480 watts of solar would allow a minimal battery size of 200 watt hours to ensure continuous 24 hour operation even in winter in my area. You can get away with much much less solar if you expect some direct sun or better solar conditions and/or a larger battery capacity.
On my boat I have about 250watt hour main battery now, plus up to 300 watt solar (200 normally stored below but panels can be deployed in overcast if needed) I also have a tow generator which can produce 30-40 watts all the time under sail, so there is really not a question of power.