Servo range for multicopters

More
28 Aug 2012 16:31 - 28 Aug 2012 16:32 #1260 by rototophe
Servo range for multicopters was created by rototophe
I am following closely this project and the awsome work you guys are doing.

Today I was looking at the protocol stacks thread and FDR mentionned at some point using channel range (servo throw) over 100% for his ladybird with the stock walkera firmware and that he wasn't able to set them over 100% (at this point in time) with Deviation. I think, if I understood well reading the thread, that the current main tendency is to keep the servo ranges no more than 100% in order to avoid damaging the actual servos. While this is plain good sense thinking that could actually handicap multicopter flyers for "stunt" and 3D flying.

If we keep the ladybird exemple, you need to set throw over 100% for pitch, ailerons and possibly rudder in order to have good fun with the bird. Since there is actually no servos on these machines it does not present any hardware hazard to set the servo travel over 100%. I think limiting throw to 100% on these flyers will render them dull to fly under Deviation.

So my first question is: Do all the assumptions I made so far correct? If yes my second queston is: Would it be possible to create an "aircraft" type, like "Airplane" and "Helicopter", such as "Multicopter" (or whatever) and allow servo ranges up to 150% (or more) for that particular aircraft type, and only for that type of aircraft? That would keep the throw inside a safe range for the other types of aircrafts by preserving hardware integrity and protect against user input errors for planes and helis (and everything with actual servos)while allowing extended throw range only for the multicopters.
Last edit: 28 Aug 2012 16:32 by rototophe.

Please Log in or Create an account to join the conversation.

More
28 Aug 2012 19:17 #1262 by FDR
Replied by FDR on topic Servo range for multicopters
I don't see it a problem that the default 100% is less then the whole valid range of what the protocol can transmit, as far as it is possibe to extend that range. It is a good starting point to fine tune the servos.

Other approach could be that 100% always means the maximum servo throw, and you should use less than that in DR or mixers most of the time. I like more the extendable 100%, because it is simpler to understand and calculate with it, then for example keep in mind that the aileron is up to 73% the aileron goes to 69%, etc. Then if somebody change the servos to other type, he would have to do the tuning of all the mixers again, instead of just adjusting the channels servo travel. It is important to note, that it is not just for extending, it can be used to scaling down too...

I think it doesn't have sense to allow this for one aircraft type and not for others. Even the whole electronic multirotors can benefit from it, if the ESCs need a different range that the 100% gives: you could use the servo travel instead of reprogramming the ESCs...

Please Log in or Create an account to join the conversation.

More
28 Aug 2012 19:51 #1267 by PhracturedBlue
Replied by PhracturedBlue on topic Servo range for multicopters
Yep, as FDR said, 100% has a meaning across the industry. Lots of companies use different values for 'max'...125%, 140%, 150% but from what I can tell the max safe range for a servo is generally 1msec to 2msec. Anything more than that may cause aliasing depending on the servo.
since 100% is defined industry-wide as +/-0.4ms from center (1.5msec). the full range of the majority of servos is +/-125%, regardless of how companies sell it.

I opened a ticket in bitbucket to track the implementation of >100% range

Please Log in or Create an account to join the conversation.

Time to create page: 0.034 seconds
Powered by Kunena Forum