Gyroscope bias estimation

A method for determining a current estimated gyroscope bias of a gyroscope, the gyroscope being configured to output rotation rate data, the method comprising:

• receiving first rotation rate data associated with a first time from the gyroscope, the first rotation rate data comprising a first rotation rate reading that indicates a rotation rate of the gyroscope about a first axis;
• calculating a rotation rate moving average associated with the first time based on the first rotation rate data and a rotation rate moving average associated with a second time earlier than the first time;
• calculating a moving standard deviation associated with the first time based on the first rotation rate data, the rotation rate moving average associated with the first time, and a moving standard deviation associated with the second time;
• determining if the moving standard deviation associated with the first time is less a threshold moving standard deviation;
• and
• in response the moving standard deviation being less than the threshold moving standard deviation, using the first rotation rate reading to update the current estimated gyroscope bias;
• wherein calculating the moving standard deviation comprises reducing the moving standard deviation associated with the second time using a moving standard deviation forget rate factor, and combining the reduced moving standard deviation with a difference between the first rotation rate reading and the rotation rate moving average associated with the first time.

A mobile device comprising:

• a gyroscope configured to output rotation rate data, the gyroscope having a gyroscope bias;
• and
• a processor configured to:
• receive first rotation rate data associated with a first time from the gyroscope, the first rotation rate data comprising a first rotation rate reading that indicates a rotation rate of the gyroscope about a first axis;
• calculate a rotation rate moving average associated with the first time based on the first rotation rate data and a rotation rate moving average associated with a second time earlier than the first time;
• calculate a moving standard deviation associated with the first time based on the first rotation rate data, the rotation rate moving average associated with the first time and a moving standard deviation associated with the second time;
• determine if the moving standard deviation associated with the first time is less a threshold moving standard deviation;
• in response the moving standard deviation being less than the threshold moving standard deviation, use the first rotation rate reading to update a current estimate of the gyroscope bias;
• wherein the first rotation rate data comprises a second rotation rate reading that indicates a rotation rate of the gyroscope about a second axis;
• calculating a separate rotation rate moving average associated with the first time for each axis based on the rotation rate reading for each axis and the rotation rate moving average for the axis for each axis associated with the second time;
• calculating a separate moving standard deviation associated with the first time for each axis based on the rotation rate reading for each axis, the rotation rate moving average for each axis associated with the second time, and a moving standard deviation for each axis associated with the second time;
• combining the moving standard deviations associated with the first time;
• determining if the combined moving standard deviation associated with the first time is less the threshold moving standard deviation;
• and
• in response the combined moving standard deviation being less than the threshold moving standard deviation, using the first rotation rate reading of the first rotation rate data to update the current estimated gyroscope bias.