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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"
#include <AP_GPS/AP_GPS.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: 0.001
// @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: 0.001
// @User: Standard
// @Param: _STR_RAT_IMAX
// @DisplayName: Steering control I gain maximum
// @Description: Steering control I gain maximum. Constrains 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
// @Param: _STR_RAT_FLTT
// @DisplayName: Steering control Target filter frequency in Hz
// @Description: Target filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _STR_RAT_FLTE
// @DisplayName: Steering control Error filter frequency in Hz
// @Description: Error filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _STR_RAT_FLTD
// @DisplayName: Steering control Derivative term filter frequency in Hz
// @Description: Derivative filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _STR_RAT_SMAX
// @DisplayName: Steering slew rate limit
// @Description: Sets an upper limit on the slew rate produced by the combined P and D gains. If the amplitude of the control action produced by the rate feedback exceeds this value, then the D+P gain is reduced to respect the limit. This limits the amplitude of high frequency oscillations caused by an excessive gain. The limit should be set to no more than 25% of the actuators maximum slew rate to allow for load effects. Note: The gain will not be reduced to less than 10% of the nominal value. A value of zero will disable this feature.
// @Range: 0 200
// @Increment: 0.5
// @User: Advanced
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
// @Increment: 0.01
// @User: Standard
// @Param: _SPEED_IMAX
// @DisplayName: Speed control I gain maximum
// @Description: Speed 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: _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
// @Param: _SPEED_FLTT
// @DisplayName: Speed control Target filter frequency in Hz
// @Description: Target filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _SPEED_FLTE
// @DisplayName: Speed control Error filter frequency in Hz
// @Description: Error filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _SPEED_FLTD
// @DisplayName: Speed control Derivative term filter frequency in Hz
// @Description: Derivative filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _SPEED_SMAX
// @DisplayName: Speed control slew rate limit
// @Description: Sets an upper limit on the slew rate produced by the combined P and D gains. If the amplitude of the control action produced by the rate feedback exceeds this value, then the D+P gain is reduced to respect the limit. This limits the amplitude of high frequency oscillations caused by an excessive gain. The limit should be set to no more than 25% of the actuators maximum slew rate to allow for load effects. Note: The gain will not be reduced to less than 10% of the nominal value. A value of zero will disable this feature.
// @Range: 0 200
// @Increment: 0.5
// @User: Advanced
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 acceleration 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
// @Increment: 0.01
// @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
// @Param: _BAL_FLTT
// @DisplayName: Pitch control Target filter frequency in Hz
// @Description: Target filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _BAL_FLTE
// @DisplayName: Pitch control Error filter frequency in Hz
// @Description: Error filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _BAL_FLTD
// @DisplayName: Pitch control Derivative term filter frequency in Hz
// @Description: Derivative filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _BAL_SMAX
// @DisplayName: Pitch control slew rate limit
// @Description: Sets an upper limit on the slew rate produced by the combined P and D gains. If the amplitude of the control action produced by the rate feedback exceeds this value, then the D+P gain is reduced to respect the limit. This limits the amplitude of high frequency oscillations caused by an excessive gain. The limit should be set to no more than 25% of the actuators maximum slew rate to allow for load effects. Note: The gain will not be reduced to less than 10% of the nominal value. A value of zero will disable this feature.
// @Range: 0 200
// @Increment: 0.5
// @User: Advanced
AP_SUBGROUPINFO(_pitch_to_throttle_pid, "_BAL_", 10, AR_AttitudeControl, AC_PID),
// @Param: _BAL_SPD_FF
// @DisplayName: Pitch control feed forward from speed
// @Description: Pitch control feed forward from speed
// @Range: 0.0 10.0
// @Increment: 0.01
// @User: Standard
AP_GROUPINFO("_BAL_SPD_FF", 11, AR_AttitudeControl, _pitch_to_throttle_speed_ff, AR_ATTCONTROL_BAL_SPEED_FF),
// @Param: _SAIL_P
// @DisplayName: Sail Heel control P gain
// @Description: Sail Heel control P gain for sailboats. Converts the error between the desired heel angle (in radians) and actual heel to a main sail output (in the range -1 to +1)
// @Range: 0.000 2.000
// @Increment: 0.01
// @User: Standard
// @Param: _SAIL_I
// @DisplayName: Sail Heel control I gain
// @Description: Sail Heel control I gain for sailboats. Corrects long term error between the desired heel angle (in radians) and actual
// @Range: 0.000 2.000
// @Increment: 0.01
// @User: Standard
// @Param: _SAIL_IMAX
// @DisplayName: Sail Heel control I gain maximum
// @Description: Sail Heel control I gain maximum. Constrains the maximum I term contribution to the main sail output (range -1 to +1)
// @Range: 0.000 1.000
// @Increment: 0.01
// @User: Standard
// @Param: _SAIL_D
// @DisplayName: Sail Heel control D gain
// @Description: Sail Heel control D gain. Compensates for short-term change in desired heel angle vs actual
// @Range: 0.000 0.100
// @Increment: 0.001
// @User: Standard
// @Param: _SAIL_FF
// @DisplayName: Sail Heel control feed forward
// @Description: Sail Heel control feed forward
// @Range: 0.000 0.500
// @Increment: 0.001
// @User: Standard
// @Param: _SAIL_FILT
// @DisplayName: Sail Heel control filter frequency
// @Description: Sail Heel control input filter. Lower values reduce noise but add delay.
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _SAIL_FLTT
// @DisplayName: Sail Heel Target filter frequency in Hz
// @Description: Target filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _SAIL_FLTE
// @DisplayName: Sail Heel Error filter frequency in Hz
// @Description: Error filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _SAIL_FLTD
// @DisplayName: Sail Heel Derivative term filter frequency in Hz
// @Description: Derivative filter frequency in Hz
// @Range: 0.000 100.000
// @Increment: 0.1
// @Units: Hz
// @User: Standard
// @Param: _SAIL_SMAX
// @DisplayName: Sail heel slew rate limit
// @Description: Sets an upper limit on the slew rate produced by the combined P and D gains. If the amplitude of the control action produced by the rate feedback exceeds this value, then the D+P gain is reduced to respect the limit. This limits the amplitude of high frequency oscillations caused by an excessive gain. The limit should be set to no more than 25% of the actuators maximum slew rate to allow for load effects. Note: The gain will not be reduced to less than 10% of the nominal value. A value of zero will disable this feature.
// @Range: 0 200
// @Increment: 0.5
// @User: Advanced
AP_SUBGROUPINFO(_sailboat_heel_pid, "_SAIL_", 12, AR_AttitudeControl, AC_PID),
// @Param: _TURN_MAX_G
// @DisplayName: Turning maximum G force
// @Description: The maximum turning acceleration (in units of gravities) that the rover can handle while remaining stable. The navigation code will keep the lateral acceleration below this level to avoid rolling over or slipping the wheels in turns
// @Units: gravities
// @Range: 0.1 10
// @Increment: 0.01
// @User: Standard
AP_GROUPINFO("_TURN_MAX_G", 13, AR_AttitudeControl, _turn_lateral_G_max, 0.6f),
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_FF, AR_ATTCONTROL_STEER_RATE_IMAX, 0.0f, AR_ATTCONTROL_STEER_RATE_FILT, 0.0f, AR_ATTCONTROL_DT),
_throttle_speed_pid(AR_ATTCONTROL_THR_SPEED_P, AR_ATTCONTROL_THR_SPEED_I, AR_ATTCONTROL_THR_SPEED_D, 0.0f, AR_ATTCONTROL_THR_SPEED_IMAX, 0.0f, AR_ATTCONTROL_THR_SPEED_FILT, 0.0f, AR_ATTCONTROL_DT),
_pitch_to_throttle_pid(AR_ATTCONTROL_PITCH_THR_P, AR_ATTCONTROL_PITCH_THR_I, AR_ATTCONTROL_PITCH_THR_D, 0.0f, AR_ATTCONTROL_PITCH_THR_IMAX, 0.0f, AR_ATTCONTROL_PITCH_THR_FILT, 0.0f, AR_ATTCONTROL_DT),
_sailboat_heel_pid(AR_ATTCONTROL_HEEL_SAIL_P, AR_ATTCONTROL_HEEL_SAIL_I, AR_ATTCONTROL_HEEL_SAIL_D, 0.0f, AR_ATTCONTROL_HEEL_SAIL_IMAX, 0.0f, AR_ATTCONTROL_HEEL_SAIL_FILT, 0.0f, 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;
}
const float desired_rate = get_turn_rate_from_lat_accel(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
// set rate_max_rads to a non-zero number to apply a limit on the desired turn rate
// return value is normally in range -1.0 to +1.0 but can be higher or lower
float AR_AttitudeControl::get_steering_out_heading(float heading_rad, float rate_max_rads, bool motor_limit_left, bool motor_limit_right, float dt)
{
// calculate the desired turn rate (in radians) from the angle error (also in radians)
float desired_rate = get_turn_rate_from_heading(heading_rad, rate_max_rads);
return get_steering_out_rate(desired_rate, motor_limit_left, motor_limit_right, dt);
}
// return a desired turn-rate given a desired heading in radians
float AR_AttitudeControl::get_turn_rate_from_heading(float heading_rad, float rate_max_rads) const
{
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_rads)) {
desired_rate = constrain_float(desired_rate, -rate_max_rads, rate_max_rads);
}
return desired_rate;
}
// 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);
}
// G limit based on speed
float speed;
if (get_forward_speed(speed)) {
// do not limit to less than 1 deg/s
const float turn_rate_max = MAX(get_turn_rate_from_lat_accel(get_turn_lat_accel_max(), speed), radians(1.0f));
_desired_turn_rate = constrain_float(_desired_turn_rate, -turn_rate_max, turn_rate_max);
}
// set PID's dt
_steer_rate_pid.set_dt(dt);
float output = _steer_rate_pid.update_all(_desired_turn_rate, _ahrs.get_yaw_rate_earth(), (motor_limit_left || motor_limit_right));
output += _steer_rate_pid.get_ff();
// constrain and return final output
return output;
}
// 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;
}
// calculate the turn rate in rad/sec given a lateral acceleration (in m/s/s) and speed (in m/s)
float AR_AttitudeControl::get_turn_rate_from_lat_accel(float lat_accel, float speed) const
{
// 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;
}
}
return lat_accel / speed;
}
// 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)
if (!speed_control_active()) {
_throttle_speed_pid.reset_filter();
_throttle_speed_pid.reset_I();
_desired_speed = speed;
}
_speed_last_ms = AP_HAL::millis();
// 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 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 = _throttle_speed_pid.update_all(desired_speed, speed, (_throttle_limit_low || _throttle_limit_high));
throttle_out += _throttle_speed_pid.get_ff();
throttle_out += 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;
// set last time speed controller was run so accelerations are limited
_speed_last_ms = now;
// reset filters and I-term
_throttle_speed_pid.reset_filter();
_throttle_speed_pid.reset_I();
// ensure desired speed is zero
_desired_speed = 0.0f;
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);
}
// balancebot pitch to throttle controller
// returns a throttle output from -100 to +100 given a desired pitch angle and vehicle's current speed (from wheel encoders)
// desired_pitch is in radians, veh_speed_pct is supplied as a percentage (-100 to +100) of vehicle's top speed
float AR_AttitudeControl::get_throttle_out_from_pitch(float desired_pitch, float vehicle_speed_pct, bool motor_limit_low, bool motor_limit_high, float dt)
{
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// if not called recently, reset input filter
const uint32_t now = AP_HAL::millis();
if ((_balance_last_ms == 0) || ((now - _balance_last_ms) > AR_ATTCONTROL_TIMEOUT_MS)) {
_pitch_to_throttle_pid.reset_filter();
_pitch_to_throttle_pid.reset_I();
}
_balance_last_ms = now;
// set PID's dt
_pitch_to_throttle_pid.set_dt(dt);
// add feed forward from speed
float output = vehicle_speed_pct * 0.01f * _pitch_to_throttle_speed_ff;
output += _pitch_to_throttle_pid.update_all(desired_pitch, _ahrs.pitch, (motor_limit_low || motor_limit_high));
output += _pitch_to_throttle_pid.get_ff();
// constrain and return final output
return output;
}
// 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().target;
}
// Sailboat heel(roll) angle controller releases sail to keep at maximum heel angle
// but does not attempt to reach maximum heel angle, ie only lets sails out, does not pull them in
float AR_AttitudeControl::get_sail_out_from_heel(float desired_heel, float dt)
{
// sanity check dt
dt = constrain_float(dt, 0.0f, 1.0f);
// if not called recently, reset input filter
const uint32_t now = AP_HAL::millis();
if ((_heel_controller_last_ms == 0) || ((now - _heel_controller_last_ms) > AR_ATTCONTROL_TIMEOUT_MS)) {
_sailboat_heel_pid.reset_filter();
_sailboat_heel_pid.reset_I();
}
_heel_controller_last_ms = now;
// set PID's dt
_sailboat_heel_pid.set_dt(dt);
_sailboat_heel_pid.update_all(desired_heel, fabsf(_ahrs.roll));
// get feed-forward
const float ff = _sailboat_heel_pid.get_ff();
// get p, constrain to be zero or negative
float p = _sailboat_heel_pid.get_p();
if (is_positive(p)) {
p = 0.0f;
}
// get i, constrain to be zero or negative
float i = _sailboat_heel_pid.get_i();
if (is_positive(i)) {
i = 0.0f;
_sailboat_heel_pid.reset_I();
}
// get d
const float d = _sailboat_heel_pid.get_d();
// constrain and return final output
return (ff + p + i + d) * -1.0f;
}
// 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 (abs(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
if (!speed_control_active() || !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;
}
// relax I terms of throttle and steering controllers
void AR_AttitudeControl::relax_I()
{
_steer_rate_pid.reset_I();
_throttle_speed_pid.reset_I();
_pitch_to_throttle_pid.reset_I();
}
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