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

This post explains the differences between RC rate, expo and Super Rate, how these settings can affect your quadcopter performance, 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 RC rate, your quad will respond more aggressively to your stick inputs. Think of RC rate as 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.

Imagine that Expo applies a “U” curve to your stick output, where it’s flatter in the middle. With 0% of expo, it means there is no sensitivity reduction, and you will get a “V” curve.

Expo is often coupled with high rates, so the pilot can perform aggressive moves when maintaining precise control around stick centre.

There is no right or wrong expo/rate value, as long as it suits you. For example, I personally have shaky fingers, so my expo might be a bit higher than others. :p

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

In the past, we used to have separate Rate settings for Pitch, Roll and Yaw, on top of RC rate.

Pitch/Roll/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 did we have another rate for each axis? Long story :)

Why additional rates were introduced, and what is “Super Expo”?

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

As “Mini Quad’s” were getting more and more popular, more pilots demanded higher rate to perform faster spins and crazier moves. 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 feature was 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!

“Super Expo” Effect Removed in Cleanflight

In 2015, Cleanflight introduced more PID controllers in the firmware, 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).

That means the Pitch/Roll rate setting that was still there will no longer give you the “super expo” effect. They are now just multipliers that simply increase the overall rate on top of existing RC rate linearly.

Update 07 Oct 2016 – “Super-Expo” is Back in Betaflight

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.

So in Betaflight the developers decided to bring it back, and it’s named “Super Rate” or “S.Rate” in Betaflight. And P/R rate was soon removed too.

What is Super Rate in Betaflight

Super Rate (or S.Rate) changes your full-stick-deflection rate, also your centre stick precision.

It’s bit like the combination of both Rate and Expo. Although it gives you more flexibility on tuning and control, but you have play around with RC Rate, Expo and S.Rate back and forth to achieve the desired curve while still maintaining the desired full-deflection rate that you like.

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), to make sure the quad respond quickly to your stick inputs. For me I usually start from somewhere between 0,9 to 1.2.

Then I crank up Super Rate for flip, rolls and acrobatics, until I am happy with the speed of rotation. Note that it also affects your centre stick sensitivity, so you might want to adjust rate again, but again Rate will affect your end point deflection…. you might need to do this forth and back a few times to get it right :)

Finally you can add a little bit of RC Expo to have a bit more precise control in the mid stick if you want. 0.05 to 0.1 is a good range to start.

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 applying Expo on the radio (TX), because it reduces your stick 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 very often, is that some people fly an over-powered mini quad, and their throttle mid is set way higher than the 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 just a tiny bit of throttle expo (<10) to get a better resolution with throttle control. It’s 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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