Introduction to Imu

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  • Topic: Cartesian coordinate system, Dimension, Angle
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  • Published : May 31, 2013
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IMU
Inertial Measurement Unit
Help you measure tilt angle and angular velocity…

Topics We’ll cover today…
• • • • • • • • What is an IMU... ? Few Examples and Videos Accelerometer Gyrometer Magnetometer Filters Euler Angles Demos

By:-

Vivek Kumar
Vipul Gupta

(viveks@)
(vipgupta@)

Abhishek sharma (abhishr@)

So... Lets Start... 
• What is an IMU...?
• • • • • • • Few Examples and Videos Accelerometer Gyrometer Magnetometer Filters Euler Angles Demos

Why do we need IMU...
• One of the main problems during autonomous mobile objects’ development is the problem of precise navigation. • In order to navigate the object it is required to know the exact position and orientation of the object in relation to the known environment.

• Size of an MEMS IMU...

What is an IMU… ?
• Inertial Measurement Unit (IMU) is an electronic device that measures a body’s velocity, orientation and gravitational forces using a combination of accelerometers, gyroscopes and sometimes magnetometers.

9dof Razor IMU

6dof IMU
https://www.sparkfun.com/products/10736 https://www.sparkfun.com/products/10121

MEMS Sensors
• MICRO ELECTRO-MECHANICAL SYSTEMS
• Currently, most of the manufactured inertial measurement units are based on MEMS technology. • Regardless of easy usability, the main advantage of such devices is considerably its small size.

Next...
• What is an IMU?

• Few Examples and Videos...
• • • • • • Accelerometer Gyrometer Magnetometer Filters Euler Angles Demos

Examples…

Applications
• Used in navigation of mobile platforms and vehicles, for autopilots of aerial ships, boats or ground units, to detect collisions and in PCs for HDD security during fall. • It is also used in photo cameras for elimination of vibration effects. • Accelerometers are for instance used for collision detection, object’s orientation measurement or as user interface like in android mobile games.

Next...
• What is an IMU? • Few Examples and Videos

• Accelerometer...
• • • • • Gyrometer Magnetometer Filters Euler Angles Demos

Accelerometer
Measures net Linear Acceleration acting on the object. And outputs values along its axis in its body frame.

Questions...
Q. Do you like when your screen rotate automatically when you rotate your phone? Like this :

Q. How many of you say Nokia 1100 has an accelerometer...?

Common Types of Accelerometers
Sensor Category
Capacitive

Key Technologies
change in capacitance related to acceleration

Piezoelectric
Piezoresistive Hall Effect Magnetoresistive

Change in pressure induces voltage converted to acceleration resistance changes with acceleration Motion converted to electrical signal by sensing of changing magnetic fields Material resistivity changes in presence of magnetic field Location of heated mass tracked during acceleration by sensing temperature

Heat Transfer

ADXL345
• The accelerometer which we’ll use is ADXL345 • A small, thin, low power, threeaxis accelerometer with high resolution (13-bit) measurement up to ±16g. Features: 1.8V to 3.6V supply Low Power: 25 to 130uA @ 2.5V SPI and I2C interfaces Up to 13bit resolution at +/-16g Tap/Double Tap detection Activity/Inactivity monitoring Free-Fall detection Dimensions: 3 x 5 x 1 mm

• Digital output data is formatted as 16-bit twos complement and is accessible through either a SPI (3- or 4-wire) or I2C digital interface.

https://www.sparkfun.com/datasheets/Sensors/Accelerometer/ADXL345.pdf

What do Accelerometer measure...?
• An accelerometer at rest on the surface of the earth will measure an acceleration g= 9.81 m/s2 due to its weight. • By contrast, accelerometers in free fall or at rest in outer space will measure zero. When It’s in free fall, It gives 0. When at rest , It gives 9.8

Questions...
Q. What is the value of accelerations in X, Y, Z axes of accelerometer 1.) if its Z-axis making an angle of 90˚ with horizontal plane. Along X-axis Along Y-axis...
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