RateControl.cpp
4.35 KB
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/****************************************************************************
*
* Copyright (c) 2019 PX4 Development Team. 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 PX4 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 RateControl.cpp
*/
#include <RateControl.hpp>
#include <px4_platform_common/defines.h>
using namespace matrix;
void RateControl::setGains(const Vector3f &P, const Vector3f &I, const Vector3f &D)
{
_gain_p = P;
_gain_i = I;
_gain_d = D;
}
void RateControl::setSaturationStatus(const MultirotorMixer::saturation_status &status)
{
_mixer_saturation_positive[0] = status.flags.roll_pos;
_mixer_saturation_positive[1] = status.flags.pitch_pos;
_mixer_saturation_positive[2] = status.flags.yaw_pos;
_mixer_saturation_negative[0] = status.flags.roll_neg;
_mixer_saturation_negative[1] = status.flags.pitch_neg;
_mixer_saturation_negative[2] = status.flags.yaw_neg;
}
Vector3f RateControl::update(const Vector3f &rate, const Vector3f &rate_sp, const Vector3f &angular_accel,
const float dt, const bool landed)
{
// angular rates error
Vector3f rate_error = rate_sp - rate;
// PID control with feed forward
const Vector3f torque = _gain_p.emult(rate_error) + _rate_int - _gain_d.emult(angular_accel) + _gain_ff.emult(rate_sp);
// update integral only if we are not landed
if (!landed) {
updateIntegral(rate_error, dt);
}
return torque;
}
void RateControl::updateIntegral(Vector3f &rate_error, const float dt)
{
for (int i = 0; i < 3; i++) {
// prevent further positive control saturation
if (_mixer_saturation_positive[i]) {
rate_error(i) = math::min(rate_error(i), 0.f);
}
// prevent further negative control saturation
if (_mixer_saturation_negative[i]) {
rate_error(i) = math::max(rate_error(i), 0.f);
}
// I term factor: reduce the I gain with increasing rate error.
// This counteracts a non-linear effect where the integral builds up quickly upon a large setpoint
// change (noticeable in a bounce-back effect after a flip).
// The formula leads to a gradual decrease w/o steps, while only affecting the cases where it should:
// with the parameter set to 400 degrees, up to 100 deg rate error, i_factor is almost 1 (having no effect),
// and up to 200 deg error leads to <25% reduction of I.
float i_factor = rate_error(i) / math::radians(400.f);
i_factor = math::max(0.0f, 1.f - i_factor * i_factor);
// Perform the integration using a first order method
float rate_i = _rate_int(i) + i_factor * _gain_i(i) * rate_error(i) * dt;
// do not propagate the result if out of range or invalid
if (PX4_ISFINITE(rate_i)) {
_rate_int(i) = math::constrain(rate_i, -_lim_int(i), _lim_int(i));
}
}
}
void RateControl::getRateControlStatus(rate_ctrl_status_s &rate_ctrl_status)
{
rate_ctrl_status.rollspeed_integ = _rate_int(0);
rate_ctrl_status.pitchspeed_integ = _rate_int(1);
rate_ctrl_status.yawspeed_integ = _rate_int(2);
}