path: root/src/lib/ecl/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.h"
#include "ecl_roll_controller.h"
#include <stdint.h>
#include <float.h>
#include <geo/geo.h>
#include <ecl/ecl.h>
#include <mathlib/mathlib.h>

ECL_RollController::ECL_RollController() :
	_last_run(0),
	_tc(0.1f),
	_last_output(0.0f),
	_integrator(0.0f),
	_rate_error(0.0f),
	_rate_setpoint(0.0f),
	_max_deflection_rad(math::radians(45.0f))
{

}

float ECL_RollController::control(float roll_setpoint, float roll, float roll_rate,
				  float scaler, bool lock_integrator, float airspeed_min, float airspeed_max, float airspeed)
{
	/* 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 */
	if (dt_micros > 500000)
		lock_integrator = true;

	float k_ff = math::max((_k_p - _k_i * _tc) * _tc - _k_d, 0.0f);
	float k_i_rate = _k_i * _tc;

	/* input conditioning */
	if (!isfinite(airspeed)) {
		/* airspeed is NaN, +- INF or not available, pick center of band */
		airspeed = 0.5f * (airspeed_min + airspeed_max);
	} else if (airspeed < airspeed_min) {
		airspeed = airspeed_min;
	}

	float roll_error = roll_setpoint - roll;
	_rate_setpoint = roll_error / _tc;

	/* limit the rate */
	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;
	}

	_rate_error = _rate_setpoint - roll_rate;


	float ilimit_scaled = _integrator_max * scaler;

	if (!lock_integrator && k_i_rate > 0.0f && airspeed > 0.5f * airspeed_min) {

		float id = _rate_error * k_i_rate * dt * scaler;

		/*
		 * anti-windup: do not allow integrator to increase into the
		 * wrong direction if actuator is at limit
		 */
		if (_last_output < -_max_deflection_rad) {
			/* only allow motion to center: increase value */
			id = math::max(id, 0.0f);
		} else if (_last_output > _max_deflection_rad) {
			/* only allow motion to center: decrease value */
			id = math::min(id, 0.0f);
		}

		_integrator += id;
	}

	/* integrator limit */
	_integrator = math::constrain(_integrator, -ilimit_scaled, ilimit_scaled);
	/* store non-limited output */
	_last_output = ((_rate_error * _k_d * scaler) + _integrator + (_rate_setpoint * k_ff)) * scaler;

	return math::constrain(_last_output, -_max_deflection_rad, _max_deflection_rad);
}

void ECL_RollController::reset_integrator()
{
	_integrator = 0.0f;
}