ecl_wheel_controller.cpp
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/****************************************************************************
*
* Copyright (c) 2013-2016 Estimation and Control Library (ECL). All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name ECL nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file ecl_wheel_controller.cpp
* Implementation of a simple PID wheel controller for heading tracking.
*
* Authors and acknowledgements in header.
*/
#include "ecl_wheel_controller.h"
#include <float.h>
#include <lib/ecl/geo/geo.h>
#include <mathlib/mathlib.h>
#include <matrix/math.hpp>
using matrix::wrap_pi;
float ECL_WheelController::control_bodyrate(const float dt, const ECL_ControlData &ctl_data)
{
/* Do not calculate control signal with bad inputs */
if (!(PX4_ISFINITE(ctl_data.body_z_rate) &&
PX4_ISFINITE(ctl_data.groundspeed) &&
PX4_ISFINITE(ctl_data.groundspeed_scaler))) {
return math::constrain(_last_output, -1.0f, 1.0f);
}
/* input conditioning */
float min_speed = 1.0f;
/* Calculate body angular rate error */
_rate_error = _rate_setpoint - ctl_data.body_z_rate; //body angular rate error
if (!ctl_data.lock_integrator && _k_i > 0.0f && ctl_data.groundspeed > min_speed) {
float id = _rate_error * dt * ctl_data.groundspeed_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);
}
/* add and constrain */
_integrator = math::constrain(_integrator + id * _k_i, -_integrator_max, _integrator_max);
}
/* Apply PI rate controller and store non-limited output */
_last_output = _rate_setpoint * _k_ff * ctl_data.groundspeed_scaler +
ctl_data.groundspeed_scaler * ctl_data.groundspeed_scaler * (_rate_error * _k_p + _integrator);
return math::constrain(_last_output, -1.0f, 1.0f);
}
float ECL_WheelController::control_attitude(const float dt, const ECL_ControlData &ctl_data)
{
/* Do not calculate control signal with bad inputs */
if (!(PX4_ISFINITE(ctl_data.yaw_setpoint) &&
PX4_ISFINITE(ctl_data.yaw))) {
return _rate_setpoint;
}
/* Calculate the error */
float yaw_error = wrap_pi(ctl_data.yaw_setpoint - ctl_data.yaw);
/* Apply P controller: rate setpoint from current error and time constant */
_rate_setpoint = yaw_error / _tc;
/* limit the rate */
if (_max_rate > 0.01f) {
if (_rate_setpoint > 0.0f) {
_rate_setpoint = (_rate_setpoint > _max_rate) ? _max_rate : _rate_setpoint;
} else {
_rate_setpoint = (_rate_setpoint < -_max_rate) ? -_max_rate : _rate_setpoint;
}
}
return _rate_setpoint;
}