Design and implementation of a 9-axis inertial measurement unit

We report on a 9-axis inertial measurement unit (IMU) which utilizes 3-axis angular velocity measurements from rate gyros and 6-axis linear acceleration measurements from three 2-axis accelerometers. This system is capable of deriving linear acceleration, angular acceleration and angular velocity via simple matrix operations, and it also releases the requirement of accelerometer installation at the center of mass as in the traditional IMU. An optimal configuration of the system is proposed based on the analysis of rigid body dynamics and matrix theory. We performed error analyses, including position, orientation, and sensor noise, and we also report the results of experimental evaluation. We believe the analysis presented in this paper would benefit the practical design of IMUs in the future.