IMU Calibration: Everything You Need to Know and More!

This article will guide you through the process of calibration and supply you with useful tips and tricks on how to do it properly!
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Last updatedLast updated: August 28, 2021

Flying a drone is an interesting experience and is fun for people of all ages. Even when you are carrying out a serious task such as controlling drones for roof inspections, you would still be getting a sense of fulfillment from carrying out perfect maneuvers and moving flawlessly.

Well, this fulfillment would only exist if the drone were calibrated because otherwise, your experience would be bumpier and less fun. How then do you calibrate, and what exactly is this IMU calibration people keep referring to? These are the questions that this article is here to answer.

Well, until you reach that point of the article where I touch on it, consider calibration to be a way of ensuring optimal control over your drone. Unfortunately, the manufacturers of drones do not exactly indicate when drones should be calibrated, and that’s another piece of information you’d have to wait for me to share. Read away and learn.

What’s an IMU?

IMU Calibration: Everything You Need to Know and More!Firstly, IMU is an acronym for Inertial Measurement Unit. In the drone or aircraft that has most likely prompted this need to research on IMUs, it is an electronic device that measures and monitors the angular velocity, specific force, and general attitude of your drone.

From the very definition, you’re probably wondering how something described as such can carry out all of these functions. An IMU does so with the use of accelerometers, magnetometers, gyroscopes, thermometers, and barometers. This makes it very essential to how drones work. Some of these might not be present in the IMU of your drone, but most will.

All of these features or sensors in the IMU would collect raw data based on the performance of the drone, and the data would then be used by the IMU to calculate and provide information such as velocity, angular rates, and attitudes. These values and, by extension, the data sourced for and crunched by IMUs are essential in determining the level of control one can exert on a drone.

Individual, the functions of the sensors in the IMU are:

  1. The accelerometer is used to measure the acceleration of the drone as caused by gravity or motion but only when it is linear
  2. The gyroscope would measure the orientation of the drone when it tilts. This would mean that it measures the angular rates and velocity of the drone. In addition to its measurement function, it would also help maintain the orientation of the drone, granting it more stability.
  3. A barometer within the IMU would help detect changes in height as a function of changes in atmospheric pressure.
  4. As you already know, a thermometer would measure temperature. In the case of an IMU within a drone, the temperature at which it is calibrated is of utmost importance as the drone will be required to be at that temperature before any future flights.

When to calibrate the IMU

IMU Calibration: Everything You Need to Know and More!We have established that the IMU of a drone is important to ensure that during flights, you have good control Trusted Source Drone Delivery Is One Step Closer To Reality : NPR Walgreens is testing out delivery from store to door by drone in Virginia, and UPS won approval to expand air delivery of medical supplies. www.npr.org over the drone. For instance, without proper calibration, your drone might misread its position or stability and give off negative inputs to correct it. This would undoubtedly make it difficult to control.

On the other hand, proper calibration would mean that your drone accurately detects linear and angular motion while also monitoring changes in altitude correctly. A tightly calibrated drone is thus, easier to control. Hence, regardless of the types of drones you might be operating, calibration is important.

Having said that, though, there is rarely a generally accepted time for when the IMU of a drone should be calibrated. Part of the reason for this is that there are many appropriate times. The following times are good enough for a calibration:

  1. After unboxing the drone, after purchasing a drone, and before taking it out for a flight, it is advisable that you calibrate its IMU first.
  2. After updating the firmware, regardless of the reason that warranted the update, the drone could be recalibrated once the update is complete.
  3. Suppose the process of warming up before flights is taking too much time. When this happens, it is an indicator that the storage temperature of the drone is far below the calibrated temperature. To shorten the time, it would be advisable to recalibrate the IMU when you get the time.
  4. If the drone hovers without interference, experience a small error during a turn or tilt, or if it doesn’t seem to be balanced. All of these problems are potentially serious ones, as any small error in the balance or movement of the drone could be compounded as the drone moves away from the calibration environment. As such, rather than ignore errors because they may seem small, it’s better to recalibrate the drone as soon as is possible. Even lightweight drones are not expected to tilt without wind.
  5. If the mobile app of the drone instructs or prompts you to do so.
  6. After a hard crash or landing, in such a crash, the sensors might get scrambled and would necessitate a calibration before the next flight. As such, if you don’t know the state of the sensors, do the right thing and calibrate the drone.

Some people are generally of the opinion that calibration should be carried out before every flight, and they follow this rule, but this regular, every-flight calibration is not necessary, especially if you haven’t been changing locations recently. Not that you should listen to your drone as it knows best; not every drone is as wind resistant as this DJI Mini 2- Ultralight and Foldable Drone.

How to check the IMU’s status

In the event of a crash or hard landing, as brought up above, the sensors of the IMU might become jarred and may not be so trustworthy. You can ascertain their trustworthiness by checking their status. This is not the only reason to check their status, and theoretically, you should check it regularly, but it is the most appropriate reason for doing so.

To conduct this check, go to the main controller settings, advanced settings and finally, sensors. On this sensor screen, you would see the sensors and three colors underneath them; green, red, and yellow. Green stands for excellent, yellow stands for good, and red stands for poor. If any of the lights under are red, you should probably carry out a calibration.

How to calibrate the IMU

IMU Calibration: Everything You Need to Know and More!Contrary to what this explanation might have implied, calibration of the IMU in drones is not a particularly difficult or complicated process. However, this doesn’t mean you shouldn’t take care during the process.

Two basic requirements for the calibration are that the drone is placed on a completely flat surface and in a cool environment. These are recommended as the calibration state is what the drone interprets as level, and if the surface tilts during calibration, your drone would automatically assume that tilted position to be its level position. Hence, whatever movements you control for would be performed using that tilted level as reference. Not that the tilt and balance referred to here is different from the environment or obstacles sensing features possessed by some drones, such as the DJI Air 2S drone.

As for the temperature, I stated earlier that the temperature at which the IMU is calibrated would determine how long it may take to warm up before flights. If the calibrated temperature is high, the warm up would be longer.

To shorten this warm up time, some users have resorted to calibrating in refrigerators, but the risk of moisture entry and extreme changes in temperature makes this practice unadvisable. Rather, calibrate at room temperature or in slightly cool conditions.

That aside, you could follow the steps outlined below to calibrate the IMU of your drone:

  1. Check the battery level to ensure it is at least 50% charged
  2. Place your drone on a completely flat surface
  3. Set the thermostat to room temperature and give the drone some time to cool down
  4. Open the drone app
  5. Turn on the drone and the controller
  6. Follow this directory: Main controller settings>advanced settings>sensors>calibrate>IMU>start
  7. Follow the instructions provided when they are provided
  8. Once the calibration is complete, restart the drone.

Final thoughts

As you would have learned, if you paid sufficient attention, your drone is no full AI Trusted Source The role of AI in drones and autonomous flight - Datascience.aero The term “Drone” has been massively overused; most of you have surely seen it time and time again in news and media articles. This term can range from small and cheap hobby aircraft available at Amazon all the way to multimillion weapons systems used on battlefields. At the moment, the most formal and internationally accepted term used to refer to these devices is RPA (Remotely Piloted Aircraft) and RPAS (Remotely Piloted Aircraft System). datascience.aero , but it is programmed to adapt to help you control it better. That’s what the calibration process is all about; giving the drone some reference points to judge its performance and your controlling instructions.

Hence, without the calibrations, many things would be off about the movement or performance of your drone, and the drone would take it to be normal. When this happens, recalibrate the drone before continuing to fly rather than ignore the problem.

I can probably spend a day waxing about the importance of IMU calibration and situations that call for it, but I’m sure you already get the point. Calibrate your drone now and say a mental “Ciao” to flight uncertainty.

References

1.
Drone Delivery Is One Step Closer To Reality : NPR
Walgreens is testing out delivery from store to door by drone in Virginia, and UPS won approval to expand air delivery of medical supplies.
2.
The role of AI in drones and autonomous flight - Datascience.aero
The term “Drone” has been massively overused; most of you have surely seen it time and time again in news and media articles. This term can range from small and cheap hobby aircraft available at Amazon all the way to multimillion weapons systems used on battlefields. At the moment, the most formal and internationally accepted term used to refer to these devices is RPA (Remotely Piloted Aircraft) and RPAS (Remotely Piloted Aircraft System).
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