Posture and body acceleration tracking by inertial and magnetic sensing: Application in behavioral analysis of free-ranging animals

This paper concerns body attitude (orientation) estimation for free ranging animal. The main idea of the proposed approach combines a quaternion-based nonlinear observer with an Iterated Least Squares Algorithm (ILSA) and exploits measurements from Micro-Electro-Mechanical-System (MEMS) sensors as 3-axis accelerometer, 3-axis magnetometer and 3-axis gyroscope to produce attitude estimates during the entire range of the observed animal's body movements. Moreover, the proposed observer allows estimating the bias in gyroscope which is used to correct the angular velocity measurements in the attitude estimation step. Since, biologists use an index of DBA for evaluating the energy consumption of the moving animal; the resulting estimations are then used to extract the Dynamic Body Acceleration (DBA) of the animal. Note that, this work is necessary in Bio-logging science and allows monitoring aspects of animal's biology (behavior, movement, and physiology) and environments. The performance of the algorithm is theoretically proven and illustrated by an attitude estimation example. Moreover, the efficiency of the proposed approach is shown with a set of experiments through sensor measurements provided by an Inertial Measurement Unit (IMU). We have also included some comparison results with another method already applied in Bio-logging field in order to point out the improvements issued from the proposed approach.