// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- #include "AC_AttitudeControl.h" #include #include // table of user settable parameters const AP_Param::GroupInfo AC_AttitudeControl::var_info[] = { // 0, 1 were RATE_RP_MAX, RATE_Y_MAX // @Param: SLEW_YAW // @DisplayName: Yaw target slew rate // @Description: Maximum rate the yaw target can be updated in Loiter, RTL, Auto flight modes // @Units: 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_CDS), // 3 was for ACCEL_RP_MAX // @Param: ACCEL_Y_MAX // @DisplayName: Acceleration Max for Yaw // @Description: Maximum acceleration in yaw axis // @Units: Centi-Degrees/Sec/Sec // @Range: 0 72000 // @Values: 0:Disabled, 18000:Slow, 36000:Medium, 54000:Fast // @Increment: 1000 // @User: Advanced AP_GROUPINFO("ACCEL_Y_MAX", 4, AC_AttitudeControl, _accel_yaw_max, AC_ATTITUDE_CONTROL_ACCEL_Y_MAX_DEFAULT_CDSS), // @Param: RATE_FF_ENAB // @DisplayName: Rate Feedforward Enable // @Description: Controls whether body-frame rate feedfoward is enabled or disabled // @Values: 0:Disabled, 1:Enabled // @User: Advanced AP_GROUPINFO("RATE_FF_ENAB", 5, AC_AttitudeControl, _rate_bf_ff_enabled, AC_ATTITUDE_CONTROL_RATE_BF_FF_DEFAULT), // @Param: ACCEL_R_MAX // @DisplayName: Acceleration Max for Roll // @Description: Maximum acceleration in roll axis // @Units: Centi-Degrees/Sec/Sec // @Range: 0 180000 // @Increment: 1000 // @Values: 0:Disabled, 72000:Slow, 108000:Medium, 162000:Fast // @User: Advanced AP_GROUPINFO("ACCEL_R_MAX", 6, AC_AttitudeControl, _accel_roll_max, AC_ATTITUDE_CONTROL_ACCEL_RP_MAX_DEFAULT_CDSS), // @Param: ACCEL_P_MAX // @DisplayName: Acceleration Max for Pitch // @Description: Maximum acceleration in pitch axis // @Units: Centi-Degrees/Sec/Sec // @Range: 0 180000 // @Increment: 1000 // @Values: 0:Disabled, 72000:Slow, 108000:Medium, 162000:Fast // @User: Advanced AP_GROUPINFO("ACCEL_P_MAX", 7, AC_AttitudeControl, _accel_pitch_max, AC_ATTITUDE_CONTROL_ACCEL_RP_MAX_DEFAULT_CDSS), // IDs 8,9,10,11 RESERVED (in use on Solo) // @Param: ANGLE_BOOST // @DisplayName: Angle Boost // @Description: Angle Boost increases output throttle as the vehicle leans to reduce loss of altitude // @Values: 0:Disabled, 1:Enabled // @User: Advanced AP_GROUPINFO("ANGLE_BOOST", 12, AC_AttitudeControl, _angle_boost_enabled, 1), // @Param: ANG_RLL_P // @DisplayName: Roll axis angle controller P gain // @Description: Roll axis angle controller P gain. Converts the error between the desired roll angle and actual angle to a desired roll rate // @Range: 3.000 12.000 // @User: Standard AP_SUBGROUPINFO(_p_angle_roll, "ANG_RLL_", 13, AC_AttitudeControl, AC_P), // @Param: ANG_PIT_P // @DisplayName: Pitch axis angle controller P gain // @Description: Pitch axis angle controller P gain. Converts the error between the desired pitch angle and actual angle to a desired pitch rate // @Range: 3.000 12.000 // @User: Standard AP_SUBGROUPINFO(_p_angle_pitch, "ANG_PIT_", 14, AC_AttitudeControl, AC_P), // @Param: ANG_YAW_P // @DisplayName: Yaw axis angle controller P gain // @Description: Yaw axis angle controller P gain. Converts the error between the desired yaw angle and actual angle to a desired yaw rate // @Range: 3.000 6.000 // @User: Standard AP_SUBGROUPINFO(_p_angle_yaw, "ANG_YAW_", 15, AC_AttitudeControl, AC_P), // @Param: ANG_LIM_TC // @DisplayName: Angle Limit (to maintain altitude) Time Constant // @Description: Angle Limit (to maintain altitude) Time Constant // @Range: 0.5 10.0 // @User: Advanced AP_GROUPINFO("ANG_LIM_TC", 16, AC_AttitudeControl, _angle_limit_tc, AC_ATTITUDE_CONTROL_ANGLE_LIMIT_TC_DEFAULT), AP_GROUPEND }; // Set output throttle and disable stabilization void AC_AttitudeControl::set_throttle_out_unstabilized(float throttle_in, bool reset_attitude_control, float filter_cutoff) { _throttle_in = throttle_in; _motors.set_throttle_filter_cutoff(filter_cutoff); if (reset_attitude_control) { relax_attitude_controllers(); } _motors.set_throttle(throttle_in); _angle_boost = 0.0f; } // Ensure attitude controller have zero errors to relax rate controller output void AC_AttitudeControl::relax_attitude_controllers() { // TODO add _ahrs.get_quaternion() _attitude_target_quat.from_rotation_matrix(_ahrs.get_rotation_body_to_ned()); _attitude_target_ang_vel = _ahrs.get_gyro(); _attitude_target_euler_angle = Vector3f(_ahrs.roll, _ahrs.pitch, _ahrs.yaw); // Set reference angular velocity used in angular velocity controller equal // to the input angular velocity and reset the angular velocity integrators. // This zeros the output of the angular velocity controller. _rate_target_ang_vel = _ahrs.get_gyro(); get_rate_roll_pid().reset_I(); get_rate_pitch_pid().reset_I(); get_rate_yaw_pid().reset_I(); } void AC_AttitudeControl::reset_rate_controller_I_terms() { get_rate_roll_pid().reset_I(); get_rate_pitch_pid().reset_I(); get_rate_yaw_pid().reset_I(); } // The attitude controller works around the concept of the desired attitude, target attitude // and measured attitude. The desired attitude is the attitude input into the attitude controller // that expresses where the higher level code would like the aircraft to move to. The target attitude is moved // to the desired attitude with jerk, acceleration, and velocity limits. The target angular velocities are fed // directly into the rate controllers. The angular error between the measured attitude and the target attitude is // fed into the angle controller and the output of the angle controller summed at the input of the rate controllers. // By feeding the target angular velocity directly into the rate controllers the measured and target attitudes // remain very close together. // // All input functions below follow the same procedure // 1. define the desired attitude the aircraft should attempt to achieve using the input variables // 2. using the desired attitude and input variables, define the target angular velocity so that it should // move the target attitude towards the desired attitude // 3. if _rate_bf_ff_enabled & _use_ff_and_input_shaping are not being used then make the target attitude // and target angular velocities equal to the desired attitude and desired angular velocities. // 4. ensure _attitude_target_quat, _attitude_target_euler_angle, _attitude_target_euler_rate and // _attitude_target_ang_vel have been defined. This ensures input modes can be changed without discontinuity. // 5. attitude_controller_run_quat is then run to pass the target angular velocities to the rate controllers and // integrate them into the target attitude. Any errors between the target attitude and the measured attitude are // corrected by first correcting the thrust vector until the angle between the target thrust vector measured // trust vector drops below 2*AC_ATTITUDE_THRUST_ERROR_ANGLE. At this point the heading is also corrected. // Command a Quaternion attitude with feedforward and smoothing void AC_AttitudeControl::input_quaternion(Quaternion attitude_desired_quat, float smoothing_gain) { // calculate the attitude target euler angles _attitude_target_quat.to_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); // ensure smoothing gain can not cause overshoot smoothing_gain = constrain_float(smoothing_gain,1.0f,1/_dt); Quaternion attitude_error_quat = _attitude_target_quat.inverse() * attitude_desired_quat; Vector3f attitude_error_angle; attitude_error_quat.to_axis_angle(attitude_error_angle); if (_rate_bf_ff_enabled & _use_ff_and_input_shaping) { // When acceleration limiting and feedforward are enabled, the sqrt controller is used to compute an euler // angular velocity that will cause the euler angle to smoothly stop at the input angle with limited deceleration // and an exponential decay specified by smoothing_gain at the end. _attitude_target_ang_vel.x = input_shaping_angle(attitude_error_angle.x, smoothing_gain, get_accel_roll_max_radss(), _attitude_target_ang_vel.x); _attitude_target_ang_vel.y = input_shaping_angle(attitude_error_angle.y, smoothing_gain, get_accel_pitch_max_radss(), _attitude_target_ang_vel.y); _attitude_target_ang_vel.z = input_shaping_angle(attitude_error_angle.z, smoothing_gain, get_accel_yaw_max_radss(), _attitude_target_ang_vel.z); // Convert body-frame angular velocity into euler angle derivative of desired attitude ang_vel_to_euler_rate(_attitude_target_euler_angle, _attitude_target_ang_vel, _attitude_target_euler_rate); } else { _attitude_target_quat = attitude_desired_quat; // Set rate feedforward requests to zero _attitude_target_euler_rate = Vector3f(0.0f, 0.0f, 0.0f); _attitude_target_ang_vel = Vector3f(0.0f, 0.0f, 0.0f); } // Call quaternion attitude controller attitude_controller_run_quat(); } // Command an euler roll and pitch angle and an euler yaw rate with angular velocity feedforward and smoothing void AC_AttitudeControl::input_euler_angle_roll_pitch_euler_rate_yaw(float euler_roll_angle_cd, float euler_pitch_angle_cd, float euler_yaw_rate_cds, float smoothing_gain) { // Convert from centidegrees on public interface to radians float euler_roll_angle = radians(euler_roll_angle_cd*0.01f); float euler_pitch_angle = radians(euler_pitch_angle_cd*0.01f); float euler_yaw_rate = radians(euler_yaw_rate_cds*0.01f); // calculate the attitude target euler angles _attitude_target_quat.to_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); // ensure smoothing gain can not cause overshoot smoothing_gain = constrain_float(smoothing_gain,1.0f,1/_dt); // Add roll trim to compensate tail rotor thrust in heli (will return zero on multirotors) euler_roll_angle += get_roll_trim_rad(); if (_rate_bf_ff_enabled & _use_ff_and_input_shaping) { // translate the roll pitch and yaw acceleration limits to the euler axis Vector3f euler_accel = euler_accel_limit(_attitude_target_euler_angle, Vector3f(get_accel_roll_max_radss(), get_accel_pitch_max_radss(), get_accel_yaw_max_radss())); // When acceleration limiting and feedforward are enabled, the sqrt controller is used to compute an euler // angular velocity that will cause the euler angle to smoothly stop at the input angle with limited deceleration // and an exponential decay specified by smoothing_gain at the end. _attitude_target_euler_rate.x = input_shaping_angle(euler_roll_angle-_attitude_target_euler_angle.x, smoothing_gain, euler_accel.x, _attitude_target_euler_rate.x); _attitude_target_euler_rate.y = input_shaping_angle(euler_pitch_angle-_attitude_target_euler_angle.y, smoothing_gain, euler_accel.y, _attitude_target_euler_rate.y); // When yaw acceleration limiting is enabled, the yaw input shaper constrains angular acceleration about the yaw axis, slewing // the output rate towards the input rate. _attitude_target_euler_rate.z = input_shaping_ang_vel(_attitude_target_euler_rate.z, euler_yaw_rate, euler_accel.z); // Convert euler angle derivative of desired attitude into a body-frame angular velocity vector for feedforward euler_rate_to_ang_vel(_attitude_target_euler_angle, _attitude_target_euler_rate, _attitude_target_ang_vel); } else { // When feedforward is not enabled, the target euler angle is input into the target and the feedforward rate is zeroed. _attitude_target_euler_angle.x = euler_roll_angle; _attitude_target_euler_angle.y = euler_pitch_angle; _attitude_target_euler_angle.z += euler_yaw_rate*_dt; // Compute quaternion target attitude _attitude_target_quat.from_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); // Set rate feedforward requests to zero _attitude_target_euler_rate = Vector3f(0.0f, 0.0f, 0.0f); _attitude_target_ang_vel = Vector3f(0.0f, 0.0f, 0.0f); } // Call quaternion attitude controller attitude_controller_run_quat(); } // Command an euler roll, pitch and yaw angle with angular velocity feedforward and smoothing void AC_AttitudeControl::input_euler_angle_roll_pitch_yaw(float euler_roll_angle_cd, float euler_pitch_angle_cd, float euler_yaw_angle_cd, bool slew_yaw, float smoothing_gain) { // Convert from centidegrees on public interface to radians float euler_roll_angle = radians(euler_roll_angle_cd*0.01f); float euler_pitch_angle = radians(euler_pitch_angle_cd*0.01f); float euler_yaw_angle = radians(euler_yaw_angle_cd*0.01f); // calculate the attitude target euler angles _attitude_target_quat.to_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); // ensure smoothing gain can not cause overshoot smoothing_gain = constrain_float(smoothing_gain,1.0f,1/_dt); // Add roll trim to compensate tail rotor thrust in heli (will return zero on multirotors) euler_roll_angle += get_roll_trim_rad(); if (_rate_bf_ff_enabled & _use_ff_and_input_shaping) { // translate the roll pitch and yaw acceleration limits to the euler axis Vector3f euler_accel = euler_accel_limit(_attitude_target_euler_angle, Vector3f(get_accel_roll_max_radss(), get_accel_pitch_max_radss(), get_accel_yaw_max_radss())); // When acceleration limiting and feedforward are enabled, the sqrt controller is used to compute an euler // angular velocity that will cause the euler angle to smoothly stop at the input angle with limited deceleration // and an exponential decay specified by smoothing_gain at the end. _attitude_target_euler_rate.x = input_shaping_angle(euler_roll_angle-_attitude_target_euler_angle.x, smoothing_gain, euler_accel.x, _attitude_target_euler_rate.x); _attitude_target_euler_rate.y = input_shaping_angle(euler_pitch_angle-_attitude_target_euler_angle.y, smoothing_gain, euler_accel.y, _attitude_target_euler_rate.y); _attitude_target_euler_rate.z = input_shaping_angle(euler_yaw_angle-_attitude_target_euler_angle.z, smoothing_gain, euler_accel.z, _attitude_target_euler_rate.z); if (slew_yaw) { _attitude_target_euler_rate.z = constrain_float(_attitude_target_euler_rate.z, -get_slew_yaw_rads(), get_slew_yaw_rads()); } // Convert euler angle derivative of desired attitude into a body-frame angular velocity vector for feedforward euler_rate_to_ang_vel(_attitude_target_euler_angle, _attitude_target_euler_rate, _attitude_target_ang_vel); } else { // When feedforward is not enabled, the target euler angle is input into the target and the feedforward rate is zeroed. _attitude_target_euler_angle.x = euler_roll_angle; _attitude_target_euler_angle.y = euler_pitch_angle; if (slew_yaw) { // Compute constrained angle error float angle_error = constrain_float(wrap_PI(euler_yaw_angle-_attitude_target_euler_angle.z), -get_slew_yaw_rads()*_dt, get_slew_yaw_rads()*_dt); // Update attitude target from constrained angle error _attitude_target_euler_angle.z = wrap_PI(angle_error + _attitude_target_euler_angle.z); } else { _attitude_target_euler_angle.z = euler_yaw_angle; } // Compute quaternion target attitude _attitude_target_quat.from_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); // Set rate feedforward requests to zero _attitude_target_euler_rate = Vector3f(0.0f, 0.0f, 0.0f); _attitude_target_ang_vel = Vector3f(0.0f, 0.0f, 0.0f); } // Call quaternion attitude controller attitude_controller_run_quat(); } // Command an euler roll, pitch, and yaw rate with angular velocity feedforward and smoothing void AC_AttitudeControl::input_euler_rate_roll_pitch_yaw(float euler_roll_rate_cds, float euler_pitch_rate_cds, float euler_yaw_rate_cds) { // Convert from centidegrees on public interface to radians float euler_roll_rate = radians(euler_roll_rate_cds*0.01f); float euler_pitch_rate = radians(euler_pitch_rate_cds*0.01f); float euler_yaw_rate = radians(euler_yaw_rate_cds*0.01f); // calculate the attitude target euler angles _attitude_target_quat.to_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); if (_rate_bf_ff_enabled & _use_ff_and_input_shaping) { // translate the roll pitch and yaw acceleration limits to the euler axis Vector3f euler_accel = euler_accel_limit(_attitude_target_euler_angle, Vector3f(get_accel_roll_max_radss(), get_accel_pitch_max_radss(), get_accel_yaw_max_radss())); // When acceleration limiting is enabled, the input shaper constrains angular acceleration, slewing // the output rate towards the input rate. _attitude_target_euler_rate.x = input_shaping_ang_vel(_attitude_target_euler_rate.x, euler_roll_rate, euler_accel.x); _attitude_target_euler_rate.y = input_shaping_ang_vel(_attitude_target_euler_rate.y, euler_pitch_rate, euler_accel.y); _attitude_target_euler_rate.z = input_shaping_ang_vel(_attitude_target_euler_rate.z, euler_yaw_rate, euler_accel.z); // Convert euler angle derivative of desired attitude into a body-frame angular velocity vector for feedforward euler_rate_to_ang_vel(_attitude_target_euler_angle, _attitude_target_euler_rate, _attitude_target_ang_vel); } else { // When feedforward is not enabled, the target euler angle is input into the target and the feedforward rate is zeroed. // Pitch angle is restricted to +- 85.0 degrees to avoid gimbal lock discontinuities. _attitude_target_euler_angle.x = wrap_PI(_attitude_target_euler_angle.x + euler_roll_rate*_dt); _attitude_target_euler_angle.y = constrain_float(_attitude_target_euler_angle.y + euler_pitch_rate*_dt, radians(-85.0f), radians(85.0f)); _attitude_target_euler_angle.z = wrap_2PI(_attitude_target_euler_angle.z + euler_yaw_rate*_dt); // Set rate feedforward requests to zero _attitude_target_euler_rate = Vector3f(0.0f, 0.0f, 0.0f); _attitude_target_ang_vel = Vector3f(0.0f, 0.0f, 0.0f); // Compute quaternion target attitude _attitude_target_quat.from_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); } // Call quaternion attitude controller attitude_controller_run_quat(); } // Command an angular velocity with angular velocity feedforward and smoothing void AC_AttitudeControl::input_rate_bf_roll_pitch_yaw(float roll_rate_bf_cds, float pitch_rate_bf_cds, float yaw_rate_bf_cds) { // Convert from centidegrees on public interface to radians float roll_rate_rads = radians(roll_rate_bf_cds*0.01f); float pitch_rate_rads = radians(pitch_rate_bf_cds*0.01f); float yaw_rate_rads = radians(yaw_rate_bf_cds*0.01f); // calculate the attitude target euler angles _attitude_target_quat.to_euler(_attitude_target_euler_angle.x, _attitude_target_euler_angle.y, _attitude_target_euler_angle.z); if (_rate_bf_ff_enabled & _use_ff_and_input_shaping) { // Compute acceleration-limited euler rates // When acceleration limiting is enabled, the input shaper constrains angular acceleration about the axis, slewing // the output rate towards the input rate. _attitude_target_ang_vel.x = input_shaping_ang_vel(_attitude_target_ang_vel.x, roll_rate_rads, get_accel_roll_max_radss()); _attitude_target_ang_vel.y = input_shaping_ang_vel(_attitude_target_ang_vel.y, pitch_rate_rads, get_accel_pitch_max_radss()); _attitude_target_ang_vel.z = input_shaping_ang_vel(_attitude_target_ang_vel.z, yaw_rate_rads, get_accel_yaw_max_radss()); // Convert body-frame angular velocity into euler angle derivative of desired attitude ang_vel_to_euler_rate(_attitude_target_euler_angle, _attitude_target_ang_vel, _attitude_target_euler_rate); } else { // When feedforward is not enabled, the quaternion is calculated and is input into the target and the feedforward rate is zeroed. Quaternion attitude_target_update_quat; attitude_target_update_quat.from_axis_angle(Vector3f(roll_rate_rads * _dt, pitch_rate_rads * _dt, yaw_rate_rads * _dt)); _attitude_target_quat = _attitude_target_quat * attitude_target_update_quat; _attitude_target_quat.normalize(); // Set rate feedforward requests to zero _attitude_target_euler_rate = Vector3f(0.0f, 0.0f, 0.0f); _attitude_target_ang_vel = Vector3f(0.0f, 0.0f, 0.0f); } // Call quaternion attitude controller attitude_controller_run_quat(); } // Calculates the body frame angular velocities to follow the target attitude void AC_AttitudeControl::attitude_controller_run_quat() { // Retrieve quaternion vehicle attitude // TODO add _ahrs.get_quaternion() Quaternion attitude_vehicle_quat; attitude_vehicle_quat.from_rotation_matrix(_ahrs.get_rotation_body_to_ned()); // Compute attitude error Vector3f attitude_error_vector; thrust_heading_rotation_angles(_attitude_target_quat, attitude_vehicle_quat, attitude_error_vector, _thrust_error_angle); // Compute the angular velocity target from the attitude error _rate_target_ang_vel = update_ang_vel_target_from_att_error(attitude_error_vector); // Add feedforward term that attempts to ensure that roll and pitch errors rotate with the body frame rather than the reference frame. _rate_target_ang_vel.x += attitude_error_vector.y * _ahrs.get_gyro().z; _rate_target_ang_vel.y += -attitude_error_vector.x * _ahrs.get_gyro().z; // Add the angular velocity feedforward, rotated into vehicle frame Quaternion attitude_target_ang_vel_quat = Quaternion(0.0f, _attitude_target_ang_vel.x, _attitude_target_ang_vel.y, _attitude_target_ang_vel.z); Quaternion attitude_error_quat = attitude_vehicle_quat.inverse() * _attitude_target_quat; Quaternion target_ang_vel_quat = attitude_error_quat.inverse()*attitude_target_ang_vel_quat*attitude_error_quat; // Correct the thrust vector and smoothly add feedforward and yaw input if(_thrust_error_angle > AC_ATTITUDE_THRUST_ERROR_ANGLE*2.0f){ _rate_target_ang_vel.z = _ahrs.get_gyro().z; }else if(_thrust_error_angle > AC_ATTITUDE_THRUST_ERROR_ANGLE){ float flip_scalar = (1.0f - (_thrust_error_angle-AC_ATTITUDE_THRUST_ERROR_ANGLE)/AC_ATTITUDE_THRUST_ERROR_ANGLE); _rate_target_ang_vel.x += target_ang_vel_quat.q2*flip_scalar; _rate_target_ang_vel.y += target_ang_vel_quat.q3*flip_scalar; _rate_target_ang_vel.z += target_ang_vel_quat.q4; _rate_target_ang_vel.z = _ahrs.get_gyro().z*(1.0-flip_scalar) + _rate_target_ang_vel.z*flip_scalar; } else { _rate_target_ang_vel.x += target_ang_vel_quat.q2; _rate_target_ang_vel.y += target_ang_vel_quat.q3; _rate_target_ang_vel.z += target_ang_vel_quat.q4; } if (_rate_bf_ff_enabled & _use_ff_and_input_shaping) { // rotate target and normalize Quaternion attitude_target_update_quat; attitude_target_update_quat.from_axis_angle(Vector3f(_attitude_target_ang_vel.x * _dt, _attitude_target_ang_vel.y * _dt, _attitude_target_ang_vel.z * _dt)); _attitude_target_quat = _attitude_target_quat * attitude_target_update_quat; _attitude_target_quat.normalize(); } } // thrust_heading_rotation_angles - calculates two ordered rotations to move the att_from_quat quaternion to the att_to_quat quaternion. // The first rotation corrects the thrust vector and the second rotation corrects the heading vector. void AC_AttitudeControl::thrust_heading_rotation_angles(Quaternion& att_to_quat, const Quaternion& att_from_quat, Vector3f& att_diff_angle, float& thrust_vec_dot) { Matrix3f att_to_rot_matrix; // earth frame to target frame att_to_quat.rotation_matrix(att_to_rot_matrix); Vector3f att_to_thrust_vec = att_to_rot_matrix*Vector3f(0.0f,0.0f,1.0f); Matrix3f att_from_rot_matrix; // earth frame to target frame att_from_quat.rotation_matrix(att_from_rot_matrix); Vector3f att_from_thrust_vec = att_from_rot_matrix*Vector3f(0.0f,0.0f,1.0f); // the cross product of the desired and target thrust vector defines the rotation vector Vector3f thrust_vec_cross = att_from_thrust_vec % att_to_thrust_vec; // the dot product is used to calculate the angle between the target and desired thrust vectors thrust_vec_dot = acosf(constrain_float(att_from_thrust_vec * att_to_thrust_vec,-1.0f,1.0f)); // Normalize the thrust rotation vector float thrust_vector_length = thrust_vec_cross.length(); if(is_zero(thrust_vector_length) || is_zero(thrust_vec_dot)){ thrust_vec_cross = Vector3f(0,0,1); thrust_vec_dot = 0.0f; }else{ thrust_vec_cross /= thrust_vector_length; } Quaternion thrust_vec_correction_quat; thrust_vec_correction_quat.from_axis_angle(thrust_vec_cross, thrust_vec_dot); thrust_vec_correction_quat = att_from_quat.inverse()*thrust_vec_correction_quat*att_from_quat; // calculate the remaining rotation required after thrust vector is rotated Quaternion heading_quat = thrust_vec_correction_quat.inverse()*att_from_quat.inverse()*att_to_quat; Vector3f rotation; thrust_vec_correction_quat.to_axis_angle(rotation); att_diff_angle.x = rotation.x; att_diff_angle.y = rotation.y; heading_quat.to_axis_angle(rotation); att_diff_angle.z = rotation.z; if(!is_zero(_p_angle_yaw.kP()) && fabsf(att_diff_angle.z) > AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS/_p_angle_yaw.kP()){ att_diff_angle.z = constrain_float(wrap_PI(att_diff_angle.z), -AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS/_p_angle_yaw.kP(), AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS/_p_angle_yaw.kP()); heading_quat.from_axis_angle(Vector3f(0.0f,0.0f,att_diff_angle.z)); att_to_quat = att_from_quat*thrust_vec_correction_quat*heading_quat; } } // calculates the velocity correction from an angle error. The angular velocity has acceleration and // deceleration limits including basic jerk limiting using smoothing_gain float AC_AttitudeControl::input_shaping_angle(float error_angle, float smoothing_gain, float accel_max, float target_ang_vel) { error_angle = wrap_PI(error_angle); // Calculate the velocity as error approaches zero with acceleration limited by accel_max_radss float ang_vel = sqrt_controller(error_angle, smoothing_gain, accel_max); // Acceleration is limited directly to smooth the beginning of the curve. float delta_ang_vel = accel_max * _dt; return constrain_float(ang_vel, target_ang_vel-delta_ang_vel, target_ang_vel+delta_ang_vel); } // limits the acceleration and deceleration of a velocity request float AC_AttitudeControl::input_shaping_ang_vel(float target_ang_vel, float desired_ang_vel, float accel_max) { if (accel_max > 0.0f) { float delta_ang_vel = accel_max * _dt; target_ang_vel += constrain_float(desired_ang_vel - target_ang_vel, -delta_ang_vel, delta_ang_vel); } else { target_ang_vel = desired_ang_vel; } return target_ang_vel; } // translates body frame acceleration limits to the euler axis Vector3f AC_AttitudeControl::euler_accel_limit(Vector3f euler_rad, Vector3f euler_accel) { float sin_phi = constrain_float(fabsf(sinf(euler_rad.x)), 0.1f, 1.0f); float cos_phi = constrain_float(fabsf(cosf(euler_rad.x)), 0.1f, 1.0f); float sin_theta = constrain_float(fabsf(sinf(euler_rad.y)), 0.1f, 1.0f); Vector3f rot_accel; if(is_zero(euler_accel.x) || is_zero(euler_accel.y) || is_zero(euler_accel.z) || (euler_accel.x < 0.0f) || (euler_accel.y < 0.0f) || (euler_accel.z < 0.0f)) { rot_accel.x = euler_accel.x; rot_accel.y = euler_accel.y; rot_accel.z = euler_accel.z; } else { rot_accel.x = euler_accel.x; rot_accel.y = MIN(euler_accel.y/cos_phi, euler_accel.z/sin_phi); rot_accel.z = MIN(MIN(euler_accel.x/sin_theta, euler_accel.y/sin_phi), euler_accel.z/cos_phi); } return rot_accel; } // Shifts earth frame yaw target by yaw_shift_cd. yaw_shift_cd should be in centidegrees and is added to the current target heading void AC_AttitudeControl::shift_ef_yaw_target(float yaw_shift_cd) { float yaw_shift = radians(yaw_shift_cd*0.01f); Quaternion _attitude_target_update_quat; _attitude_target_update_quat.from_axis_angle(Vector3f(0.0f, 0.0f, yaw_shift)); _attitude_target_quat = _attitude_target_update_quat*_attitude_target_quat; } // Convert a 321-intrinsic euler angle derivative to an angular velocity vector void AC_AttitudeControl::euler_rate_to_ang_vel(const Vector3f& euler_rad, const Vector3f& euler_rate_rads, Vector3f& ang_vel_rads) { float sin_theta = sinf(euler_rad.y); float cos_theta = cosf(euler_rad.y); float sin_phi = sinf(euler_rad.x); float cos_phi = cosf(euler_rad.x); ang_vel_rads.x = euler_rate_rads.x - sin_theta * euler_rate_rads.z; ang_vel_rads.y = cos_phi * euler_rate_rads.y + sin_phi * cos_theta * euler_rate_rads.z; ang_vel_rads.z = -sin_phi * euler_rate_rads.y + cos_theta * cos_phi * euler_rate_rads.z; } // Convert an angular velocity vector to a 321-intrinsic euler angle derivative // Returns false if the vehicle is pitched 90 degrees up or down bool AC_AttitudeControl::ang_vel_to_euler_rate(const Vector3f& euler_rad, const Vector3f& ang_vel_rads, Vector3f& euler_rate_rads) { float sin_theta = sinf(euler_rad.y); float cos_theta = cosf(euler_rad.y); float sin_phi = sinf(euler_rad.x); float cos_phi = cosf(euler_rad.x); // When the vehicle pitches all the way up or all the way down, the euler angles become discontinuous. In this case, we just return false. if (is_zero(cos_theta)) { return false; } euler_rate_rads.x = ang_vel_rads.x + sin_phi * (sin_theta/cos_theta) * ang_vel_rads.y + cos_phi * (sin_theta/cos_theta) * ang_vel_rads.z; euler_rate_rads.y = cos_phi * ang_vel_rads.y - sin_phi * ang_vel_rads.z; euler_rate_rads.z = (sin_phi / cos_theta) * ang_vel_rads.y + (cos_phi / cos_theta) * ang_vel_rads.z; return true; } // Update rate_target_ang_vel using attitude_error_rot_vec_rad Vector3f AC_AttitudeControl::update_ang_vel_target_from_att_error(Vector3f attitude_error_rot_vec_rad) { Vector3f rate_target_ang_vel; // Compute the roll angular velocity demand from the roll angle error if (_use_ff_and_input_shaping) { rate_target_ang_vel.x = sqrt_controller(attitude_error_rot_vec_rad.x, _p_angle_roll.kP(), constrain_float(get_accel_roll_max_radss()/2.0f, AC_ATTITUDE_ACCEL_RP_CONTROLLER_MIN_RADSS, AC_ATTITUDE_ACCEL_RP_CONTROLLER_MAX_RADSS)); }else{ rate_target_ang_vel.x = _p_angle_roll.kP() * attitude_error_rot_vec_rad.x; } // Compute the pitch angular velocity demand from the roll angle error if (_use_ff_and_input_shaping) { rate_target_ang_vel.y = sqrt_controller(attitude_error_rot_vec_rad.y, _p_angle_pitch.kP(), constrain_float(get_accel_pitch_max_radss()/2.0f, AC_ATTITUDE_ACCEL_RP_CONTROLLER_MIN_RADSS, AC_ATTITUDE_ACCEL_RP_CONTROLLER_MAX_RADSS)); }else{ rate_target_ang_vel.y = _p_angle_pitch.kP() * attitude_error_rot_vec_rad.y; } // Compute the yaw angular velocity demand from the roll angle error if (_use_ff_and_input_shaping) { rate_target_ang_vel.z = sqrt_controller(attitude_error_rot_vec_rad.z, _p_angle_yaw.kP(), constrain_float(get_accel_yaw_max_radss()/2.0f, AC_ATTITUDE_ACCEL_Y_CONTROLLER_MIN_RADSS, AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS)); }else{ rate_target_ang_vel.z = _p_angle_yaw.kP() * attitude_error_rot_vec_rad.z; } return rate_target_ang_vel; } // Run the roll angular velocity PID controller and return the output float AC_AttitudeControl::rate_target_to_motor_roll(float rate_target_rads) { float current_rate_rads = _ahrs.get_gyro().x; float rate_error_rads = rate_target_rads - current_rate_rads; // pass error to PID controller get_rate_roll_pid().set_input_filter_d(rate_error_rads); get_rate_roll_pid().set_desired_rate(rate_target_rads); float integrator = get_rate_roll_pid().get_integrator(); // Ensure that integrator can only be reduced if the output is saturated if (!_motors.limit.roll_pitch || ((integrator > 0 && rate_error_rads < 0) || (integrator < 0 && rate_error_rads > 0))) { integrator = get_rate_roll_pid().get_i(); } // Compute output in range -1 ~ +1 float output = get_rate_roll_pid().get_p() + integrator + get_rate_roll_pid().get_d(); // Constrain output return constrain_float(output, -1.0f, 1.0f); } // Run the pitch angular velocity PID controller and return the output float AC_AttitudeControl::rate_target_to_motor_pitch(float rate_target_rads) { float current_rate_rads = _ahrs.get_gyro().y; float rate_error_rads = rate_target_rads - current_rate_rads; // pass error to PID controller get_rate_pitch_pid().set_input_filter_d(rate_error_rads); get_rate_pitch_pid().set_desired_rate(rate_target_rads); float integrator = get_rate_pitch_pid().get_integrator(); // Ensure that integrator can only be reduced if the output is saturated if (!_motors.limit.roll_pitch || ((integrator > 0 && rate_error_rads < 0) || (integrator < 0 && rate_error_rads > 0))) { integrator = get_rate_pitch_pid().get_i(); } // Compute output in range -1 ~ +1 float output = get_rate_pitch_pid().get_p() + integrator + get_rate_pitch_pid().get_d(); // Constrain output return constrain_float(output, -1.0f, 1.0f); } // Run the yaw angular velocity PID controller and return the output float AC_AttitudeControl::rate_target_to_motor_yaw(float rate_target_rads) { float current_rate_rads = _ahrs.get_gyro().z; float rate_error_rads = rate_target_rads - current_rate_rads; // pass error to PID controller get_rate_yaw_pid().set_input_filter_all(rate_error_rads); get_rate_yaw_pid().set_desired_rate(rate_target_rads); float integrator = get_rate_yaw_pid().get_integrator(); // Ensure that integrator can only be reduced if the output is saturated if (!_motors.limit.yaw || ((integrator > 0 && rate_error_rads < 0) || (integrator < 0 && rate_error_rads > 0))) { integrator = get_rate_yaw_pid().get_i(); } // Compute output in range -1 ~ +1 float output = get_rate_yaw_pid().get_p() + integrator + get_rate_yaw_pid().get_d(); // Constrain output return constrain_float(output, -1.0f, 1.0f); } // Enable or disable body-frame feed forward void AC_AttitudeControl::accel_limiting(bool enable_limits) { if (enable_limits) { // If enabling limits, reload from eeprom or set to defaults if (is_zero(_accel_roll_max)) { _accel_roll_max.load(); } if (is_zero(_accel_pitch_max)) { _accel_pitch_max.load(); } if (is_zero(_accel_yaw_max)) { _accel_yaw_max.load(); } } else { _accel_roll_max = 0.0f; _accel_pitch_max = 0.0f; _accel_yaw_max = 0.0f; } } // Return tilt angle limit for pilot input that prioritises altitude hold over lean angle float AC_AttitudeControl::get_althold_lean_angle_max() const { // convert to centi-degrees for public interface return ToDeg(_althold_lean_angle_max) * 100.0f; } // Proportional controller with piecewise sqrt sections to constrain second derivative float AC_AttitudeControl::sqrt_controller(float error, float p, float second_ord_lim) { if (second_ord_lim < 0.0f || is_zero(second_ord_lim) || is_zero(p)) { return error*p; } float linear_dist = second_ord_lim/sq(p); if (error > linear_dist) { return safe_sqrt(2.0f*second_ord_lim*(error-(linear_dist/2.0f))); } else if (error < -linear_dist) { return -safe_sqrt(2.0f*second_ord_lim*(-error-(linear_dist/2.0f))); } else { return error*p; } } // Inverse proportional controller with piecewise sqrt sections to constrain second derivative float AC_AttitudeControl::stopping_point(float first_ord_mag, float p, float second_ord_lim) { if (second_ord_lim > 0.0f && !is_zero(second_ord_lim) && is_zero(p)) { return (first_ord_mag*first_ord_mag)/(2.0f*second_ord_lim); } else if ((second_ord_lim < 0.0f || is_zero(second_ord_lim)) && !is_zero(p)) { return first_ord_mag/p; } else if ((second_ord_lim < 0.0f || is_zero(second_ord_lim)) && is_zero(p)) { return 0.0f; } // calculate the velocity at which we switch from calculating the stopping point using a linear function to a sqrt function float linear_velocity = second_ord_lim/p; if (fabsf(first_ord_mag) < linear_velocity) { // if our current velocity is below the cross-over point we use a linear function return first_ord_mag/p; } else { float linear_dist = second_ord_lim/sq(p); float overshoot = (linear_dist/2.0f) + sq(first_ord_mag)/(2.0f*second_ord_lim); if (first_ord_mag > 0){ return overshoot; } else { return -overshoot; } } } // Return roll rate step size in centidegrees/s that results in maximum output after 4 time steps float AC_AttitudeControl::max_rate_step_bf_roll() { float alpha = get_rate_roll_pid().get_filt_alpha(); float alpha_remaining = 1-alpha; return 2.0f*_motors.get_throttle_hover()*AC_ATTITUDE_RATE_RP_CONTROLLER_OUT_MAX/((alpha_remaining*alpha_remaining*alpha_remaining*alpha*get_rate_roll_pid().kD())/_dt + get_rate_roll_pid().kP()); } // Return pitch rate step size in centidegrees/s that results in maximum output after 4 time steps float AC_AttitudeControl::max_rate_step_bf_pitch() { float alpha = get_rate_pitch_pid().get_filt_alpha(); float alpha_remaining = 1-alpha; return 2.0f*_motors.get_throttle_hover()*AC_ATTITUDE_RATE_RP_CONTROLLER_OUT_MAX/((alpha_remaining*alpha_remaining*alpha_remaining*alpha*get_rate_pitch_pid().kD())/_dt + get_rate_pitch_pid().kP()); } // Return yaw rate step size in centidegrees/s that results in maximum output after 4 time steps float AC_AttitudeControl::max_rate_step_bf_yaw() { float alpha = get_rate_yaw_pid().get_filt_alpha(); float alpha_remaining = 1-alpha; return 2.0f*_motors.get_throttle_hover()*AC_ATTITUDE_RATE_RP_CONTROLLER_OUT_MAX/((alpha_remaining*alpha_remaining*alpha_remaining*alpha*get_rate_yaw_pid().kD())/_dt + get_rate_yaw_pid().kP()); }