Sourceless tracking of human posture using small inertial/magnetic sensors

Human body posture can be tracked in real-time using small inexpensive inertial/magnetic sensor modules to measure the orientation of individual limb segments. To perform this task inertial/magnetic sensors generally contain: three orthogonally mounted angular rate sensors, three orthogonally mounted accelerometers, and three orthogonally mounted magnetometers. These sensors must be small and light enough to be securely attached to major limb segments and avoid user encumbrance. Sensor data must be processed by an efficient filtering algorithm that is able to produce accurate orientation estimates without singularities in all attitudes and does not require still periods to correct for drift. This paper discusses the design of a sourceless body tracking system with an emphasis on sensor and efficient filter design. Various methods for mitigating small transient orientation errors due to variability in the direction of the local magnetic field vector are also described.