Merge pull request #1312 from PX4/airspeed_fix

Deal with zero airspeed measurements

src/modules/fw_att_control/fw_att_control_main.cpp

@@ -145,6 +145,7 @@ private:
 	perf_counter_t	_nonfinite_output_perf;		/**< performance counter for non finite output */
 
 	bool		_setpoint_valid;		/**< flag if the position control setpoint is valid */
+	bool		_debug;				/**< if set to true, print debug output */
 
 	struct {
 		float tconst;
@@ -324,7 +325,8 @@ FixedwingAttitudeControl::FixedwingAttitudeControl() :
 	_nonfinite_input_perf(perf_alloc(PC_COUNT, "fw att control nonfinite input")),
 	_nonfinite_output_perf(perf_alloc(PC_COUNT, "fw att control nonfinite output")),
 /* states */
-	_setpoint_valid(false)
+	_setpoint_valid(false),
+	_debug(false)
 {
 	/* safely initialize structs */
 	_att = {};
@@ -700,7 +702,8 @@ FixedwingAttitudeControl::task_main()
 						perf_count(_nonfinite_input_perf);
 					}
 				} else {
-					airspeed = _airspeed.true_airspeed_m_s;
+					/* prevent numerical drama by requiring 0.5 m/s minimal speed */
+					airspeed = math::max(0.5f, _airspeed.true_airspeed_m_s);
 				}
 
 				/*
@@ -785,7 +788,7 @@ FixedwingAttitudeControl::task_main()
 					speed_body_v = _att.R[0][1] * _global_pos.vel_n + _att.R[1][1] * _global_pos.vel_e + _att.R[2][1] * _global_pos.vel_d;
 					speed_body_w = _att.R[0][2] * _global_pos.vel_n + _att.R[1][2] * _global_pos.vel_e + _att.R[2][2] * _global_pos.vel_d;
 				} else	{
-					if (loop_counter % 10 == 0) {
+					if (_debug && loop_counter % 10 == 0) {
 						warnx("Did not get a valid R\n");
 					}
 				}
@@ -808,7 +811,7 @@ FixedwingAttitudeControl::task_main()
 						_roll_ctrl.reset_integrator();
 						perf_count(_nonfinite_output_perf);
 
-						if (loop_counter % 10 == 0) {
+						if (_debug && loop_counter % 10 == 0) {
 							warnx("roll_u %.4f", (double)roll_u);
 						}
 					}
@@ -821,7 +824,7 @@ FixedwingAttitudeControl::task_main()
 					if (!isfinite(pitch_u)) {
 						_pitch_ctrl.reset_integrator();
 						perf_count(_nonfinite_output_perf);
-						if (loop_counter % 10 == 0) {
+						if (_debug && loop_counter % 10 == 0) {
 							warnx("pitch_u %.4f, _yaw_ctrl.get_desired_rate() %.4f,"
 								" airspeed %.4f, airspeed_scaling %.4f,"
 								" roll_sp %.4f, pitch_sp %.4f,"
@@ -845,7 +848,7 @@ FixedwingAttitudeControl::task_main()
 					if (!isfinite(yaw_u)) {
 						_yaw_ctrl.reset_integrator();
 						perf_count(_nonfinite_output_perf);
-						if (loop_counter % 10 == 0) {
+						if (_debug && loop_counter % 10 == 0) {
 							warnx("yaw_u %.4f", (double)yaw_u);
 						}
 					}
@@ -853,13 +856,13 @@ FixedwingAttitudeControl::task_main()
 					/* throttle passed through */
 					_actuators.control[3] = (isfinite(throttle_sp)) ? throttle_sp : 0.0f;
 					if (!isfinite(throttle_sp)) {
-						if (loop_counter % 10 == 0) {
+						if (_debug && loop_counter % 10 == 0) {
 							warnx("throttle_sp %.4f", (double)throttle_sp);
 						}
 					}
 				} else {
 					perf_count(_nonfinite_input_perf);
-					if (loop_counter % 10 == 0) {
+					if (_debug && loop_counter % 10 == 0) {
 						warnx("Non-finite setpoint roll_sp: %.4f, pitch_sp %.4f", (double)roll_sp, (double)pitch_sp);
 					}
 				}