MPU6000 data sheet indicates that variation on gyro ZRO across temperature range from -40 to +85 is +-20 deg/sec.
The limits on the gyro bias states have been increased to allow for this.
To enable the EKF to accommodate such large gyro bias values in yaw without the yaw error wrapping, leading to continual heading drift, an unwrap function has been applied to the compass heading error.
This method checks for consistency between accelerometer readings and switches to the unit with the lowest vibration of the difference exceeds 0.3g
The threshold of 1.7 m/s/s corresponds to a maximum tilt error of 10 deg assuming one IMU is good, one is bad and the EKF is using the bad IMU.
This commit changes the way libraries headers are included in source files:
- If the header is in the same directory the source belongs to, so the
notation '#include ""' is used with the path relative to the directory
containing the source.
- If the header is outside the directory containing the source, then we use
the notation '#include <>' with the path relative to libraries folder.
Some of the advantages of such approach:
- Only one search path for libraries headers.
- OSs like Windows may have a better lookup time.
This prevents bad inertial or GPS data combined with the post takeoff heading alignment check used by plane from resulting in earth field states that have an incorrect declination
Prolonged yaw rotations with gyro scale factor errors can cause yaw errors and gyro bias estimation errors to build up to a point where EKF health checks fail.
This patch introduces the following protections:
1) The assumed yaw gyro error is scaled using a filtered yaw rate and an assumed 3% scale factor error (MPU6000 data sheet)
2) When the filtered yaw rate magnitude is greater than 1 rad/sec, the Z gyro bias process noise is zeroed and the state variance set to zero to inhibit modification of the bias state
3) When the filtered yaw rate magnitude is greater than 1 rad/sec, the magnetometer quaternion corrections are scaled by a factor of four to maintain tighter alignment with the compass
The interface definition has been modified so that it returns true for a position obtained usin geither the normal inertial navigation calculation, or a raw GPS measurement.
This enables this function to be used to set a home position before flight.
If a calculated position is not available, the function will return a value based on raw GPS or last calculation if available, but the status will be set to false to indicate that it cannot be used for control.
Range finder and optical flow data can drop-out and be reliable very close to ground. these patches enable the takeoff to be more relaibly detected and constrain optical flow navigation drift in the first part of takeoff.
Paul Riseborough
Randy Mackay
Andrew Tridgell
Paul Riseborough
Gustavo Jose de Sousa
Jonathan Challinger