zr-v4/libraries/AC_AttitudeControl/AC_AttitudeControl.cpp

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-

#include "AC_AttitudeControl.h"
#include <AP_HAL.h>

extern const AP_HAL::HAL& hal;

// table of user settable parameters
const AP_Param::GroupInfo AC_AttitudeControl::var_info[] PROGMEM = {

    // @Param: RATE_RP_MAX
    // @DisplayName: Angle Rate Roll-Pitch max
    // @Description: maximum rotation rate in roll/pitch axis requested by angle controller used in stabilize, loiter, rtl, auto flight modes
    // @Unit: Centi-Degrees/Sec
    // @Range: 90000 250000
    // @Increment: 500
    // @User: Advanced
    AP_GROUPINFO("RATE_RP_MAX", 0, AC_AttitudeControl, _angle_rate_rp_max, AC_ATTITUDE_CONTROL_RATE_RP_MAX_DEFAULT),

    // @Param: RATE_Y_MAX
    // @DisplayName: Angle Rate Yaw max
    // @Description: maximum rotation rate in roll/pitch axis requested by angle controller used in stabilize, loiter, rtl, auto flight modes
    // @Unit: Centi-Degrees/Sec
    // @Range: 90000 250000
    // @Increment: 500
    // @User: Advanced
    AP_GROUPINFO("RATE_Y_MAX",  1, AC_AttitudeControl, _angle_rate_y_max, AC_ATTITUDE_CONTROL_RATE_Y_MAX_DEFAULT),

    // @Param: SLEW_YAW
    // @DisplayName: Yaw target slew rate
    // @Description: Maximum rate the yaw target can be updated in Loiter, RTL, Auto flight modes
    // @Unit: Centi-Degrees/Sec
    // @Range: 500 18000
    // @Increment: 100
    // @User: Advanced
    AP_GROUPINFO("SLEW_YAW",    2, AC_AttitudeControl, _slew_yaw, AC_ATTITUDE_CONTROL_SLEW_YAW_DEFAULT),

    AP_GROUPEND
};

//
// high level controllers
//

// init_targets - resets target angles to current angles
void AC_AttitudeControl::init_targets()
{
    // set earth frame angle targets to current lean angles
    _angle_ef_target.x = _ahrs.roll_sensor;
    _angle_ef_target.y = _ahrs.pitch_sensor;
    _angle_ef_target.z = _ahrs.yaw_sensor;

    // clear body frame angle errors
    _angle_bf_error.x = 0;
    _angle_bf_error.y = 0;
    _angle_bf_error.z = 0;

    // clear body frame feed forward rates
    _rate_bf_feedforward.x = 0;
    _rate_bf_feedforward.y = 0;
    _rate_bf_feedforward.z = 0;
}

//
// methods to be called by upper controllers to request and implement a desired attitude
//

// angleef_rp_rateef_y - attempts to maintain a roll and pitch angle and yaw rate (all earth frame)
void AC_AttitudeControl::angleef_rp_rateef_y(float roll_angle_ef, float pitch_angle_ef, float yaw_rate_ef)
{
    Vector3f    rate_ef_feedforward;    // earth frame feedforward rate
    Vector3f    angle_ef_error;         // earth frame angle errors
    
    // set earth-frame angle targets for roll and pitch and calculate angle error
    _angle_ef_target.x = roll_angle_ef;
    angle_ef_error.x = wrap_180_cd_float(_angle_ef_target.x - _ahrs.roll_sensor);

    _angle_ef_target.y = pitch_angle_ef;
    angle_ef_error.y = wrap_180_cd_float(_angle_ef_target.y - _ahrs.pitch_sensor);

    // set earth-frame feed forward rate for yaw
    rate_ef_feedforward.z = yaw_rate_ef;

    // increment the yaw angle target
    _angle_ef_target.z += yaw_rate_ef * _dt;
    _angle_ef_target.z = wrap_360_cd_float(_angle_ef_target.z);

    // calculate angle error with maximum of +- max_angle_overshoot
    angle_ef_error.z = wrap_180_cd_float(_angle_ef_target.z - _ahrs.yaw_sensor);
    angle_ef_error.z  = constrain_float(angle_ef_error.z, -AC_ATTITUDE_RATE_STAB_YAW_OVERSHOOT_ANGLE_MAX, AC_ATTITUDE_RATE_STAB_YAW_OVERSHOOT_ANGLE_MAX);

    // update yaw angle target to be within max_angle_overshoot of our current heading
    _angle_ef_target.z = wrap_360_cd_float(angle_ef_error.z + _ahrs.yaw_sensor);

    // convert earth-frame angle errors to body-frame angle errors
    rate_ef_targets_to_bf(angle_ef_error, _angle_bf_error);

    // convert earth-frame feed forward rates to body-frame feed forward rates
    rate_ef_targets_to_bf(rate_ef_feedforward, _rate_bf_feedforward);

    // convert body-frame angle errors to body-frame rate targets
    update_stab_rate_bf_targets();

    // add body frame rate feed forward
    _rate_bf_target += _rate_bf_feedforward;

    // body-frame to motor outputs should be called separately
}

// angleef_rpy - attempts to maintain a roll, pitch and yaw angle (all earth frame)
//  if yaw_slew is true then target yaw movement will be gradually moved to the new target based on the SLEW_YAW parameter
void AC_AttitudeControl::angleef_rpy(float roll_angle_ef, float pitch_angle_ef, float yaw_angle_ef, bool slew_yaw)
{
    Vector3f    angle_ef_error;

    // set earth-frame angle targets
    _angle_ef_target.x = roll_angle_ef;
    _angle_ef_target.y = pitch_angle_ef;
    _angle_ef_target.z = yaw_angle_ef;

    // calculate earth frame errors
    angle_ef_error.x = wrap_180_cd_float(_angle_ef_target.x - _ahrs.roll_sensor);
    angle_ef_error.y = wrap_180_cd_float(_angle_ef_target.y - _ahrs.pitch_sensor);
    angle_ef_error.z = wrap_180_cd_float(_angle_ef_target.z - _ahrs.yaw_sensor);

    // convert earth-frame angle errors to body-frame angle errors
    rate_ef_targets_to_bf(angle_ef_error, _angle_bf_error);

    // convert body-frame angle errors to body-frame rate targets
    update_stab_rate_bf_targets();

    if (slew_yaw) {
        _rate_bf_target.z = constrain_float(_rate_bf_target.z,-_slew_yaw,_slew_yaw);
    }

    // body-frame to motor outputs should be called separately
}

// rateef_rpy - attempts to maintain a roll, pitch and yaw rate (all earth frame)
void AC_AttitudeControl::rateef_rpy(float roll_rate_ef, float pitch_rate_ef, float yaw_rate_ef)
{
    Vector3f    rate_ef_feedforward;
    Vector3f    angle_ef_error;

    // update the rate feed forward
    rate_ef_feedforward.x = roll_rate_ef;
    rate_ef_feedforward.y = pitch_rate_ef;
    rate_ef_feedforward.z = yaw_rate_ef;

    // increment the roll angle target
    _angle_ef_target.x += roll_rate_ef * _dt;
    _angle_ef_target.x = wrap_180_cd(_angle_ef_target.x);

    // ensure targets are within the lean angle limits
    // To-Do: make angle_max part of the AP_Vehicle class
    _angle_ef_target.x  = constrain_float(_angle_ef_target.x, -_aparm.angle_max, _aparm.angle_max);

    // calculate angle error with maximum of +- max angle overshoot
    angle_ef_error.x = wrap_180_cd(_angle_ef_target.x - _ahrs.roll_sensor);
    angle_ef_error.x  = constrain_float(angle_ef_error.x, -AC_ATTITUDE_RATE_STAB_ROLL_OVERSHOOT_ANGLE_MAX, AC_ATTITUDE_RATE_STAB_ROLL_OVERSHOOT_ANGLE_MAX);

    // To-Do: handle check for traditional heli's motors.motor_runup_complete
    // To-Do: reset target angle to current angle if motors not spinning

    // update roll angle target to be within max angle overshoot of our roll angle
    _angle_ef_target.x = wrap_180_cd(angle_ef_error.x + _ahrs.roll_sensor);

    // increment the pitch angle target
    _angle_ef_target.y += pitch_rate_ef * _dt;
    _angle_ef_target.y = wrap_180_cd(_angle_ef_target.y);

    // ensure targets are within the lean angle limits
    // To-Do: make angle_max part of the AP_Vehicle class
    _angle_ef_target.y  = constrain_float(_angle_ef_target.y, -_aparm.angle_max, _aparm.angle_max);

    // calculate angle error with maximum of +- max angle overshoot
    // To-Do: should we do something better as we cross 90 degrees?
    angle_ef_error.y = wrap_180_cd(_angle_ef_target.y - _ahrs.pitch_sensor);
    angle_ef_error.y  = constrain_float(angle_ef_error.y, -AC_ATTITUDE_RATE_STAB_PITCH_OVERSHOOT_ANGLE_MAX, AC_ATTITUDE_RATE_STAB_PITCH_OVERSHOOT_ANGLE_MAX);

    // To-Do: handle check for traditional heli's motors.motor_runup_complete
    // To-Do: reset target angle to current angle if motors not spinning

    // update pitch angle target to be within max angle overshoot of our pitch angle
    _angle_ef_target.y = wrap_180_cd(angle_ef_error.y + _ahrs.pitch_sensor);

    // increment the yaw angle target
    _angle_ef_target.z += yaw_rate_ef * _dt;
    _angle_ef_target.z = wrap_360_cd(_angle_ef_target.z);

    // calculate angle error with maximum of +- max angle overshoot
    angle_ef_error.z = wrap_180_cd(_angle_ef_target.z - _ahrs.yaw_sensor);
    angle_ef_error.z  = constrain_float(angle_ef_error.z, -AC_ATTITUDE_RATE_STAB_YAW_OVERSHOOT_ANGLE_MAX, AC_ATTITUDE_RATE_STAB_YAW_OVERSHOOT_ANGLE_MAX);

    // update yaw angle target to be within max angle overshoot of our current heading
    _angle_ef_target.z = wrap_360_cd(angle_ef_error.z + _ahrs.yaw_sensor);

    // convert earth-frame angle errors to body-frame angle errors
    rate_ef_targets_to_bf(angle_ef_error, _angle_bf_error);

    // convert earth-frame rates to body-frame rates
    rate_ef_targets_to_bf(rate_ef_feedforward, _rate_bf_feedforward);

    // convert body-frame angle errors to body-frame rate targets
    update_stab_rate_bf_targets();

    // add body frame rate feed forward
    _rate_bf_target += _rate_bf_feedforward;

    // body-frame to motor outputs should be called separately
}

// ratebf_rpy - attempts to maintain a roll, pitch and yaw rate (all body frame)
void AC_AttitudeControl::ratebf_rpy(float roll_rate_bf, float pitch_rate_bf, float yaw_rate_bf)
{
    // Update angle error
    update_stab_rate_bf_errors();

    // convert body-frame angle errors to body-frame rate targets
    update_stab_rate_bf_targets();

    // update the rate feed forward
    _rate_bf_feedforward.x = roll_rate_bf;
    _rate_bf_feedforward.y = pitch_rate_bf;
    _rate_bf_feedforward.z = yaw_rate_bf;

    // body-frame rate commands added
    _rate_bf_target += _rate_bf_feedforward;

    // body-frame to motor outputs should be called separately
}

//
// rate_controller_run - run lowest level body-frame rate controller and send outputs to the motors
//      should be called at 100hz or more
//
void AC_AttitudeControl::rate_controller_run()
{
    // call rate controllers and send output to motors object
    // To-Do: should the outputs from get_rate_roll, pitch, yaw be int16_t which is the input to the motors library?
    // To-Do: skip this step if the throttle out is zero?
    _motors.set_roll(rate_bf_to_motor_roll(_rate_bf_target.x));
    _motors.set_pitch(rate_bf_to_motor_pitch(_rate_bf_target.y));
    _motors.set_yaw(rate_bf_to_motor_yaw(_rate_bf_target.z));
}

//
// earth-frame <-> body-frame conversion functions
//
// rate_ef_targets_to_bf - converts earth frame rate targets to body frame rate targets
void AC_AttitudeControl::rate_ef_targets_to_bf(const Vector3f& rate_ef_target, Vector3f& rate_bf_target)
{
    // convert earth frame rates to body frame rates
    rate_bf_target.x = rate_ef_target.x - _ahrs.sin_pitch() * rate_ef_target.z;
    rate_bf_target.y = _ahrs.cos_roll()  * rate_ef_target.y + _ahrs.sin_roll() * _ahrs.cos_pitch() * rate_ef_target.z;
    rate_bf_target.z = -_ahrs.sin_roll() * rate_ef_target.y + _ahrs.cos_pitch() * _ahrs.cos_roll() * rate_ef_target.z;
}

// rate_bf_targets_to_ef - converts body frame rate targets to earth frame rate targets
void AC_AttitudeControl::rate_bf_targets_to_ef(const Vector3f& rate_bf_target, Vector3f& rate_ef_target)
{
    // convert earth frame rates to body frame rates
    rate_ef_target.x = rate_bf_target.x - _ahrs.sin_roll() * (_ahrs.sin_pitch()/_ahrs.cos_pitch()) * rate_bf_target.y - _ahrs.cos_roll() * (_ahrs.sin_pitch()/_ahrs.cos_pitch()) * rate_bf_target.z;
    rate_ef_target.y = _ahrs.cos_roll()  * rate_bf_target.y - _ahrs.sin_roll() * rate_bf_target.z;
    rate_ef_target.z = (_ahrs.sin_roll() / _ahrs.cos_pitch()) * rate_bf_target.y + (_ahrs.cos_roll() / _ahrs.cos_pitch()) * rate_bf_target.z;
}

//
// protected methods
//

//
// stabilized rate controller (body-frame) methods
//

// update_stab_rate_bf_errors - calculates body frame angle errors
//   body-frame feed forward rates (centi-degrees / second) taken from _angle_bf_error
//   angle errors in centi-degrees placed in _angle_bf_error
void AC_AttitudeControl::update_stab_rate_bf_errors()
{
    // roll - calculate body-frame angle error by integrating body-frame rate error
    _angle_bf_error.x += (_rate_bf_feedforward.x - (_ins.get_gyro().x * AC_ATTITUDE_CONTROL_DEGX100)) * _dt;
    // roll - limit maximum error
    _angle_bf_error.x = constrain_float(_angle_bf_error.x, -AC_ATTITUDE_RATE_STAB_ROLL_OVERSHOOT_ANGLE_MAX, AC_ATTITUDE_RATE_STAB_ROLL_OVERSHOOT_ANGLE_MAX);


    // pitch - calculate body-frame angle error by integrating body-frame rate error
    _angle_bf_error.y += (_rate_bf_feedforward.y - (_ins.get_gyro().y * AC_ATTITUDE_CONTROL_DEGX100)) * _dt;
    // pitch - limit maximum error
    _angle_bf_error.y = constrain_float(_angle_bf_error.y, -AC_ATTITUDE_RATE_STAB_PITCH_OVERSHOOT_ANGLE_MAX, AC_ATTITUDE_RATE_STAB_PITCH_OVERSHOOT_ANGLE_MAX);


    // yaw - calculate body-frame angle error by integrating body-frame rate error
    _angle_bf_error.z += (_rate_bf_feedforward.z - (_ins.get_gyro().z * AC_ATTITUDE_CONTROL_DEGX100)) * _dt;
    // yaw - limit maximum error
    _angle_bf_error.z = constrain_float(_angle_bf_error.z, -AC_ATTITUDE_RATE_STAB_YAW_OVERSHOOT_ANGLE_MAX, AC_ATTITUDE_RATE_STAB_YAW_OVERSHOOT_ANGLE_MAX);

    // To-Do: handle case of motors being disarmed or g.rc_3.servo_out == 0 and set error to zero
}

// update_stab_rate_bf_targets - converts body-frame angle error to body-frame rate targets for roll, pitch and yaw axis
//   targets rates in centi-degrees taken from _angle_bf_error
//   results in centi-degrees/sec put into _rate_bf_target
void AC_AttitudeControl::update_stab_rate_bf_targets()
{
    // stab roll calculation
    _rate_bf_target.x = _pi_angle_roll.kP() * _angle_bf_error.x;
    // constrain roll rate request
    if (_flags.limit_angle_to_rate_request) {
        _rate_bf_target.x = constrain_float(_rate_bf_target.x,-_angle_rate_rp_max,_angle_rate_rp_max);
    }

    // stab pitch calculation
    _rate_bf_target.y = _pi_angle_pitch.kP() * _angle_bf_error.y;
    // constrain pitch rate request
    if (_flags.limit_angle_to_rate_request) {
        _rate_bf_target.y = constrain_float(_rate_bf_target.y,-_angle_rate_rp_max,_angle_rate_rp_max);
    }

    // stab yaw calculation
    _rate_bf_target.z = _pi_angle_yaw.kP() * _angle_bf_error.z;
    // constrain yaw rate request
    if (_flags.limit_angle_to_rate_request) {
        _rate_bf_target.z = constrain_float(_rate_bf_target.z,-_angle_rate_y_max,_angle_rate_y_max);
    }
}

//
// body-frame rate controller
//

// rate_bf_to_motor_roll - ask the rate controller to calculate the motor outputs to achieve the target rate in centi-degrees / second
float AC_AttitudeControl::rate_bf_to_motor_roll(float rate_target_cds)
{
    float p,i,d;            // used to capture pid values for logging
    float current_rate;     // this iteration's rate
    float rate_error;       // simply target_rate - current_rate

    // get current rate
    // To-Do: make getting gyro rates more efficient?
    current_rate = (_ins.get_gyro().x * AC_ATTITUDE_CONTROL_DEGX100);

    // calculate error and call pid controller
    rate_error = rate_target_cds - current_rate;
    p = _pid_rate_roll.get_p(rate_error);

    // get i term
    i = _pid_rate_roll.get_integrator();

    // update i term as long as we haven't breached the limits or the I term will certainly reduce
    if (!_motors.limit.roll_pitch || ((i>0&&rate_error<0)||(i<0&&rate_error>0))) {
        i = _pid_rate_roll.get_i(rate_error, _dt);
    }

    // get d term
    d = _pid_rate_roll.get_d(rate_error, _dt);

    // constrain output and return
    return constrain_float((p+i+d), -AC_ATTITUDE_RATE_RP_CONTROLLER_OUT_MAX, AC_ATTITUDE_RATE_RP_CONTROLLER_OUT_MAX);

    // To-Do: allow logging of PIDs?
}

// rate_bf_to_motor_pitch - ask the rate controller to calculate the motor outputs to achieve the target rate in centi-degrees / second
float AC_AttitudeControl::rate_bf_to_motor_pitch(float rate_target_cds)
{
    float p,i,d;            // used to capture pid values for logging
    float current_rate;     // this iteration's rate
    float rate_error;       // simply target_rate - current_rate

    // get current rate
    // To-Do: make getting gyro rates more efficient?
    current_rate = (_ins.get_gyro().y * AC_ATTITUDE_CONTROL_DEGX100);

    // calculate error and call pid controller
    rate_error = rate_target_cds - current_rate;
    p = _pid_rate_pitch.get_p(rate_error);

    // get i term
    i = _pid_rate_pitch.get_integrator();

    // update i term as long as we haven't breached the limits or the I term will certainly reduce
    if (!_motors.limit.roll_pitch || ((i>0&&rate_error<0)||(i<0&&rate_error>0))) {
        i = _pid_rate_pitch.get_i(rate_error, _dt);
    }

    // get d term
    d = _pid_rate_pitch.get_d(rate_error, _dt);

    // constrain output and return
    return constrain_float((p+i+d), -AC_ATTITUDE_RATE_RP_CONTROLLER_OUT_MAX, AC_ATTITUDE_RATE_RP_CONTROLLER_OUT_MAX);

    // To-Do: allow logging of PIDs?
}

// rate_bf_to_motor_yaw - ask the rate controller to calculate the motor outputs to achieve the target rate in centi-degrees / second
float AC_AttitudeControl::rate_bf_to_motor_yaw(float rate_target_cds)
{
    float p,i,d;            // used to capture pid values for logging
    float current_rate;     // this iteration's rate
    float rate_error;       // simply target_rate - current_rate

    // get current rate
    // To-Do: make getting gyro rates more efficient?
    current_rate = (_ins.get_gyro().z * AC_ATTITUDE_CONTROL_DEGX100);

    // calculate error and call pid controller
    rate_error  = rate_target_cds - current_rate;
    p = _pid_rate_yaw.get_p(rate_error);

    // separately calculate p, i, d values for logging
    p = _pid_rate_yaw.get_p(rate_error);

    // get i term
    i = _pid_rate_yaw.get_integrator();

    // update i term as long as we haven't breached the limits or the I term will certainly reduce
    if (!_motors.limit.yaw || ((i>0&&rate_error<0)||(i<0&&rate_error>0))) {
        i = _pid_rate_yaw.get_i(rate_error, _dt);
    }

    // get d value
    d = _pid_rate_yaw.get_d(rate_error, _dt);

    // constrain output and return
    return constrain_float((p+i+d), -AC_ATTITUDE_RATE_YAW_CONTROLLER_OUT_MAX, AC_ATTITUDE_RATE_YAW_CONTROLLER_OUT_MAX);

    // To-Do: allow logging of PIDs?
}


//
// throttle functions
//

 // set_throttle_out - to be called by upper throttle controllers when they wish to provide throttle output directly to motors
 // provide 0 to cut motors
void AC_AttitudeControl::set_throttle_out(int16_t throttle_out, bool apply_angle_boost)
{
    if (apply_angle_boost) {
        _motors.set_throttle(get_angle_boost(throttle_out));
    }else{
        _motors.set_throttle(throttle_out);
        // clear angle_boost for logging purposes
        _angle_boost = 0;
    }

    // update compass with throttle value
    // To-Do: find another method to grab the throttle out and feed to the compass.  Could be done completely outside this class
    //compass.set_throttle((float)g.rc_3.servo_out/1000.0f);
}

// get_angle_boost - returns a throttle including compensation for roll/pitch angle
// throttle value should be 0 ~ 1000
int16_t AC_AttitudeControl::get_angle_boost(int16_t throttle_pwm)
{
    float temp = _ahrs.cos_pitch() * _ahrs.cos_roll();
    int16_t throttle_out;

    temp = constrain_float(temp, 0.5f, 1.0f);

    // reduce throttle if we go inverted
    temp = constrain_float(9000-max(labs(_ahrs.roll_sensor),labs(_ahrs.pitch_sensor)), 0, 3000) / (3000 * temp);

    // apply scale and constrain throttle
    // To-Do: move throttle_min and throttle_max into the AP_Vehicles class?
    throttle_out = constrain_float((float)(throttle_pwm-_motors.throttle_min()) * temp + _motors.throttle_min(), _motors.throttle_min(), 1000);

    // record angle boost for logging
    _angle_boost = throttle_out - throttle_pwm;

    return throttle_out;
}