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198 lines
7.1 KiB
198 lines
7.1 KiB
/**************************************************************************** |
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* |
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* Copyright (c) 2013 Estimation and Control Library (ECL). All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* 3. Neither the name ECL nor the names of its contributors may be |
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* used to endorse or promote products derived from this software |
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* without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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* POSSIBILITY OF SUCH DAMAGE. |
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* |
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****************************************************************************/ |
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/** |
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* @file ecl_pitch_controller.cpp |
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* Implementation of a simple orthogonal pitch PID controller. |
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* |
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* Authors and acknowledgements in header. |
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*/ |
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#include "ecl_pitch_controller.h" |
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#include <math.h> |
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#include <stdint.h> |
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#include <float.h> |
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#include <geo/geo.h> |
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#include <ecl/ecl.h> |
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#include <mathlib/mathlib.h> |
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#include <systemlib/err.h> |
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ECL_PitchController::ECL_PitchController() : |
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ECL_Controller("pitch"), |
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_max_rate_neg(0.0f), |
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_roll_ff(0.0f) |
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{ |
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} |
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ECL_PitchController::~ECL_PitchController() |
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{ |
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} |
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float ECL_PitchController::control_attitude(const struct ECL_ControlData &ctl_data) |
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{ |
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/* Do not calculate control signal with bad inputs */ |
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if (!(PX4_ISFINITE(ctl_data.pitch_setpoint) && |
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PX4_ISFINITE(ctl_data.roll) && |
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PX4_ISFINITE(ctl_data.pitch) && |
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PX4_ISFINITE(ctl_data.airspeed))) { |
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perf_count(_nonfinite_input_perf); |
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warnx("not controlling pitch"); |
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return _rate_setpoint; |
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} |
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/* Calculate the error */ |
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float pitch_error = ctl_data.pitch_setpoint - ctl_data.pitch; |
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/* Apply P controller: rate setpoint from current error and time constant */ |
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_rate_setpoint = pitch_error / _tc; |
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/* limit the rate */ |
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if (_max_rate > 0.01f && _max_rate_neg > 0.01f) { |
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if (_rate_setpoint > 0.0f) { |
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_rate_setpoint = (_rate_setpoint > _max_rate) ? _max_rate : _rate_setpoint; |
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} else { |
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_rate_setpoint = (_rate_setpoint < -_max_rate_neg) ? -_max_rate_neg : _rate_setpoint; |
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} |
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} |
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return _rate_setpoint; |
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} |
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float ECL_PitchController::control_bodyrate(const struct ECL_ControlData &ctl_data) |
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{ |
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/* Do not calculate control signal with bad inputs */ |
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if (!(PX4_ISFINITE(ctl_data.roll) && |
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PX4_ISFINITE(ctl_data.pitch) && |
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PX4_ISFINITE(ctl_data.pitch_rate) && |
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PX4_ISFINITE(ctl_data.yaw_rate) && |
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PX4_ISFINITE(ctl_data.yaw_rate_setpoint) && |
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PX4_ISFINITE(ctl_data.airspeed_min) && |
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PX4_ISFINITE(ctl_data.airspeed_max) && |
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PX4_ISFINITE(ctl_data.scaler))) { |
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perf_count(_nonfinite_input_perf); |
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return math::constrain(_last_output, -1.0f, 1.0f); |
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} |
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/* get the usual dt estimate */ |
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uint64_t dt_micros = ecl_elapsed_time(&_last_run); |
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_last_run = ecl_absolute_time(); |
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float dt = (float)dt_micros * 1e-6f; |
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/* lock integral for long intervals */ |
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bool lock_integrator = ctl_data.lock_integrator; |
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if (dt_micros > 500000) { |
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lock_integrator = true; |
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} |
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/* Transform setpoint to body angular rates (jacobian) */ |
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_bodyrate_setpoint = cosf(ctl_data.roll) * _rate_setpoint + |
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cosf(ctl_data.pitch) * sinf(ctl_data.roll) * ctl_data.yaw_rate_setpoint; |
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/* apply turning offset to desired bodyrate setpoint*/ |
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/* flying inverted (wings upside down)*/ |
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bool inverted = false; |
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float constrained_roll; |
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/* roll is used as feedforward term and inverted flight needs to be considered */ |
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if (fabsf(ctl_data.roll) < math::radians(90.0f)) { |
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/* not inverted, but numerically still potentially close to infinity */ |
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constrained_roll = math::constrain(ctl_data.roll, math::radians(-80.0f), math::radians(80.0f)); |
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} else { |
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/* inverted flight, constrain on the two extremes of -pi..+pi to avoid infinity */ |
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inverted = true; |
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/* note: the ranges are extended by 10 deg here to avoid numeric resolution effects */ |
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if (ctl_data.roll > 0.0f) { |
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/* right hemisphere */ |
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constrained_roll = math::constrain(ctl_data.roll, math::radians(100.0f), math::radians(180.0f)); |
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} else { |
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/* left hemisphere */ |
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constrained_roll = math::constrain(ctl_data.roll, math::radians(-100.0f), math::radians(-180.0f)); |
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} |
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} |
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/* input conditioning */ |
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float airspeed = constrain_airspeed(ctl_data.airspeed, ctl_data.airspeed_min, ctl_data.airspeed_max); |
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/* Calculate desired body fixed y-axis angular rate needed to compensate for roll angle. |
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For reference see Automatic Control of Aircraft and Missiles by John H. Blakelock, pg. 175 |
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Availible on google books 8/11/2015: |
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https://books.google.com/books?id=ubcczZUDCsMC&pg=PA175#v=onepage&q&f=false*/ |
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float body_fixed_turn_offset = (fabsf((CONSTANTS_ONE_G / airspeed) * |
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tanf(constrained_roll) * sinf(constrained_roll))); |
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if (inverted) { |
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body_fixed_turn_offset = -body_fixed_turn_offset; |
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} |
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/* Finally add the turn offset to your bodyrate setpoint*/ |
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_bodyrate_setpoint += body_fixed_turn_offset; |
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_rate_error = _bodyrate_setpoint - ctl_data.pitch_rate; |
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if (!lock_integrator && _k_i > 0.0f) { |
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float id = _rate_error * dt * ctl_data.scaler; |
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/* |
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* anti-windup: do not allow integrator to increase if actuator is at limit |
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*/ |
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if (_last_output < -1.0f) { |
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/* only allow motion to center: increase value */ |
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id = math::max(id, 0.0f); |
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} else if (_last_output > 1.0f) { |
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/* only allow motion to center: decrease value */ |
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id = math::min(id, 0.0f); |
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} |
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_integrator += id; |
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} |
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/* integrator limit */ |
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//xxx: until start detection is available: integral part in control signal is limited here |
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float integrator_constrained = math::constrain(_integrator * _k_i, -_integrator_max, _integrator_max); |
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/* Apply PI rate controller and store non-limited output */ |
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_last_output = _bodyrate_setpoint * _k_ff * ctl_data.scaler + |
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_rate_error * _k_p * ctl_data.scaler * ctl_data.scaler |
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+ integrator_constrained; //scaler is proportional to 1/airspeed |
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// 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); |
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// warnx("roll: _last_output %.4f", (double)_last_output); |
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return math::constrain(_last_output, -1.0f, 1.0f); |
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}
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