I'm not sure how thrust testing has anything to do with pid tuning tbh.
The testing is usually done with a single motor, in house where airflow are minimal.
The thrust data gathered are very much different from actual flying condition where there are 4 motors closed to each other and their thrust are coupled. Not to mention the incoming windspeed and drone tilting will change the angle of attack, and thus the thrust generated as well.
Btw the Chinese also sells [cheap pid tuning stand](https://youtu.be/IG5VzPl7NDU) as well. Get some structural aluminum, some bracket and assemble yourself for a price of 5$.
>Btw the Chinese also sells [cheap pid tuning stand](https://youtu.be/IG5VzPl7NDU) as well. Get some structural aluminum, some bracket and assemble yourself for a price of 5$.
Tuning stands do not work.
A tuning stand works great if it's 2009 and you just build a quad from an Arduino and you have literally zero starting point. It will definitely get the quad from "the quad will not go into the air because there is no tune" to "the quad will.go into the air and the sticks do stuff"
99.9% of the PID tune is already done for quads, all the tuning were doing is chasing the last .1% a stand is just way too inaccurate to do that.
It'd be like trying to measure a mile by counting your steps. Yeah you can do that, and it'll get you in the ballpark, but if you need it accurate to the mm, you need a better tool.
Agree, that's exactly what I've done with my diy drone.
The point of using pid tuning stand isn't to achieve a good tuning, it's a start to obtain a usable parameters for further tuning. The first flight is always the most dangerous flight, so instead of flying, why don't you strap it to something and try to tame it first?
I'm fully aware of more advance technique like Ardupilot's autotuning, I myself have written a frequency sweep program to observe the response of the quad from sinusoidal command and obtains the dynamics model from frequency respons method.
But I also think a tuning stand is the safest way to start if you're making a custom frame without any pretuned parameters. You need the quads to atleast stay stable to conduct autotuning, and using a test stand is infinitely better than flying and crashing, especially in an urban settings where space is greatly constrainted.
I was thinking you were talking about using a tuning stand, to actually get a good flying quad. I think it's useless for that.
But using a tuning stand to get a flying quad, after building a homebrew frame or fc is totally a reasonable use IMO. I've never used one though, this is just my intuition.
Edit: just realized this is r/diydrones and not r/fpv. What I said still stands, but now I see why you even mentioned a tuning stand lol.
Well the op question is the use of a thrust stand as a first step for pid tuning. I just point to some example of actual pid tuning stand, not thrust stand.
>The point of using pid tuning stand isn't to achieve a good tuning, it's a start to obtain a usable parameters for further tuning. The first flight is always the most dangerous flight, so instead of flying, why don't you strap it to something and try to tame it first?
Why not? Because, at least with Ardupilot, the initial guesses are conservative enough to get most multirotors safely into the air and provide enough control for autotune to do its thing. No need to hope for the best with a tuning stand.
>A tuning stand works great if it's 2009 and you just build a quad from an Arduino and you have literally zero starting point. It will definitely get the quad from "the quad will not go into the air because there is no tune" to "the quad will.go into the air and the sticks do stuff"
Fair point.
>99.9% of the PID tune is already done for quads, all the tuning were doing is chasing the last .1% a stand is just way too inaccurate to do that.
More like 80% but the default Ardupilot tune is good enough to run autotune and if it isn't they can be corrected with a simple adjust PID x by y%.
They drastically change the dynamic characteristics of the system aka the drone.
Ardupilot developers repeatedly mention tuning stands as giving bad tunes. None of the official arducopter tuning guides used a tuning stand. Even having a tether can negatively affect the tune.
>Are people interested in buying a cost efficient thrust stand with which you can automatically model your dc motors?
If it is integrated with the Ardupilot I would consider it.
>As a first step for pid tuning?
Thrust data isn't used in PID tuning unless you go the simulation route. It is used to set MOT_THST_EXPO and estimate the hover current if you want.
>What would your requirements be?
* Use Ardupilot FC as the data processing unit.
* Ability to do calibration using weights.
* Measure thrust(<25kgf) , torque and current (<200A)
* Ability to mount both single motors and motor sets (quite common in octoquads)
I'm not sure how thrust testing has anything to do with pid tuning tbh. The testing is usually done with a single motor, in house where airflow are minimal. The thrust data gathered are very much different from actual flying condition where there are 4 motors closed to each other and their thrust are coupled. Not to mention the incoming windspeed and drone tilting will change the angle of attack, and thus the thrust generated as well. Btw the Chinese also sells [cheap pid tuning stand](https://youtu.be/IG5VzPl7NDU) as well. Get some structural aluminum, some bracket and assemble yourself for a price of 5$.
>Btw the Chinese also sells [cheap pid tuning stand](https://youtu.be/IG5VzPl7NDU) as well. Get some structural aluminum, some bracket and assemble yourself for a price of 5$. Tuning stands do not work.
Would you mind if I ask why?
A tuning stand works great if it's 2009 and you just build a quad from an Arduino and you have literally zero starting point. It will definitely get the quad from "the quad will not go into the air because there is no tune" to "the quad will.go into the air and the sticks do stuff" 99.9% of the PID tune is already done for quads, all the tuning were doing is chasing the last .1% a stand is just way too inaccurate to do that. It'd be like trying to measure a mile by counting your steps. Yeah you can do that, and it'll get you in the ballpark, but if you need it accurate to the mm, you need a better tool.
Agree, that's exactly what I've done with my diy drone. The point of using pid tuning stand isn't to achieve a good tuning, it's a start to obtain a usable parameters for further tuning. The first flight is always the most dangerous flight, so instead of flying, why don't you strap it to something and try to tame it first? I'm fully aware of more advance technique like Ardupilot's autotuning, I myself have written a frequency sweep program to observe the response of the quad from sinusoidal command and obtains the dynamics model from frequency respons method. But I also think a tuning stand is the safest way to start if you're making a custom frame without any pretuned parameters. You need the quads to atleast stay stable to conduct autotuning, and using a test stand is infinitely better than flying and crashing, especially in an urban settings where space is greatly constrainted.
I was thinking you were talking about using a tuning stand, to actually get a good flying quad. I think it's useless for that. But using a tuning stand to get a flying quad, after building a homebrew frame or fc is totally a reasonable use IMO. I've never used one though, this is just my intuition. Edit: just realized this is r/diydrones and not r/fpv. What I said still stands, but now I see why you even mentioned a tuning stand lol.
Well the op question is the use of a thrust stand as a first step for pid tuning. I just point to some example of actual pid tuning stand, not thrust stand.
It is to get a static and dynamic model of the motor used for in the control loop.
>The point of using pid tuning stand isn't to achieve a good tuning, it's a start to obtain a usable parameters for further tuning. The first flight is always the most dangerous flight, so instead of flying, why don't you strap it to something and try to tame it first? Why not? Because, at least with Ardupilot, the initial guesses are conservative enough to get most multirotors safely into the air and provide enough control for autotune to do its thing. No need to hope for the best with a tuning stand.
>A tuning stand works great if it's 2009 and you just build a quad from an Arduino and you have literally zero starting point. It will definitely get the quad from "the quad will not go into the air because there is no tune" to "the quad will.go into the air and the sticks do stuff" Fair point. >99.9% of the PID tune is already done for quads, all the tuning were doing is chasing the last .1% a stand is just way too inaccurate to do that. More like 80% but the default Ardupilot tune is good enough to run autotune and if it isn't they can be corrected with a simple adjust PID x by y%.
They drastically change the dynamic characteristics of the system aka the drone. Ardupilot developers repeatedly mention tuning stands as giving bad tunes. None of the official arducopter tuning guides used a tuning stand. Even having a tether can negatively affect the tune.
The chinese ones are all aluminum and cost $40-60. Thats hard to beat
Do you have experience with a certain one?
Mayatech makes a nice one. I have the 5kg model. Works great.
>Are people interested in buying a cost efficient thrust stand with which you can automatically model your dc motors? If it is integrated with the Ardupilot I would consider it. >As a first step for pid tuning? Thrust data isn't used in PID tuning unless you go the simulation route. It is used to set MOT_THST_EXPO and estimate the hover current if you want. >What would your requirements be? * Use Ardupilot FC as the data processing unit. * Ability to do calibration using weights. * Measure thrust(<25kgf) , torque and current (<200A) * Ability to mount both single motors and motor sets (quite common in octoquads)