What is an Inertial Measurement Unit? And Why Would the World Be a Different Place Without IMU?

For many years, scientists have made significant progress in understanding how humans perceive their surroundings and use that information to navigate. Technology has grown to the point that we are flying unmanned devices, such as drones, and they are even available as toys for children.


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You've probably seen the flying drones. Drones are incredible, remote-controlled flying machines that can do everything from taking images and films to delivering items. But what enables them to fly so effortlessly?


Drones are just one type of flying machine that makes use of IMU (Inertial Measurement Unit) sensors. To fly in any direction, the flight controller collect, present IMU data, and transfers it to the motor electronic speed controllers (ESC). These electrical speed controllers tell the quadcopter's motors how much thrust and speed they need to fly or hover.


Let's take a closer look at IMU now:

What is the Inertial Measurement Unit (IMU)?

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An IMU tracks the movement of the moving body in three dimensions. One or more accelerometers in an inertial measurement device detect the rate of acceleration. Using one or more gyroscopes, the IMU detects changes in rotational properties such as pitch, roll, and yaw.


How does an IMU calculate an object's heading?


The heading of an object is the direction in which it is traveling. An IMU requires two sensors to calculate headings: a gyroscope to sense angular rate and an accelerometer to sense linear acceleration. An IMU is typically made up of three accelerometers and three gyroscopes. If necessary, three magnetometers were also used. One for each of the axes: roll, pitch, and yaw. Rotation about the front-to-back axis is known as roll. Rotation about the side-to-side axis is known as pitch, and rotation about the vertical axis is known as yaw. The sensing environment gets more exact when combined with GPS signals.


An IMU typically consists of:

  • Gyroscopes: provides angular orientation

  • Accelerometers: provides axis orientation

  • Magnetometers (optional): measurement of the magnetic field surrounding the system.

IMU use cases


An IMU tracks a body in three-dimensional space. It is especially used in navigation systems, where they are used in inertial navigation systems (INS) in unmanned aerial vehicles (UAVs), robotics, and wearable electronics. They continuously track the orientation of a moving body and are used to calculate a flying object's position relative to its starting point.



Inertial measurement units are used in all airborne, sea, and land vehicles. Examples include aircraft: jets, gliders, aircraft missiles, powered parachutes, motor gliders, vertical take-off and landing (VOTL) planes, snow skis, skis and boards, and helicopters. These applications use the same technology for range and direction finding and return to home.


Engineers at NASA's Jet Propulsion Laboratory (JPL) have used IMUs to measure station-keeping forces that allowed the Curiosity rover to conduct its perilous landing. They are also currently using IMUs to navigate and maximize the payload onboard the Mars Reconnaissance Orbiter.


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IMUs are also used in some computer gaming systems to track the position of the player's body in three-dimensional space. Weather sensors also use IMU. These instruments, such as altimeters and barometers, measure atmospheric pressure, height above sea level, the time of day, etc. An IMU in altimeter systems determines the vertical distance between the observer and the surface. The altimeter measures the amount of air pressure above the observer using a barometric pressure sensor. The IMU tracks the height difference when barometric pressure drops. Temperature changes can also be measured. A barometric pressure sensor measures atmospheric pressure, elevation, temperature, and the rate of temperature change. Depending on the readings, an IMU can detect changes in altitude.


Types of IMUs


The Inertial Measurement Unit comes in diverse types. Dual Inertial Measurement Unit of the Global Positioning System, the Differential GPS Compatible Inertial Measurement Unit, the Multiple Axis Adaptive Inertial Measurement Unit, and a variety of velocity sensors are some examples.


Conclusion


An inertial measurement unit, or IMU, is a device that measures and reports a body’s specific force, angular rate, and sometimes the orientation of the body, using a combination of accelerometers, gyroscopes, and sometimes magnetometers. IMUs are typically used in conjunction with an INS (Inertial Navigation System) or GNSS (Global Navigation Satellite System) receiver, providing complementary information to dead reckoning calculations.


Control and stabilization, navigation and correction, and measurement and testing are some of the main applications of IMU sensors. However, common markets are unmanned systems control, mobile mapping applications on land, air, or sea, and any payload that requires stabilization or pointing. IMUs are key components of the INS/GNSS systems used in airplanes, ships, missiles, and even satellites.


Cheers!