VTol + quad tailsitter mixer file

y2kare · April 24, 2017, 11:10pm

for my VTOL quad tailsitter I am using the elevons for yaw control in MC mode and the for YPR in FW mode so i was wondering will this be a valid mixer file if i combine groups 0 and 1

R: 4+ 10000 10000 0 0

mixer for the elevons

M: 4
O: 7500 7500 0 -10000 10000
S: 0 2 10000 10000 0 -10000 10000
S: 1 0 -10000 -10000 0 -10000 10000
S: 1 1 10000 10000 0 -10000 10000
S: 1 2 -10000 -10000 0 -10000 10000

M: 4
O: 7500 7500 0 -10000 10000
S: 0 2 -10000 -10000 0 -10000 10000
S: 1 0 -10000 -10000 0 -10000 10000
S: 1 1 10000 10000 0 -10000 10000
S: 1 2 -10000 -10000 0 -10000 10000

dagar · May 2, 2017, 3:37pm

Just curious if you tried this? I wouldn’t expect it to work, but I’ve never tried. PX4 handles this kind of thing in the VTOL controller.

github.com

PX4/Firmware/blob/master/src/modules/vtol_att_control/tailsitter.cpp#L454


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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


using namespace matrix;


Tailsitter::Tailsitter(VtolAttitudeControl *attc) :
	VtolType(attc)
{
	_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");
	_params_handles_tailsitter.fw_pitch_sp_offset = param_find("FW_PSP_OFF");
}


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;


	param_get(_params_handles_tailsitter.fw_pitch_sp_offset, &v);
	_params_tailsitter.fw_pitch_sp_offset = math::radians(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.
	*/


	Eulerf euler = 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:
			float time_since_trans_start = (float)(hrt_absolute_time() - _vtol_schedule.transition_start) * 1e-6f;


			// check if we have reached pitch angle to switch to MC mode
			if (pitch >= PITCH_TRANSITION_BACK || time_since_trans_start > _params->back_trans_duration) {
				_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) {
		_flag_was_in_trans_mode = true;


		if (_vtol_schedule.flight_mode == TRANSITION_BACK) {
			// calculate rotation axis for transition.
			_q_trans_start = Quatf(_v_att->q);
			Vector3f z = -_q_trans_start.dcm_z();
			_trans_rot_axis = z.cross(Vector3f(0, 0, -1));


			// as heading setpoint we choose the heading given by the direction the vehicle points
			float yaw_sp = atan2f(z(1), z(0));


			// the intial attitude setpoint for a backtransition is a combination of the current fw pitch setpoint,
			// the yaw setpoint and zero roll since we want wings level transition
			_q_trans_start = Eulerf(0.0f, _fw_virtual_att_sp->pitch_body, yaw_sp);


			// attitude during transitions are controlled by mc attitude control so rotate the desired attitude to the
			// multirotor frame
			_q_trans_start = _q_trans_start * Quatf(Eulerf(0, -M_PI_2_F, 0));


		} else if (_vtol_schedule.flight_mode == TRANSITION_FRONT_P1) {
			// initial attitude setpoint for the transition should be with wings level
			_q_trans_start = Eulerf(0.0f, _mc_virtual_att_sp->pitch_body, _mc_virtual_att_sp->yaw_body);
			Vector3f x = Dcmf(Quatf(_v_att->q)) * Vector3f(1, 0, 0);
			_trans_rot_axis = -x.cross(Vector3f(0, 0, -1));
		}


		_q_trans_sp = _q_trans_start;
	}


	// tilt angle (zero if vehicle nose points up (hover))
	float tilt = acosf(_q_trans_sp(0) * _q_trans_sp(0) - _q_trans_sp(1) * _q_trans_sp(1) - _q_trans_sp(2) * _q_trans_sp(
				   2) + _q_trans_sp(3) * _q_trans_sp(3));


	if (_vtol_schedule.flight_mode == TRANSITION_FRONT_P1) {


		const float trans_pitch_rate = M_PI_2_F / _params->front_trans_duration;


		if (tilt < M_PI_2_F - _params_tailsitter.fw_pitch_sp_offset) {
			_q_trans_sp = Quatf(AxisAnglef(_trans_rot_axis,
						       time_since_trans_start * trans_pitch_rate)) * _q_trans_start;
		}


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


		const float trans_pitch_rate = M_PI_2_F / _params->back_trans_duration;


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


		if (tilt > 0.01f) {
			_q_trans_sp = Quatf(AxisAnglef(_trans_rot_axis,
						       time_since_trans_start * trans_pitch_rate)) * _q_trans_start;
		}
	}


	_v_att_sp->thrust_body[2] = _mc_virtual_att_sp->thrust_body[2];


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


	_v_att_sp->timestamp = hrt_absolute_time();


	const Eulerf euler_sp(_q_trans_sp);
	_v_att_sp->roll_body = euler_sp.phi();
	_v_att_sp->pitch_body = euler_sp.theta();
	_v_att_sp->yaw_body = euler_sp.psi();


	_q_trans_sp.copyTo(_v_att_sp->q_d);
	_v_att_sp->q_d_valid = true;
}


void Tailsitter::waiting_on_tecs()
{
	// copy the last trust value from the front transition
	_v_att_sp->thrust_body[0] = _thrust_transition;
}


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


	// allow fw yawrate control via multirotor roll actuation. this is useful for vehicles
	// which don't have a rudder to coordinate turns
	if (_params->diff_thrust == 1) {
		_mc_roll_weight = 1.0f;
	}
}


/**
* Write data to actuator output topic.
*/
void Tailsitter::fill_actuator_outputs()
{
	_actuators_out_0->timestamp = hrt_absolute_time();
	_actuators_out_0->timestamp_sample = _actuators_mc_in->timestamp_sample;


	_actuators_out_1->timestamp = hrt_absolute_time();
	_actuators_out_1->timestamp_sample = _actuators_fw_in->timestamp_sample;


	_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;


	if (_vtol_schedule.flight_mode == FW_MODE) {
		_actuators_out_0->control[actuator_controls_s::INDEX_THROTTLE] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_THROTTLE];


	} else {
		_actuators_out_0->control[actuator_controls_s::INDEX_THROTTLE] =
			_actuators_mc_in->control[actuator_controls_s::INDEX_THROTTLE];
	}


	if (_params->elevons_mc_lock && _vtol_schedule.flight_mode == MC_MODE) {
		_actuators_out_1->control[actuator_controls_s::INDEX_ROLL] = 0;
		_actuators_out_1->control[actuator_controls_s::INDEX_PITCH] = 0;


	} else {
		_actuators_out_1->control[actuator_controls_s::INDEX_ROLL] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_ROLL];
		_actuators_out_1->control[actuator_controls_s::INDEX_PITCH] =
			_actuators_fw_in->control[actuator_controls_s::INDEX_PITCH];
	}
}

This file has been truncated. show original

y2kare · May 2, 2017, 6:22pm

The mixer file worked just fine. I had to simulate airspeed using a high-speed fan for fixed wing mode, that’s when the elevons started working.

Although I am working to enable differential rpm now for YAW in FW mode. I tried your suggestion to set _params_tiltrotor.diff_thrust to 1 but i didn’t notice any change in rpm ( i changed the diff_thrust_scale to 1 as well)