AC_AttControl: check accel_rp_max instead of rate_bff_ff_enabled

We use the accel_rp_max, accel_y_max to check whether to apply accel
limiting or not.  This is related to separate from the
body-frame-feed-forward.

libraries/AC_AttitudeControl/AC_AttitudeControl.cpp

@@ -103,7 +103,7 @@ void AC_AttitudeControl::angle_ef_roll_pitch_rate_ef_yaw_smooth(float roll_angle
     float rate_ef_desired;
     float angle_to_target;
 
-    if (_rate_bf_ff_enabled) {
+    if (_accel_rp_max > 0.0f) {
 
     	// calculate earth-frame feed forward roll rate using linear response when close to the target, sqrt response when we're further away
     	angle_to_target = roll_angle_ef - _angle_ef_target.x;
@@ -145,7 +145,7 @@ void AC_AttitudeControl::angle_ef_roll_pitch_rate_ef_yaw_smooth(float roll_angle
     	_rate_ef_desired.y = 0;
     }
 
-    if (_rate_bf_ff_enabled) {
+    if (_accel_y_max > 0.0f) {
     	// set earth-frame feed forward rate for yaw
         rate_change_limit = _accel_y_max * _dt;
 
@@ -221,7 +221,7 @@ void AC_AttitudeControl::angle_ef_roll_pitch_rate_ef_yaw(float roll_angle_ef, fl
 
     // add body frame rate feed forward
     if (_rate_bf_ff_enabled) {
-        _rate_bf_target += _rate_bf_desired;
+        _rate_bf_target.z += _rate_bf_desired.z;
     }
 
     // body-frame to motor outputs should be called separately
@@ -348,7 +348,7 @@ void AC_AttitudeControl::rate_bf_roll_pitch_yaw(float roll_rate_bf, float pitch_
     float rate_change, rate_change_limit;
 
     // update the rate feed forward with angular acceleration limits 
-    if (_rate_bf_ff_enabled) {
+    if (_accel_rp_max > 0.0f) {
     	rate_change_limit = _accel_rp_max * _dt;
 
     	rate_change = roll_rate_bf - _rate_bf_desired.x;
@@ -363,7 +363,7 @@ void AC_AttitudeControl::rate_bf_roll_pitch_yaw(float roll_rate_bf, float pitch_
     	_rate_bf_desired.y = pitch_rate_bf;
     }
 
-    if (_rate_bf_ff_enabled) {
+    if (_accel_y_max > 0.0f) {
         rate_change_limit = _accel_y_max * _dt;
 
         rate_change = yaw_rate_bf - _rate_bf_desired.z;
@@ -375,7 +375,13 @@ void AC_AttitudeControl::rate_bf_roll_pitch_yaw(float roll_rate_bf, float pitch_
 
     // body-frame rate commands added
     if (_rate_bf_ff_enabled) {
-        _rate_bf_target += _rate_bf_desired;
+        if (_accel_rp_max > 0.0f) {
+            _rate_bf_target.x += _rate_bf_desired.x;
+            _rate_bf_target.y += _rate_bf_desired.y;
+        }
+        if (_accel_y_max > 0.0f) {
+            _rate_bf_target.z += _rate_bf_desired.z;
+        }
     }
 }