AP_Landing: Add more interfaces from vehicle code

Fixs up some documentation about expected return values

libraries/AP_Landing/AP_Landing.cpp

@@ -239,6 +239,10 @@ bool AP_Landing::is_flaring(void) const
 }
 
 // return true while the aircraft is performing a landing approach
+// when true the vehicle will:
+//   - disable ground steering
+//   - call setup_landing_glide_slope() and adjust_landing_slope_for_rangefinder_bump()
+//   - will be considered flying if sink rate > 0.2, and can trigger crash detection
 bool AP_Landing::is_on_approach(void) const
 {
     if (!flags.in_progress) {
@@ -253,7 +257,23 @@ bool AP_Landing::is_on_approach(void) const
     }
 }
 
+// return true while the aircraft is allowed to perform ground steering
+bool AP_Landing::is_ground_steering_allowed(void) const
+{
+    if (!flags.in_progress) {
+        return true;
+    }
+
+    switch (type) {
+    case TYPE_STANDARD_GLIDE_SLOPE:
+        return type_slope_is_on_approach();
+    default:
+        return true;
+    }
+}
+
 // return true when at the last stages of a land when an impact with the ground is expected soon
+// when true is_flying knows that the vehicle was expecting to stop flying, possibly because of a hard impact
 bool AP_Landing::is_expecting_impact(void) const
 {
     if (!flags.in_progress) {
@@ -353,6 +373,20 @@ int32_t AP_Landing::constrain_roll(const int32_t desired_roll_cd, const int32_t
     }
 }
 
+// returns true if landing provided a Location structure with the current target altitude
+bool AP_Landing::get_target_altitude_location(Location &location)
+{
+    if (!flags.in_progress) {
+        return false;
+    }
+
+    switch (type) {
+    case TYPE_STANDARD_GLIDE_SLOPE:
+    default:
+        return false;
+    }
+}
+
 /*
  * Determine how aligned heading_deg is with the wind. Return result
  * is 1.0 when perfectly aligned heading into wind, -1 when perfectly
@@ -394,7 +428,10 @@ int32_t AP_Landing::get_target_airspeed_cm(void)
     case TYPE_STANDARD_GLIDE_SLOPE:
         return type_slope_get_target_airspeed_cm();
     default:
-        return SpdHgt_Controller->get_land_airspeed();
+        // don't return the landing airspeed, because if type is invalid we have
+        // no postive indication that the land airspeed has been configured or
+        // how it was meant to be utilized
+        return SpdHgt_Controller->get_target_airspeed();
     }
 }
 
@@ -450,3 +487,20 @@ void AP_Landing::log(void) const
     }
 }
 
+/*
+ * returns true when throttle should be suppressed while landing
+ */
+bool AP_Landing::is_throttle_suppressed(void) const
+{
+    if (!flags.in_progress) {
+        return false;
+    }
+
+    switch (type) {
+    case TYPE_STANDARD_GLIDE_SLOPE:
+        return type_slope_is_throttle_suppressed();
+    default:
+        return false;
+    }
+}
+

libraries/AP_Landing/AP_Landing.h

@@ -78,8 +78,11 @@ public:
     bool request_go_around(void);
     bool is_flaring(void) const;
     bool is_on_approach(void) const;
+    bool is_ground_steering_allowed(void) const;
+    bool is_throttle_suppressed(void) const;
     void handle_flight_stage_change(const bool _in_landing_stage);
     int32_t constrain_roll(const int32_t desired_roll_cd, const int32_t level_roll_limit_cd);
+    bool get_target_altitude_location(Location &location);
 
     // helper functions
     bool restart_landing_sequence(void);
@@ -121,7 +124,6 @@ private:
     // calculated approach slope during auto-landing: ((prev_WP_loc.alt - next_WP_loc.alt)*0.01f - flare_sec * sink_rate) / get_distance(prev_WP_loc, next_WP_loc)
     float slope;
 
-
     AP_Mission &mission;
     AP_AHRS &ahrs;
     AP_SpdHgtControl *SpdHgt_Controller;
@@ -184,5 +186,5 @@ private:
     bool type_slope_is_flaring(void) const;
     bool type_slope_is_on_approach(void) const;
     bool type_slope_is_expecting_impact(void) const;
-
+    bool type_slope_is_throttle_suppressed(void) const;
 };

libraries/AP_Landing/AP_Landing_Slope.cpp

@@ -388,3 +388,8 @@ void AP_Landing::type_slope_log(void) const
                                             (double)initial_slope,
                                             (double)alt_offset);
 }
+
+bool AP_Landing::type_slope_is_throttle_suppressed(void) const
+{
+    return type_slope_stage == SLOPE_STAGE_FINAL;
+}