path: root/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp

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/**
 * @file ecl_pitch_controller.cpp
 * Implementation of a simple orthogonal pitch PID controller.
 *
 * Authors and acknowledgements in header.
 */

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

ECL_PitchController::ECL_PitchController() :
	ECL_Controller("pitch"),
	_max_rate_neg(0.0f),
	_roll_ff(0.0f)
{
}

ECL_PitchController::~ECL_PitchController()
{
}

float ECL_PitchController::control_attitude(const struct ECL_ControlData &ctl_data)
{
	float roll = ctl_data.roll;

	/* Do not calculate control signal with bad inputs */
	if (!(isfinite(ctl_data.pitch_setpoint) &&
	      isfinite(roll) &&
	      isfinite(ctl_data.pitch) &&
	      isfinite(ctl_data.airspeed))) {
		perf_count(_nonfinite_input_perf);
		warnx("not controlling pitch");
		return _rate_setpoint;
	}

	/* flying inverted (wings upside down) ? */
	bool inverted = false;

	/* roll is used as feedforward term and inverted flight needs to be considered */
	if (fabsf(roll) < math::radians(90.0f)) {
		/* not inverted, but numerically still potentially close to infinity */
		roll = math::constrain(roll, math::radians(-80.0f), math::radians(80.0f));

	} else {
		/* inverted flight, constrain on the two extremes of -pi..+pi to avoid infinity */

		/* note: the ranges are extended by 10 deg here to avoid numeric resolution effects */
		if (roll > 0.0f) {
			/* right hemisphere */
			roll = math::constrain(roll, math::radians(100.0f), math::radians(180.0f));

		} else {
			/* left hemisphere */
			roll = math::constrain(roll, math::radians(-100.0f), math::radians(-180.0f));
		}
	}

	/* calculate the offset in the rate resulting from rolling  */
	//xxx needs explanation and conversion to body angular rates or should be removed
	float turn_offset = fabsf((CONSTANTS_ONE_G / ctl_data.airspeed) *
				  tanf(roll) * sinf(roll)) * _roll_ff;

	if (inverted) {
		turn_offset = -turn_offset;
	}

	/* Calculate the error */
	float pitch_error = ctl_data.pitch_setpoint - ctl_data.pitch;

	/*  Apply P controller: rate setpoint from current error and time constant */
	_rate_setpoint =  pitch_error / _tc;

	/* add turn offset */
	_rate_setpoint += turn_offset;

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

	if (_max_rate > 0.01f && _max_rate_neg > 0.01f) {
		if (_rate_setpoint > 0.0f) {
			_rate_setpoint = (_rate_setpoint > _max_rate) ? _max_rate : _rate_setpoint;

		} else {
			_rate_setpoint = (_rate_setpoint < -_max_rate_neg) ? -_max_rate_neg : _rate_setpoint;
		}

	}

	return _rate_setpoint;
}

float ECL_PitchController::control_bodyrate(const struct ECL_ControlData &ctl_data)
{
	/* Do not calculate control signal with bad inputs */
	if (!(isfinite(ctl_data.roll) &&
	      isfinite(ctl_data.pitch) &&
	      isfinite(ctl_data.pitch_rate) &&
	      isfinite(ctl_data.yaw_rate) &&
	      isfinite(ctl_data.yaw_rate_setpoint) &&
	      isfinite(ctl_data.airspeed_min) &&
	      isfinite(ctl_data.airspeed_max) &&
	      isfinite(ctl_data.scaler))) {
		perf_count(_nonfinite_input_perf);
		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 (!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 = cosf(ctl_data.roll) * _rate_setpoint +
			     cosf(ctl_data.pitch) * sinf(ctl_data.roll) * ctl_data.yaw_rate_setpoint;

	/* Transform estimation to body angular rates (jacobian) */
	float pitch_bodyrate = cosf(ctl_data.roll) * ctl_data.pitch_rate +
			       cosf(ctl_data.pitch) * sinf(ctl_data.roll) * ctl_data.yaw_rate;

	_rate_error = _bodyrate_setpoint - pitch_bodyrate;

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

		float id = _rate_error * dt * ctl_data.scaler;

		/*
		 * 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;
	}

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

	/* Apply PI rate controller and store non-limited output */
	_last_output = _bodyrate_setpoint * _k_ff * ctl_data.scaler +
		       _rate_error * _k_p * ctl_data.scaler * ctl_data.scaler
		       + integrator_constrained;  //scaler is proportional to 1/airspeed
//	warnx("pitch: _integrator: %.4f, _integrator_max: %.4f, airspeed %.4f, _k_i %.4f, _k_p: %.4f", (double)_integrator, (double)_integrator_max, (double)airspeed, (double)_k_i, (double)_k_p);
//	warnx("roll: _last_output %.4f", (double)_last_output);
	return math::constrain(_last_output, -1.0f, 1.0f);
}