AP_NavEKF: Improve rate of accel bias learning before flight

libraries/AP_NavEKF/AP_NavEKF.cpp

@@ -2048,7 +2048,12 @@ void NavEKF::FuseVelPosNED()
             // calculate weighting used by fuseVelPosNED to do IMU accel data blending
             // this is used to detect and compensate for aliasing errors with the accelerometers
             // provide for a first order lowpass filter to reduce noise on the weighting if required
-            IMU1_weighting = 1.0f * (K1 / (K1 + K2)) + 0.0f * IMU1_weighting; // filter currently inactive
+            // set weighting to 0.5 when on ground to allow more rapid learning of bias errors without 'ringing' in bias estimates
+            if (vehicleArmed) {
+                IMU1_weighting = 1.0f * (K1 / (K1 + K2)) + 0.0f * IMU1_weighting; // filter currently inactive
+            } else {
+                IMU1_weighting = 0.5f;
+            }
             // apply an innovation consistency threshold test, but don't fail if bad IMU data
             // calculate the test ratio
             velTestRatio = innovVelSumSq / (varVelSum * sq(_gpsVelInnovGate));