PX4-Autopilot/src/modules/vtol_att_control/tailsitter.cpp

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/**
* @file tailsitter.cpp
*
* @author Roman Bapst 		<bapstroman@gmail.com>
* @author David Vorsin     <davidvorsin@gmail.com>
*
*/

#include "tailsitter.h"
#include "vtol_att_control_main.h"

#define ARSP_YAW_CTRL_DISABLE 4.0f	// airspeed at which we stop controlling yaw during a front transition
#define THROTTLE_TRANSITION_MAX 0.25f	// maximum added thrust above last value in transition
#define PITCH_TRANSITION_FRONT_P1 -1.1f	// pitch angle to switch to TRANSITION_P2
#define PITCH_TRANSITION_BACK -0.25f	// pitch angle to switch to MC

Tailsitter::Tailsitter(VtolAttitudeControl *attc) :
	VtolType(attc),
	_thrust_transition_start(0.0f),
	_yaw_transition(0.0f),
	_pitch_transition_start(0.0f)
{
	_vtol_schedule.flight_mode = MC_MODE;
	_vtol_schedule.transition_start = 0;

	_mc_roll_weight = 1.0f;
	_mc_pitch_weight = 1.0f;
	_mc_yaw_weight = 1.0f;

	_flag_was_in_trans_mode = false;

	_params_handles_tailsitter.front_trans_dur_p2 = param_find("VT_TRANS_P2_DUR");
}

Tailsitter::~Tailsitter()
{

}

void
Tailsitter::parameters_update()
{
	float v;

	/* vtol front transition phase 2 duration */
	param_get(_params_handles_tailsitter.front_trans_dur_p2, &v);
	_params_tailsitter.front_trans_dur_p2 = v;
}

void Tailsitter::update_vtol_state()
{

	/* simple logic using a two way switch to perform transitions.
	 * after flipping the switch the vehicle will start tilting in MC control mode, picking up
	 * forward speed. After the vehicle has picked up enough and sufficient pitch angle the uav will go into FW mode.
	 * For the backtransition the pitch is controlled in MC mode again and switches to full MC control reaching the sufficient pitch angle.
	*/

	matrix::Eulerf euler = matrix::Quatf(_v_att->q);
	float pitch = euler.theta();

	if (!_attc->is_fixed_wing_requested()) {

		switch (_vtol_schedule.flight_mode) { // user switchig to MC mode
		case MC_MODE:
			break;

		case FW_MODE:
			_vtol_schedule.flight_mode 	= TRANSITION_BACK;
			_vtol_schedule.transition_start = hrt_absolute_time();
			break;

		case TRANSITION_FRONT_P1:
			// failsafe into multicopter mode
			_vtol_schedule.flight_mode = MC_MODE;
			break;

		case TRANSITION_BACK:

			// check if we have reached pitch angle to switch to MC mode
			if (pitch >= PITCH_TRANSITION_BACK) {
				_vtol_schedule.flight_mode = MC_MODE;
			}

			break;
		}

	} else {  // user switchig to FW mode

		switch (_vtol_schedule.flight_mode) {
		case MC_MODE:
			// initialise a front transition
			_vtol_schedule.flight_mode 	= TRANSITION_FRONT_P1;
			_vtol_schedule.transition_start = hrt_absolute_time();
			break;

		case FW_MODE:
			break;

		case TRANSITION_FRONT_P1: {

				bool airspeed_condition_satisfied = _airspeed->indicated_airspeed_m_s >= _params->transition_airspeed;
				airspeed_condition_satisfied |= _params->airspeed_disabled;

				// check if we have reached airspeed  and pitch angle to switch to TRANSITION P2 mode
				if ((airspeed_condition_satisfied && pitch <= PITCH_TRANSITION_FRONT_P1) || can_transition_on_ground()) {
					_vtol_schedule.flight_mode = FW_MODE;
				}

				break;
			}

		case TRANSITION_BACK:
			// failsafe into fixed wing mode
			_vtol_schedule.flight_mode = FW_MODE;
			break;
		}
	}

	// map tailsitter specific control phases to simple control modes
	switch (_vtol_schedule.flight_mode) {
	case MC_MODE:
		_vtol_mode = ROTARY_WING;
		_vtol_vehicle_status->vtol_in_trans_mode = false;
		_flag_was_in_trans_mode = false;
		break;

	case FW_MODE:
		_vtol_mode = FIXED_WING;
		_vtol_vehicle_status->vtol_in_trans_mode = false;
		_flag_was_in_trans_mode = false;
		break;

	case TRANSITION_FRONT_P1:
		_vtol_mode = TRANSITION_TO_FW;
		_vtol_vehicle_status->vtol_in_trans_mode = true;
		break;

	case TRANSITION_BACK:
		_vtol_mode = TRANSITION_TO_MC;
		_vtol_vehicle_status->vtol_in_trans_mode = true;
		break;
	}
}

void Tailsitter::update_transition_state()
{
	float time_since_trans_start = (float)(hrt_absolute_time() - _vtol_schedule.transition_start) * 1e-6f;

	if (!_flag_was_in_trans_mode) {
		// save desired heading for transition and last thrust value
		_yaw_transition = _v_att_sp->yaw_body;
		//transition should start from current attitude instead of current setpoint
		matrix::Eulerf euler = matrix::Quatf(_v_att->q);
		_pitch_transition_start = euler.theta();
		_thrust_transition_start = _v_att_sp->thrust;
		_flag_was_in_trans_mode = true;
	}

	if (_vtol_schedule.flight_mode == TRANSITION_FRONT_P1) {

		// create time dependant pitch angle set point + 0.2 rad overlap over the switch value
		_v_att_sp->pitch_body = _pitch_transition_start	- fabsf(PITCH_TRANSITION_FRONT_P1 - _pitch_transition_start) *
					time_since_trans_start / _params->front_trans_duration;
		_v_att_sp->pitch_body = math::constrain(_v_att_sp->pitch_body, PITCH_TRANSITION_FRONT_P1 - 0.2f,
							_pitch_transition_start);

		_v_att_sp->thrust = _mc_virtual_att_sp->thrust;

		// disable mc yaw control once the plane has picked up speed
		if (_airspeed->indicated_airspeed_m_s > ARSP_YAW_CTRL_DISABLE) {
			_mc_yaw_weight = 0.0f;

		} else {
			_mc_yaw_weight = 1.0f;
		}

		_mc_roll_weight = 1.0f;
		_mc_pitch_weight = 1.0f;

	} else if (_vtol_schedule.flight_mode == TRANSITION_BACK) {

		if (!flag_idle_mc) {
			flag_idle_mc = enable_mc_motors();
		}

		// create time dependant pitch angle set point stating at -pi/2 + 0.2 rad overlap over the switch value
		_v_att_sp->pitch_body = M_PI_2_F + _pitch_transition_start + fabsf(PITCH_TRANSITION_BACK + 1.57f) *
					time_since_trans_start / _params->back_trans_duration;
		_v_att_sp->pitch_body = math::constrain(_v_att_sp->pitch_body, -2.0f, PITCH_TRANSITION_BACK + 0.2f);


		_v_att_sp->thrust = _mc_virtual_att_sp->thrust;

		// keep yaw disabled
		_mc_yaw_weight = 0.0f;

		// smoothly move control weight to MC
		_mc_roll_weight = _mc_pitch_weight = time_since_trans_start / _params->back_trans_duration;

	}

	_mc_roll_weight = math::constrain(_mc_roll_weight, 0.0f, 1.0f);
	_mc_yaw_weight = math::constrain(_mc_yaw_weight, 0.0f, 1.0f);
	_mc_pitch_weight = math::constrain(_mc_pitch_weight, 0.0f, 1.0f);

	// compute desired attitude and thrust setpoint for the transition

	_v_att_sp->timestamp = hrt_absolute_time();
	_v_att_sp->roll_body = 0.0f;
	_v_att_sp->yaw_body = _yaw_transition;

	math::Quaternion q_sp;
	q_sp.from_euler(_v_att_sp->roll_body, _v_att_sp->pitch_body, _v_att_sp->yaw_body);
	memcpy(&_v_att_sp->q_d[0], &q_sp.data[0], sizeof(_v_att_sp->q_d));
}

void Tailsitter::waiting_on_tecs()
{
	// copy the last trust value from the front transition
	_v_att_sp->thrust = _thrust_transition;
}

void Tailsitter::update_mc_state()
{
	VtolType::update_mc_state();

	// set idle speed for rotary wing mode
	if (!flag_idle_mc) {
		flag_idle_mc = enable_mc_motors();
	}
}

void Tailsitter::update_fw_state()
{
	VtolType::update_fw_state();

	if (flag_idle_mc) {
		flag_idle_mc = !disable_mc_motors();
	}
}

/**
* Write data to actuator output topic.
*/
void Tailsitter::fill_actuator_outputs()
{
	switch (_vtol_mode) {
	case ROTARY_WING:
		_actuators_out_0->timestamp = _actuators_mc_in->timestamp;
		_actuators_out_0->control[actuator_controls_s::INDEX_ROLL] = _actuators_mc_in->control[actuator_controls_s::INDEX_ROLL];
		_actuators_out_0->control[actuator_controls_s::INDEX_PITCH] =
			_actuators_mc_in->control[actuator_controls_s::INDEX_PITCH];
		_actuators_out_0->control[actuator_controls_s::INDEX_YAW] = _actuators_mc_in->control[actuator_controls_s::INDEX_YAW];
		_actuators_out_0->control[actuator_controls_s::INDEX_THROTTLE] =
			_actuators_mc_in->control[actuator_controls_s::INDEX_THROTTLE];

		_actuators_out_1->timestamp = _actuators_mc_in->timestamp;

		if (_params->elevons_mc_lock) {
			_actuators_out_1->control[0] = 0;
			_actuators_out_1->control[1] = 0;

		} else {
			// NOTE: There is no mistake in the line below, multicopter yaw axis is controlled by elevon roll actuation!
			_actuators_out_1->control[actuator_controls_s::INDEX_ROLL] =
				_actuators_mc_in->control[actuator_controls_s::INDEX_YAW];	//roll elevon
			_actuators_out_1->control[actuator_controls_s::INDEX_PITCH] =
				_actuators_mc_in->control[actuator_controls_s::INDEX_PITCH];	//pitch elevon
		}

		break;

	case FIXED_WING:
		// in fixed wing mode we use engines only for providing thrust, no moments are generated
		_actuators_out_0->timestamp = _actuators_fw_in->timestamp;
		_actuators_out_0->control[actuator_controls_s::INDEX_ROLL] = 0;
		_actuators_out_0->control[actuator_controls_s::INDEX_PITCH] = 0;
		_actuators_out_0->control[actuator_controls_s::INDEX_YAW] = 0;
		_actuators_out_0->control[actuator_controls_s::INDEX_THROTTLE] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_THROTTLE];

		_actuators_out_1->control[actuator_controls_s::INDEX_ROLL] =
			-_actuators_fw_in->control[actuator_controls_s::INDEX_ROLL];	// roll elevon
		_actuators_out_1->control[actuator_controls_s::INDEX_PITCH] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_PITCH];	// pitch elevon
		_actuators_out_1->control[actuator_controls_s::INDEX_YAW] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_YAW];	// yaw
		_actuators_out_1->control[actuator_controls_s::INDEX_THROTTLE] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_THROTTLE];	// throttle
		break;

	case TRANSITION_TO_FW:
	case TRANSITION_TO_MC:
		// in transition engines are mixed by weight (BACK TRANSITION ONLY)
		_actuators_out_0->timestamp = _actuators_mc_in->timestamp;
		_actuators_out_1->timestamp = _actuators_mc_in->timestamp;
		_actuators_out_0->control[actuator_controls_s::INDEX_ROLL] = _actuators_mc_in->control[actuator_controls_s::INDEX_ROLL]
				* _mc_roll_weight;
		_actuators_out_0->control[actuator_controls_s::INDEX_PITCH] =
			_actuators_mc_in->control[actuator_controls_s::INDEX_PITCH] * _mc_pitch_weight;
		_actuators_out_0->control[actuator_controls_s::INDEX_YAW] = _actuators_mc_in->control[actuator_controls_s::INDEX_YAW] *
				_mc_yaw_weight;
		_actuators_out_0->control[actuator_controls_s::INDEX_THROTTLE] =
			_actuators_mc_in->control[actuator_controls_s::INDEX_THROTTLE];

		// NOTE: There is no mistake in the line below, multicopter yaw axis is controlled by elevon roll actuation!
		_actuators_out_1->control[actuator_controls_s::INDEX_ROLL] = -_actuators_fw_in->control[actuator_controls_s::INDEX_ROLL]
				* (1 - _mc_yaw_weight);
		_actuators_out_1->control[actuator_controls_s::INDEX_PITCH] =
			_actuators_mc_in->control[actuator_controls_s::INDEX_PITCH] * _mc_pitch_weight;
		// **LATER** + (_actuators_fw_in->control[actuator_controls_s::INDEX_PITCH] + _params->fw_pitch_trim) *(1 - _mc_pitch_weight);
		_actuators_out_1->control[actuator_controls_s::INDEX_THROTTLE] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_THROTTLE];
		break;
	}
}