It can be super frustrating when you spend ages building or calibrating your drone or quadcopter only to have it be super wobbly as soon as it takes off. Fear, not the wobbles are almost always fixable and here we will run through all of the things that you can do to keep it flying stable and true. Here are the simple checks and tunings for “why does my drone wobble”.
If your drone is wobbling there are a couple of initial checks that you need to make. Firstly, if your drone is in the self-leveling mode you need to check the P gain – this is the power of self-leveling. Too high and it’ll cause wobbling. To low and it will be slow to self-level. Play with this setting until you can get your drone wobble-free. Also, take the time to calibrate the electronic speed controller (ESC) and check the motor direction.
Check out my YouTube video if you want a video explaining this article:
Of course, there are a number of tiny adjustments that can send your drone into a wobble without you realizing it. Here’s what you need to check to make sure your drone wobbles are a thing of the past…
Do this first: Tuning your PID
As you find out more and more about building drones you’ll understand the importance of tuning your PID. And as all drone builders will tell you – there is equal parts art and science in tuning PID values.
PID stands for Proportional, Integral, Derivative and can be tuned on a range of drone software. Don’t be put off by the naming of these gains they are really just a fancy way of saying the following:
- P looks at the present error – if the current setting is far away from the set point the P setting will push to keep it close to the set point. The further away it is the harder it will push.
- I is the knowledge gained from past errors – this looks at past errors (caused by continuous external forces) and will counteract them.
- D is a prediction of future errors – as P starts pushing the value close to the set point the D value will stop you from massively overshooting.
The Effect Of Each PID Parameter
As you start playing with your drone’s PID values you’ll notice that each value affects the drone in different ways. Let’s take a look at each value in a little more value.
Remember to save a copy of your current values before you start mucking around too much with your settings. It can be easy to throw them way off!
Safety – REMOVE the props at this point!
The P value (also known as the gain value – is one of the most important aspects of regulating the flight of a drone.
The value determines how hard the drone should work to correct itself to achieve the desired flight path (controlled by the controller transmission). It can be both too high or too low:
- Too high and the drone will oscillate. This is symptomatic of aggressive overcorrection by the drone and you’ll see high-frequency oscillations.
- Too low and the copter will feel like it is slow to respond and you may even hear the motors spool up slowly.
To find a good p-value you should gradually increase the P value until the drone starts to oscillate then set this value to 50%.
I gain is the setting that determines how hard the drone should respond to external forces – like holding it’s position in wind or due to an off center of mass ( quite easily caused by upgrading components of your drone.
- Too high and the drone will feel unresponsive
- Too low and you’ll find that you have to manually correct your drones flight pattern.
You want to leave the I value as low as possible without have to correct the flight pattern manually.
The D gain is like a shock absorber for the P value.
- If the D value is too low the drone will nor react rapidly enough.
- If the D value to too high the drone will oscillate with rapid small amplitude oscillations. It can also decrease the quads response and cause the drone to feel sluggish.
Increase the D gain until the drone starts to oscillate will small rapid oscillations. Reduce to 50% of this value.
Check out this video. It is a great practical resource for visually assessing your PID values and how they need to change:
What is the best method to estimate PID parameters?
You can also mathematically simulate the best PID values for a given quad copter – however this is starting to get pretty serious and will require you to be very comfortable with advanced maths and mathmatics sofware like Matlab.
Some papers that will help you get started are:
For most drone flyers, however, at this point you’ll be able to get rid of most wobble features without haveing to worry too much about the maths behind it all.
You can figure it out through trial and error! Maybe at this point you haven’t quite managed to stop your drone from wobbling…
You’ll need to check these other aspects of your drone set up:
Calibrate the ESC
Always check the documentation for the brand of ESC that you are using. An “all at once” approach has been noted to work well for most ESCs and can be seen in the video below:
There are some ESCs that do not require calibration but check with the documentation if you can change the settings.
What about a DJI drone?
If you are here due to wobbles with your DJI drone you need to look for your IMU calibration settings. IMU stands for inertial measurement unit and uses data from an accelerometer, gyroscope, thermometer and barometer to determine the drones movements and potision.
A lot of the time the DJI GO4 app will prompt you to recalibrate the IMU or compass if it senses an issue. Always follow this advice and calibrate the drone’s sensors. In many cases, it won’t allow you to take off without recalibrating anyway.
Check flight controller arrow
The flight controller in the drone is responsible for directing the RPM of each motor. It is a small circuit board that sitsin the body of the drone.
Most flight controllers have an arrow pointing to the front of the drone. Make sure that if you have been playing about with the flight controller you tell the software otherwise your drone will spin out of control.
Check which motor starts when connected to a computer
If you are building your own drone take a moment to connect the drone to a computer. The software that you are using should have an option to spin each motor separately.
Make sure that your pops are off at this point!
When you start up motor one does the right motor start up? It is critical that each of your motors are spinning as directed by the flight controller.
Without correct signal to the correct motor your copter will very quickly wobble and crash.
Are your motors spinning the right direction?
Make sure that each motor is spinning in the right direction.
On a four motor set up – two motors should be spinning clockwise and two should be spinning anticlockwise.
The final word
Take the time to really check your PID tuning and do a couple of test flights to make sure you are happy with the settings and you are not seeing any large scale oscillations.