# References

First of all,it could be useful to define some references  used along the project.

Let’s start to name the 4 motors using a number and a orientation reference:

I’ll call motor0 ( M0) ,motor1 (M1) ,motor2 (M2) e motor3 (M3).

(the index starts from 0 because it is more useful when programming in python: an array index starts from 0)

Looking the quadcopter from above , the motors are numbered in counterclock wise.

Considering a cartesian reference system:

• positive X is exiting M0 with direction M2-M0
• positive Y is exiting M1 with direction M3-M1
• positive Z is exiting from the motor plan

In aviation, they are using the following terminology:

• trottle: vertical movement
• roll: rotation along the fuselage
• pitch: trasversal rotation respect the fuselage , along the wings.it is also called  nick.
• yaw: rotation perpendicular the fuselage and the wings.

Considering the simmetry of the quadcopter, we can assume:

• roll: rotation along X
• pitch: rotation along Y
• yaw: rotation along Z

Dimensions are always in mm ,degrees, seconds