The true role of accelerometers in quadrotor's Inertial Navigation System

Quadrotors are Vertical Take-Off and Landing (VTOL) vehicles which use Inertial Measurement Units (IMU) in the heart of their navigation and instrumentation systems. Mostly, IMUs containing three accelerometers are used to measure the tilt angles and robot's position (attitude and location) when they are integrated in an Inertial Navigation System (INS). The role of the accelerometers in this INS is measuring both the vehicle's linear accelerations and the gravity. As an exception for VTOL platforms, in this paper it is shown that the values measured by the accelerometers of a quadrotor are affected by neither the vehicle's linear accelerations nor the gravity. Therefore, different elements affecting on the quadrotor's accelerometers are studied and it is shown that the most significant element is the quadrotor's linear velocity expressed in the earth frame. So, it is shown that using the accelerometers to measure the vehicle's linear velocity is possible in quadrotors, whereas their measurements are not suitable to be used to estimate the tilt angles and position. The simulation results are presented in a previous version of this paper [1] and, following that, the experimental results are shown here to validate the proposed idea. This research is developed using a Genetic Algorithm (GA) based method.