px4-firmware/attitude_fw/ecl_yaw_controller.cpp

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/**
 * @file ecl_yaw_controller.cpp
 * Implementation of a simple orthogonal coordinated turn yaw PID controller.
 *
 * Authors and acknowledgements in header.
 */

#include "ecl_yaw_controller.h"
#include <stdint.h>
#include <float.h>
#include <geo/geo.h>
#include <ecl/ecl.h>
#include <mathlib/mathlib.h>
#include <systemlib/err.h>
#include <ecl/ecl.h>

ECL_YawController::ECL_YawController() :
	ECL_Controller("yaw"),
	_coordinated_min_speed(1.0f),
	_coordinated_method(0)
{
}

ECL_YawController::~ECL_YawController()
{
}

float ECL_YawController::control_attitude(const struct ECL_ControlData &ctl_data)
{
	switch (_coordinated_method) {
	case COORD_METHOD_OPEN:
		return control_attitude_impl_openloop(ctl_data);

	case COORD_METHOD_CLOSEACC:
		return control_attitude_impl_accclosedloop(ctl_data);

	default:
		static hrt_abstime last_print = 0;

		if (ecl_elapsed_time(&last_print) > 5e6) {
			warnx("invalid param setting FW_YCO_METHOD");
			last_print = ecl_absolute_time();
		}
	}

	return _rate_setpoint;
}

float ECL_YawController::control_bodyrate(const struct ECL_ControlData &ctl_data)
{
	switch (_coordinated_method) {
	case COORD_METHOD_OPEN:
	case COORD_METHOD_CLOSEACC:
		return control_bodyrate_impl(ctl_data);

	default:
		static hrt_abstime last_print = 0;

		if (ecl_elapsed_time(&last_print) > 5e6) {
			warnx("invalid param setting FW_YCO_METHOD");
			last_print = ecl_absolute_time();
		}
	}

	return math::constrain(_last_output, -1.0f, 1.0f);
}

float ECL_YawController::control_attitude_impl_openloop(const struct ECL_ControlData &ctl_data)
{
	/* Do not calculate control signal with bad inputs */
	if (!(PX4_ISFINITE(ctl_data.roll) &&
	      PX4_ISFINITE(ctl_data.pitch) &&
	      PX4_ISFINITE(ctl_data.speed_body_u) &&
	      PX4_ISFINITE(ctl_data.speed_body_v) &&
	      PX4_ISFINITE(ctl_data.speed_body_w) &&
	      PX4_ISFINITE(ctl_data.roll_rate_setpoint) &&
	      PX4_ISFINITE(ctl_data.pitch_rate_setpoint))) {
		return _rate_setpoint;
	}

//	static int counter = 0;
	/* Calculate desired yaw rate from coordinated turn constraint / (no side forces) */
	_rate_setpoint = 0.0f;

	if (sqrtf(ctl_data.speed_body_u * ctl_data.speed_body_u + ctl_data.speed_body_v * ctl_data.speed_body_v +
		  ctl_data.speed_body_w * ctl_data.speed_body_w) > _coordinated_min_speed) {
		float denumerator = (ctl_data.speed_body_u * cosf(ctl_data.roll) * cosf(ctl_data.pitch) +
				     ctl_data.speed_body_w * sinf(ctl_data.pitch));

		if (fabsf(denumerator) > FLT_EPSILON) {
			_rate_setpoint = (ctl_data.speed_body_w * ctl_data.roll_rate_setpoint +
					  9.81f * sinf(ctl_data.roll) * cosf(ctl_data.pitch) +
					  ctl_data.speed_body_u * ctl_data.pitch_rate_setpoint * sinf(ctl_data.roll)) /
					 denumerator;

//			warnx("yaw: speed_body_u %.f speed_body_w %1.f roll %.1f pitch %.1f denumerator %.1f _rate_setpoint %.1f", speed_body_u, speed_body_w, denumerator, _rate_setpoint);
		}

//		if(counter % 20 == 0) {
//			warnx("denumerator: %.4f, speed_body_u: %.4f, speed_body_w: %.4f, cosf(roll): %.4f, cosf(pitch): %.4f, sinf(pitch): %.4f", (double)denumerator, (double)speed_body_u, (double)speed_body_w, (double)cosf(roll), (double)cosf(pitch), (double)sinf(pitch));
//		}
	}

	/* limit the rate */ //XXX: move to body angluar rates

	if (_max_rate > 0.01f) {
		_rate_setpoint = (_rate_setpoint > _max_rate) ? _max_rate : _rate_setpoint;
		_rate_setpoint = (_rate_setpoint < -_max_rate) ? -_max_rate : _rate_setpoint;
	}


//	counter++;

	if (!PX4_ISFINITE(_rate_setpoint)) {
		warnx("yaw rate sepoint not finite");
		_rate_setpoint = 0.0f;
	}

	return _rate_setpoint;
}

float ECL_YawController::control_bodyrate_impl(const struct ECL_ControlData &ctl_data)
{
	/* Do not calculate control signal with bad inputs */
	if (!(PX4_ISFINITE(ctl_data.roll) && PX4_ISFINITE(ctl_data.pitch) && PX4_ISFINITE(ctl_data.pitch_rate) &&
	      PX4_ISFINITE(ctl_data.yaw_rate) && PX4_ISFINITE(ctl_data.pitch_rate_setpoint) &&
	      PX4_ISFINITE(ctl_data.airspeed_min) && PX4_ISFINITE(ctl_data.airspeed_max) &&
	      PX4_ISFINITE(ctl_data.scaler))) {
		return math::constrain(_last_output, -1.0f, 1.0f);
	}

	/* get the usual dt estimate */
	uint64_t dt_micros = ecl_elapsed_time(&_last_run);
	_last_run = ecl_absolute_time();
	float dt = (float)dt_micros * 1e-6f;

	/* lock integral for long intervals */
	bool lock_integrator = ctl_data.lock_integrator;

	if (dt_micros > 500000) {
		lock_integrator = true;
	}

	/* input conditioning */
	float airspeed = ctl_data.airspeed;

	if (!PX4_ISFINITE(airspeed)) {
		/* airspeed is NaN, +- INF or not available, pick center of band */
		airspeed = 0.5f * (ctl_data.airspeed_min + ctl_data.airspeed_max);

	} else if (airspeed < ctl_data.airspeed_min) {
		airspeed = ctl_data.airspeed_min;
	}


	/* Transform setpoint to body angular rates (jacobian) */
	_bodyrate_setpoint = -sinf(ctl_data.roll) * ctl_data.pitch_rate_setpoint +
			     cosf(ctl_data.roll) * cosf(ctl_data.pitch) * _rate_setpoint;

	/* Close the acceleration loop if _coordinated_method wants this: change body_rate setpoint */
	if (_coordinated_method == COORD_METHOD_CLOSEACC) {
		//XXX: filtering of acceleration?
		_bodyrate_setpoint -= (ctl_data.acc_body_y / (airspeed * cosf(ctl_data.pitch)));
	}

	/* Calculate body angular rate error */
	_rate_error = _bodyrate_setpoint - ctl_data.yaw_rate; //body angular rate error

	if (!lock_integrator && _k_i > 0.0f && airspeed > 0.5f * ctl_data.airspeed_min) {

		float id = _rate_error * dt;

		/*
		 * anti-windup: do not allow integrator to increase if actuator is at limit
		 */
		if (_last_output < -1.0f) {
			/* only allow motion to center: increase value */
			id = math::max(id, 0.0f);

		} else if (_last_output > 1.0f) {
			/* only allow motion to center: decrease value */
			id = math::min(id, 0.0f);
		}

		_integrator += id * _k_i;
	}

	/* integrator limit */
	//xxx: until start detection is available: integral part in control signal is limited here
	float integrator_constrained = math::constrain(_integrator, -_integrator_max, _integrator_max);

	/* Apply PI rate controller and store non-limited output */
	_last_output = (_bodyrate_setpoint * _k_ff + _rate_error * _k_p + integrator_constrained) * ctl_data.scaler *
		       ctl_data.scaler;  //scaler is proportional to 1/airspeed
	//warnx("yaw:_last_output: %.4f, _integrator: %.4f, _integrator_max: %.4f, airspeed %.4f, _k_i %.4f, _k_p: %.4f", (double)_last_output, (double)_integrator, (double)_integrator_max, (double)airspeed, (double)_k_i, (double)_k_p);


	return math::constrain(_last_output, -1.0f, 1.0f);
}

float ECL_YawController::control_attitude_impl_accclosedloop(const struct ECL_ControlData &ctl_data)
{
	/* dont set a rate setpoint */
	return 0.0f;
}