Parameters guide

[DamienVT]

Hello,

I tried to use openrowingmonitor but I need some help to adapt parameters.
I take temporarily the Raspberry Pi 3 of my arcade cabinet to test before to purchase a new one for my rowing machine.
I think that a Pi Zero W should be enough for the purpose.
So, my rowing machine is a DKN R-320 (https://www.dknstore.com/rameurs/973-rameur-r-320-5412002204600.html).
I followed the detailed Set up of Open Rowing Monitor instruction and use the original configuration.
When I do 10 stroke, I have 20 on the web interface.

I tried to modify the number of impulse per revolution on RowingEngine.js.
But I did not see any difference.
What should I modify ?
In my case, it's an air flywheel, not a liquid or a massive.

How to stop a workout ?
Is it possible to add a button in the web interface to shutdown properly the Raspberry ?

Last question, where can I see debug or logfile ?

Thank you for your reply.
Regards.
Damien

[laberning]

Hi Damien,

great that you tried the Open Rowing Monitor for your Rowing Machine! Yes, you are absolutely right - the Pi Zero W could be a good fit with this project. So far I don't own one, but let me know if this project runs with it and I will add it to the documentation.

If the stroke rate is off that probably means that the stroke phases (drive and recovery) are not detected correctly in your case. To be honest I expected that this detection currently might not work reliably with all machines, since so far it is not very robust against imprecise measurements. We could have a look at a raw recording of the flywheel measurements to see what is going on there.
For this, uncomment this line in app/server.js (change the filename to something matching your recording).

// fs.appendFile('recordings/wrx700_2magnets_long.csv', `${dataPoint}\n`, (err) => { if (err) log.error(err) })

Afterwards start the application and do ten even rowing strokes. Stop the application again (ctrl + c) and then send me that csv-file.

To start the application (and also to see the logs) you could first stop the system service sudo systemctl stop openrowingmonitor and then just start it temporarily via ssh: cd /opt/openrowingmonitor and then sudo npm start. To see more log output, change the log level in app/config.js.

The parameters that you'll have to modify are omegaDotDivOmegaSquare , jMoment and numOfImpulsesPerRevolution, but that will only make sense after we get the stroke detection right for your rowing machine. I'll move those parameters into a config file soon with proper descriptions so it is easier to customize and also allows creation of presets for different rower models.

Yes, adding a shutdown button to the web UI is easy to do. I'll add it to the backlog, but it's something that will come after evolving the frontend into a proper web application.

[laberning]

That data looks much better than the previous one 😄.
With a bit of luck you should now be able to get a nice estimate of omegaDotDivOmegaSquare, if you set the log level of RowingEngine to info in config.js.
You could calculate jMoment if you disassemble your flywheel and measure all the parts, but it's probably easier to experiment with different values until you find a value that gives you a reasonable wattage.

[DamienVT]

Hi Lars,
Thank you very much for your help.
My rowing machine is now connected :-)

I did some tries to have a good omegaDotDivOmegaSquare.
I did not disassemble my flywheel, because there a flywheel that is also a belt pulley for the wind turbine.

I decrease a little the jMoment to have a reasonable wattage.

I keep the liquidFlywheel = true because I think that the drive detection is not good with false for my air machine as you can see in the following chart.

I did recording with MyHomeFit app, that works well, but just an issue when I want to stop the workout.
I will check with Holger to know if the issue is from his app or from Open Rowing Monitor.

After a little print, my test configuration fit well for the time I find my final configuration.
The touch screen is good to open web-browser and to go in full screen, and after workout to close properly the Raspberry Pi.

[laberning]

I really like your setup with the Raspi Touchscreen. Looks pretty good!

Glad that you could figure out a configuration that works well with your rower.

Would be great if you could send me the parameters that work well with your rower. I'll add presets for rowers to the configuration file and then I could add yours as well.

The stroke detection for solid flywheels is completely untested (as I only have a water rower), so quite possible that it does not work. Maybe you can send me a recording of sensor data. I plan to revisit that section of the engine soon to harden the detection a bit and then I could also test with data of another rower...

[DamienVT]

Hi Lars,
The parameters for my rower (DKN R-320 with sensor reverse trough the flywheel instead of spring clutch) are:
numOfImpulsesPerRevolution = 1
omegaDotDivOmegaSquare = 0.019
jMoment = 0.4
liquidFlywheel = true

For omegaDotDivOmegaSquare, maybe the parameter is not always good because my rower have a tension control knob that progressively open or close a air damper.
Maybe a dynamic use of the averager can be helpful.

Please find a sample recording, but it was when the rower was open. I can do a new one more longer if you want.
R320_7_open2.csv

[laberning]

Feeding the damping constant back into the model is a good idea. I will make that an option in the rowers preset.

I know that some rowers (i.e. the Concept 2) do something similar to automatically adjust the damping constant, when it changes (either because of changing the resistance of the air damper or because of dirt). I withdrew that idea for my water rower, since the damping constant is not very stable. But it should work fine with a rower like yours...