AC_AttitudeControl: AC_PosControl: Separate landing and terrain following.

libraries/AC_AttitudeControl/AC_PosControl.cpp

@@ -805,6 +805,7 @@ void AC_PosControl::init_z()
     _pid_accel_z.reset_filter();
 
     // initialise vertical offsets
+    _pos_offset_target_z = 0.0;
     _pos_offset_z = 0.0;
     _vel_offset_z = 0.0;
     _accel_offset_z = 0.0;
@@ -870,11 +871,33 @@ void AC_PosControl::input_vel_accel_z(float &vel, const float accel, bool ignore
 
 /// set_pos_target_z_from_climb_rate_cm - adjusts target up or down using a commanded climb rate in cm/s
 ///     using the default position control kinematic path.
-///     ignore_descent_limit turns off output saturation handling to aid in landing detection. ignore_descent_limit should be true unless landing.
-void AC_PosControl::set_pos_target_z_from_climb_rate_cm(const float vel, bool ignore_descent_limit)
+///     The zero target altitude is varied to follow pos_offset_z
+void AC_PosControl::set_pos_target_z_from_climb_rate_cm(const float vel)
 {
-    float vel2 = vel;
-    input_vel_accel_z(vel2, 0, ignore_descent_limit);
+    // remove terrain offsets for flat earth assumption
+    _pos_target.z -= _pos_offset_z;
+    _vel_desired.z -= _vel_offset_z;
+    _accel_desired.z -= _accel_offset_z;
+
+    float vel_temp = vel;
+    input_vel_accel_z(vel_temp, 0, false);
+
+    // update the vertical position, velocity and acceleration offsets
+    update_pos_offset_z(_pos_offset_target_z);
+
+    // add terrain offsets
+    _pos_target.z += _pos_offset_z;
+    _vel_desired.z += _vel_offset_z;
+    _accel_desired.z += _accel_offset_z;
+}
+
+/// land_at_climb_rate_cm - adjusts target up or down using a commanded climb rate in cm/s
+///     using the default position control kinematic path.
+///     ignore_descent_limit turns off output saturation handling to aid in landing detection. ignore_descent_limit should be true unless landing.
+void AC_PosControl::land_at_climb_rate_cm(const float vel, bool ignore_descent_limit)
+{
+    float vel_temp = vel;
+    input_vel_accel_z(vel_temp, 0, ignore_descent_limit);
 }
 
 /// input_pos_vel_accel_z - calculate a jerk limited path from the current position, velocity and acceleration to an input position velocity and acceleration.

libraries/AC_AttitudeControl/AC_PosControl.h

@@ -196,10 +196,15 @@ public:
     ///     The parameter limit_output specifies if the velocity and acceleration limits are applied to the sum of commanded and correction values or just correction.
     virtual void input_vel_accel_z(float &vel, const float accel, bool ignore_descent_limit, bool limit_output = true);
 
-    /// set_pos_target_z_from_climb_rate_cm - adjusts target up or down using a climb rate in cm/s
+    /// set_pos_target_z_from_climb_rate_cm - adjusts target up or down using a commanded climb rate in cm/s
+    ///     using the default position control kinematic path.
+    ///     The zero target altitude is varied to follow pos_offset_z
+    void set_pos_target_z_from_climb_rate_cm(const float vel);
+
+    /// land_at_climb_rate_cm - adjusts target up or down using a commanded climb rate in cm/s
     ///     using the default position control kinematic path.
     ///     ignore_descent_limit turns off output saturation handling to aid in landing detection. ignore_descent_limit should be true unless landing.
-    void set_pos_target_z_from_climb_rate_cm(const float vel, bool ignore_descent_limit);
+    void land_at_climb_rate_cm(const float vel, bool ignore_descent_limit);
 
     /// input_pos_vel_accel_z - calculate a jerk limited path from the current position, velocity and acceleration to an input position velocity and acceleration.
     ///     The function takes the current position, velocity, and acceleration and calculates the required jerk limited adjustment to the acceleration for the next time dt.
@@ -296,6 +301,9 @@ public:
 
     /// Offset
 
+    /// set_pos_offset_target_z_cm - set altitude offset target in cm above home
+    void set_pos_offset_target_z_cm(float pos_offset_target_z) { _pos_offset_target_z = pos_offset_target_z; }
+
     /// set_pos_offset_z_cm - set altitude offset in cm above home
     void set_pos_offset_z_cm(float pos_offset_z) { _pos_offset_z = pos_offset_z; }
 
@@ -461,6 +469,7 @@ protected:
     Vector3f    _accel_target;          // acceleration target in NEU cm/s/s
     Vector3f    _limit_vector;          // the direction that the position controller is limited, zero when not limited
     Vector2f    _vehicle_horiz_vel;     // velocity to use if _flags.vehicle_horiz_vel_override is set
+    float       _pos_offset_target_z;   // vertical position offset target in NEU cm from home
     float       _pos_offset_z;          // vertical position offset in NEU cm from home
     float       _vel_offset_z;          // vertical velocity offset in NEU cm/s calculated by pos_to_rate step
     float       _accel_offset_z;        // vertical acceleration offset in NEU cm/s/s