It’s been a while since I had time to work on my Ardusailboat. However, I wanted to share a bit that is relevant about wind sensing on the sailboats.
I think the cheapest way to get accurate wind estimation is by using a cheap magnetic rotary encoder and a Modern Devices hot wire anemometer, but I am still developing the 3D printed wind vane to ensure reliable operation on a boat. An off-the shelf solution is more likely to work and is more expensive.
I wrote up a derivation of the out-of-plane wind vane measurement you described, Ari. Windvane_Eq_Derivation.pdf (179.1 KB)
With my classmates Jane and Alex, I experimented with persistent-state wind estimation via UKF or EKF (video here). I think that a simple low-pass filter is still the best way to go.
The wind estimation in the code currently estimates true wind without storing the direct wind vane measurement, then subtracts off the AHRS yaw to determine the apparent wind direction for trimming the sails. While this works very well, it may be technically better to pipe the wind vane output directly to the trim PID so the sail directly utilizes the angle of attack reported by the sensor.
I spoke to an engineer at an unnamed major high-performance catamaran racing program who confirmed that the industry standard algorithm for true-wind estimation does the following:
Applies the trigonometric correction from heel due to the windvane plane being misaligned with the plane of the ocean
Subtracts the wind vector induced by the swing rate of the mast (roll, pitch, yaw rate).
Subtracts the boat velocity vector to get true wind.
The engineer also recommended positioning wind instruments well forward and above the top of the mast to minimize updraft. Additionally, an exponential correction can be applied to determine a standardized wind speed at an altitude of 10m, which is above the boundary layer.
Anyway, I wish you the best, Ari. While the above considerations are interesting, I probably won’t suggest any major changes to Ardupilot because it seems to work quite well. Thank you for your work, Peter.
Thank you for your note, Tim. It is encouraging to see a new generation of engineers coming up to replace us geezers. Very nice presentation.
I’m not looking to change any code in Rover, and certainly not asking anyone else to. I’m not even sure I’m going to use Rover with this boat. At this stage, all I want is the equivalent of a wind instrument on a full-size boat, with all the error such instruments include. I imagine that if I use a NMEA 0183 vane like @iampete describes, I can feed the serial into my FrSky RX and have a Lua script that displays the raw angles on my Taranis.
Another question: what are y’all using to get electrical signals below decks? Are there reliable watertight connectors you can recommend? Right now, I have wires going though the deck and I caulk around them. It’s a simple solution that works with the two servos I have now, but as I start to run additional wires (wind sensor, antennas) down from the mast, I want a more flexible solution.
I’m not much help here I’m afraid, wires through the deck and caulk (or hot glue) is my my current solution. The main obstacle on my smaller boats is having a big enough flat spot on the hull for a proper waterproof bulkhead connector.
My thinking is to make as few holes on deck as possible.
I was lucky on my Laser, there is only one hole, that’s were the original antenna would stick up. The hole is more a moulded tube on the plastic deck sticking up some 1-2 cm. I was able to squeeze a thin antenna cable, a rj45 LAN cable and a 5v wire for a camera in the stern.
The lan cable supports a NMEA wind instrument, an external compass, a motor throttle and a servo control of a wing sail.
I stuck all cables through an earphone rubber part on the top. Never had any problem with water inside.
The pictures of wind instruments in you post, that would be very useful to have in a GCS when sailing remote.
Do you know of any ground control sw currently have it?
I am not aware of any, no. If you’re willing to pay $500 for one of the Raymarines in the photo, I’m sure you can get NMEA out of your GCS and hook the physical display to that :=)
I’m thinking about writing a Lua script for OpenTX. Similar idea to yaapu telemetry, but of course much simpler. What radio TX do you use?
Hi Ari,
Its the same model as @iampete using. It was a very new model at the time we got excited
If you read more on that link they have other models with bluetooth so no need to put wires through deck
I think they also have a model with a compass in it.
Stand alone wind instrument: Cool idea!
My TX is a Walkera Devo10, flashed with Deviation open source firmware https://deviationtx.com
It is an exciting product. I have a physical, rotating windex on the sail now. Being able to see it (if the boat is close enough) if very helpful. I Hate to lose that.
I suppose you could build one out of a servo, really :=)
Maybe some more details on the TX thing…
The tx is just used to generate PPM signals the the RFD900x link for telemetry and PPM.
So all data comes nicely to the RFD unit and then via Bluetooth to the GCS.
Come to think of it, the NMEA link to calypso instruments have several third party software that can display the data like your picture. But I have no idea how to get the data to those softwares…
There are phone and PC apps for full-size boats that can read in NMEA data and serve as virtual displays. http://opencpn.org/ is a good place to start down that rabit hole.
Or get two RS232-to-TTL inverters and: vane<->MAX232<->RFD900<-ether->RFD900<->MAX232<->WindInstrument.
Oh, thanks Ari, this is a bit over my head
But I will research it.
Yes, I know what you mean, sailing with a normal sail you have one enormous view of where the wind is coming from and doing to the boat, but with your fixed type of wing you have no idea, very similar to the Wing sail rig on my Laser. Very different animal and really need some instrument to sail it.
Hi All, just starting the journey on Sailboat. I’m looking at an endurance offshore project and have everything I need but cannot get my head around the wind sensor. This boat will be in one of the worst areas of ocean in the world and I fully expect it to be rolled and smashed by the tops of waves. As yet, I have not found a wind sensor that is waterproof and which could withstand a roll.
I read in the first post about the ultrasonic sensor that it was was not waterproof. If it is waterproof, that’s perfect.
I am pretty across all things NMEA, I have built and raced ocean racing yachts for most of my life. While the sensor on top of a mast would be impervious to rain and wind driven spray, I have never seen one survive a yacht rolling over. This is more a factor that the mast didn’t survive.
If the ultrasonic one can handle immersion, I will order that one.
As I say if you can find a better one that is not supported by the code I can look at adding it in. For such a project you definitely need the right thing. Those 3D ones from gill instruments look very nice, I believe that is what SailDrone uses.
I contacted www.r-p-r.co.uk who supply the LCJ Captuers CV7 anemometers in the UK. They confirmed with the manufacturer that the CV7-OEM module (100g) is IP67 rated. Their UK retail price for the CV7 is nearly the same as the Calypso wired model, but I think you may get the Calypso for less from Europe.
