VTOL: Smarter pusher ramp up during front transtitions for standard VTOLs (#20394)

New param VT_PSHER_SLEW for ramping up throttle of pusher during front/back transition, that replaces the old VT_PSHER_RMP_DT param.

src/lib/parameters/param_translation.cpp

@@ -259,5 +259,16 @@ bool param_modify_on_import(bson_node_t node)
 		}
 	}
 
+	// 2022-11-11: translate VT_F_TRANS_THR/VT_PSHER_RMP_DT -> VT_PSHER_SLEW
+	{
+		if (strcmp("VT_PSHER_RMP_DT", node->name) == 0) {
+			strcpy(node->name, "VT_PSHER_SLEW");
+			double _param_vt_f_trans_thr = param_find("VT_F_TRANS_THR");
+			node->d = _param_vt_f_trans_thr / node->d;
+			PX4_INFO("copying %s -> %s", "VT_PSHER_RMP_DT", "VT_PSHER_SLEW");
+			return true;
+		}
+	}
+
 	return false;
 }

src/modules/vtol_att_control/standard.cpp

@@ -231,13 +231,14 @@ void Standard::update_transition_state()
 	}
 
 	if (_vtol_schedule.flight_mode == vtol_mode::TRANSITION_TO_FW) {
-		if (_param_vt_psher_rmp_dt.get() <= 0.0f) {
+		if (_param_vt_psher_slew.get() <= FLT_EPSILON) {
 			// just set the final target throttle value
 			_pusher_throttle = _param_vt_f_trans_thr.get();
 
 		} else if (_pusher_throttle <= _param_vt_f_trans_thr.get()) {
 			// ramp up throttle to the target throttle value
-			_pusher_throttle = _param_vt_f_trans_thr.get() * time_since_trans_start / _param_vt_psher_rmp_dt.get();
+			_pusher_throttle = math::min(_pusher_throttle +
+						     _param_vt_psher_slew.get() * _dt, _param_vt_f_trans_thr.get());
 		}
 
 		_airspeed_trans_blend_margin = _param_vt_arsp_trans.get() - _param_vt_arsp_blend.get();
@@ -291,9 +292,8 @@ void Standard::update_transition_state()
 
 		if (time_since_trans_start >= _param_vt_b_rev_del.get()) {
 			// Handle throttle reversal for active breaking
-			float thrscale = (time_since_trans_start - _param_vt_b_rev_del.get()) / (_param_vt_psher_rmp_dt.get());
+			_pusher_throttle = math::constrain((time_since_trans_start - _param_vt_b_rev_del.get())
-			thrscale = math::constrain(thrscale, 0.0f, 1.0f);
+							   * _param_vt_psher_slew.get(), 0.0f, _param_vt_b_trans_thr.get());
-			_pusher_throttle = thrscale * _param_vt_b_trans_thr.get();
 		}
 
 		// continually increase mc attitude control as we transition back to mc mode

src/modules/vtol_att_control/standard.h

@@ -84,7 +84,7 @@ private:
 	void parameters_update() override;
 
 	DEFINE_PARAMETERS_CUSTOM_PARENT(VtolType,
-					(ParamFloat<px4::params::VT_PSHER_RMP_DT>) _param_vt_psher_rmp_dt,
+					(ParamFloat<px4::params::VT_PSHER_SLEW>) _param_vt_psher_slew,
 					(ParamFloat<px4::params::VT_B_TRANS_RAMP>) _param_vt_b_trans_ramp,
 					(ParamFloat<px4::params::FW_PSP_OFF>) _param_fw_psp_off,
 					(ParamFloat<px4::params::VT_B_REV_OUT>) _param_vt_b_rev_out,

src/modules/vtol_att_control/standard_params.c

@@ -108,7 +108,7 @@ PARAM_DEFINE_FLOAT(VT_B_REV_OUT, 0.0f);
  *
  * Set this to a value greater than 0 to give the motor time to spin down.
  *
- * unit s
+ * @unit s
  * @min 0
  * @max 10
  * @increment 1
@@ -118,14 +118,16 @@ PARAM_DEFINE_FLOAT(VT_B_REV_OUT, 0.0f);
 PARAM_DEFINE_FLOAT(VT_B_REV_DEL, 0.0f);
 
 /**
- * Pusher throttle ramp up window
+ * Pusher throttle ramp up slew rate
  *
- * Defines the time window during which the pusher throttle will be ramped up linearly to VT_F_TRANS_THR during a transition
+ * Defines the slew rate of the puller/pusher throttle during transitions.
- * to fixed wing mode. Zero or negative values will produce an instant throttle rise to VT_F_TRANS_THR.
+ * Zero will deactivate the slew rate limiting and thus produce an instant throttle
+ * rise to the transition throttle VT_F_TRANS_THR.
  *
- * @max 20
+ * @unit 1/s
+ * @min 0
  * @increment 0.01
  * @decimal 2
  * @group VTOL Attitude Control
  */
-PARAM_DEFINE_FLOAT(VT_PSHER_RMP_DT, 3.0f);
+PARAM_DEFINE_FLOAT(VT_PSHER_SLEW, 0.33f);