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ardupilot/libraries/APM_Control/AR_AttitudeControl.cpp

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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <AP_Math/AP_Math.h>
#include <AP_HAL/AP_HAL.h>
#include "AR_AttitudeControl.h"
extern const AP_HAL::HAL& hal;
const AP_Param::GroupInfo AR_AttitudeControl::var_info[] = {
// @Param: _STR_RAT_P
// @DisplayName: Steering control rate P gain
// @Description: Steering control rate P gain. Converts the turn rate error (in radians/sec) to a steering control output (in the range -1 to +1)
// @Range: 0.000 2.000
// @Increment: 0.01
// @User: Standard
// @Param: _STR_RAT_I
// @DisplayName: Steering control I gain
// @Description: Steering control I gain. Corrects long term error between the desired turn rate (in rad/s) and actual
// @Range: 0.000 2.000
// @Increment: 0.01
// @User: Standard
// @Param: _STR_RAT_IMAX
// @DisplayName: Steering control I gain maximum
// @Description: Steering control I gain maximum. Constraings the steering output (range -1 to +1) that the I term will generate
// @Range: 0.000 1.000
// @Increment: 0.01
// @User: Standard
// @Param: _STR_RAT_D
// @DisplayName: Steering control D gain
// @Description: Steering control D gain. Compensates for short-term change in desired turn rate vs actual
// @Range: 0.000 0.400
// @Increment: 0.001
// @User: Standard
// @Param: _STR_RAT_FF
// @DisplayName: Steering control feed forward
// @Description: Steering control feed forward
// @Range: 0.000 3.000
// @Increment: 0.001
// @User: Standard
// @Param: _STR_RAT_FILT
// @DisplayName: Steering control filter frequency
// @Description: Steering control input filter. Lower values reduce noise but add delay.
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
AP_SUBGROUPINFO(_steer_rate_pid, "_STR_RAT_", 1, AR_AttitudeControl, AC_PID),
// @Param: _SPEED_P
// @DisplayName: Speed control P gain
// @Description: Speed control P gain. Converts the error between the desired speed (in m/s) and actual speed to a motor output (in the range -1 to +1)
// @Range: 0.010 2.000
// @Increment: 0.01
// @User: Standard
// @Param: _SPEED_I
// @DisplayName: Speed control I gain
// @Description: Speed control I gain. Corrects long term error between the desired speed (in m/s) and actual speed
// @Range: 0.000 2.000
// @User: Standard
// @Param: _SPEED_IMAX
// @DisplayName: Speed control I gain maximum
// @Description: Speed control I gain maximum. Constraings the maximum motor output (range -1 to +1) that the I term will generate
// @Range: 0.000 1.000
// @Increment: 0.01
// @User: Standard
// @Param: _SPEED_D
// @DisplayName: Speed control D gain
// @Description: Speed control D gain. Compensates for short-term change in desired speed vs actual
// @Range: 0.000 0.400
// @Increment: 0.001
// @User: Standard
// @Param: _SPEED_FF
// @DisplayName: Speed control feed forward
// @Description: Speed control feed forward
// @Range: 0.000 0.500
// @Increment: 0.001
// @User: Standard
// @Param: _SPEED_FILT
// @DisplayName: Speed control filter frequency
// @Description: Speed control input filter. Lower values reduce noise but add delay.
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
AP_SUBGROUPINFO(_throttle_speed_pid, "_SPEED_", 2, AR_AttitudeControl, AC_PID),
// @Param: _ACCEL_MAX
// @DisplayName: Speed control acceleration (and deceleration) maximum in m/s/s
// @Description: Speed control acceleration (and deceleration) maximum in m/s/s. 0 to disable acceleration limiting
// @Range: 0.0 10.0
// @Increment: 0.1
// @Units: m/s/s
// @User: Standard
AP_GROUPINFO("_ACCEL_MAX", 3, AR_AttitudeControl, _throttle_accel_max, AR_ATTCONTROL_THR_ACCEL_MAX),
// @Param: _BRAKE
// @DisplayName: Speed control brake enable/disable
// @Description: Speed control brake enable/disable. Allows sending a reversed output to the motors to slow the vehicle.
// @Values: 0:Disable,1:Enable
// @User: Standard
AP_GROUPINFO("_BRAKE", 4, AR_AttitudeControl, _brake_enable, 1),
// @Param: _STOP_SPEED
// @DisplayName: Speed control stop speed
// @Description: Speed control stop speed. Motor outputs to zero once vehicle speed falls below this value
// @Range: 0.00 0.50
// @Increment: 0.01
// @Units: m/s
// @User: Standard
AP_GROUPINFO("_STOP_SPEED", 5, AR_AttitudeControl, _stop_speed, AR_ATTCONTROL_STOP_SPEED_DEFAULT),
// @Param: _STR_ANG_P
// @DisplayName: Steering control angle P gain
// @Description: Steering control angle P gain. Converts the error between the desired heading/yaw (in radians) and actual heading/yaw to a desired turn rate (in rad/sec)
// @Range: 1.000 10.000
// @Increment: 0.1
// @User: Standard
AP_SUBGROUPINFO(_steer_angle_p, "_STR_ANG_", 6, AR_AttitudeControl, AC_P),
// @Param: _STR_ACC_MAX
// @DisplayName: Steering control angular acceleration maximum
// @Description: Steering control angular acceleartion maximum (in deg/s/s). 0 to disable acceleration limiting
// @Range: 0 1000
// @Increment: 0.1
// @Units: deg/s/s
// @User: Standard
AP_GROUPINFO("_STR_ACC_MAX", 7, AR_AttitudeControl, _steer_accel_max, AR_ATTCONTROL_STEER_ACCEL_MAX),
// @Param: _STR_RAT_MAX
// @DisplayName: Steering control rotation rate maximum
// @Description: Steering control rotation rate maximum in deg/s. 0 to remove rate limiting
// @Range: 0 1000
// @Increment: 0.1
// @Units: deg/s
// @User: Standard
AP_GROUPINFO("_STR_RAT_MAX", 8, AR_AttitudeControl, _steer_rate_max, AR_ATTCONTROL_STEER_RATE_MAX),
// @Param: _DECEL_MAX
// @DisplayName: Speed control deceleration maximum in m/s/s
// @Description: Speed control and deceleration maximum in m/s/s. 0 to use ATC_ACCEL_MAX for deceleration
// @Range: 0.0 10.0
// @Increment: 0.1
// @Units: m/s/s
// @User: Standard
AP_GROUPINFO("_DECEL_MAX", 9, AR_AttitudeControl, _throttle_decel_max, 0.00f),
// @Param: _BAL_P
// @DisplayName: Pitch control P gain
// @Description: Pitch control P gain for BalanceBots. Converts the error between the desired pitch (in radians) and actual pitch to a motor output (in the range -1 to +1)
// @Range: 0.000 2.000
// @Increment: 0.01
// @User: Standard
// @Param: _BAL_I
// @DisplayName: Pitch control I gain
// @Description: Pitch control I gain for BalanceBots. Corrects long term error between the desired pitch (in radians) and actual pitch
// @Range: 0.000 2.000
// @User: Standard
// @Param: _BAL_IMAX
// @DisplayName: Pitch control I gain maximum
// @Description: Pitch control I gain maximum. Constrains the maximum motor output (range -1 to +1) that the I term will generate
// @Range: 0.000 1.000
// @Increment: 0.01
// @User: Standard
// @Param: _BAL_D
// @DisplayName: Pitch control D gain
// @Description: Pitch control D gain. Compensates for short-term change in desired pitch vs actual
// @Range: 0.000 0.100
// @Increment: 0.001
// @User: Standard
// @Param: _BAL_FF
// @DisplayName: Pitch control feed forward
// @Description: Pitch control feed forward
// @Range: 0.000 0.500
// @Increment: 0.001
// @User: Standard
// @Param: _BAL_FILT
// @DisplayName: Pitch control filter frequency
// @Description: Pitch control input filter. Lower values reduce noise but add delay.
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
AP_SUBGROUPINFO(_pitch_to_throttle_pid, "_BAL_", 10, AR_AttitudeControl, AC_PID),
AP_GROUPEND
};
AR_AttitudeControl::AR_AttitudeControl(AP_AHRS &ahrs) :
_ahrs(ahrs),
_steer_angle_p(AR_ATTCONTROL_STEER_ANG_P),
_steer_rate_pid(AR_ATTCONTROL_STEER_RATE_P, AR_ATTCONTROL_STEER_RATE_I, AR_ATTCONTROL_STEER_RATE_D, AR_ATTCONTROL_STEER_RATE_IMAX, AR_ATTCONTROL_STEER_RATE_FILT, AR_ATTCONTROL_DT, AR_ATTCONTROL_STEER_RATE_FF),
_throttle_speed_pid(AR_ATTCONTROL_THR_SPEED_P, AR_ATTCONTROL_THR_SPEED_I, AR_ATTCONTROL_THR_SPEED_D, AR_ATTCONTROL_THR_SPEED_IMAX, AR_ATTCONTROL_THR_SPEED_FILT, AR_ATTCONTROL_DT),
_pitch_to_throttle_pid(AR_ATTCONTROL_PITCH_THR_P, AR_ATTCONTROL_PITCH_THR_I, AR_ATTCONTROL_PITCH_THR_D, AR_ATTCONTROL_PITCH_THR_IMAX, AR_ATTCONTROL_PITCH_THR_FILT, AR_ATTCONTROL_DT)
{
AP_Param::setup_object_defaults(this, var_info);
}
// return a steering servo output from -1.0 to +1.0 given a desired lateral acceleration rate in m/s/s.
// positive lateral acceleration is to the right.
float AR_AttitudeControl::get_steering_out_lat_accel(float desired_accel, bool motor_limit_left, bool motor_limit_right, float dt)
{
// record desired accel for reporting purposes
_steer_lat_accel_last_ms = AP_HAL::millis();
_desired_lat_accel = desired_accel;
// get speed forward
float speed;
if (!get_forward_speed(speed)) {
// we expect caller will not try to control heading using rate control without a valid speed estimate
// on failure to get speed we do not attempt to steer
return 0.0f;
}
// enforce minimum speed to stop oscillations when first starting to move
if (fabsf(speed) < AR_ATTCONTROL_STEER_SPEED_MIN) {
if (is_negative(speed)) {
speed = -AR_ATTCONTROL_STEER_SPEED_MIN;
} else {
speed = AR_ATTCONTROL_STEER_SPEED_MIN;
}
}
// Calculate the desired steering rate given desired_accel and speed
const float desired_rate = desired_accel / speed;
return get_steering_out_rate(desired_rate, motor_limit_left, motor_limit_right, dt);
}
// return a steering servo output from -1 to +1 given a heading in radians
float AR_AttitudeControl::get_steering_out_heading(float heading_rad, float rate_max, bool motor_limit_left, bool motor_limit_right, float dt)
{
// calculate heading error (in radians)
const float yaw_error = wrap_PI(heading_rad - _ahrs.yaw);
// Calculate the desired turn rate (in radians) from the angle error (also in radians)
float desired_rate = _steer_angle_p.get_p(yaw_error);
// limit desired_rate if a custom pivot turn rate is selected, otherwise use ATC_STR_RAT_MAX
if (is_positive(rate_max)) {
desired_rate = constrain_float(desired_rate, -rate_max, rate_max);
}
return get_steering_out_rate(desired_rate, motor_limit_left, motor_limit_right, dt);
}
// return a steering servo output from -1 to +1 given a
// desired yaw rate in radians/sec. Positive yaw is to the right.
float AR_AttitudeControl::get_steering_out_rate(float desired_rate, bool motor_limit_left, bool motor_limit_right, float dt)
{
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// if not called recently, reset input filter and desired turn rate to actual turn rate (used for accel limiting)
const uint32_t now = AP_HAL::millis();
if ((_steer_turn_last_ms == 0) || ((now - _steer_turn_last_ms) > AR_ATTCONTROL_TIMEOUT_MS)) {
_steer_rate_pid.reset_filter();
_steer_rate_pid.reset_I();
_desired_turn_rate = _ahrs.get_yaw_rate_earth();
}
_steer_turn_last_ms = now;
// acceleration limit desired turn rate
if (is_positive(_steer_accel_max)) {
const float change_max = radians(_steer_accel_max) * dt;
desired_rate = constrain_float(desired_rate, _desired_turn_rate - change_max, _desired_turn_rate + change_max);
}
_desired_turn_rate = desired_rate;
// rate limit desired turn rate
if (is_positive(_steer_rate_max)) {
const float steer_rate_max_rad = radians(_steer_rate_max);
_desired_turn_rate = constrain_float(_desired_turn_rate, -steer_rate_max_rad, steer_rate_max_rad);
}
// Calculate the steering rate error (rad/sec)
// We do this in earth frame to allow for rover leaning over in hard corners
const float rate_error = (_desired_turn_rate - _ahrs.get_yaw_rate_earth());
// set PID's dt
_steer_rate_pid.set_dt(dt);
// record desired rate for logging purposes only
_steer_rate_pid.set_desired_rate(_desired_turn_rate);
// pass error to PID controller
_steer_rate_pid.set_input_filter_all(rate_error);
// get feed-forward
const float ff = _steer_rate_pid.get_ff(_desired_turn_rate);
// get p
const float p = _steer_rate_pid.get_p();
// get i unless non-skid-steering rover at low speed or steering output has hit a limit
float i = _steer_rate_pid.get_integrator();
if ((is_negative(rate_error) && !motor_limit_left) || (is_positive(rate_error) && !motor_limit_right)) {
i = _steer_rate_pid.get_i();
}
// get d
const float d = _steer_rate_pid.get_d();
// constrain and return final output
return (ff + p + i + d);
}
// get latest desired turn rate in rad/sec (recorded during calls to get_steering_out_rate)
float AR_AttitudeControl::get_desired_turn_rate() const
{
// return zero if no recent calls to turn rate controller
if ((_steer_turn_last_ms == 0) || ((AP_HAL::millis() - _steer_turn_last_ms) > AR_ATTCONTROL_TIMEOUT_MS)) {
return 0.0f;
}
return _desired_turn_rate;
}
// get latest desired lateral acceleration in m/s/s (recorded during calls to get_steering_out_lat_accel)
float AR_AttitudeControl::get_desired_lat_accel() const
{
// return zero if no recent calls to lateral acceleration controller
if ((_steer_lat_accel_last_ms == 0) || ((AP_HAL::millis() - _steer_lat_accel_last_ms) > AR_ATTCONTROL_TIMEOUT_MS)) {
return 0.0f;
}
return _desired_lat_accel;
}
// get actual lateral acceleration in m/s/s. returns true on success
bool AR_AttitudeControl::get_lat_accel(float &lat_accel) const
{
float speed;
if (!get_forward_speed(speed)) {
return false;
}
lat_accel = speed * _ahrs.get_yaw_rate_earth();
return true;
}
// return a throttle output from -1 to +1 given a desired speed in m/s (use negative speeds to travel backwards)
// motor_limit should be true if motors have hit their upper or lower limits
// cruise speed should be in m/s, cruise throttle should be a number from -1 to +1
float AR_AttitudeControl::get_throttle_out_speed(float desired_speed, bool motor_limit_low, bool motor_limit_high, float cruise_speed, float cruise_throttle, float dt)
{
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// get speed forward
float speed;
if (!get_forward_speed(speed)) {
// we expect caller will not try to control heading using rate control without a valid speed estimate
// on failure to get speed we do not attempt to steer
return 0.0f;
}
// if not called recently, reset input filter and desired speed to actual speed (used for accel limiting)
const uint32_t now = AP_HAL::millis();
if (!speed_control_active()) {
_throttle_speed_pid.reset_filter();
_desired_speed = speed;
}
_speed_last_ms = now;
// acceleration limit desired speed
_desired_speed = get_desired_speed_accel_limited(desired_speed, dt);
// set PID's dt
_throttle_speed_pid.set_dt(dt);
// calculate speed error and pass to PID controller
const float speed_error = desired_speed - speed;
_throttle_speed_pid.set_input_filter_all(speed_error);
// record desired speed for logging purposes only
_throttle_speed_pid.set_desired_rate(desired_speed);
// get feed-forward
const float ff = _throttle_speed_pid.get_ff(desired_speed);
// get p
const float p = _throttle_speed_pid.get_p();
// get i unless moving at low speed or motors have hit a limit
float i = _throttle_speed_pid.get_integrator();
if ((is_negative(speed_error) && !motor_limit_low && !_throttle_limit_low) || (is_positive(speed_error) && !motor_limit_high && !_throttle_limit_high)) {
i = _throttle_speed_pid.get_i();
}
// get d
const float d = _throttle_speed_pid.get_d();
// calculate base throttle (protect against divide by zero)
float throttle_base = 0.0f;
if (is_positive(cruise_speed) && is_positive(cruise_throttle)) {
throttle_base = desired_speed * (cruise_throttle / cruise_speed);
}
// calculate final output
float throttle_out = (ff+p+i+d+throttle_base);
// clear local limit flags used to stop i-term build-up as we stop reversed outputs going to motors
_throttle_limit_low = false;
_throttle_limit_high = false;
// protect against reverse output being sent to the motors unless braking has been enabled
if (!_brake_enable) {
// if both desired speed and actual speed are positive, do not allow negative values
if ((desired_speed >= 0.0f) && (throttle_out <= 0.0f)) {
throttle_out = 0.0f;
_throttle_limit_low = true;
} else if ((desired_speed <= 0.0f) && (throttle_out >= 0.0f)) {
throttle_out = 0.0f;
_throttle_limit_high = true;
}
}
// final output throttle in range -1 to 1
return throttle_out;
}
// return a throttle output from -1 to +1 to perform a controlled stop. returns true once the vehicle has stopped
float AR_AttitudeControl::get_throttle_out_stop(bool motor_limit_low, bool motor_limit_high, float cruise_speed, float cruise_throttle, float dt, bool &stopped)
{
// get current system time
const uint32_t now = AP_HAL::millis();
// if we were stopped in the last 300ms, assume we are still stopped
bool _stopped = (_stop_last_ms != 0) && (now - _stop_last_ms) < 300;
// get deceleration limited speed
float desired_speed_limited = get_desired_speed_accel_limited(0.0f, dt);
// get speed forward
float speed;
if (!get_forward_speed(speed)) {
// could not get speed so assume stopped
_stopped = true;
} else {
// if desired speed is zero and vehicle drops below _stop_speed consider it stopped
if (is_zero(desired_speed_limited) && fabsf(speed) <= fabsf(_stop_speed)) {
_stopped = true;
}
}
// set stopped status for caller
stopped = _stopped;
// if stopped return zero
if (stopped) {
// update last time we thought we were stopped
_stop_last_ms = now;
return 0.0f;
}
// clear stopped system time
_stop_last_ms = 0;
// run speed controller to bring vehicle to stop
return get_throttle_out_speed(desired_speed_limited, motor_limit_low, motor_limit_high, cruise_speed, cruise_throttle, dt);
}
// for balancebot
// return a throttle output from -1 to +1, given a desired pitch angle
// desired_pitch is in radians
float AR_AttitudeControl::get_throttle_out_from_pitch(float desired_pitch, bool armed, float dt)
{
//reset I term and return if disarmed
if (!armed){
_pitch_to_throttle_pid.reset_I();
return 0.0f;
}
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
const uint32_t now = AP_HAL::millis();
// if not called recently, reset input filter
if ((_balance_last_ms == 0) || ((now - _balance_last_ms) > (AR_ATTCONTROL_TIMEOUT_MS))) {
_pitch_to_throttle_pid.reset_filter();
} else {
_pitch_to_throttle_pid.set_dt(dt);
}
_balance_last_ms = now;
// calculate pitch error
const float pitch_error = desired_pitch - _ahrs.pitch;
// pitch error is given as input to PID contoller
_pitch_to_throttle_pid.set_input_filter_all(pitch_error);
// record desired speed for logging purposes only
_pitch_to_throttle_pid.set_desired_rate(desired_pitch);
// return output of PID controller
return constrain_float(_pitch_to_throttle_pid.get_pid(), -1.0f, +1.0f);
}
// get latest desired pitch in radians for reporting purposes
float AR_AttitudeControl::get_desired_pitch() const
{
// if not called recently, return 0
if ((_balance_last_ms == 0) || ((AP_HAL::millis() - _balance_last_ms) > AR_ATTCONTROL_TIMEOUT_MS)) {
return 0.0f;
}
return _pitch_to_throttle_pid.get_pid_info().desired;
}
// get forward speed in m/s (earth-frame horizontal velocity but only along vehicle x-axis). returns true on success
bool AR_AttitudeControl::get_forward_speed(float &speed) const
{
Vector3f velocity;
if (!_ahrs.get_velocity_NED(velocity)) {
// use less accurate GPS, assuming entire length is along forward/back axis of vehicle
if (AP::gps().status() >= AP_GPS::GPS_OK_FIX_3D) {
if (labs(wrap_180_cd(_ahrs.yaw_sensor - AP::gps().ground_course_cd())) <= 9000) {
speed = AP::gps().ground_speed();
} else {
speed = -AP::gps().ground_speed();
}
return true;
} else {
return false;
}
}
// calculate forward speed velocity into body frame
speed = velocity.x*_ahrs.cos_yaw() + velocity.y*_ahrs.sin_yaw();
return true;
}
float AR_AttitudeControl::get_decel_max() const
{
if (is_positive(_throttle_decel_max)) {
return _throttle_decel_max;
} else {
return _throttle_accel_max;
}
}
// check if speed controller active
bool AR_AttitudeControl::speed_control_active() const
{
// active if there have been recent calls to speed controller
if ((_speed_last_ms == 0) || ((AP_HAL::millis() - _speed_last_ms) > AR_ATTCONTROL_TIMEOUT_MS)) {
return false;
}
return true;
}
// get latest desired speed recorded during call to get_throttle_out_speed. For reporting purposes only
float AR_AttitudeControl::get_desired_speed() const
{
// return zero if no recent calls to speed controller
if (!speed_control_active()) {
return 0.0f;
}
return _desired_speed;
}
// get acceleration limited desired speed
float AR_AttitudeControl::get_desired_speed_accel_limited(float desired_speed, float dt) const
{
// return input value if no recent calls to speed controller
// apply no limiting when ATC_ACCEL_MAX is set to zero
const uint32_t now = AP_HAL::millis();
if ((_speed_last_ms == 0) || ((now - _speed_last_ms) > AR_ATTCONTROL_TIMEOUT_MS) || !is_positive(_throttle_accel_max)) {
return desired_speed;
}
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// use previous desired speed as basis for accel limiting
float speed_prev = _desired_speed;
// if no recent calls to speed controller limit based on current speed
if (!speed_control_active()) {
get_forward_speed(speed_prev);
}
// acceleration limit desired speed
float speed_change_max;
if (fabsf(desired_speed) < fabsf(_desired_speed) && is_positive(_throttle_decel_max)) {
speed_change_max = _throttle_decel_max * dt;
} else {
speed_change_max = _throttle_accel_max * dt;
}
return constrain_float(desired_speed, speed_prev - speed_change_max, speed_prev + speed_change_max);
}
// get minimum stopping distance (in meters) given a speed (in m/s)
float AR_AttitudeControl::get_stopping_distance(float speed) const
{
// get maximum vehicle deceleration
const float accel_max = get_accel_max();
// avoid divide by zero
if ((accel_max <= 0.0f) || is_zero(speed)) {
return 0.0f;
}
// assume linear deceleration
return 0.5f * sq(speed) / accel_max;
}
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