Fast IMU Autonomous Alignment, Gyroscope and Accelerometer Measurement Improvement by Input Reconstruction

Accuracies of initial alignment and gyroscopic drift in the presence of fast maneuvers and the settling time of gyroscopes and accelerometers govern navigation performances of Inertial Measurement Units (IMU) and of their associated Inertial Navigation (sub) Systems (INS). Most measuring devices include some electromechanical device, which has a time lag. In the case of IMU, the integration of measurements, which lag corresponding accelerations or gyroscopic rates, has a detrimental effect on estimated velocity, position and attitude.The proposed design consist in using an observer dynamical model representative of corresponding IMU sensor dynamics and a Higher Order Sliding Mode (HOSM) injector, feeding this observer with a signal referred as reconstructed input such that its output matches actual measured output. The reconstructed input has a lag several orders of magnitude smaller than the normal input. The proposed SBIR work is a re-visit of the autonomous calibration problem using Higher Order Sliding Mode (HOSM) control solutions. The HOSM approach allows the separation of complex Multiple-Input, Multiple-Output control problem into a set of simpler Single-Input, Single-Output control problems. This approach achieves faster convergence and settling times, and is robust to system and gyroscope noise.Approved for Public Release | 18-MDA-9522 (23 Feb 18)