Questions related to alternate power meter with KICKR trainer (smart trainer)

[jon...@gmail.com]

Hi, 

I've played with and used GC for years when analyzing my training data and now that the training mode has really matured, I'm using it for my indoor trainer (KICKR Snap).

I'm using it on Ubuntu 20.04 running GC v3.6-DEV2101 right now.

I've searched the older topics and know that multiple power inputs are accepted to some level now but I could not find solid answers to my questions below.

I'm dealing with my outside rides using a 4iiii power meter, which reads very different from the KICKR power measurement. I purchased another 4iiii power meter to play with on GC but I'm not sure the best way to use the 4iiii power meter in the case of ERG mode.

My questions:

1. Wahoo KICKR allows one to pair an external power meter to the trainer to allow the KICKR to use the external power measurement instead of its own. Is this they way to go for GC and using the external power meter for the KICKR ERG, etc? If not, how should I set this up?

2. You can only do this "Power Match" feature described in #1 with an Apple IOS version of the app and I now have all Android devices. Does the external power meter ANT ID actually get managed by the trainer's onboard computer or is this ERG resistance tracking being done by the app? (I don't want to assume anything.) If onboard KICKR, anyone have a workaround for no IOS apps?

3. I'm trying several things with my device profiles. I'll use the following values for my example in this larger question:

4iiii power meter: 1234

KICKR trainer: 5678

I set my profile this way and I get the power reading from the external power meter (4iiii) as desired:  1234p, 5678p, 5678f

I'm wondering if I should leave off the KICKR power like this: 1234p, 5678f

Which is the power way to describe using the 4iiii external power meter for my reading and for ERG control?

Thank you for your help!

[Ale Martinez]

From your description it looks like that feature is implemented in the iOS app, not in trainer firmware.

GoldenCheetah doesn’t have a feature like that, it is a pending request: https://github.com/GoldenCheetah/GoldenCheetah/issues/1789

To setup multiple sensors see https://github.com/GoldenCheetah/GoldenCheetah/wiki/FAQ-TRAIN#how-can-i-use-multiple-sensors-in-a-train-session

[jon...@gmail.com]

Inline

On Thursday, March 25, 2021 at 9:23:57 AM UTC-4 Ale Martinez wrote:

From your description it looks like that feature is implemented in the iOS app, not in trainer firmware.

 

That is a question that I have been unable to determine from searching forums, etc. and for reaching out to Wahoo tech support.  I have a technical hardware/software background but unfortunately, you get tier 1 support from them and they probably don't want to disclose their implementation. If this feedback between the KICKR power meter and brake for ERG mode is done purely through the fitness software, then I don't care about Android support.  If the KICKR control board is doing the feedback using the ANT+ ID of the external power meter, then I have a problem.

GoldenCheetah doesn’t have a feature like that, it is a pending request: https://github.com/GoldenCheetah/GoldenCheetah/issues/1789

To setup multiple sensors see https://github.com/GoldenCheetah/GoldenCheetah/wiki/FAQ-TRAIN#how-can-i-use-multiple-sensors-in-a-train-session

I jumped on the multiple sensor option now that it is implemented. Here is what happened:

I created 2 device profiles: 

    #1 with HR sensor, 4IIII power meter, KICKR power meter, KICKR fitness equipment (In this order)

    #2 with HR sensor, 4IIII power meter, KICKR fitness equipment (In this order)

Next, I created a structured ERG workout. Trying both profiles, I observed that the target power wasn't matching up with measured power, which leads me to believe that the KICKR was using its internal power meter for ERG feedback.

I am willing to run tests, do some debugging, etc. Just let me know what you want me to do and hopefully I can build our knowledge base.

[Ale Martinez]

El jueves, 25 de marzo de 2021 a la(s) 11:34:16 UTC-3, Clif Jones escribió:

Inline

On Thursday, March 25, 2021 at 9:23:57 AM UTC-4 Ale Martinez wrote:

From your description it looks like that feature is implemented in the iOS app, not in trainer firmware.

 

That is a question that I have been unable to determine from searching forums, etc. and for reaching out to Wahoo tech support.  I have a technical hardware/software background but unfortunately, you get tier 1 support from them and they probably don't want to disclose their implementation. If this feedback between the KICKR power meter and brake for ERG mode is done purely through the fitness software, then I don't care about Android support.  If the KICKR control board is doing the feedback using the ANT+ ID of the external power meter, then I have a problem.

I have no additional information, but if that feature were implemented in trainer firmware it would be independent of the App you use to control it. If it is only available when using the iOS app then it is likely implemented there.

 

GoldenCheetah doesn’t have a feature like that, it is a pending request: https://github.com/GoldenCheetah/GoldenCheetah/issues/1789

To setup multiple sensors see https://github.com/GoldenCheetah/GoldenCheetah/wiki/FAQ-TRAIN#how-can-i-use-multiple-sensors-in-a-train-session

I jumped on the multiple sensor option now that it is implemented. Here is what happened:

I created 2 device profiles: 

    #1 with HR sensor, 4IIII power meter, KICKR power meter, KICKR fitness equipment (In this order)

This is a no go, as explained in the wiki you should not pair both Kickr power meter and Kicker FEC, it is redundant and creates problems.

 

    #2 with HR sensor, 4IIII power meter, KICKR fitness equipment (In this order)

You can play with the order, in principle the first power meter reading is available as Power and the second as AltPower, IIRC this is also explained in the wiki.

Control uses FEC and is open loop, received power readings don't affect the next target power.

[Clif Jones]

Thanks Ale.

Open-loop is the key piece of information then.  This implies that sending 250W ERG to the KICKR sets the brake at a level where its own power meter measure would be 250W, which would result in my case a higher wattage being measured on the 4IIII external power meter.

In my digging around the forums there seems to be at least 2 ways to do this so I'll ask:  

What is the intended way to compensate for the difference.  The ERG workout calls for 250W, which in my case I'd want it to translate to a lower value going to the KICKR.  I don't particularly want to re-work the training plan files to be the lower value unless that is my only choice.  With that latest builds, what would be the best approach?  Thank you for your advice!

[Ale Martinez]

El jueves, 25 de marzo de 2021 a la(s) 22:16:28 UTC-3, Clif Jones escribió:

Thanks Ale.

Open-loop is the key piece of information then.  This implies that sending 250W ERG to the KICKR sets the brake at a level where its own power meter measure would be 250W, which would result in my case a higher wattage being measured on the 4IIII external power meter.

In my digging around the forums there seems to be at least 2 ways to do this so I'll ask:  

What is the intended way to compensate for the difference.  The ERG workout calls for 250W, which in my case I'd want it to translate to a lower value going to the KICKR.  I don't particularly want to re-work the training plan files to be the lower value unless that is my only choice.  With that latest builds, what would be the best approach?  Thank you for your advice!

It is easy to scale a workout in Workout Editor, there is a tutorial in http://www.goldencheetah.org/#section-tutorials

[Clif Jones]

Thanks. That seems to be a workaround at best but I guess it is an option.  The more that I think about this, the more I question that the iOS device is doing the closed-loop function as an iOS device cannot talk ANT+ directly.  I used to have an iPhone before going back to Android and did use this feature with their training app. You go into the setup and provide the ANT+ ID and as I understand it, the ID was stored in the KICKR. I am going to do a little Bluetooth reverse engineering and digging to see if I can find some more options.

[Ale Martinez]

El viernes, 26 de marzo de 2021 a la(s) 09:52:19 UTC-3, Clif Jones escribió:

Thanks. That seems to be a workaround at best but I guess it is an option.  The more that I think about this, the more I question that the iOS device is doing the closed-loop function as an iOS device cannot talk ANT+ directly.  I used to have an iPhone before going back to Android and did use this feature with their training app. You go into the setup and provide the ANT+ ID and as I understand it, the ID was stored in the KICKR. I am going to do a little Bluetooth reverse engineering and digging to see if I can find some more options.

It is likely using BTLE, the Kickr can be controlled that way, GC v3.6 can also use that option.

As I commented in my first response the closed loop control is a pending feature, the problem it is not that nobody figured what to do, but to find someone having the proper test environment and the willingness to dedicate their time to implement and test it.

[MyJunk Junk]

From some other indoor training apps like TR / SufferFest / TrainerDay etc, there is power match and the way it's described is that it just uses the outdoor PM (eg: your 4iiii) and compare that value to the Indoor PM (trainer)  and then the app scales the Erg Mode Wattage that it sends to the trainer. So, it's likely the app which is doing the "closed loop" power delta/matching.

I'm not exactly sure of how it's being done (algorithm wise) but I saw the issue liked by Ale talks about using an alpha-beta filter. I'm no mathematician so reading the wikipedia on the alpha beta made me more confused.

eg: 

(No PowerMatching)

Erg mode workout calls for 100w

4iiii is reading 120w

Trainer is reading at 100w (following the prescribed Erg Mode workout level)

(with PowerMatching)

Erg mode calls for 100w

4iii is reading 120w

Trainer Reading at 100w

Delta = 120-100.= 20w

so PowerMatch will dictate that the ErgMode workout will auto scale down to 80w.

This power match algorithm will do constant checking and figure out the delta and auto-adjust the erg mode value. 

Here's one w/ some graphical explanation

https://forums.trainerday.com/t/how-does-the-new-power-match-work/14/28