How does the autopilot work?

[[163233]]

Another thought, Navionics advertise routing as a feature of the chart packs, does that mean they include software for that or is it just a compatibility flag for the plotter's routing?

In which case you might get a different route depending on which charts you're using as well...

 

[capnsensible]

I provided the link to show that they are called autopilots. It's not up for debate, if you go to Raymarine or B&G they list a bunch of autopilots, therefore I bought an autopilot because that's what they sell and therefore the thing I own is called an autopilot. Call it what you like, but the people making them call them this so that's their actual name as far as I'm concerned.

If I Google autohelm it returns a bunch of tiller based solutions which are actually called Tiller Pilots so from the look of it the term helm is the only one not used by anyone in the industry!

Edit to add - my autopilot is nowhere near the helm and doesn't drive the helm ?

Our Hydrovane is generally referred to as 'Robbie the rudder'. A couple we met in Mindelo some years ago called theirs 'Carly ' as in Simon, you're so....vain.

 

[lustyd]

My brother called his tiller pilot Fred after our Granddad. It was slightly broken so although it generally started in a straight line it would eventually veer off as if drunk and cause mayhem ? My new autopilot is George, his middle name, but so far none of the shenanigans!

 

[DJE]

My brother called his tiller pilot Fred after our Granddad. It was slightly broken so although it generally started in a straight line it would eventually veer off as if drunk and cause mayhem ? My new autopilot is George, his middle name, but so far none of the shenanigans!

I did once know a crew who called their autopilot "Pontius"

 

[DJE]

I'm more likely to be setting it to steer a course that takes me up tide a bit, so there's something in hand if the wind changes.
There are several ways of getting from A to B with a GPS etc, no one of them is always better than any other.
It can be good to know what options are available.

It was very handy approaching Portland Bill when the tidal offset angle steadily increased from 5 degrees to about 25 degrees but the pilot kept us on track.

 

[westhinder]

Yes, setting up a route on a chartplotter can be very helpful - eg sailing the Swedish rocky leads.
But that doesn’t mean you need to get the autopilot to alter course based on the route waypoints.

Manual change of course better:
- 5 seconds per waypoint to manually look around the alter course ain’t a big overhead, also
- it is generally better to set waypoints a safe distance off dangers - but if conditions benign and not busy, we will often curve the corner gently in multiple small steps, and often taking slight short cuts that are perfectly safe done under manual control but not under automatic control

This is exactly the way it works for me too.
The original owner of the boat decided not to link autopilot and plotter because he was convinced any changes in course had to be deliberate and made consciously by the watchkeeper. I agree with this philosophy and have never felt the need to integrate the two.

 

[Buck Turgidson]

Anyone using a wind vane steering system or an autopilot in wind mode has decided course changes are ok without acknowledgement. I strap my tiller and let her make her own way to windward. It's just a case of monitoring. You can of course set alarms for heading or wind changes but I've got enough alarms already.

 

[dunedin]

Not sure if this is still relevant, but I've just noticed this option in my B&G's menus:

Your post seems to have been ignored, perhaps because it is the answer ;-)

But confirms what I assumed, it will depend on chart plotter make, model and software version. Clearly some B&G plotters now have this option.
Haven’t seen that option on either of our Raymarine plotters, but may exist on Lighthouse3 software which is not supported on either of our plotters.
Again why it would be useful in real world is a mystery, as even doing cross Atlantic we were using weather routing to select course to steer. Steering a Great Circle course we would have got there at least 2 days later, and some of the race fleet sailed nearly 30% more than the GC course to get their best angles.

 

[Buck Turgidson]

Your post seems to have been ignored, perhaps because it is the answer ;-)

But confirms what I assumed, it will depend on chart plotter make, model and software version. Clearly some B&G plotters now have this option.
Haven’t seen that option on either of our Raymarine plotters, but may exist on Lighthouse3 software which is not supported on either of our plotters.
Again why it would be useful in real world is a mystery, as even doing cross Atlantic we were using weather routing to select course to steer. Steering a Great Circle course we would have got there at least 2 days later, and some of the race fleet sailed nearly 30% more than the GC course to get their best angles.

It's the answer to a different question.
The OP was how does it do it. The answer is cross track error correction.

 

[prv]

My new autopilot is George, his middle name

Both of ours have also been called George; I'm told it's an RAF tradition.

Pete

 

[AntarcticPilot]

Both of ours have also been called George; I'm told it's an RAF tradition.

Pete

The autopilot on a submersible piloted by Dan Dare on Venus was also called George!

 

[ip485]

I provided the link to show that they are called autopilots. It's not up for debate, if you go to Raymarine or B&G they list a bunch of autopilots, therefore I bought an autopilot because that's what they sell and therefore the thing I own is called an autopilot. Call it what you like, but the people making them call them this so that's their actual name as far as I'm concerned.

If I Google autohelm it returns a bunch of tiller based solutions which are actually called Tiller Pilots so from the look of it the term helm is the only one not used by anyone in the industry!

Edit to add - my autopilot is nowhere near the helm and doesn't drive the helm

I like it!

However, in all seriousness I dont know which Google you are using, but mine gives lots of references to autohelm as well. I rather get the impression it all started with autohelms, and gradually autopilot drifted in? Perhaps as someone else said Raymarine copyrighted, but I am surprised it could have been copyrighted.

Why do you keep the dog in the cockpit - the dog is trained to bite the pilot if he attempts to take over control.

Mine is a Raymarine autopilot (helm), I have a Garmin one in the rubber band job. I am guessing the yacht ones have improved since my ST6001 which I find quite clunky, and sometimes I am minded to change it if the latest are truly better. It has the habit of disconnecting occasionally for no apparent reason (not because of too much load on the helm) and takes time to set up to steer a course with a lot of w/p's, but it is pretty good. The standard of the aircraft ones is truly amazing these days. You can truly engage at 600 feet and it will navigate a dozen or more w/ps, position on the approach and take the aircraft down to minima (and below were it legal). All very impressive as to what is possible.

 

[TernVI]

Coincidentally, just found the manual for my Magellan 320.
This dates back to about 1998 I think.
It still works, and gets the time and date right unlike a later Garmin I have.

RMBGeneric Navigation Information (immediately follows RMC) 1 2 3 4 5 6 7 8 9 10 11 12 13 14RMB,A,X.XX,a,c--c,c--c,1111.11,a,yyyyy.yy,a,x.x,x.x,x.x,A *hh1 Data Status (A = valid, V = invalid)2-3 XTE, naut. miles and direction to steer (L or R) [If XTEexceeds 9.99 NM, display 9.99 in field 2.]4 Origin waypoint ID5 Destination waypoint ID6-7 Destination Waypoint Latitude (N or S)8-9 Destination Waypoint Longitude (E or W)10 Range naut. miles, present fix to destination waypointGreat Circle. [If range exceeds 999.9 nm, display 999.9.]11 Bearing, True, Great Circle, Present fix to dest. waypoint12 Closing velocity to destination, knots13 Arrival (OR’ed arrival circle and crossing of line which isperpendicular to the course line and which passes throughthe destination waypoint.)14 CHECKSUM (Mandatory in this sentence.

So the default is great circle. That's on a little handheld running off a couple of AAs, so the computation can't be anything that would load a modern plotter.

The little box claims to output all the autopilot information, including 'heading to steer'.
I don't immediately see how it can know what heading to steer without a compass input?
If your xte is due to tide or leeway, surely you need some real heading info, as distinct from COG, to generate what you or I would call a 'course to steer'?
Or does it just make guesses along the lines of ' you're off to the right, left 'and down a bit!'?

 

[TernVI]

I like it!

However, in all seriousness I dont know which Google you are using, but mine gives lots of references to autohelm as well. I rather get the impression it all started with autohelms, and gradually autopilot drifted in? Perhaps as someone else said Raymarine copyrighted, but I am surprised it could have been copyrighted.

Back in the late 80s, the 'autohelm' brand of gadgets were made by a company called 'Nautech'. I'm fairly sure of that.
I think the company was sold and became 'Autohelm LTD' or similar.
Then sold again to 'Raytheon', a large US tech conglomerate who also made missiles and stuff.
Raytheon hived off several divisions including Raymarine and Raywire.
Raymarine been sold/taken over at least once since.

The 'autohelm' (trade) name predates Raymarine by quite a few years. I think it had been around a fair while when I first knew them in the 80s?
I don't know what other electronic steering for yachts was around in those days, or what small commercial stuff used.
The 60s jargon was more 'self steering' and 'gyro'?

Maybe in the early days, Autohelm cornered the market and the trade name was used generically like 'Hoover' or 'Jetski'?

Remember that there was not much racing where electric steering was allowed, so it was a much smaller market?

 

[ip485]

Tern this is a very interesting history, thank you. It is interesting how names change and evolve. I suppose as with aviation it was logical that it should respectively be autopilot and autohelm, although I guess autoskipper might just have been possible. Back in my racing days the skipper was very rarely on the helm mind you. With the best and latest autohelms it would be interesting to see how they fair against a good helsmen over a straight course and without any tacking, just responding to the wind and waves. I have a sneeky feeling some would do pretty well, but not as well as a really good helm who would have the advantage of anticipation seeing both the gusts on the water before they arrived and the swell in the same way.

 

[TernVI]

Some of the DIY vane steering gears were known to be very quick upwind compared to human helms.
I wonder if 'production' gears sacrificed performance for robustness?
Or whether the DIYers in the 60s tuned their gears to the boats, maybe unknowingly, experimenting a lot.

I have an AYRS book on self steering. From the 60s.There is basically no maths in it, which surprises me.
It's a feedback control system, lots of people in the 60s worked with the maths of all that. Proper maths, calculus and funny symbols, none of your 'beat it to death with a spreadsheet' crap.

 

[mjcoon]

Some of the DIY vane steering gears were known to be very quick upwind compared to human helms.
I wonder if 'production' gears sacrificed performance for robustness?
Or whether the DIYers in the 60s tuned their gears to the boats, maybe unknowingly, experimenting a lot.

I have an AYRS book on self steering. From the 60s.There is basically no maths in it, which surprises me.
It's a feedback control system, lots of people in the 60s worked with the maths of all that. Proper maths, calculus and funny symbols, none of your 'beat it to death with a spreadsheet' crap.

I recommend "Helmsmen and Heroes: Control theory as a key to past and future" by Prof William Gosling. (Which I should put on my list to re-read...)

 

[johnalison]

This is exactly the way it works for me too.
The original owner of the boat decided not to link autopilot and plotter because he was convinced any changes in course had to be deliberate and made consciously by the watchkeeper. I agree with this philosophy and have never felt the need to integrate the two.

Mine came linked as part of the system, not having had this facility on my previous boat. The ability to follow a track is not something I need to use regularly but it can be a godsend on a long coastal motoring leg. Setting the boat to follow a track from, say, Dungeness to Beachy Head leaves the helm free to indulge his fancies as he only needs to keep half an eye on the Xtrack error. An alarm can be set if needed, and there is no significant tidal offset. It might be worth looking out for pot markers too, and I reckon that anything that makes a passage easier improves watch-keeping.

 

[john_morris_uk]

I think your batteries will run out long before you discover whether doing a great circle route or not

Actually, I am still struggling to see any valid reason to integrate my plotters to the autopilot. Whilst I am generally a gadget person, and lots of on board integration, I have that option disabled.
Unless aiming to send boat from one marina to another unattended whilst I drive the car there, I always want to set the autopilot on course, and ALWAYS want to decide when to change to next waypoint (just to give visual check that safe to alter course). Takes less than 5 seconds to alter course manually, and much safer.

I agree 99% of the time. Cross more than one tide, it's rarely fastest just to chase the XTE. Down tide, or up tide, it might be best - although up tide, I'll be looking for eddies as we pass headlands and comparing SOG and COG and speed through the water.

Our Hydrovane is generally referred to as 'Robbie the rudder'. A couple we met in Mindelo some years ago called theirs 'Carly ' as in Simon, you're so....vain.

Harry the Hydrovane - surely?

And don't call me Shirley ever again.

 

[johnalison]

I agree 99% of the time. Cross more than one tide, it's rarely fastest just to chase the XTE. Down tide, or up tide, it might be best - although up tide, I'll be looking for eddies as we pass headlands and comparing SOG and COG and speed through the water.

Maybe for you, but many of our cruises involved long legs without a cross tide. From Essex to the West Country, or around the Southern Baltic were our hunting-grounds for many years. There is no law against following a track across the Channel. It’s just a lousy way of doing it.