Portable electronic device adapted to compensate for gyroscope bias

A portable electronic device, comprising:

• a gyroscope for detecting the rotational velocity of the device;
• an accelerometer for detecting the acceleration experienced by the device;
• a magnetometer for determining the position and orientation of the device with respect to a magnetic field;
• and
• at least one processor coupled with the gyroscope, the accelerometer and the magnetometer, the at least one processor adapted to:
• determine a first attitude matrix and a second attitude matrix using data from the accelerometer and the magnetometer, each attitude matrix being a 3×3 matrix that describes the orientation of the portable electronic device with respect to a global coordinate system;
• determine a difference between the first attitude matrix and the second attitude matrix;
• estimate a rotational velocity based on the difference between the first attitude matrix and the second attitude matrix;
• and
• compensate for an output from the gyroscope to generate a compensated output that compensates for the gyroscope bias using the estimated rotational velocity.

A method for compensating for gyroscope bias on a portable electronic device having a gyroscope, an accelerometer and an electronic compass, the method comprising:

• determining a first attitude matrix and a second attitude matrix using data from the accelerometer and the electronic compass, each attitude matrix being a 3×3 matrix that describes the orientation of the portable electronic device with respect to a global coordinate system;
• estimating a rotational velocity based on a difference between the first attitude matrix and the second attitude matrix;
• and
• compensating for an output from the gyroscope to generate a compensated output that compensates for the gyroscope bias using the estimated rotational velocity.