As I was reading the documentation for tuning for the arducopter, I came across Transmitter based tuning. I know there is autotune feature and auto-learn feature in arducopter updated firmware. Do people still use transmitter-based tuning and how safe is it to do it rather than autotune?
“Safer” isn’t how it should be viewed. Transmitter based tuning is a completely manual tuning method. So, if you have experience manually tuning and flight log analysis with Ardupilot it can be the most efficient way to do so. Without that experience Auto Tune should be used. Even with tuning experience Auto Tune can be the best approach.
Yeah, that makes sense.
On a similar note, before we want to go with autotune, it is said to have a stable flight with Alt hold mode. Before Alt hold mode, Stabilize flight mode is recommended. So, when we are flying for the first time with the default tuning parameters how do we go about flying without crashing? Shouldn’t we have to do some manual tuning? or is the auto-tuning going to happen when on stabilize mode in the background?
Before you can autotune you need to set the initial parameters and make sure it’s flying well enough to allow you to run autotune.
- Flight in stabilized mode. Make sure it’s even flyable. If there are oscillations you will need to reduce the PID values by 50% until it’s flyable.
- Flight in Alt hold. This will set the hover throttle position, and give you the data for setting the notch filters.
- If all is good then you can autotune. I’m not sure if there is still a debate about auto tune from Alt Hold or from loiter. I’ve done both and had good results.
Many people are tempted to start in loiter and try RTL on their first flight, but that’s not a good idea. If the initial tune isn’t good enough that can end in a yard sale of drone parts really quick.
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What @Allister said!
Regarding oscillation; sometimes you can actually see/hear it other times not. In any case the log should be reviewed and the Motor Outputs graphed at a minimum. The Rate data can tell you a lot also but you have to know what you are looking for. And, if the motors burn your fingers upon landing you have a problem.
If when you run Auto Tune you get messages stating “failure to level” then some manual tuning is required before Auto Tune will run properly. This message is a safeguard actually. Unless you have experience with this it’s not always clear what has to be changed to fix the problem.
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That’s very helpful to put things into order. Thank you!
How would we check for oscillations?
What values in logs would be able to tell us about the direction of oscillation? Maybe the desired and actual pitch and roll? Can anything else in the log tell us how much to change the PID values?
I mentioned 2. Motor Outputs (RCOU>Cx) and Rate (RATE>Rout & Pout). You often can see oscillation in the achieved Pitch and Roll (ATT>Roll & Pitch) but the oscillation we are talking about here (pre-tune) are often severe. When using Desired vs actual Pitch/Roll that’s typically when you are fine tuning. Although, a bad Auto Tune will show up there.
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Today, we completed building a cage from PVC pipes for the drone to protect it from crashes. We calibrated with the cage and tried to fly in the stabilize mode. The drone crashes before flying in less than 20 seconds. I have added the link to the video and the logs. Could you be able to help us figure out the reason for the crash? It bumped the ground before it went flying. The bump might have caused some oscillation. Other than that we are unsure what changes to make.
https://drive.google.com/file/d/1wjWAI4ii_bqtqzhPf52d3doPxMy76UpO/view?usp=share_link
https://drive.google.com/file/d/1O39sb3J-rN5rZVhW8Jq50rlP6RkA6dME/view?usp=share_link
Get rid of the cage and proceed normally with 1st flight and tuning. It barely had enough thrust to fly and then you switched to Land Mode and the outputs saturated so no stability. Cages and tethers as a perceived method of protection are a mistake. You cannot advance with any configuration or tuning with them present.
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To elaborate for your team who thinks the cage is a good idea:
- Nothing useful can be learned from the use of the cage. The flight conditions present are nothing close to what they will be w/o it. So what’s the point in using it? Protecting expensive hardware? I saw some of that hardware go flying when it crashed because the cage was there. Follow the configuration, calibration and pre-tuning steps and then move on to 1st flight to collect data for the notch filter.
- As I said, with the cage mass there is insufficient thrust/weight for proper stability not to mention where the CG moved with that floppy contraption. Before things went real bad the average motor output was ~1750us. This leaves very little headroom for stabilizing the craft.
- do not engage Land or RTL mode until the craft is tuned.
Thank you for the insight. If we are not using the LAND mode to land, do we just reduce the throttle and disarm it manually?
Another question we have is about the manual tuning. What is the best method to tune the drone? What we have been seeing is that the drone ascends gently and hovers very well in the alt-hold mode. But we still crash-landed and we didn’t figure out why we crashed. We may have used the pitch and the roll throttle to the maximum the tuning was not good enough.
Maybe if we have performed autotune when it was hovering very stably, then we would have gotten a good tune already. What do you suggest?
Yes.
With Auto Tune, already covered that.
Under what circumstances are you talking about now?
Advice has already been given in this regard.
I am sorry for the redundant questions.
I understand that autotune is the best way to tune but since we have to start manually with stabilize mode and perform manual PID tuning before that, I am concerned that we might have to crash multiple times until we achieve that stability with this method of trial and error.
You don’t know that yet. You should take the suggestions I made a week ago. Here they are again:
INS_ACCEL_FILTER,10
INS_LOG_BAT_MASK,1
INS_LOG_BAT_OPT,4
Make a short hover flight in AltHold for a minute or so and land (not land mode, just land it manually). Review the log file for Oscillation and to configure the Notch filter.
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