helicopter: add switch to engage main motor

For helicopters it's useful (e.g. during bringup) to be able to disable
the main rotor while the tail is still controlled to safely land.

src/modules/control_allocator/ActuatorEffectiveness/ActuatorEffectivenessHelicopter.cpp

@@ -132,7 +132,8 @@ void ActuatorEffectivenessHelicopter::updateSetpoint(const matrix::Vector<float,
 	const float collective_pitch = math::interpolateN(-control_sp(ControlAxis::THRUST_Z), _geometry.pitch_curve);
 
 	// actuator mapping
-	actuator_sp(0) = throttle;
+	actuator_sp(0) = mainMotorEnaged() ? throttle : NAN;
+
 	actuator_sp(1) = control_sp(ControlAxis::YAW)
 			 + fabsf(collective_pitch) * _geometry.yaw_collective_pitch_scale
 			 + throttle * _geometry.yaw_throttle_scale;
@@ -147,23 +148,16 @@ void ActuatorEffectivenessHelicopter::updateSetpoint(const matrix::Vector<float,
 	}
 }
 
-float ActuatorEffectivenessHelicopter::throttleSpoolupProgress()
+bool ActuatorEffectivenessHelicopter::mainMotorEnaged()
 {
-	vehicle_status_s vehicle_status;
+	manual_control_switches_s manual_control_switches;
 
-	if (_vehicle_status_sub.update(&vehicle_status)) {
-		_armed = vehicle_status.arming_state == vehicle_status_s::ARMING_STATE_ARMED;
-		_armed_time = vehicle_status.armed_time;
+	if (_manual_control_switches_sub.update(&manual_control_switches)) {
+		_main_motor_engaged = manual_control_switches.engage_main_motor_switch == manual_control_switches_s::SWITCH_POS_NONE
+				      || manual_control_switches.engage_main_motor_switch == manual_control_switches_s::SWITCH_POS_ON;
 	}
 
-	const float time_since_arming = (hrt_absolute_time() - _armed_time) / 1e6f;
-	const float spoolup_progress = time_since_arming / _geometry.spoolup_time;
-
-	if (_armed && spoolup_progress < 1.f) {
-		return spoolup_progress;
-	}
-
-	return 1.f;
+	return _main_motor_engaged;
 }
 
 float ActuatorEffectivenessHelicopter::throttleSpoolupProgress()

src/modules/control_allocator/ActuatorEffectiveness/ActuatorEffectivenessHelicopter.hpp

@@ -39,6 +39,7 @@
 
 #include <uORB/Subscription.hpp>
 #include <uORB/topics/vehicle_status.h>
+#include <uORB/topics/manual_control_switches.h>
 
 class ActuatorEffectivenessHelicopter : public ModuleParams, public ActuatorEffectiveness
 {
@@ -77,6 +78,7 @@ public:
 			    ActuatorVector &actuator_sp) override;
 private:
 	float throttleSpoolupProgress();
+	bool mainMotorEnaged();
 
 	void updateParams() override;
 
@@ -104,4 +106,7 @@ private:
 	uORB::Subscription _vehicle_status_sub{ORB_ID(vehicle_status)};
 	bool _armed{false};
 	uint64_t _armed_time{0};
+
+	uORB::Subscription _manual_control_switches_sub{ORB_ID(manual_control_switches)};
+	bool _main_motor_engaged{true};
 };