AC_WPNAV:make speed changes during missions obey WPNAV_ACCEL

Includes commits by rmackay9
AC_WPNav: fixup max speed acceleration
AC_WPNav: simplify the initialisation of poscontrol's max speed
          Changed at Leonard's request to keep things simpler

libraries/AC_WPNav/AC_WPNav.cpp

@@ -118,6 +118,9 @@ void AC_WPNav::wp_and_spline_init()
     // initialise feed forward velocity to zero
     _pos_control.set_desired_velocity_xy(0.0f, 0.0f);
 
+    // initialize the desired wp speed if not already done
+    _wp_desired_speed_xy_cms = _wp_speed_cms;
+
     // initialise position controller speed and acceleration
     _pos_control.set_max_speed_xy(_wp_speed_cms);
     _pos_control.set_max_accel_xy(_wp_accel_cmss);
@@ -133,11 +136,9 @@ void AC_WPNav::wp_and_spline_init()
 /// set_speed_xy - allows main code to pass target horizontal velocity for wp navigation
 void AC_WPNav::set_speed_xy(float speed_cms)
 {
-    // range check new target speed and update position controller
+    // range check target speed
     if (speed_cms >= WPNAV_WP_SPEED_MIN) {
-        _pos_control.set_max_speed_xy(speed_cms);
-        // flag that wp leash must be recalculated
-        _flags.recalc_wp_leash = true;
+        _wp_desired_speed_xy_cms = speed_cms;
     }
 }
 
@@ -494,6 +495,9 @@ bool AC_WPNav::update_wpnav()
     _pos_control.set_max_accel_xy(_wp_accel_cmss);
     _pos_control.set_max_accel_z(_wp_accel_z_cmss);
 
+    // wp_speed_update - update _pos_control.set_max_speed_xy if speed change has been requested
+    wp_speed_update(dt);
+
     // advance the target if necessary
     if (!advance_wp_target_along_track(dt)) {
         // To-Do: handle inability to advance along track (probably because of missing terrain data)
@@ -783,6 +787,9 @@ bool AC_WPNav::update_spline()
     // get dt from pos controller
     float dt = _pos_control.get_dt();
 
+    // wp_speed_update - update _pos_control.set_max_speed_xy if speed change has been requested
+    wp_speed_update(dt);
+
     // advance the target if necessary
     if (!advance_spline_target_along_track(dt)) {
         // To-Do: handle failure to advance along track (due to missing terrain data)
@@ -1031,3 +1038,33 @@ float AC_WPNav::get_slow_down_speed(float dist_from_dest_cm, float accel_cmss)
         return target_speed;
     }
 }
+
+/// wp_speed_update - calculates how to handle speed change requests
+void AC_WPNav::wp_speed_update(float dt)
+{
+    // return if speed has not changed
+    float curr_max_speed_xy_cms = _pos_control.get_max_speed_xy();
+    if (is_equal(_wp_desired_speed_xy_cms, curr_max_speed_xy_cms)) {
+        return;
+    }
+    // calculate speed change
+    if (_wp_desired_speed_xy_cms > curr_max_speed_xy_cms) {
+        // speed up is requested so increase speed within limit set by WPNAV_ACCEL
+        curr_max_speed_xy_cms += _wp_accel_cmss * dt;
+        if (curr_max_speed_xy_cms > _wp_desired_speed_xy_cms) {
+            curr_max_speed_xy_cms = _wp_desired_speed_xy_cms;
+        }
+    } else if (_wp_desired_speed_xy_cms < curr_max_speed_xy_cms) {
+        // slow down is requested so reduce speed within limit set by WPNAV_ACCEL
+        curr_max_speed_xy_cms -= _wp_accel_cmss * dt;
+        if (curr_max_speed_xy_cms < _wp_desired_speed_xy_cms) {
+            curr_max_speed_xy_cms = _wp_desired_speed_xy_cms;
+        }
+    }
+
+    // update position controller speed
+    _pos_control.set_max_speed_xy(curr_max_speed_xy_cms);
+    
+    // flag that wp leash must be recalculated
+    _flags.recalc_wp_leash = true;
+}

libraries/AC_WPNav/AC_WPNav.h

@@ -247,6 +247,9 @@ protected:
 
     /// get_slow_down_speed - returns target speed of target point based on distance from the destination (in cm)
     float get_slow_down_speed(float dist_from_dest_cm, float accel_cmss);
+    
+    /// wp_speed_update - calculates how to change speed when changes are requested
+    void wp_speed_update(float dt);
 
     /// spline protected functions
 
@@ -288,6 +291,7 @@ protected:
 
     // waypoint controller internal variables
     uint32_t    _wp_last_update;        // time of last update_wpnav call
+    float       _wp_desired_speed_xy_cms;   // desired wp speed in cm/sec
     Vector3f    _origin;                // starting point of trip to next waypoint in cm from ekf origin
     Vector3f    _destination;           // target destination in cm from ekf origin
     Vector3f    _pos_delta_unit;        // each axis's percentage of the total track from origin to destination