??? Who do that ???
You just have to lay your aircraft still (not moving) during boot.
Yes, I’m aware. What I’m asking is if it’s necessary to have this calibration take place on every boot.
I guess one reason why we would want to do this is because one might be powering up on a moving object such as a boat?
That would be the opposite then. To operate off a moving vehicle such as a boat, you would need to turn off the gyro calibration on boot anyway.
Sorry if I have got the wrong end of the stick but I am now a tad confused. I thought the original point of the thread was about needing to do the calibration on boot or in other words could it be turned off/and or bypassed?
There is an option to turn Off INS_GYR_CAL (set to 0) in the full parameter list (Firmware 3.5.x).
See Boat Mode,
Startup on a moving platform
One of the benefits of the new EKF2 estimator is that it allows for rapid estimation of gyro offset without doing a gyro calibration on startup. This makes it possible to startup and arm on a moving platform by setting the INS_GYR_CAL parameter to zero (to disable gyro calibration on boot). This should be a big help when flying off boats.
Marc
Right. I am questioning the need for gyro cal to take place on every boot. Versus the one time when you’re doing the initial 3d accel calibration, set it and forget it. Leaving INS_GYR_CAL turned off.
From what I know, gyro readings drift with temperature. So unless you always boot in same temerature, gyro should be re-calibrated.
Except the Pixhawk 2.1 is heated and will always rise up to the temperature at which it was calibrated during initial configuration. Meaning, far more accurate than booting up and calibrating at 10C then continuing to rise through 45-50C
If you are willing to risk crashing to save a few seconds on the ground, have at it…
That’s not helpful. I’m asking what the implications are, and why vs why not. Is it beneficial at this point in firmware and hardware to do it on every boot? Or is it actually better to use the known really good calibration done when you do the initial 3D Accel Cal procedure and just stick with that. Doing the calibration at every boot opens up a point of failure on every boot. If the calibration is bad due to movement or temperature for example, you won’t know it until you take off and it’s all out of whack. If there is nothing be gained, then it really serves no purpose.
It has nothing at all to do with saving time, since gyro cal is a fraction of a second to begin with.
1 Like
That is what I think should be fixed, if not already.
There were countless reports of “Bad Gyro Health” error from Pixhawk 2.1 and they were told to reboot after the temp reached target.
Keep recalibrating while disarmed is possibly worse in your case.
Also, I’m sure Earth’s rotation can be read by gyro but not sure if it’s enough to cause problems.
(see “Foucault pendulum”)
To me, the implications are intuitively obvious, but I suppose that is based on the fact that I worked with inertial guidance and navigation systems when I was in the US Navy.
The short answer is accelerometers measure linear acceleration and gyros measure angular velocity. If the gyros are not calibrated or cannot be calibrated (Bad Gyro Health) the measured angular velocities are either not accurate or absent. The flight controller will not function properly and the aircraft is not safe to fly.
Read this: https://en.wikipedia.org/wiki/Inertial_navigation_system
I don’t know what is the exact calibration performed within the Autopilot code, but I assume it is the bias compensation (i.e. gyro levels on still vehicle).
From what I know gyro bias isn’t so constant and does drift a bit over a time for many reasons (electrical/magnetic noise, degradation, shocks etc.)
But gyro bias also has a noticeable drift with temperature changing.
So agree with @Pedals2Paddles here, it seems wrong to perform a calibration on start (cold sensor).
Gyro bias needs to be calibrated from time to time (vehicle configuration change, crash).
But there also could be other points that I’m not aware of.
I think you’re missing a critical point here. I’m not suggesting we don’t calibrate the gyros at all. I’m suggesting simply not doing it at every single boot. Gyro calibration takes place when you do the initial 3D Accel calibration. And it will continue to use that calibration if you never do it again.
Saying the same thing over and over again and expecting attitudes to change is futile. That being the case, Y’All do what you want, but I’m not about to turn off gyro calibration…
I keep saying it over and over because you’re ignoring it. Nowhere am I suggesting turning off gyro calibration. In all of your replies, you have ignored my questions and answered something else.
1 Like
I understand what you mean from your very first post. What is so hard to understand.
can we do gyro calibration during setup only once? Duh…
P2P, I think I can clear things up. The 3D accel calibration does not calibrate the gyros. It is for getting the differences between the 3 accels. The scale factors and the offsets. When it calibrates at boot it is getting the gyro offsets. That’s when the copter needs to be still. The EKF is so good now that it quickly figures out the gyro offsets on the fly. You could do a gyro cal while sitting still on the bench then set the parameter to 0 if you want, like if it’s windy and you copter moves a little on its gear or you are on a boat.
It sure does. At the very first sitting level right side up stage, it does do a gyro calibration.