tiltrotor: expose tilting duration of backtransition in param

Instead of hard-coding the tilting duration (from FW to MC tilt),
expose it as a parameter (VT_BT_TILT_DUR). The default is the same
as the hard-coded value previously (1s).
Slower tilting mechanisms need a higher value here, while for smaller
ones a too high value results in unnecessary delays till the motors
are in hover configuration.

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

src/modules/vtol_att_control/tiltrotor.cpp

@@ -45,10 +45,9 @@
 using namespace matrix;
 using namespace time_literals;
 
-#define  FRONTTRANS_THR_MIN 0.25f
-#define BACKTRANS_THROTTLE_DOWNRAMP_DUR_S 0.5f;
-#define BACKTRANS_THROTTLE_UPRAMP_DUR_S 0.5f;
-#define BACKTRANS_MOTORS_UPTILT_DUR_S 1.0f;
+#define FRONTTRANS_THR_MIN 0.25f
+#define BACKTRANS_THROTTLE_DOWNRAMP_DUR_S 0.5f
+#define BACKTRANS_THROTTLE_UPRAMP_DUR_S 0.5f
 
 Tiltrotor::Tiltrotor(VtolAttitudeControl *attc) :
 	VtolType(attc)
@@ -321,7 +320,8 @@ void Tiltrotor::update_transition_state()
 		// tilt rotors back once motors are idle
 		if (_time_since_trans_start > BACKTRANS_THROTTLE_DOWNRAMP_DUR_S) {
 
-			float progress = (_time_since_trans_start - BACKTRANS_THROTTLE_DOWNRAMP_DUR_S) / BACKTRANS_MOTORS_UPTILT_DUR_S;
+			float progress = (_time_since_trans_start - BACKTRANS_THROTTLE_DOWNRAMP_DUR_S) / math::max(_param_vt_bt_tilt_dur.get(),
+					 0.1f);
 			progress = math::constrain(progress, 0.0f, 1.0f);
 			_tilt_control = moveLinear(_param_vt_tilt_fw.get(), _param_vt_tilt_mc.get(), progress);
 		}
@@ -458,7 +458,7 @@ void Tiltrotor::blendThrottleDuringBacktransition(float scale, float target_thro
 
 float Tiltrotor::timeUntilMotorsAreUp()
 {
-	return BACKTRANS_THROTTLE_DOWNRAMP_DUR_S + BACKTRANS_MOTORS_UPTILT_DUR_S;
+	return BACKTRANS_THROTTLE_DOWNRAMP_DUR_S + _param_vt_bt_tilt_dur.get();
 }
 
 float Tiltrotor::moveLinear(float start, float stop, float progress)

src/modules/vtol_att_control/tiltrotor.h

@@ -99,7 +99,8 @@ class Tiltrotor : public VtolType
 					(ParamFloat<px4::params::VT_TILT_TRANS>) _param_vt_tilt_trans,
 					(ParamFloat<px4::params::VT_TILT_FW>) _param_vt_tilt_fw,
 					(ParamFloat<px4::params::VT_TILT_SPINUP>) _param_vt_tilt_spinup,
-					(ParamFloat<px4::params::VT_TRANS_P2_DUR>) _param_vt_trans_p2_dur
+					(ParamFloat<px4::params::VT_TRANS_P2_DUR>) _param_vt_trans_p2_dur,
+					(ParamFloat<px4::params::VT_BT_TILT_DUR>) _param_vt_bt_tilt_dur
 				       )
 
 };

src/modules/vtol_att_control/tiltrotor_params.c

@@ -98,3 +98,17 @@ PARAM_DEFINE_FLOAT(VT_TILT_SPINUP, 0.0f);
  * @group VTOL Attitude Control
  */
 PARAM_DEFINE_FLOAT(VT_TRANS_P2_DUR, 0.5f);
+
+/**
+ * Duration motor tilt up in backtransition
+ *
+ * Time in seconds it takes to tilt form VT_TILT_FW to VT_TILT_MC.
+ *
+ * @unit s
+ * @min 0.1
+ * @max 10
+ * @increment 0.1
+ * @decimal 1
+ * @group VTOL Attitude Control
+ */
+PARAM_DEFINE_FLOAT(VT_BT_TILT_DUR, 1.f);