Stable Flight with an iPhone

Stable Flight with an iPhone

Some Crazyfliers seem to have trouble learning how to fly with the iPhone mobile client. I hope this entry can ease the learning curve for those people just new to the Crazyflie 2 who are using only a mobile client. This guide is written for iPhone (because that’s what I have and use) but most of it is probably applicable to Android as well.

If you find it a little hard to learn how to control your Crazyflie 2 with the Crazyflie iPhone client, read on…

1) You can customize the settings and should. I prefer using “Mode 2,” since it’s like a video game, which puts the thrust on the left thumb (up and down) along with yaw (side to side). Pitch (up and down) and roll (side to side) are on the right thumb. Yaw is a bit tricky at first because it changes where the “head” is pointing and makes pitch and roll control inputs seem strange sometimes. I find it’s best to disable yaw when first starting out — just to reduce the number inputs you have to deal with.

To set up your controller in “Mode 2,” go to the “Settings” screen and touch “Mode 2” in the “Control mode” section.
iPhone Client - Settings

iPhone Client - Mode 2

To disable yaw, touch “Custom” in the “Control sensitivity” section. Then set the following values: Pitch/roll: 25, Thrust: 80, Yaw rate: 0. This emulates “Slow” sensitivity mode with yaw disabled. Close the “Settings” screen and return back to the “Control” screen.
iPhone Client - Custom

iPhone Client - Pitch

iPhone Client - Thrust

iPhone Client - Yaw

2) Connect the client. Turn on your Crazyflie 2.0 and once the heartbeat led (M1- red) is flashing, touch “Connect” on the iPhone client control screen.

iPhone Client - Connect

3) Get Airborne!

3a) Take off. To enable control you must place both thumbs on the control screen. You do not have to leave them there to continue controlling the Crazyflie. This is important to note because I find it easier to maintain stable take off (and control in the air) if I remove my right thumb (pitch and roll) from the screen – just during take off. Then I won’t accidentally input pitch or roll when taking off. I only put my right thumb on the control screen if I need to make minor adjustments.
iPhone Client - Activate

iPhone Client - Controls

The key to a good take-off is to get the Crazyflie in the air quickly. A slow take-off with a long, slow ramp up in thrust makes for a delayed hover near the ground and will nearly always result in a crash — until you are very practiced at it. The rotor wash creates a lot of turbulence near the ground and that makes it exceptionally hard to maintain stability.

With just the left thumb on the screen, rock your thumb up to quickly move the thrust to nearly maximum (our sensitivity setup will only allow the thrust to get to 80% anyway so you won’t hit max thrust even if the indicator shows it maxing out on the screen). That said, don’t over-thrust or you’ll find yourself in the ceiling!

iPhone Client - Take Off

As soon as you’ve got the Crazyflie in the air, at least three or four feet above ground, bring the thrust back down a little. You’ll get a quick rise, then the Crazyflie will start to sink down. As it starts the descent, use very minor movements with your thumb to increase the thrust. Slowly, you’ll find the equilibrium to get it to even buoyancy where it can hover and maybe rise and fall a little with very minor thumb corrections.

I can’t stress enough that your thumb movements here should be very subtle. No sliding up and down the control screen — that is too drastic. Just a tiny little push up or down — sometimes it will even feel like your thumb is not sliding at all, only rocking back and forth. During this balancing stage, you might find you need to make some picth and roll corrections. That’s OK, just put your right thumb to the screen and again make very subtle motion.

3b) Hovering and moving around. They key to further flight is a delicate touch. You shouldn’t be sliding your thumbs all over the screen. A calm, rocking of your thumbs forward and backward or side to side is all it takes. Drastic movement creates big changes in the atitude and altitiude which you then have to correct and can quite possibly over-compensate for. This starts the viscious cycle of over-correcting over-corrections and will result in a crash when the Crazyflie finally gets away from you. You don’t want gross movement, only small, fractional corrections. Subtlety and minor movements are the key here. I can’t stress this enough!

These steps, and a little practice, is all it takes to achieve stable flight with the Crazyflie 2 iPhone client. Once you’ve got a few battery cycles under your belt with this “No Yaw” configuration, you’ll be ready to start using the “Slow” config. After you’ve mastered yaw control and “Slow” is not enough for you, try “Fast” but be wary, “Fast” control mode is for very advanced pilots! It’s exceptionally easy to lose your Crazyflie.

Good luck and happy flying!

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