Plane: TKOFF_THR_MIN is applied to SLT transitions

Also split in_transition() to forward and backward.

ArduPlane/Attitude.cpp

@@ -204,9 +204,9 @@ float Plane::stabilize_pitch_get_pitch_out()
 #endif
     // if LANDING_FLARE RCx_OPTION switch is set and in FW mode, manual throttle,throttle idle then set pitch to LAND_PITCH_DEG if flight option FORCE_FLARE_ATTITUDE is set
 #if HAL_QUADPLANE_ENABLED
-    const bool quadplane_in_transition = quadplane.in_transition();
+    const bool quadplane_in_frwd_transition = quadplane.in_frwd_transition();
 #else
-    const bool quadplane_in_transition = false;
+    const bool quadplane_in_frwd_transition = false;
 #endif
 
     int32_t demanded_pitch = nav_pitch_cd + int32_t(g.pitch_trim * 100.0) + SRV_Channels::get_output_scaled(SRV_Channel::k_throttle) * g.kff_throttle_to_pitch;
@@ -219,7 +219,7 @@ float Plane::stabilize_pitch_get_pitch_out()
        - throttle stick at zero thrust
        - in fixed wing non auto-throttle mode
     */
-    if (!quadplane_in_transition &&
+    if (!quadplane_in_frwd_transition &&
         !control_mode->is_vtol_mode() &&
         !control_mode->does_auto_throttle() &&
         flare_mode == FlareMode::ENABLED_PITCH_TARGET &&

ArduPlane/quadplane.cpp

@@ -813,6 +813,10 @@ bool QuadPlane::setup(void)
     pilot_speed_z_max_dn.convert_centi_parameter(AP_PARAM_INT16);
     pilot_accel_z.convert_centi_parameter(AP_PARAM_INT16);
 
+    // Provisionally assign the SLT thrust type.
+    // It will be overwritten by tailsitter or tiltorotor setups.
+    thrust_type = ThrustType::SLT;
+
     tailsitter.setup();
 
     tiltrotor.setup();
@@ -3968,11 +3972,28 @@ bool QuadPlane::is_vtol_land(uint16_t id) const
 }
 
 /*
-  return true if we are in a transition to fwd flight from hover
+  return true if we are in any kind of transition
  */
 bool QuadPlane::in_transition(void) const
 {
-    return available() && transition->active();
+    return in_frwd_transition() || in_back_transition();
+}
+
+/*
+  return true if we are in a transition to fwd flight from hover
+ */
+bool QuadPlane::in_frwd_transition(void) const
+{
+    return available() && transition->active_frwd();
+}
+
+/*
+  return true if we are in a transition to hover from fwd flight
+ */
+bool QuadPlane::in_back_transition(void) const
+{
+    // By default the 
+    return available() && transition->active_back();
 }
 
 /*
@@ -4351,11 +4372,16 @@ bool SLT_Transition::allow_update_throttle_mix() const
     return !(quadplane.assisted_flight && (transition_state == TRANSITION_AIRSPEED_WAIT || transition_state == TRANSITION_TIMER));
 }
 
-bool SLT_Transition::active() const
+bool SLT_Transition::active_frwd() const
 {
     return quadplane.assisted_flight && ((transition_state == TRANSITION_AIRSPEED_WAIT) || (transition_state == TRANSITION_TIMER));
 }
 
+bool SLT_Transition::active_back() const
+{
+    return false;
+}
+
 /*
   limit VTOL roll/pitch in POSITION1, POSITION2 and waypoint controller. This serves three roles:
    1) an expanding envelope limit on pitch to prevent sudden pitch at the start of a back transition

ArduPlane/quadplane.h

@@ -76,6 +76,13 @@ public:
     void control_auto(void);
     bool setup(void);
 
+    enum class ThrustType : uint8_t {
+        SLT=0, // Traditional quadplane, with a pusher motor and independent multicopter lift.
+        TAILSITTER,
+        TILTROTOR,
+    };
+    ThrustType get_thrust_type(void) {return thrust_type;}
+
     void vtol_position_controller(void);
     void setup_target_position(void);
     void takeoff_controller(void);
@@ -103,10 +110,9 @@ public:
     // abort landing, only valid when in a VTOL landing descent
     bool abort_landing(void);
 
-    /*
-      return true if we are in a transition to fwd flight from hover
-    */
     bool in_transition(void) const;
+    bool in_frwd_transition(void) const;
+    bool in_back_transition(void) const;
 
     bool handle_do_vtol_transition(enum MAV_VTOL_STATE state) const;
 
@@ -198,6 +204,9 @@ private:
     AP_Enum<AP_Motors::motor_frame_class> frame_class;
     AP_Enum<AP_Motors::motor_frame_type> frame_type;
 
+    // Types of different "quadplane" configurations.
+    ThrustType thrust_type;
+
     // Initialise motors to allow passing it to tailsitter in its constructor
     AP_MotorsMulticopter *motors = nullptr;
     const struct AP_Param::GroupInfo *motors_var_info;

ArduPlane/servos.cpp

@@ -51,7 +51,7 @@ void Plane::throttle_slew_limit(SRV_Channel::Aux_servo_function_t func)
         slewrate = g.takeoff_throttle_slewrate;
     }
 #if HAL_QUADPLANE_ENABLED
-    if (g.takeoff_throttle_slewrate != 0 && quadplane.in_transition()) {
+    if (g.takeoff_throttle_slewrate != 0 && quadplane.in_frwd_transition()) {
         slewrate = g.takeoff_throttle_slewrate;
     }
 #endif
@@ -555,10 +555,20 @@ float Plane::apply_throttle_limits(float throttle_in)
 
     // Handle throttle limits for transition conditions.
 #if HAL_QUADPLANE_ENABLED
-    if (quadplane.in_transition()) {
+    if (quadplane.in_frwd_transition()) {
         if (aparm.takeoff_throttle_max != 0) {
             max_throttle = aparm.takeoff_throttle_max.get();
         }
+
+        // Apply minimum throttle limits only for SLT thrust types.
+        // The other types don't support it well.
+        if (quadplane.get_thrust_type() == QuadPlane::ThrustType::SLT
+            && control_mode->does_auto_throttle()
+        ) {
+            if (aparm.takeoff_throttle_min.get() != 0) {
+                min_throttle = MAX(min_throttle, aparm.takeoff_throttle_min.get());
+            }
+        }
     }
 #endif
 
@@ -793,7 +803,7 @@ void Plane::servos_twin_engine_mix(void)
 void Plane::force_flare(void)
 {
 #if HAL_QUADPLANE_ENABLED
-    if (quadplane.in_transition() && plane.arming.is_armed()) { //allows for ground checking of flare tilts
+    if (quadplane.in_frwd_transition() && plane.arming.is_armed()) { //allows for ground checking of flare tilts
         return;
     }
     if (control_mode->is_vtol_mode()) {

ArduPlane/tailsitter.cpp

@@ -208,6 +208,8 @@ void Tailsitter::setup()
         return;
     }
 
+    quadplane.thrust_type = QuadPlane::ThrustType::TAILSITTER;
+
     // Set tailsitter transition rate to match old calculation
     if (!transition_rate_fw.configured()) {
         transition_rate_fw.set_and_save(transition_angle_fw / (quadplane.transition_time_ms/2000.0f));

ArduPlane/tailsitter.h

@@ -175,7 +175,9 @@ public:
 
     uint8_t get_log_transition_state() const override { return static_cast<uint8_t>(transition_state); }
 
-    bool active() const override { return transition_state != TRANSITION_DONE; }
+    bool active_frwd() const override { return transition_state == TRANSITION_ANGLE_WAIT_FW; }
+
+    bool active_back() const override { return transition_state == TRANSITION_ANGLE_WAIT_VTOL; }
 
     bool show_vtol_view() const override;
 

ArduPlane/tiltrotor.cpp

@@ -106,6 +106,8 @@ void Tiltrotor::setup()
         return;
     }
 
+    quadplane.thrust_type = QuadPlane::ThrustType::TILTROTOR;
+
     _is_vectored = tilt_mask != 0 && type == TILT_TYPE_VECTORED_YAW;
 
     // true if a fixed forward motor is configured, either throttle, throttle left  or throttle right.

ArduPlane/transition.h

@@ -36,7 +36,9 @@ public:
 
     virtual uint8_t get_log_transition_state() const = 0;
 
-    virtual bool active() const = 0;
+    virtual bool active_frwd() const = 0;
+
+    virtual bool active_back() const = 0;
 
     virtual bool show_vtol_view() const = 0;
 
@@ -85,7 +87,9 @@ public:
 
     uint8_t get_log_transition_state() const override { return static_cast<uint8_t>(transition_state); }
 
-    bool active() const override;
+    bool active_frwd() const override;
+
+    bool active_back() const override;
 
     bool show_vtol_view() const override;