We discuss new Rotor Bones series updates, quad copters we have been flying lately and how to dial in or lock in your multirotor.
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Cheers
Neil.
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Anyway, nooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo × a sideways 8 squared. Nonsense is a very important part of the hobby and more importantly the community y'all have fostered if not built.
Lastly, give JB back his "clicky thing"! :D
Thanks for much fun for many days may we all know many more. Thanks as well for sharing with the bigger family.
Frank
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Andre
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I believe that the so-called "nonsense" is what gives the podcasts the human factor. The podcast at least in my opinion is the equivalent of being able to sit at that table with you guys. Sometimes conversations get off topic. But thats what happens when friends are enjoying each others company.
Many thanks for all that you do
Randy
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I haven't flown a single multirotor, but have flown those $20 3ch helis.
Is there a setup or a certain scratch build (ish?) tri/quad setup that you would recommend to a beginner?
Thanks.
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I love your podcast! Talking about multirotors will definitely help people get their multirotor dialed in, you guys are great!
I'd like to give my opinion about 'heading hold', 'locked in', and I'll try to explain what P and I gains do. I hope this will give you a little bit more understanding, because I hear that you guys have trouble explaining it. I'd like to think I understand what all this means, and I'll try to give an explanation for it. I hope I can find the right words to explain it well.
I'd like to note that I have a background experience with mainly helicopters, so bear with me if I sometimes refer to that ;).
Heading Hold
What I understand from Josh is that heading hold is the same as autolevel. This is not true. Heading hold was first introduced in tail gyros for helicopters. Before that, there was only rate mode. The difference is the following: in rate mode, if the gyro detects motion, it will counteract that, until the motion is gone. Heading hold knows where the heading is (say, it is at 0 degrees). If the tail gets deflected, it will counteract and also put it back to the 0 degrees, whereas the rate mode would only counteract and bring it to a stop (at a different location than 0 degrees).
Translating this to a multirotor, it means that the control board wants whichever axis (for example, roll axis) to be at a certain position, and it will keep it there. If the multirotor gets deflected, the board will adjust, give inputs to the motors, to get back the the position. This is NOT autolevel. Autolevel simply means that the control board wants a different postion relative to the stick inputs on your transmitter.
As far as I know, multirotos don't have rate mode. This is something from the past, when heading hold in gyro's wasn't invented yet.
Locked In
Locked in means, that (in acro mode) you put the multirotor (or helicopter, sorry I can't resist ;) ) in a certain attitude and it stays there without moving/being squirrly. For example, you put the aircraft perfectly level, and it stays perfectly level. Sure it may start drifting with the wind, but the attitude of the aircraft remains the same. In my opinion, this is what's called 'locked in'.
As Alex says, this can apply to both docile and acrobatic aircrafts. Also in autolevel, an aircraft can be locked in. For example, if you keep your aileron stick at the same position, your aircraft should also stay at the same bank angle.
PI gains
Ok, the hard part. Let's start with P gain.
In these explanations, you need to have the perspective of the control board, NOT the input of the transmitter. Let's assume 1 arm of the multirotor, with motor attached. The board wants to have this arm at a certain heading, we will call this heading 0. Now as the arm gets deflected by an outside force (like wind), the board needs to correct. So say the arm drops a little, 1 degree. P gain tells the board how STRONG the motor needs to respond. So for example, with 1 degree drop, the motor has to increase thrust by 5%. In this case, a 2 degree drop will increase the thrust by 10% (this need not be linear though, but for sake of simplicity, let's stick with this). If you increase your gain, the motor will respond more strongly, so in case of a 1 degree drop it will now increase by e.g. 7%. 2 degrees of drop will result in 14% increase in thrust, and so on.
Now as the arm is rising due to the increase in thrust, the thrust will decrease. So it's going from 2 degrees (14%) to 1 degree (7%) to 0 degrees (0%). (note, again, this is 0% extra thrust, so there is still thrust to hover your multirotor).
So if your gain is too low, the motor won't give enough trust to compensate for the deflection, and your multirotor will feel sluggish. Not 'locked in', as described above. The other extreme is too high gain: the arm is being forced back with so much force, that there is an overshoot! As the arm gets too high, the motor will decrease too much power, so the arm will drop too fast, and motor power is increased again, but too much, etc. so this causes oscillation. Typically, you increase your gain until you find this oscillation, and then you back off your gain a little and that's it!
So that is P gain. All great. But what is I gain? That's a little harder.
Let's assume you've set up your P gain pretty well as described above. Now inertia and response time of your motor/prop comes into play. We'll take the same example as above: your arm is lower than where the control board wants it to be, and it's giving the motor extra power to get back to 0 degrees. Now, as your arm is rising to neutral, 0 degrees, the motor will hit 0% extra thrust at exactly 0 degrees. But the arm still has momentum moving up, and additionally the motor is still in the course of slowing down to neutral thrust (0%). So the arm is going to overshoot. Hmm but didn't we just correct for that by backing off the P gain a little? Yes and no, that'll come later.
This is where the I gain comes in. The control board is going to give the command to the motor to slow down to 0% slightly ahead of time, before the arm actually reaches 0 degrees, to offset the slowness in response of the motor/prop. How strongly it does this, depends on the I gain. If you increase the I gain, it'll give the command for 0% very early. So if you have a motor/prop/ESC combo that responds slow to control inputs, you need to increase your I gain.
You will find, that as you find the optimum I gain, you'll be able to increase the P gain ever so little, because now there is less overshoot, which caused you to decrease the P gain.
Geez, this has become quite a response...
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For dt750 motors and others that mount the same, a single TINY drop of loctite 640 to one side of the mount surface (not the set/grub screw, but adjacent) will settle things nicely for motors you don't intend to dismount often. Removal may take the touch of a soldering iron close to the drop from outside.
For motors dismounted more often, loctite 222 is wonderful. Removal is simple, but the dot may need reapplied after a hard wreck or ten.
Again, not for bolt/screw threads, but rather flat to flat contact of the mount to the "hub" and only a tiny dot is needed unless you acquire a very loose fitting one.
Frank
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Frank
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I especially noticed it right at the beginning with the car alarm... before that would have been at least 5 minutes of joke cracking and stuff that make us smile and enjoy the podcasts. But in this case it was more like Josh sweating buckets getting nervoius because of it being off topic, trying to ignore the happenings at the same time as just appologizing. Please, lighten up... that seriousness and nervousness, and the attempt to eliminate random randomness is exactly what I for one was hoping would never happen to you guys. I could tell you wern't feeling comfortable with this recording, that it was more stressful. If people want pure talking heads giving facts with no humanity whatsoever, they should listen to the RCG podcasts instead!
I prefere a 2 hour podcasts with half facts and half antics and mayhem than an hour podcast of just pure facts dished out in a nervious fashion... what those complainers don't realise is that they probably got the same amount of pure RC stuff out of this podcast as they would have gotten out of one of your more fun and subsequently longer podcasts, which is much more enjoyable to listen to...
I know you guys are reading feedback because for you the community is important, but let me tell you: the feedback was VERY wrong in this case
I still love you lots though guys!
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