Method for filtering the signals arising from a sensor assembly comprising at least one sensor for measuring a vector physical field which is substantially constant over time and in space in a reference frame

A portable device for reducing disturbances in signals arising from a sensor assembly comprising at least one sensor for measuring a physical vector field which is substantially constant over time and in space in a reference frame, said sensor assembly being tied in motion to a moving frame, said moving frame moving in the reference frame, further comprising a processor operative to:

• apply a first transformation to the measurements of the sensor of the sensor assembly in which the measurements are provided in the moving frame to a pseudo reference frame, wherein the pseudo reference frame is derived by time-integration of gyroscope measurements without absolute orientation information, with the aid of a first change-of-frame operator (R(t)) by rotation between the moving frame and the pseudo reference frame;
• apply a filter to the measurements thus transformed in the pseudo reference frame to reduce disturbances in the measurements of the sensor;
• apply a second transformation to the measurements filtered by said filter with the aid of a second change-of-frame operator (R−1(t)) by rotation between the pseudo reference frame and the moving frame, the second change-of-frame operator being the inverse of said first operator;
• and output the filtered measurements after applying the second transformation.

A sensor processing unit for reducing disturbances in signals arising from a sensor assembly comprising at least one sensor for measuring a physical vector field which is substantially constant over time and in space in a reference frame, said sensor assembly being tied in motion to a moving frame, said moving frame moving in the reference frame, the sensor processing unit comprising a processor operative to:

• apply a first transformation to the measurements of the sensor of the sensor assembly in which the measurements are provided in the moving frame to a pseudo reference frame, wherein the pseudo reference frame is derived by time-integration of gyroscope measurements without absolute orientation information, with the aid of a first change-of-frame operator (R(t)) by rotation between the moving frame and the pseudo reference frame;
• apply a filter to the measurements thus transformed in the pseudo reference frame to reduce disturbances in the measurements of the sensor;
• apply a second transformation to the measurements filtered by said filter with the aid of a second change-of-frame operator (R−1(t)) by rotation between the pseudo reference frame and the moving frame, the second change-of-frame operator being the inverse of said first operator;
• and output the filtered measurements after applying the second transformation.