Implementation of Rotation Modulation Scheme for INS in an Experimental Environment Using MEMS-based Sensors

Abstract

Inexpensive commercial off-the-shelf (COTS) inertial measurement units (IMUs) are an attractive choice for autonomous systems due to their size, cost, and power consumption. However, in practice, their adoption for use in inertial navigation systems (INS) imposes performance limitations. When used in INS, micro-electro-mechanical systems (MEMS) sensors suffer from bias, scale-factor error, misalignment, and other effects that limit performance. This thesis investigates whether rotation modulation can attenuate persistent measurement residuals from a low-cost MEMS IMU relative to an identical IMU that is static relative to the rotating IMU. The experimental dynamic angular navigation through controlled excitation (DANCE) apparatus is a dual-IMU data-logging apparatus constructed using a Teensy 4.1 microcontroller, two identical ICM-20948 IMUs, an AS5047U magnetic encoder, a BLDC motor and motor controller, and an SD-card logging system. One IMU, termed the rotating IMU (RIMU), is mounted to a rotating assembly. At the same time, the stationary IMU (SIMU) is fixed to the apparatus body and used as a simultaneously logged comparison baseline. This work presents the hardware architecture, data-logging firmware, calibration procedures, processing pipeline, and estimator implementation used to evaluate rotation modulation with low-cost MEMS-based IMUs. The experimental results show that rotation modulation reduced the magnitude of the window-averaged horizontal RIMU gyroscope measurement residual by transforming persistent sensor-frame components into spin-synchronous body-frame content. However, the tests did not demonstrate repeatable rotation-induced improvements in roll and pitch estimation, estimator innovation, or static inertial drift relative to the SIMU. The results therefore support the expected measurement-level modulation mechanism while also showing that the effect did not translate into improved estimator- or navigation-level behavior under the tested conditions. Practical limitations included encoder alignment, timing uncertainty, mechanical and electrical disturbances, and installation errors.