Question:
Can PID values interchange between different FC's tuned on the same quad?

I'm building a new mini-quad on a PixRacer (arducopter) and it is nearly identical to another one I previously built and tuned with a mini Revolution (dRonin). The frame is the superlight Diatone Blade 180.
The revo dronin build is 'Autotuned' and flies great with near zero effort. I'm kind of spoiled because I have no experience manually tuning PID's. Thus I want to just transfer the values over to the new pixracer arducopter build. If anything, just for a good starting point.
btw, arducopter's autotune is very intense, long duration requiring more than one full charge batt, large space, and is said not to work well with mini-quads. dRonin's autotune is a 75-sec process and I've done quite a few new quad tunes, up to 280mm in my living room.

Does PID values have some inherant dependancies like gyro/sampling rates, making them not interchangable? Another thought I have may be, the PID's can be transferable in similar flight stacks architecture in the same family (dRonin is from same TauLabs/OpenPilot/LibrePilot/cleanFlight/etc), but may not be compatiable with dramatically different flight stacks (like arducopter/px4/etc).

Comments?

Thanks,
yelrx8

I can flash Betaflight 3.1.7 onto a Revo F4, BF F4 or Revolt and all will fly about the same with default settings. BUT when you're talking about changing from dRonin firmware to APM, do not try to carry over any settings, they will be totally different and you'll be setting yourself up for disaster. Besides, if you're going to a new SW/FW, wouldn't you want to start from scratch and learn everything you can about the new system? And even if you're flashing new firmware onto the same board, you should always start over again as many defaults may have changed, and new features added or even removed.

(24-Apr-2017, 08:26 PM)RENOV8R Wrote: I can flash Betaflight 3.1.7 onto a Revo F4, BF F4 or Revolt and all will fly about the same with default settings.  BUT when you're talking about changing from dRonin firmware to APM, do not try to carry over any settings, they will be totally different and you'll be setting yourself up for disaster.  Besides, if you're going to a new SW/FW, wouldn't you want to start from scratch and learn everything you can about the new system?  And even if you're flashing new firmware onto the same board, you should always start over again as many defaults may have changed, and new features added or even removed.

I was talking about just the PID numerical values, nothing about complete parameters sets. 

Off top of my head, the 9 'inner loop' rate values and the 3 'outer loop' attitude values.

You should not assume that PID values are portable in any way, not even between different versions of the same firmware and certainly never between different firmwares or different hardware.

Sampling rates, filter settings, gyro hardware and flight algorithms all have unique influences on how a craft is tuned. The concept of inner and outer loop values is unique to OpenPilot derived firmware and cannot be translated to Betaflight or Arducopter which both use different approaches in their flight control code.

"I've done quite a few new quad tunes, up to 280mm in my living room."

The fact that you haven't damaged your living room or your person so far is more down to luck than anything else and if you keep on doing this, it's only a matter of time before you learn the hard way why this is really bad idea.

The only place you should fly a powerful quadcopter is outside! The fact that you've got away with unsafe practices so far will only make you even less careful and sooner or later, your lack of respect for the genuine danger that a powerful quad represents will cost you dearly.

Please, be safe and don't encourage other people to take risks that can have devastating consequences.

(25-Apr-2017, 08:37 AM)unseen Wrote: You should not assume that PID values are portable in any way, not even between different versions of the same firmware and certainly never between different firmwares or different hardware.

Sampling rates, filter settings, gyro hardware and flight algorithms all have unique influences on how a craft is tuned. The concept of inner and outer loop values is unique to OpenPilot derived firmware and cannot be translated to Betaflight or Arducopter which both use different approaches in their flight control code.

"I've done quite a few new quad tunes, up to 280mm in my living room."

The fact that you haven't damaged your living room or your person so far is more down to luck than anything else and if you keep on doing this, it's only a matter of time before you learn the hard way why this is really bad idea.

The only place you should fly a powerful quadcopter is outside! The fact that you've got away with unsafe practices so far will only make you even less careful and sooner or later, your lack of respect for the genuine danger that a powerful quad represents will cost you dearly.

Please, be safe and don't encourage other people to take risks that can have devastating consequences.

I concur with everything above  

After more researching, there are too many differences with how all flight stacks handle just basic flight that 'PID' are only similar in name, and nothing else.
Further observations, the tuned dRonin values and default dRonin values are out of range values for Arducopter.  That alone is immediate red flag.

I proceeded to try starting with the default Arducopter values last night.  After more fiddling with values and settings, it resulted in 3 pairs of broken props!   The settings are way out of range for a 'gentle lift and hover', at least for this light overpowered quads.  I'm (now) total in agreement with you, tuning is not a living room exercise, at least not arducopter!

As I've mentioned earlier, I've been spoiled (and lucky) using a friendly flight stack like dRonin.  The default values are completely good enough to gently get off the ground and autotune in a controlled manner (even in a confined space).  I've previously completed 7 successful builds with dRonin, before this arducopter attempt.

While I'm glad to hear you might be getting my point, it makes no difference from a safety point of view if you have "a friendly flight stack" or not. Thinking that way breeds contempt and encourages you to continue doing things which still have a real chance of going horribly wrong.

A quad can go out of control for many different reasons. For example, a faulty ESC might work until the point where you get the quad up into its first ever hover and then fail suddenly causing the quad to completely lose control - often with the remaining propellers spinning at maximum throttle as the flight controller fights to stabilise the craft - and in the worst case, come flying straight at your face. When something like that happens, it happens really quickly and you will have no way to avoid it at close range.

Maybe you'll get away with doing this kind of thing 100 times before something unexpected happens, maybe only one more time. Do a Google image search for "quadcopter injury". Study the pictures. Then ask yourself what level of risk you are prepared to accept that you might end up with similar injuries.

Think about the fact that the larger the propellers and the higher the motor speed and power is, the severity of the injuries rises to a clear risk of death very quickly. If there are ever other people in the room when you are doing your "home tuning", how much risk are you prepared to accept that you might inflict those kind of injuries on someone you care about?

I know you might think I'm harping on about this, but I don't think you understand that this kind of accident is most often caused by an unanticipated mechanical, electrical or software problem. You can't ensure that none of these things might happen. The chances of a sudden loss of control are still there regardless of your skill level. A skilled quad builder obviously has a slightly smaller risk than a first time builder who hasn't learned to solder, but the risk is still there. Given the poor quality control on some of the parts we buy from China and the fact that the ever changing flight control software we use is never bug free, the risk of unexpected failure is real and significant.

tl;dr

If you disregard safety in this hobby, you will, sooner or later, suffer the consequences. Safety is about minimising the risks when the unexpected happens. Because it's about dealing with unexpected stuff, you have to follow safe procedures every time, not just when you assume there are risks!

My 250mm APM auto tuned inside of a few minutes - in an open park in a calm day. It was honestly super easy AFTE4 I resolved build/mechanical issues with the Quad.

Set up and try it - it does work