Support negative thrust for back transition

src/modules/vtol_att_control/standard.cpp

@@ -143,7 +143,7 @@ Standard::parameters_update()
 
 	/* reverse throttle */
 	param_get(_params_handles_standard.reverse_throttle, &v);
-	_params_standard.reverse_throttle = math::constrain(v, 0.0f, 1.0f);
+	_params_standard.reverse_throttle = math::constrain(v, -1.0f, 1.0f);
 
 	/* mpc cruise speed */
 	param_get(_params_handles_standard.mpc_xy_cruise, &_params_standard.mpc_xy_cruise);
@@ -186,13 +186,12 @@ void Standard::update_vtol_state()
 				_flag_enable_mc_motors = true;
 				_vtol_schedule.transition_start = hrt_absolute_time();
 
-				if (_params_handles_standard.reverse_output > FLT_EPSILON) {
-					_pusher_throttle = _params_standard.reverse_throttle;
-					_reverse_output = _params_standard.reverse_output;
+				_pusher_throttle = _params_standard.reverse_throttle;
+				_reverse_output = _params_standard.reverse_output;
 
-				} else {
+				// prevent positive thrust without control channel activated
+				if (_pusher_throttle > FLT_EPSILON && _reverse_output < 0.01f) {
 					_pusher_throttle = 0.0f;
-					_reverse_output = 0.0f;
 				}
 			}
 

src/modules/vtol_att_control/vtol_att_control_params.c

@@ -250,9 +250,10 @@ PARAM_DEFINE_FLOAT(VT_B_REV_OUT, 0.0f);
 
 /**
  * Thottle output during back transition
- * This is only enabled when VT_B_REV_OUT is enabled and is used for active breaking with reverse thrust
+ * For ESCs and mixers that support reverse thrust on low PWM values set this to a negative value to apply active breaking
+ * For ESCs that support thrust reversal with a control channel please set VT_B_REV_OUT and set this to a positive value to apply active breaking
  *
- * @min 0
+ * @min -1
  * @max 1
  * @increment 0.01
  * @decimal 2