minimum follow target alt of 8 m added, protecting against nan values in pos controller, fixing ci build error

src/modules/mc_pos_control/mc_pos_control_main.cpp

@@ -1417,10 +1417,16 @@ MulticopterPositionControl::task_main()
 					_vel_sp(1) = (_pos_sp(1) - _pos(1)) * _params.pos_p(1);
 				}
 
+				// guard against any bad velocity values
+
+				bool velocity_valid = PX4_ISFINITE(_pos_sp_triplet.current.vx) &&
+									  PX4_ISFINITE(_pos_sp_triplet.current.vy) &&
+									  _pos_sp_triplet.current.velocity_valid;
+
 				// do not go slower than the follow target velocity when position tracking is active (set to valid)
 
 				if(_pos_sp_triplet.current.type == position_setpoint_s::SETPOINT_TYPE_FOLLOW_TARGET &&
-					_pos_sp_triplet.current.velocity_valid &&
+					velocity_valid &&
 					_pos_sp_triplet.current.position_valid) {
 
 					math::Vector<3> ft_vel(_pos_sp_triplet.current.vx, _pos_sp_triplet.current.vy, 0);
@@ -1444,7 +1450,7 @@ MulticopterPositionControl::task_main()
 					// track target using velocity only
 
 				} else if (_pos_sp_triplet.current.type == position_setpoint_s::SETPOINT_TYPE_FOLLOW_TARGET &&
-					_pos_sp_triplet.current.velocity_valid) {
+						velocity_valid) {
 
 					_vel_sp(0) = _pos_sp_triplet.current.vx;
 					_vel_sp(1) = _pos_sp_triplet.current.vy;

src/modules/navigator/follow_target.cpp

@@ -45,7 +45,6 @@
 #include <stdbool.h>
 #include <math.h>
 #include <fcntl.h>
-#include <float.h>
 
 #include <systemlib/err.h>
 
@@ -78,8 +77,6 @@ FollowTarget::FollowTarget(Navigator *navigator, const char *name) :
 	_target_vel.zero();
 	_target_distance.zero();
 	_target_position_offset.zero();
-
-	_rot_matrix = (_follow_position_matricies[_follow_target_position]);
 }
 
 FollowTarget::~FollowTarget()
@@ -97,7 +94,7 @@ void FollowTarget::on_activation()
 
 	_follow_offset = _param_tracking_dist.get() < 1.0F ? 1.0F : _param_tracking_dist.get();
 
-	_follow_target_position = (FollowTargetPosition) _param_tracking_side.get();
+	_follow_target_position = _param_tracking_side.get();
 
 	if((_follow_target_position > FOLLOW_FROM_LEFT) || (_follow_target_position < FOLLOW_FROM_RIGHT)) {
 		_follow_target_position = FOLLOW_FROM_BEHIND;

src/modules/navigator/follow_target.h

@@ -72,7 +72,7 @@ private:
 		WAIT_FOR_TARGET_POSITION
 	};
 
-	enum FollowTargetPosition {
+	enum {
 		FOLLOW_FROM_RIGHT,
 		FOLLOW_FROM_BEHIND,
 		FOLLOW_FROM_FRONT,
@@ -103,7 +103,7 @@ private:
 	control::BlockParamInt _param_tracking_side;
 
 	FollowTargetState _follow_target_state;
-	FollowTargetPosition _follow_target_position;
+	int _follow_target_position;
 
 	int _follow_target_sub;
 	float _step_time_in_ms;

src/modules/navigator/mission_block.cpp

@@ -469,7 +469,7 @@ MissionBlock::set_follow_target_item(struct mission_item_s *item, float min_clea
 		item->lon = target.lon;
 		item->altitude = _navigator->get_home_position()->alt;
 
-		if (min_clearance > 0.0f) {
+		if (min_clearance > 8.0f) {
 			item->altitude += min_clearance;
 		} else {
 			item->altitude += 8.0f; // if min clearance is bad set it to 8.0 meters (well above the average height of a person)