2012/Group 1/IMU

The Inertial Measurement Unit is implemented as a class in our controller, and its task is to read the accelerometer, gyroscope, magnetometer and height sensor and combine the data into a reliable signal for orientation (pitch, roll, yaw) and height. It implements a simplified Kalman filter.

Coordinate systems
In the image our global coordinate system is illustrated. The origin lies in the center of gravity of the quadcopter. The z-axis points towards the sky (zenith), the x-axis towards the magnetic northpole and the y-axis then automatically towards the west since it is a right-hand coordinate system. The pitch, roll and yaw angles are then defined as the angles that the quadcopter makes relative to the global coordinate system. The body coordinate system of the copter is defined as z-axis normal to the plane of the propellors and the x axis towards the front of the copter, y-axis automatically to the left. If the pitch, roll and yaw are all zero, the body coordinate system exactly aligns with the global coordinate system.