Sensors and GPS for Drones and Quadcopters

1. Introduction and functionality

1.1 Sensors for quadcopters and drones

The name of this model construction division, which was completely new just a few years ago, has developed. At the beginning there was the term 'quadcopter'. Since many model makers also build systems with six or eight propellers, there are also the terms 'hexacopter' and 'octocopter'. These different designs are also referred to with the general term of the multicopter.

The term 'drone' has also been used for these systems since around 2010. This term is originally known for military flight systems. This refers to unmanned flying objects that can fly autonomously via GPS or also remotely. It is important that they are unmanned, i.e. that no pilot is sitting in the cockpit. In principle, this can mean the systems of all possible flight principles, i.e. in addition to quad- and multicopters also fixedwing aircraft, as well as helicopters. In colloquial terms, however, the term drone has now almost become a synonym for quadcopter or general multicopter. This book only deals with this colloquial term drone, i.e. with the quad- or multicopters. The unmanned fixed-wing aircraft are therefore not dealt with here.

The sensors used have also evolved. The first quadcopters only had gyros in two or three axes. This resulted in high demands on the pilot of the drone. The acceleration sensors were added later, the combination allowed an automatic angular control. Then came the compass, the air pressure sensor and the GPS. Today all types and other sensors are used, which greatly simplifies the control of the drones. The sensors are the key for a simple control. The aim of this booklet is to explain their function in context with drones.

1.2 Steering mechanism and technical background

Quadrocopters are aircraft with four propellers. They have the same control capabilities as helicopters. Figure 1 illustrates this. The stick assignment of the remote control, as shown in Figure 2, is most commonly selected. However there are also model pilots who swap the left and right sides.

Figure 1: Steering possibilities.

Figure 2: Stick assignment.

‘Nick’ describes the tilting forward and backward. For that purpose, the stick of the remote control needs to be moved upwards (tilting forward) and downwards (tilting backward).

‘Roll’ describes the tilting to the left and right. The stick needs to be moved to the left and the right side.

‘Yaw’ describes the rotation around the vertical axis (z). The left stick needs to be moved to the left (counterclockwise yaw, view from top side) or the right (clockwise yaw, view from top side).

‘Gas’ describes the movement along the vertical axis (z). If the left stick is moved down, it means descent flight, and if the left stick is moved up into the full throttle position, it means climb flight.

1.3 Physical movement

The immediate question is now how a quadrocopter can be controlled physically with the above functions. A helicopter will again serve as a comparison.

‘Nick’ and ‘Roll’ are there realized with a so-called swash plate. This provides at the end an angle-shift of the main rotor force axis to the fuselage. ‘Gas’ is provided by