“RC Rate” vs “Roll/Pitch/Yaw Rate” for Mini Quad

I was asked about the difference between RC rate and Pitch/Roll/Yaw rates, so here is my understanding of what they are, how they affect your quadcopter based on Betaflight/Cleanflight firmware, and how to set them up.

You might be also interested in PID tuning.

What is RC Rate and Expo?

In a nutshell, RC rate set the speed of rotation for stick travel. Expo adjusts the centre-stick softness against full-stick speed.

RC Rate

RC Rate is the multiplier on your Radio Transmitter inputs for all 3-axis: pitch, roll and yaw (one value for all 3 axis). If you increase this your quad will respond more aggressively to your stick inputs. This is basically the stick sensitivity setting.

RC Expo

Generally, Expo is a value between 0% and 100%. By increasing it, it reduces the sensitivity of your stick input around the centre stick (imagine a U curve, where it’s flatter in the middle). 0% = no Expo, it means no sensitivity reduction, and you get a V curve.

Expo is often used with high rates, so the pilot can have precise control near centre sticks, but yet can do more aggressive aerobatics with stick end points.

There is no right or wrong expo value, as long as it suits you. I have shaky fingers, so my expo is a bit higher than other people’s. :p

History of Pitch/Roll/Yaw Rate, and Super Rate

Pitch, Roll and Yaw rates change the speed at which the quad moves in a given angle or rotation. For example, if you increase ROLL RATE, the quad will spin around roll axis faster and more than at a lower rate.

You might wonder, we already have RC rate, why do we have another rate for each axis? Long story :)

When P/R Rate Was Introduced, Thanks to “Super Expo”

As we know the origin of Baseflight, Cleanflight and Betaflight were Multiwii, and back then it only had RC rate and Expo, that was it.

Later on, more and more crazy pilots started flying those little beasts called “Mini Quad”. They found Multiwii didn’t spin fast enough when doing flips and rolls, so additional rates were added in MW2.3 PID controller, to relaxed the PIDs as stick deflection increases, and increase the maximum rotation rate at extreme stick deflection.

This effect is known as “Super Expo” at the time – basically it means you can have relatively moderate stick sensitivity around mid sticks for “normal flying maneuvers”, and yet super fast roll/flip at stick end points.

With MW2.3 PID controller, Pitch/Roll/Yaw Rates have some influence on PID Controller. For example by increasing pitch/roll rate, you get faster spins, but your multicopter might feel less in control at stick end points. Also, it affects all-round stick range and not just the end points!

No more Super Expo in Cleanflight – P/R/Y Rates are now just Multipliers

Some time later, Cleanflight introduced more PID controllers, such as Re-Write and Luxfloat. In these PID controllers, P/R Rates no longer have an effect on PID values (however it still does have effects for controller 0, 4, 5 and 6).

P/R rate setting was still in the software for Re-Write and Luxfloat, although they won’t give you the “super expo” effect like they were designed to do. They simply linearly increase the overall rate on top of existing RC rate. Same with R/P Expo.

As for Yaw Rate, it’s explained in Cleanflight documentation that, “in PID Controllers 0 and 5, it acts as a PID reduction as explained above. In PID Controllers 1-4, it acts as a stick sensitivity multiplier, as explained above.”

Update 07 Oct 2016 – “Super-Expo” is Back in Betaflight – Super Rate to Replace P/R Rate

Flyduino’s KISS FC is another branch of Multiwii. They inherited the “Super-Expo” feature in their PID Controller, and it was particularly popular within their users.

At the time, Boris (Betaflight developer) was focus on Re-Write and Luxfloat PID controller (by removing all other PID C’s). As we mentioned earlier, these PID Controllers don’t have “Super Expo” effect. But due to how cool it is, he decided to implement it for those PID controllers in Betaflight.

And he later changed the naming of P/R rate to Super Rate.

What is Super Rate

Super Rate modulates the end points of the stick curves. When adjusting Super Rate, only the end points of the curve changes, the center remains the same.

It basically makes the end portion of your sticks more or less sensitive, so you can control the speed of rotation only at the end of the stick.

How to set RC Rate/Expo and Super Rate?

I mostly fly FPV in acro mode and I always tune RC rate first by cruising around (no flips/rolls).

Then I crank up Super Rate for flip, rolls and acrobatics, until I am happy with the speed of rotation.

Finally I will add a little bit of RC Expo to have a bit more fine control in the mid stick.

You might want to further fine tune RC Rate/Expo and Super rate to make sure the quad isn’t too twitchy around the centre stick.

One thing I notice from all the different flight controller software is, they all have different ranges of PID, rates and expo number scaling. So I never bother trying to relate those values from one to the other, just whether the value should be lower or higher.

Also, avoid setting expo on the radio (TX), because it reduces your stick value resolution. ONLY set Expo in the flight controller

Throttle Mid and Expo

Lastly, Next to RC rate and expo, you also have Throttle Mid and Throttle Expo.

THROTTLE MID is default at mid throttle, but in my opinion this should be set to a value where your quad hovers. If you have to raise your throttle stick past the centre to hover, increase it. If your quad has higher power-to-weight ratio than 2, (hover at less than 50% throttle), you might want to drop it, so it’s easier to control your altitude. You need to use this with some throttle expo, otherwise it won’t do anything. If you set Expo = 0, you can ignore throttle mid.

One funny situation I see all the time is, some people fly a over-powered mini quad, and their throttle mid is way too high than its hover point, and they cannot land it without crash into the ground. :D

THROTTLE EXPO is how flat you want your throttle mid to be on a curve, so the flatter curve, the softer response it will give you. I personally use no expo or just a little expo (<10), you get better resolution with throttle control. Especially useful when flying proximity and racing.

26 thoughts on ““RC Rate” vs “Roll/Pitch/Yaw Rate” for Mini Quad

  1. supernull

    Now it’s march of 2017 and some things seem to be different. Like when you write “I personally use no expo or just a little expo (<10)", the throttle expo now goes from 0 to 1, so <10 would be <0.1 today, right? Also when you write about throttle mid, "You need to use this with some throttle expo, otherwise it won’t do anything." is this statement still true today? So if I want to make use of throttle mid, I have to set expo to something like 0.05? Thanks!

    Reply
    1. Oscar Post author

      Yes you are right, these firmware keep changing stuff it’s impossible to keep track of and update all the articles :D
      But I will try when I have time! thank you for the comment!

      Reply
  2. Dave

    Hey man, I’ve recently taken an interest in flying quadcopters, I got a JJRC1000A to start off with and just learning how to get the damn thing to hover was a nightmare, it took me several weeks of playing around with it before I could fly it around my livingroom comfortably without constantly banging off walls and doors!!

    Then I went out and bought the Syma X5C which I find a whole lot easier to fly, I’m able to cruise around outdoors with the Syma no problem at all.

    But now I wanted to move onto something a bit bigger and better, also my dad has the Phantom 4 Pro which I’ve had the chance to fly it several times and it was an amazing experience, however, one thing that has me scratching my head with the Phantom, I thought with these high end drones like the DJI ones that the right stick that controls the left and right roll would always remain left and right regardless of the drones orientation, so you could just look at your display that’s connected to your controller and you’d be using that to know the drones orientation, I always thought this was how it’d be for flying FPV, or am I completely missing something?

    I’ve searched all over the net to try and find an answer to this but I can’t seem to find anything at all, so I am hoping you could enlighten me here.

    I mean surely people who fly in FPV through buildings around trees etc aren’t having to be thinking when and where those controls will be reversed, I figured you could use the display on the P4 controller for FPV instead of goggles??

    Hope you get back to me, thanks in advance.

    Reply
    1. Chris

      If I understand you right, you’re saying the phantom’s orientation with regards to the pilot is what controls what direction the pitch, roll controls move the quad? If so, this is called headless mode. Usually it’s only used for line-of-sight flying, because as you said, it makes fpv confusing. I’ve flown a Phantom 3 pro (iirc), and it didn’t do this, I suspect it is a setting that could be turned on or off somewhere in the labyrinth of the dji app. Don’t ask me how though, I don’t have a clue how those things work :)

      Reply
  3. joe

    Hey thanks for the help, i have a question though. i changed my rates. but i cant figure out how to get my “roll” to move only the quad right or left without adding in pitch. Right now as it stands my roll and pitch move simultaneously causing a front ward tilt when trying to “roll right”. is there a way to tune the quad so roll and pitch dont work together at the same time?

    Reply
    1. Oscar Post author

      no they shouldn’t move the same time if you are only controlling pitch or roll :D
      are you taking into account your camera tilt angle? with the tilt the quad will feel like it’s pitching and rolling the same time when you are doing a roll…

      Reply
  4. James

    Yes im using the open source cx20 and i have an issue with the battery getting drained real quick like few seconds on giving it throttle. Just need to know what i can do to make it quit draining the battery and its fully charged.

    Reply
  5. Robin

    I am new to rate mode and have 3 modes setup (selected using a 3 way switch on the TX)
    Angle and horizon “feel” fine but when I go into acro I do feel it needs a little expo
    -possibly a mixture of me being new to flying acro and deadband being set at 6 because of jitter…mainly me being a ‘newbie’ thing though :)
    I can fly helis so am kind of surprised I’m struggling a little- but my 250 quad seems more reactive/skittish than my Trex250 heli!

    I have added some expo on the TX for AIL and ELE (15%) , but only when acro is selected and it does seem to be helping massively and I could possibly afford to lower it slightly – I can’t see how to only apply expo on the ‘acro’ mode in Cleanflight and leave angle and horizon without, so I guess I’m going to go with this method for now and slowly reduce till I have the skill speed and accuracy of BanniUK..(In my dreams!)
    Weaning myself off horizon is the goal :D

    Reply
    1. Oscar Post author

      Only way i can see is to have separate profile for different modes… but really you should get used to rate mode and completely forget about self-level mode :) All top pilots only fly rate mode.

      Reply
      1. DeeHawk

        I’ll challenge anyone who thinks they can LOS better through a proximity track without gyro. :D
        It’s horrible for FPV tho :)
        Nice compilation of tuning tips yet again!

  6. Spencer

    Hey Oscar,

    You have helped me countless times in the past, but in this case your post was detrimental.

    mmix is now zero based instead of 1 based. If you define motor mixes starting from 1 it will not acknowledge them until you specify a motor 0 mmix. This can be very confusing based on your tutorial. Also: these settings are very helpful to know:

    mixer custom
    mmix reset

    And finally, this website helped me figure out the issue I was having… so credit due: iforce2d.net/mixercalc/

    Spencer

    Reply
    1. Oscar Post author

      are you commenting on the right post? I don’t think I talked about mixer in this article?
      I am assuming you are referring to the “custom motor mixer” post… that was written back in early 2015… cleanflight decided to keep changing things around (including the name of the function), being a part time blogger, i tried my best to amend it and keep it up to day… but there are times I just can’t keep up with things… so if there was any confusion caused I apologise.

      I would also really appreciate it if you could point out which part of the article isn’t correct or clear… I don’t use mmix for a very long time and I start to forget about some of the details. (and that’s why I like to document/blog things)

      Reply
  7. Newbie

    Hi Oscar !

    I dont speak well english and i am new with cf and naze32.
    Your explanation of these are very easy to understand than cf docs.

    THANK YOU!

    Reply
  8. Mike

    Hi Oscar
    New to quads. Just built 280 with scorpion motors, BL Heli 20 amp esc, Naze 32 ver6, dx8 tx, Orange 615x using ppm and Clean Flight set up. On throttle up the quad noses over. I rechecked setup and same results. In motors tab in cleanflight the motors do not come up even when using transmitter but come up even with master motor tab.
    Where do I start looking for problem.
    Thanks
    Mike

    Reply
  9. Paul

    Hi Oscar,
    Are your certain that throttle mid has an effect if the expo is off?

    My mini quad is 7:1 power to weight and I have the crash on landing problem :) I tried throttle mid at both 20% and 80% and it didn’t seem to have any effect at all. I’m using luxfloat…

    Reply
  10. Antonio

    Congratulations for the excellent tutorials and articles técnicos.Qual would be quieter fee for “exponential” more suitable for one who never flew and will learn for the first time.

    Reply
  11. Ondrej

    Hi Oscar,
    I was playing with the Y/P/R rate lately. I was looking for the meaning of the numbers and still was not able to figure it out. In the CF forum, i found repeatedly, that the Y/P/R rate is multiplier. Well, i doubt that, because the default value is 0, as far as i can remember. Do you know, how these rates are processed in the PIDs?

    Reply
    1. Oscar Post author

      Hi Ondrej, like i mentioned in the post, it depends on PID controllers, these rates don’t necessary affect PID.
      for PID C 1 and 2, they only affect your stick sensitivity, saying they are multipliers so it’s easier to understand for people, it’s not like you really multiply the stick values with the Rate Number… no! :)
      Not sure what you are trying to do… just turn it up or down to where you see fit :) for normal users like myself… i see there is no need to dig deeper than that unless you are a developer, or you have having massive problems with it…

      Reply
  12. Holger

    I always tought it’s recommended to set Expo in the Tx and not the FC? Most pro pilots don’t seem to touch the Expo settings in Cleanflight at all.

    Reply
      1. Holger

        I was curious about this topic and got an detailed explanation from joshuabardwell on why to prefer FC expo over Tx expo: rcgroups.com/forums/showpost.php?p=32705942&postcount=999

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