A novel motion sensor with nine degrees of freedom

In this paper, a group of new multi-axis MEMS sensors including triaxial gyroscope (ITG-3200), triaxial accelerometer (ADXL345) and triaxial magnetometer (HMC5843) are incorporated to develop a motion sensor with nine degrees of freedom (9D), which can communicate with personal computer through a Bluetooth wireless module. A simplified three-dimensional orientation estimation method is proposed in this paper to implement real-time estimation of triaxial orientation. To test accuracy of the new sensor system, validation experiments by using reference measurements of a commercially available measurement system were performed in a gait laboratory. Experiment results supported that the wireless 9D sensor can be used to measure 3D orientations with an acceptable precision.