diff options
Diffstat (limited to 'src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp')
-rw-r--r-- | src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp b/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp new file mode 100644 index 000000000..2eb58abd6 --- /dev/null +++ b/src/lib/ecl/attitude_fw/ecl_pitch_controller.cpp @@ -0,0 +1,149 @@ +/**************************************************************************** + * + * Copyright (c) 2013 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_pitch_controller.cpp + * Implementation of a simple orthogonal pitch PID controller. + * + * Authors and acknowledgements in header. + */ + +#include "ecl_pitch_controller.h" +#include <math.h> +#include <stdint.h> +#include <float.h> +#include <geo/geo.h> +#include <ecl/ecl.h> +#include <mathlib/mathlib.h> + +ECL_PitchController::ECL_PitchController() : + _last_run(0), + _last_output(0.0f), + _integrator(0.0f), + _rate_error(0.0f), + _rate_setpoint(0.0f), + _max_deflection_rad(math::radians(45.0f)) +{ +} + +float ECL_PitchController::control(float pitch_setpoint, float pitch, float pitch_rate, float roll, 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_roll_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; + } + + /* flying inverted (wings upside down) ? */ + bool inverted = false; + + /* roll is used as feedforward term and inverted flight needs to be considered */ + if (fabsf(roll) < math::radians(90.0f)) { + /* not inverted, but numerically still potentially close to infinity */ + roll = math::constrain(roll, math::radians(-80.0f), math::radians(80.0f)); + } else { + /* inverted flight, constrain on the two extremes of -pi..+pi to avoid infinity */ + + /* note: the ranges are extended by 10 deg here to avoid numeric resolution effects */ + if (roll > 0.0f) { + /* right hemisphere */ + roll = math::constrain(roll, math::radians(100.0f), math::radians(180.0f)); + } else { + /* left hemisphere */ + roll = math::constrain(roll, math::radians(-100.0f), math::radians(-180.0f)); + } + } + + /* calculate the offset in the rate resulting from rolling */ + float turn_offset = fabsf((CONSTANTS_ONE_G / airspeed) * + tanf(roll) * sinf(roll)) * _roll_ff; + if (inverted) + turn_offset = -turn_offset; + + float pitch_error = pitch_setpoint - pitch; + /* rate setpoint from current error and time constant */ + _rate_setpoint = pitch_error / _tc; + + /* add turn offset */ + _rate_setpoint += turn_offset; + + _rate_error = _rate_setpoint - pitch_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_roll_ff)) * scaler; + + return math::constrain(_last_output, -_max_deflection_rad, _max_deflection_rad); +} + +void ECL_PitchController::reset_integrator() +{ + _integrator = 0.0f; +} |