Inertial Motion Capture Calibration

A method of inertial motion capture calibration with respect to a subject having multiple segments connected by joints, wherein each segment has affixed at least one sensing unit, each sensing unit containing at least a 3D gyroscope and a 3D accelerometer, the method comprising:

• defining unknown 3D position vectors from the sensing units to corresponding joint centers;
• collecting 3D accelerometer and 3D gyroscope data from the sensing units;
• predicting position and orientation trajectories of the sensing units by integration of the 3D accelerometer and 3D gyroscope data;
• generating 3D joint position constraints by equating 3D joint center positions derived from the predicted position and orientation of two sensing units attached to adjoining segments and the unknown 3D position vectors;
• and
• estimating the unknown 3D position vectors and the sensing unit trajectories by applying the 3D joint position constraints.

A system of inertial motion capture calibration with respect to a subject having N segments connected by joints, wherein N>1, the system comprising:

• at least one sensing unit affixed to each segment, each sensing unit containing at least a 3D gyroscope and a 3D accelerometer;
• and
• a controller configured to:
• define unknown 3D orientations between sensing units and the corresponding segments the sensing units are attached to;
• collect 3D accelerometer and 3D gyroscope data from the sensing units;
• predict 3D position and 3D orientation trajectories of the sensing units by integration of the 3D accelerometer and 3D gyroscope data;
• derive 3D joint center positions from the predicted position and orientation of the sensing units;
• generate 3D joint position constraints by equating pairs of 3D joint center positions derived from sensing units on adjoining segments;
• update the sensing unit trajectories by applying the 3D joint position constraints;
• generate a set of at least 3N independent segment orientation constraints, each constraint being a scalar function operating on a 3D orientation of a segment at one or more time instants;
• and
• estimate the unknown 3D orientations by applying the segment orientation constraints.

A non-transitory computer-readable medium having stored thereon computer-executable instructions for performing inertial motion capture calibration with respect to a subject having N segments connected by joints, wherein N>1, with at least one sensing unit affixed to each segment, each sensing unit containing at least a 3D gyroscope and a 3D accelerometer, the computer-executable instructions comprising:

• defining unknown 3D orientations between sensing units and the corresponding segments to which the sensing units are attached;
• collecting 3D accelerometer and 3D gyroscope data from the sensing units;
• predicting 3D position and 3D orientation trajectories of the sensing units by integration of the 3D accelerometer and 3D gyroscope data;
• deriving 3D joint center positions from the predicted position and orientation of the sensing units;
• generating 3D joint position constraints by equating pairs of 3D joint center positions derived from sensing units on adjoining segments;
• updating the sensing unit trajectories by applying the 3D joint position constraints;
• generating a set of at least 3N independent segment orientation constraints, each constraint being a scalar function operating on a 3D orientation of a segment at one or more time instants;
• and
• estimating the unknown 3D orientations by applying the segment orientation constraints.