Online magnetic calibration of a cutting edge 9-axis wireless Inertial Measurement Unit

In the last years there has been increasing interest on Inertial Measurement Units (IMUs) in several fields, because they can provide a measurement of the orientation, velocity, and acceleration at low cost with high performance. The main reason of the low cost is the possibility to find inertial sensors, as accelerometers, gyroscopes and magnetometers, based on Micro-Electro-Mechanical Systems (MEMS) made by silicon, with further advantages of small dimensions and mass production from the main semiconductor suppliers. In this paper, we present the development of the ultra miniaturized wireless IMU, WB-4 (Waseda Bioinstrumentation number 4), with a 3-axis accelerometer, 3-axis gyroscope and 3-axis magnetometer. Additionally, we illustrate, together with results, the algorithms used for the data filtering and calibration, with particular emphasis on a new methodology for the online calibration of the digital magnetometer.