AP_Soaring: Move drift check to separate function and check drift with reference to mission segment, allowing drift in right direction. LOITER target, not current position, is now used.

ArduPlane/soaring.cpp

@@ -64,7 +64,24 @@ void Plane::update_soaring() {
         // Update thermal estimate and check for switch back to AUTO
         g2.soaring_controller.update_thermalling();  // Update estimate
 
-        const SoaringController::LoiterStatus loiterStatus = g2.soaring_controller.check_cruise_criteria();
+        Vector2f prev_wp, next_wp;
+
+        // If previous mode was AUTO and there was a previous NAV command, we can use previous and next wps for drift calculation.
+        if (previous_mode->mode_number() == Mode::Number::AUTO) {
+            AP_Mission::Mission_Command current_nav_cmd = mission.get_current_nav_cmd();
+            AP_Mission::Mission_Command prev_nav_cmd;
+
+            if (!(mission.get_next_nav_cmd(mission.get_prev_nav_cmd_with_wp_index(), prev_nav_cmd) &&
+                   prev_nav_cmd.content.location.get_vector_xy_from_origin_NE(prev_wp) &&
+                current_nav_cmd.content.location.get_vector_xy_from_origin_NE(next_wp))) {
+                prev_wp.x = 0.0;
+                prev_wp.y = 0.0;
+                next_wp.x = 0.0;
+                next_wp.y = 0.0;
+            }
+        }
+
+        const SoaringController::LoiterStatus loiterStatus = g2.soaring_controller.check_cruise_criteria(prev_wp/100, next_wp/100);
 
         if (loiterStatus == SoaringController::LoiterStatus::THERMAL_GOOD_TO_KEEP_LOITERING) {
             // Reset loiter angle, so that the loiter exit heading criteria

libraries/AP_Soaring/AP_Soaring.cpp

@@ -126,7 +126,7 @@ const AP_Param::GroupInfo SoaringController::var_info[] = {
     // @Description: The previous mode will be restored if the horizontal distance to the thermalling start location exceeds this value. 0 to disable.
     // @Range: 0 1000
     // @User: Advanced
-    AP_GROUPINFO("MAX_DRIFT", 16, SoaringController, max_drift, 0),
+    AP_GROUPINFO("MAX_DRIFT", 16, SoaringController, max_drift, -1),
 
     // @Param: MAX_RADIUS
     // @DisplayName: (Optional) Maximum distance from home
@@ -187,7 +187,7 @@ bool SoaringController::check_thermal_criteria()
 }
 
 
-SoaringController::LoiterStatus SoaringController::check_cruise_criteria()
+SoaringController::LoiterStatus SoaringController::check_cruise_criteria(Vector2f prev_wp, Vector2f next_wp)
 {
     if (!soar_active) {
         _cruise_criteria_msg_last = SOARING_DISABLED;
@@ -197,11 +197,6 @@ SoaringController::LoiterStatus SoaringController::check_cruise_criteria()
     LoiterStatus result = THERMAL_GOOD_TO_KEEP_LOITERING;
     const float alt = _vario.alt;
 
-    Vector3f position;
-    if (!_ahrs.get_relative_position_NED_home(position)) {
-        return SOARING_DISABLED;
-    }
-
     if (alt > alt_max) {
         result = ALT_TOO_HIGH;
         if (result != _cruise_criteria_msg_last) {
@@ -224,7 +219,7 @@ SoaringController::LoiterStatus SoaringController::check_cruise_criteria()
             if (result != _cruise_criteria_msg_last) {
                 gcs().send_text(MAV_SEVERITY_INFO, "Not climbing");
             }
-        } else if (!(max_drift<0) && (powf(position.x - _thermal_start_pos.x, 2) + powf(position.y - _thermal_start_pos.y, 2)) > powf(max_drift,2)) {
+        } else if (check_drift(prev_wp, next_wp)) {
             result = DRIFT_EXCEEDED;
             if (result != _cruise_criteria_msg_last) {
                 gcs().send_text(MAV_SEVERITY_INFO, "Drifted too far");
@@ -364,3 +359,49 @@ void SoaringController::set_throttle_suppressed(bool suppressed)
     // Let the TECS know.
     _spdHgt.set_gliding_requested_flag(suppressed);
 }
+
+bool SoaringController::check_drift(Vector2f prev_wp, Vector2f next_wp)
+{
+    // Check for -1 (disabled)
+    if (max_drift<0) {
+        return false;
+    }
+
+    // Check against the estimated thermal.
+    Vector2f position(_ekf.X[2], _ekf.X[3]);
+
+    Vector2f start_pos(_thermal_start_pos.x, _thermal_start_pos.y);
+
+    Vector2f mission_leg = next_wp - prev_wp;
+
+    if (prev_wp.is_zero() || mission_leg.length() < 0.1) {
+        // Simple check of distance from initial start point.
+        return (position - start_pos).length() > max_drift;
+    } else {
+        // Regard the effective start point as projected onto mission leg.
+        // Calculate drift parallel and perpendicular to mission leg.
+        // Drift parallel and in direction of mission leg is acceptable.
+        Vector2f effective_start, vec1, vec2;
+
+        // Calculate effective start point (on mission leg).
+        vec1 = (start_pos - prev_wp).projected(mission_leg);
+        effective_start = prev_wp + vec1;
+
+        // Calculate parallel and perpendicular offsets.
+        vec2 = position - effective_start;
+
+        float parallel      = vec2 * mission_leg.normalized();
+        float perpendicular = (vec2 - mission_leg.normalized()*parallel).length();
+
+       // Check if we've drifted beyond the next wp.
+        if (parallel>(next_wp - effective_start).length()) {
+            return true;
+        }
+
+        // Check if we've drifted too far laterally or backwards. We don't count positive parallel offsets
+        // as these are favourable (towards next wp)
+        parallel = parallel>0 ? 0 : parallel;
+
+        return (powf(parallel,2)+powf(perpendicular,2)) > powf(max_drift,2);;
+    }
+}

libraries/AP_Soaring/AP_Soaring.h

@@ -90,7 +90,7 @@ public:
     void get_target(Location & wp);
     bool suppress_throttle();
     bool check_thermal_criteria();
-    LoiterStatus check_cruise_criteria();
+    LoiterStatus check_cruise_criteria(Vector2f prev_wp, Vector2f next_wp);
     void init_thermalling();
     void init_cruising();
     void update_thermalling();
@@ -110,6 +110,8 @@ public:
 
     void update_vario();
 
+    bool check_drift(Vector2f prev_wp, Vector2f next_wp);
+
 private:
     // slow down messages if they are the same. During loiter we could smap the same message. Only show new messages during loiters
     LoiterStatus _cruise_criteria_msg_last;