px4-firmware/attitude_fw/ecl_roll_controller.cpp

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

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

ECL_RollController::ECL_RollController() :
	ECL_Controller("roll")
{
}

ECL_RollController::~ECL_RollController()
{
}

float ECL_RollController::control_attitude(const struct ECL_ControlData &ctl_data)
{
	/* Do not calculate control signal with bad inputs */
	if (!(PX4_ISFINITE(ctl_data.roll_setpoint) && PX4_ISFINITE(ctl_data.roll))) {
		perf_count(_nonfinite_input_perf);
		return _rate_setpoint;
	}

	/* Calculate error */
	float roll_error = ctl_data.roll_setpoint - ctl_data.roll;

	/* Apply P controller */
	_rate_setpoint = roll_error / _tc;

	/* 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;
	}

	return _rate_setpoint;
}

float ECL_RollController::control_bodyrate(const struct ECL_ControlData &ctl_data)
{
	/* Do not calculate control signal with bad inputs */
	if (!(PX4_ISFINITE(ctl_data.pitch) &&
	      PX4_ISFINITE(ctl_data.roll_rate) &&
	      PX4_ISFINITE(ctl_data.yaw_rate) &&
	      PX4_ISFINITE(ctl_data.yaw_rate_setpoint) &&
	      PX4_ISFINITE(ctl_data.airspeed_min) &&
	      PX4_ISFINITE(ctl_data.airspeed_max) &&
	      PX4_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;
	}

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

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

	if (!lock_integrator && _k_i > 0.0f) {

		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);
	//warnx("roll: _integrator: %.4f, _integrator_max: %.4f", (double)_integrator, (double)_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

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