NMEA 2000 to NMEA 0183


Paul Osterberg
 

I have replaced all my instruments to Raymarine and also a new ACU 400 Autopilot computer, They all do communicate via NMEA 2000, and it work OK.  I can steer in wind vane mode or in track mode with the new ACU 400 computer.
I have my old Autohelm autopilot installed, and connected that one via NMEA 0183 to the Raymarine multi functional display/plotter, Now it can steer in Track mode i.e steer towards way point. More important is to steer according to wind angle. but do not understand how I get wind information from my NMEA 2000 back bone, I had hoped that the wind information should be communicated via my plotter who is connected to the backbone and show all kind of info from my NME 2000 instrument, and connected to the Autohelm via NMEA 0183.
Anyone know how to fix this?
Paul on SY Kerpa ASM#259


Germain Jean-Pierre
 

Hello Paul,

We have an ACP 400 with Lecombe & Schmidt hydraulic drive; we are very pleased as it is much smoother and steers the boat well through the a single P70 control.(I have a spare P70 if needed). A 3 way switch allows selection of Hyd/Elec or off.

All functions are avail through the P70 for both units.

GL.

JP Germain, SY Eleuthera, SM 007




On 20 Feb 2019, at 10:53, Paul Osterberg <osterberg.paul.l@...> wrote:

I have replaced all my instruments to Raymarine and also a new ACU 400 Autopilot computer, They all do communicate via NMEA 2000, and it work OK.  I can steer in wind vane mode or in track mode with the new ACU 400 computer.
I have my old Autohelm autopilot installed, and connected that one via NMEA 0183 to the Raymarine multi functional display/plotter, Now it can steer in Track mode i.e steer towards way point. More important is to steer according to wind angle. but do not understand how I get wind information from my NMEA 2000 back bone, I had hoped that the wind information should be communicated via my plotter who is connected to the backbone and show all kind of info from my NME 2000 instrument, and connected to the Autohelm via NMEA 0183.
Anyone know how to fix this?
Paul on SY Kerpa ASM#259


Bill Kinney <greatketch@...>
 

Paul,

At this point our boat is ALMOST fully switched over to NMEA2000. But like you, our  backup autopilot is an older model that only speaks NMEA0183. 

We use an Actisense NGW-1 to convert the data on the NMEA2000 bus to a format compatible with NMEA0183. It translates the data on the new bus for our computer, and our old autopilot. It has worked well for us. 

Bill Kinney
SM160, Harmonie
Georgetown, Bahamas


Cathy & Guillaume
 

Hi Paul,

In addition to the Actisense device, you can also check the Simrad AT10 for two way communication 0183 - 2000, a little less expensive (at least in Europe). I just bought it (with an additional Simnet - 2000 cable) and will install it on my next visit to our boat. This was recommended by Jose, from s/v Ipanema, and is working well for him.

Best,

Guillaume

s/v Carpathia III – SM2K #293


Paul Osterberg
 

Hello JP, 
I can'y say I'm very happy with my new ACU 400 unit, it works well going up wind but as soon the waves are behind of the beam, it over steer all the time, and I have sometimes to take over to hand steer, no not pleased at all. talked to a boat neighbor yesterday and he have similar problem. Therefor yesterday I installed my old unit, so now I can easily switch between the old and the new unit as well as between linear drive and rotary drive. be interested to see which one that perform the best. the only drawback with the old unit I do not get the wind info.
Paul SY Kerpa SM#259


Paul Osterberg
 

Thank you Bill I have to look into that solution I do not know how often I will use the old unit so have to judge the cost and effort for the need/usefulness.
Paul on SY Kerpa


Brent Cameron
 

Paul, it sounds like your autopilot gain and response settings are off.  I’m not familiar with your exact unit but most autopilots have settings for Wind Trim, Rudder Gain, Counter Rudder and Response.  They are basically just little programable logic controllers (PLC’s) that act to minimimize the difference between the input value (course, heading, wind angle, etc) and the set point. To do this, they NEED small pertubutions and then based on the size of the deviation, they apply a correction. For us, those perturbations are usually waves!  

Anyway, that correction takes three main forms. The most oblivious is the Rudder Gain. I’m really going to dumb it down (there are text books written on control algorithms) but you can think of gain like boosting the effect of the correction (i.e. how much rudder to use to get it back on course after the pertubution). Too little and it won’t work. Too much and you over correct and that can set up a nasty cycle of the boat wandering all over the place and never getting back on course. This isn’t exactly right but for your purposes, the analogy works. The second main variable is the Counter Rudder which you can think of as how big an opposite movement of the helm is required to stop the turning motion.  Too big, and the boat overshoots and wanders all over the place.  The balance between the Rudder Gain and Counter Rudder is crucial to goood course keeping. The two settings should be pretty close to each other and certainly no more than two settings apart.  If you were helming the boat, you wouldn’t wind the wheel from crank to crank to adjust for small deviations... you’d use the smallest adjustment you could, so again, the goal is to find the minimum setting that will get the boat back on course.  But it is also tied into the Response. 

For the Response, you can think of that as how many corrections per minute it uses to get the boat back on course. Think of it as if you were making a correction how often you’d want to wait to try the next one. The higher the Response the faster it will act but again it can be set too high so that the rudder is moving all the time which of course really runs down your battery but also causes the boat to hunt. If you watch a good pilot or helmsman, he/she won’t slavishly turn the wheel on every wave but rather averages out the boat’s course to minimize the steering but maintain heading. You want your autopilot to do that. In light conditions, you should knock the response way down to conserve power and reduce hunting but in frisky conditions and especially when steering on wind angle, you’ll need to run it up. A lot of people set it and leave it alone but unless your autopilot has auto response (I’ve seen that the B&G ones change the response based on boat speed which can be a crude approximation), you should adjust it for the conditions.  (The rudder gain and counter rudder are usually autoset during provisioning and then not played with much after that as they are really tied into how well the boat handles excepting if it changes as it gets more frisky). 

The wind trim function allows you to set the sensitivity when acting in wind mode. This is often over-looked but if you are struggling to keep your wind angle, try this rather than the response.  A high value results in the boat following every gust and shift which might be wanted during light conditions with flat water upwind or on downwind on spinnaker but you want a low value when the winds and waves come up on a reach. Most people just leave them at default but that doesn’t optimize your boat’s or your autopilot’s performance. 

Finally, a pet peeve of mine, is to really watch your boat’s Rudder Angle when on autopilot. These autopilots all have Rudder Angle displays but you can also see it by marking your wheel at top dead centre and noting when it is off. I used to be a commercial pilot and it drove me absolutely bonkers to watch other pilots flop on the autopilot and then sit there obliviously when the autopilot keeps adding trim as the plane changed speeds and conditions. It’s the same in our boats. When the wind changes, the sails become out of balance and if you’ve got much rudder on at all, it basically means you’re dragging a big brake in the water. It is literally screaming at you to adjust the sails!  A wee bit of rudder helps us keep the boat stable but that’s really a WEE bit. I hated flying with guys who gripped the wheel like a baseball bat because they couldn’t feel the airplane and they’d constantly overcontrol it and we’d be flinging ourselves across the skies. As a former instructor, I used to teach that you only needed to hold it by the tips of your fingers and feel the pressures. You can’t do that if the plane or boat is out of trim. Same for your autopilot. Get the boat in trim, and your rudder actions (and battery usage) will go WAY down. 

So, to net it out. Make a note of any settings before you change them so you can easily get back to them if needed. Next time there is no wind and you are motoring on a long passage with not much wind,  try playing with the Rudder Gain, Response and Counter Rudder settings (one at a time) while watching your wake. That will give you a really good idea of the effect of each. 

When setting Response, take it off autopilot and hand steer it. Note how often you are correcting it and then set the Response to match that (assuming that you aren’t one of those people who steers the boat from lock to lock on every wave). 

Finally, and most importantly, remember that the autopilot can only respond to HISTORY. It can’t predict what is going to happen, it just responds to what did happen. That’s YOUR job. Knowing how they work and when to mess with the settings is important to optimize your boat’s (and your autopilot’s) performance. 

Again, people that understand control theory are probably screaming under their breath about calculus and integrals but for the layperson, these analogies work. 


Brent Cameron, Future SM2K owner

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Brent Cameron

Future Super Maramu 2000 Owner & Amel Owner Registry Moderator

Oro-Medonte, Ontario, Canada


Paul Osterberg
 

Thank you Brent The  New unit does not have many settings one can do,
Respons level: Performance, Cruising or Leisure.
Rudder Damping 
And vessel typ 
I have tried to figure out how to set them but they do not make much difference, except for Respons level in leisure the course deviation seams to be less, I had guessed for the opposite
Paul
SY Kerpa SM#259




Bill Kinney <greatketch@...>
 

Brent,

I hereby nominate you to write the next generation of manuals for Navico (B&G/Simrad/Lawerence)

Your explanation of the settings and adjustment on an autopilot is about 3 orders of magnitude better than ANYTHING Navico has published in the last  10 years.

Bill Kinney
SM160, Harmonie
Georgetown, Bahamas


Brent Cameron
 

Hi Paul.  I had a look at the manual of the ACU 400 and you are right in that they have dumbed down the controls a bit to make it easier for the end user.  The Response level seems straightforward enough... performance would be when you want it to be highly responsive (i.e. acting faster) while Leisure would be when you don't need it to react that fast (so like what I had said above (higher Response = Performance, lower = Leisure).  I guess they felt that three levels was probably enough, I like to fidget a bit more than that but for the average person, I'm sure it's fine.  They still sort of have Rudder Gain and Counter Rudder but they've integrated it into the Boat Type, Rudder Limit and Hard Over Time/Drive Check functions.  If you have a rudder sensor, they can figure some of that out automagically it looks like (the Rudder Limits and Hard Over Time specifically).  Basically what they are doing is calculating the required gain settings from the responsiveness of the rudder and an approximation of the boat speed (sailboat or sailboat (slow turn) and rudder response times).  I would check to make sure that your boat is set properly for SAILBOAT or SAILBOAT (SLOW TURN) and that the Rudder Drive/Hard Over Times are set properly (HOT is only used if you don't have a rudder angle transducer as it can figure it out if you have one).  If you still find it is acting a bit slow, try changing the boat type up to Catamaran or slow powerboat as that's bumping the gain function.     I'm surprised that they don't have a Wind Trim function for the Evo units but I guess that they were having trouble with people not understanding how it overrides the gain/response of the regular settings.  You can have similar function but you'll need to boost the Response during changing conditions.  You'd think with all the electronics in these things that they'd give you MORE choices (even if they put it behind an "advanced settings" menu) rather than less.  Good luck!


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Brent Cameron

Future Super Maramu 2000 Owner & Amel Owner Registry Moderator

Oro-Medonte, Ontario, Canada


Brent Cameron
 

Thanks Bill.  Having a strong Physics/Calculus background plus being a pilot and then a process control designer when I was still young and smart made it easy for me to understand these things. I did spend quite a bit of time with Kent's (rather excellent IMHO) B&G/Simrad system and know what you mean about their manuals.  I think a lot of these manufacturers are in a tough spot... if they open up the control settings too much there are those of us who will fiddle with them and drive up their support costs when the boat is acting wildly but then if they dumb them down too much, they don't perform as they should.    


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Brent Cameron

Future Super Maramu 2000 Owner & Amel Owner Registry Moderator

Oro-Medonte, Ontario, Canada