Dual Rates and Expo...
 
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Dual Rates and Expo?

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(@meowguy)
New Member Customer
Joined: 5 years ago
Posts: 2
Topic starter  

After setting up my Trex 700 and using panel 13 to configure Beginner, Sport, Acro, and 3D, modes, does this eliminate, and take the place of,  the use of Dual Rates and Expo configuration on the Transmitter? 

Thank you, Jim


   
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(@customercare)
Reputable Member Admin Registered
Joined: 6 years ago
Posts: 1123
 

Yes, the Beginner, Sport, Acro and 3D modes change, among other things, the Expo and rotation speed values for Aileron, Elevator and Tail (in flybarless control units, instead of reducing the rotation commands with the dual rate, the maximum rotation speed values measured by the gyroscopes in Degrees per second are reduced).
The default values are usually appreciated and used by the majority of users. However, they can also be modified by going to the Advanced section.

BR


   
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(@meowguy)
New Member Customer
Joined: 5 years ago
Posts: 2
Topic starter  

Thank you.  That is what I thought, but was not sure.  Perhaps that could be mentioned in the side bar of Panel 13 in the future.

Regards,

Jim


   
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(@roman-sibbert)
New Member Customer
Joined: 8 months ago
Posts: 2
 

Hello,

I want to bring up this topic again because there are some uncertainties for me, even after a thourough search via Google etc.

Since recently I'm using a Brain2 in my Specter V2 and think it's much more user-friendly than the Micobeast Plus used in my LOGO550. But still there is one thing I miss very much with the Brain2: The ability to set D/R and Expo via the Transmitter. In the setup it is explicitly said that those settings must be not used in the transmitter.

The approach used by the Brain was explained in this thread, nevertheless it isn't obvious to me how a Expo-Setting in the transmitter would be harmful. In my understanding it should be irrelevant to the Brain2 wether the correlation between stick movement and transmitted target position is linear or not, as the FCU always only sees the currently demanded target position. Same applys to D/R: Of course I matched my stick travel to 100% deflection in the Brain-Software during base setting. But if later I use D/R in my transmitter it should be just like I never use the full available steering throw, given D/R is lower than 100%. Or is D/R only a problem if set higher than 100%?

From my own experience I know it works fine with the MB Plus, and VStabi points out that D/R and Expo in the transmitter can be used without restrictions.

My specific question is: Does it really affect the controlling performance of the Brain2 if I use the mentionend settings in the TX, or is this usage simply not recommended because it could generate weird/unpredicted behaviour just because of an unmatching combination of settings? For example I read about people who set Expo to 0 in the advanced menu and then used the TX setting...

What I think is a nice compromise is the Dial function available, nevertheless a direct setting in the transmitter would be the most comfortable and intuitive.

Furthermore I would like to make a suggestion for an improvement regarding the Dial function: I think it would be nice to be able to assign more than one parameter to one setting channel: Then you could for example set Expo for Aileron and Roll at the same time, making sure that both cyclic functions are having the exact same value. And if you really want to differ between them, you can still assign them individually...

 

Kind Regards,

Roman


   
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(@customercare)
Reputable Member Admin Registered
Joined: 6 years ago
Posts: 1123
 

We don't seem to have written in the instructions that dual rate and expo on the transmitter cannot be used after completing the configuration of our flight controllers.
Can you help us by telling us where you read that in our instructions?

Let's try to clarify these two points again.

When setting up the flight controllers it is INDISPENSABLE that Dual Rate be turned off on the transmitter in order to make adjustments to the maximum channel excursions in Wizard panel 5, in order to make adjustments to the maximum collective pitch and maximum cyclic pitch in Wizard panel 8, and the maximum tail control excursions in Wizard panel 9.

Also regarding Dual Rate which is used to reduce the maximum rates of rotation on the three axes of the model, it can of course be used but, as we have repeatedly explained, we do not recommend it because it reduces the resolution and accuracy of the commands making them " granular."
The commands sent by the transmitter are digital signals and therefore stepped signals. For example, with a resolution of 1024 bits you have 1024 "steps" of maximum resolution, but transmitters transmit all 1024 steps only when the excursions (ATVs) are raised to maximum.
Normally, a transmitter leaves by default a margin of 20 percent more on the maximum value and 20 percent less on the minimum value. So the steps that are normally actually transmitted have a resolution of only 614 steps.
By activating a dual ratio of 30% on the transmitter, the number of steps handled by the stick excursions drops to only 584 "steps."
292 steps of positive travel relative to stick center and 292 steps of negative travel relative to stick center.
This makes the controls very " granular" and also it is no longer possible to manage intermediate values between one step and the next.

In flight controllers that process 32-bit commands this "granularity" of digital commands is obviously impossible to be felt.
For this reason instead of using Dual Rates on the transmitter it is much better (but not indispensable) to use for the different parameters used by the three Setups by the flight controllers different values of the maximum rates of rotation processed at 32 bits.
For the same reason, in panel 5 it is necessary to increase the maximum and minimum excursions of all channels sent by the transmitters: Increasing the resolution and accuracy of the commands handled by the sticks.
For the same reason, the CCPM mixers should not be handled by the transmitters but by the flight controllers that process the 32-bit signals of the various channels at 64 bits.

As for exponentials, however, those used by default by the flight controllers are used to linearize nonlinear servo commands.
In fact, it is well known that vertical link movements are maximum when the servo horns are in the center (at 90°) and vertical link movements decrease as the rotation of the servo horns up or down increases. The default values of the exponentials set in the flight controllers make the vertical movements of the links more linear.
Only in the very rare cases where linear servos are used (slider servos with endless screws) should the values of the exponentials in the flight controllers be set to zero.

However, on the transmitter "can" also be added higher exponential values that help beginners who do not yet know how to dose the controls well to have less effect in controlling the sticks around their center position.


   
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(@roman-sibbert)
New Member Customer
Joined: 8 months ago
Posts: 2
 

Hello,

thanks very much for the detailed answer. I wanted to attach a screenschot of the instructions associated to panel five. As I was doing this I recognized that it might be a problem regarding the translation... I'm using the software in German language, and there it reads like expo MUST be off, because it is managed by the FCU and varies depending on flight style and current operation, like e.g. rescue. Nevertheless, I somehow am not allowed to attach anything. But obviously you know how Panel five looks...

My exact backtranslation of the German wording would be: ”The expo is managed by the BRAIN, as well as changes in values and dependencies on the chosen flight style or during several other operations (like rescue), thereby all of those must be turned off in the transmitter.“ 

Because this clearly refers to flight-operation following later it is less than obvious that you are still allowed to use transmitter expo after the base setup is finished.

And the english version in my opinion is still not absolutely clear that the usage of TX expo isn't forbidden, I would firstly understand it like you have to set expo in the software. Especially as I use expo in the first place to influence steering behaviour around the stick centre, as it is the classic usage of the functionality e.g. in aeroplanes. That the Brain uses it to linearize the non-linear behaviour of a servo didn't come to my mind until you explained it here.

 


   
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