To Rate Mode or not?

[Jason Asch]

Hi all, I've been debating during tail set up to use rate mode to find a neutral point while hovering. Or just make sure the tail slider is in a neutral point when the servo is at 90 degrees and let the Ikon/brain find the neutral point within the full travel set in the basic.

Any thoughts or insights into which is preferred? I know in the "old days" of flybar and basic gyros the rate method was preferred and considered general practice for tail setup. Yet all of today's flybarless gyros just require an end point calibration and all seems that work just fine. They have pre comp Etc to tune out imperfections.

In short, why technically, would rate mode be beneficial or a deterrent for today's Ikon or Brian?

Thanks in advance!

[minatrix]

I asked a similar question recently.

Answer is no, unless you plan on flying in rate mode, rate mode setup is unnecessary and not beneficial to HH setup.

OTS knows the ikon. You can find his response in second to last post.

https://www.helifreak.com/showthread.php?t=714863

[Grimmy]

Originally Posted by minatrix

I asked a similar question recently.

Answer is no, unless you plan on flying in rate mode, rate mode setup is unnecessary and not beneficial to HH setup.

OTS knows the ikon. You can find his response in second to last post.

https://www.helifreak.com/showthread.php?t=714863

I have to disagree with you on this. Would you have to do it to fly, no. But if you don't go through the process and if you didn't have the tail mechanically set right (I'm not talking off by a lot, but will just say off more than a few turns of the tail control rod) the gyros would have to work more to hold the tail. Where this comes into play is for tail holding during maneuvers. I had this problem on my E7SE, where 90% of the time it would hold, but if I did some really hard pitch pumps, the tail would blow out all the time. I went into rate mode and the tail would drift, so I adjusted my tail control rod to get right of the drift, and the problem went away. I actually needed to decrease my gain about 5 points in windy conditions.

So, while it is not necessary, I think it's a good idea so you don't have the potential for tail holding issues later on.

[vtown nick]

Originally Posted by Jason Asch

Hi all, I've been debating during tail set up to use rate mode to find a neutral point while hovering. Or just make sure the tail slider is in a neutral point when the servo is at 90 degrees and let the Ikon/brain find the neutral point within the full travel set in the basic.

Any thoughts or insights into which is preferred? I know in the "old days" of flybar and basic gyros the rate method was preferred and considered general practice for tail setup. Yet all of today's flybarless gyros just require an end point calibration and all seems that work just fine. They have pre comp Etc to tune out imperfections.

In short, why technically, would rate mode be beneficial or a deterrent for today's Ikon or Brian?

Thanks in advance!

I have tried it both ways over the years and if you are flying a good tail servo it won't make any changes in flight one way or the other. I have since been setting up as close to the same travel both ways on my helis now viewing from the advance menu on the servos tab for servo #4. Having it hold in rate mode used to be the best way to eliminate tail kick on my trex 250 way back when. But every heli I've flown since I just set up even.

The most important thing in your tail set up will be smooth, very smooth sliding tail mechanics and having all the geometry set up right. With that you will see good tail results. From there you have many tuning options to dial the tail in.

[minatrix]

Originally Posted by Grimmy

I have to disagree with you on this. Would you have to do it to fly, no. But if you don't go through the process and if you didn't have the tail mechanically set right (I'm not talking off by a lot, but will just say off more than a few turns of the tail control rod) the gyros would have to work more to hold the tail. Where this comes into play is for tail holding during maneuvers. I had this problem on my E7SE, where 90% of the time it would hold, but if I did some really hard pitch pumps, the tail would blow out all the time. I went into rate mode and the tail would drift, so I adjusted my tail control rod to get right of the drift, and the problem went away. I actually needed to decrease my gain about 5 points in windy conditions.



So, while it is not necessary, I think it's a good idea so you don't have the potential for tail holding issues later on.

It's not me your disagreeing with. I am simply repeating what OTS has stated.
He is one of the primary flight testers for iKon development, and surely knows the unit extremely well. You can trust what he says regarding a rate mode setup on the iKon. Idk which other units this applies equally to, but we're talking about the iKon/brain, and if your gonna take tuning advice for the iKon from anyone, dat guy knows his stuff.

Did you even read his post?

[Grimmy]

Yes I did read his post. That's why I stated that you could fly it like that, but you might have tail holding issues, just like I did. Checking for tail drift in rate mode further verifies that you are mechanically set properly.

[AllanNg]

Like a car, a plane, fins, stabilizers, wheels, designed and placed in a way to help them drive/fly straight before human or electronic interventions. A bad or out of alignment car can be driven straight, but for sure you will constantly have to compensate and even tougher in aggressive constant turnings. Same idea here applies to heli and if you think about it, the thing needs the tail rotor to keep it straight and this is done by counter pitch. This is exactly what rate mode does, find a good point/counter pitch to keep the heli straight before gyro correction takes over.

Required? Up to you. Logical? Yes. I do this to all my helis.

[Inverted2112]

I was on the fence about this for a relatively long time, until doing a proper rate mode set-up on my Warp sorted out a tail problem (running MSH Brain).

[pctomlin]

Leveled swash and rate mode tail are a norm for me, call it anal or whatever. The less correction of a bad setup the FBL is doing the better it performs in my opinion. Don't believe, take a poorly setup heli out and see how flat and stationary it will piro, then be meticulous in setting things up correctly and try piroing again. The car alignment is a great analogy.

Oh, by the way, iKon/Brain are great FBL units.

[Jason Asch]

When setting the Brain/Ikon into rate mode is there a number it should be at so it doesn't spin out of control? If its recommended to get to 45% for HH should I go -45%?

[pctomlin]

I use Spektrum and setting in transmitter is 57% for 45% in iKon HH mode and -57% for 45% in iKon rate mode.

[BrunkBird]

when you say the gyro does not have to work as hard when mechanical setup is done in rate mode, what part of the gyro are you talking about? the electrical parts or the cpu itself?

[Jason Asch]

Good question, if it's in a neutral point mechanically how hard could the gyro have to work to keep it straight. Isn't that what it's designed to do? In HH mode that is.

[DannyvG]

The gyro doesn't have to work. It's just a calculation which is always error=desired-actual and the error is multiplied by the controller gains but it doesn't care if the error is zero or nonzero it just results in a requested servo position. The only goal of tail setup should be to have the servo horn 90 degrees to the control rod when the tail linkage is also at 90 degrees to the control rod this will result in as close to linear gain in the mechanics as possible making it better to control with the linear control loop. And often this is pretty close to a neutral rate mode setup but that shouldn't be the goal imho.

[mamartin]

Originally Posted by Jason Asch

Good question, if it's in a neutral point mechanically how hard could the gyro have to work to keep it straight. Isn't that what it's designed to do? In HH mode that is.

I honestly can't say what happens within the system itself other than when this is done properly the servo is centered and at its nuetral center position when th heli is in a stationary hover and when Rate mode is used to optimize your tail mechanics.

I know there are a lot if guys that don't follow this method of setup.

CG is important still as well yet there are a lot of guys that don't even check it during there build nor adjust there components accordingly to achieve a proper CG.
The flybarless system can correct well enough to not really see any adverse affects at least to those users that don't know any different.

The reason Im using CG as a comparison is because proper CG is very similar to rate mode setup.

If you don't properly CG your heli yes you can tune it so that it flies descent but why?

If you take the time to figure out a good component layout and get your CG balanced it just tunes in and flies so so much better.
Everything falls into place an your not being required to do a lot of wild hair pulling tuning flights to get it dialed in.
Same with rate mode.

I'm not an electronics engineer, just a regular PLC technician, I know electric but don't have a clue on electronic components and there inner workings so I can't honestly give you a description of why it's better.

Personal experience has taught me that it is.
Also after several emails back and fourth with the BrainDev discussing this very same topic back in the beginning of the year he verified that it is the best practice to use in order to optimize the tail mechanics before moving on to tuning the tail in after initially setup.

That's not saying you have to use it.
I do believe you will be much happier with the end result and I also believe you will find that it was easier nailing down the tail in the end by using this method.

It's 5 to 10 minutes worth of work at most to know your setup is mechanically optimized.

[BrainDev]

The mechanical setting in Rate mode is not indispensable.
But if you do, it's better.
In a PID sistem the values of accumulation of error, have however their maximum positive and maximum negative limit values (Left | Right).
If the tail is mechanically perfectly calibrated in rate mode, there is no error, so the PID correction values in holding mode stay around zero and thus possible corrections/excursion to positive and to negative are maximum.
If the tail is not mechanically calibrated in rate mode, in Holding Mode, the PID values will be shifted (much or little) compared to zero and this for the correction of the mechanical error. In this state the possible interventions of the PID will be "limited" in one of the two directions.
If the correction values are shifted from the center/zero, the room/space before going to their maximum value limit (saturation) is less/limited.
As absurd, if the mechanical error was very high, the tail could no longer correct in one of the two direction.
One of the big error that many beginner do, is to think that the zero/center tail position correspond to a position of the tail blades at 0 degree. This is a very big error to manage not only from Brain but for all/any tail gyros.

[DannyvG]

Originally Posted by BrainDev

If the tail is not mechanically calibrated in rate mode, in Holding Mode, the PID values will be shifted (much or little) compared to zero and this for the correction of the mechanical error. In this state the possible interventions of the PID will be "limited" in one of the two directions.

That sounds like the limitations/drawback of a very simple anti windup scheme. I would presume the anti windup would take the actuator limits in account and not work in some fixed range as you seem to suggest. In that case I can see the benefit of rate mode setup but I think it shouldn't be necessary with other anti windup strategies.

[Jason Asch]

Rate mode it is for this guy! Thank you so much for all of your input especially BrainDev 👍

[minatrix]

Yes thanks for chiming in BrainDev

[ARM_Coder]

What I don't get about the rate mode setup improving the HH performance is: the setup is made in a stationary hover so the tail doesn't drift in this condition, right?

Well, most of the time the flight will be radically different from a stationary hover, so the torque will almost never be the same from that one used for calibration. This is true even in a tame flight, let alone during hard 3D.

So the meticulous setup done during the hover won't be correct for all other flight regimes anyway. Those who want to fly in rate mode will likely tweak the RevoMix settings to account for torque changes, but for HH, it looks like a moot point IMO.

Any input here will be appreciated.