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AC_AttitudeControl: Seperate thrust vector correction into a separate function

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Leonard Hall 2021-04-15 00:50:26 +09:30 committed by Peter Barker
parent 5b0f107631
commit 86a157ce59
2 changed files with 51 additions and 36 deletions
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75
libraries/AC_AttitudeControl/AC_AttitudeControl.cpp
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@ -608,7 +608,7 @@ void AC_AttitudeControl::attitude_controller_run_quat()
// Compute attitude error
Vector3f attitude_error_vector;
thrust_heading_rotation_angles(_attitude_target_quat, attitude_vehicle_quat, attitude_error_vector, _thrust_error_angle);
thrust_heading_rotation_angles(_attitude_target_quat, attitude_vehicle_quat, attitude_error_vector, _thrust_angle, _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);
@ -618,7 +618,11 @@ void AC_AttitudeControl::attitude_controller_run_quat()
// 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);
// rotation from the target frame to the vehicle frame
Quaternion to_to_from_quat = attitude_vehicle_quat.inverse() * _attitude_target_quat;
// target angle velocity vector in the vehicle frame
Quaternion desired_ang_vel_quat = to_to_from_quat * attitude_target_ang_vel_quat * to_to_from_quat.inverse();
// Correct the thrust vector and smoothly add feedforward and yaw input
@ -645,71 +649,78 @@ void AC_AttitudeControl::attitude_controller_run_quat()
_attitude_target_quat.normalize();
}
// ensure Quaternions stay normalized
// ensure Quaternion stay normalised
_attitude_target_quat.normalize();
// Record error to handle EKF resets
_attitude_ang_error = attitude_vehicle_quat.inverse() * _attitude_target_quat;
}
// 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& attitude_target_quat, const Quaternion& attitude_vehicle_quat, Vector3f& attitude_error_vector, float& thrust_error_angle)
// thrust_heading_rotation_angles - calculates two ordered rotations to move the attitude_vehicle_quat quaternion to the attitude_target_quat quaternion.
// The maximum error in the yaw axis is limited based on the angle yaw P value and acceleration.
void AC_AttitudeControl::thrust_heading_rotation_angles(Quaternion& attitude_target_quat, const Quaternion& attitude_vehicle_quat, Vector3f& attitude_error_vector, float& thrust_angle, float& thrust_error_angle)
{
Matrix3f att_to_rot_matrix; // rotation from the target body frame to the inertial frame.
attitude_target_quat.rotation_matrix(att_to_rot_matrix);
Vector3f att_to_thrust_vec = att_to_rot_matrix * Vector3f(0.0f, 0.0f, 1.0f);
Quaternion thrust_vec_correction_quat;
thrust_vector_rotation_angles(attitude_target_quat, attitude_vehicle_quat, thrust_vec_correction_quat, attitude_error_vector, thrust_angle, thrust_error_angle);
Matrix3f att_from_rot_matrix; // rotation from the current body frame to the inertial frame.
attitude_vehicle_quat.rotation_matrix(att_from_rot_matrix);
Vector3f att_from_thrust_vec = att_from_rot_matrix * Vector3f(0.0f, 0.0f, 1.0f);
// Todo: Limit roll an pitch error based on output saturation and maximum error.
// Limit Yaw Error based on maximum acceleration - Update to include output saturation and maximum error.
// Currently the limit is based on the maximum acceleration using the linear part of the SQRT controller.
// This should be updated to be based on an angle limit, saturation, or unlimited based on user defined parameters.
Quaternion yaw_vec_correction_quat;
if (!is_zero(_p_angle_yaw.kP()) && fabsf(attitude_error_vector.z) > AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS / _p_angle_yaw.kP()) {
attitude_error_vector.z = constrain_float(wrap_PI(attitude_error_vector.z), -AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS / _p_angle_yaw.kP(), AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS / _p_angle_yaw.kP());
yaw_vec_correction_quat.from_axis_angle(Vector3f(0.0f, 0.0f, attitude_error_vector.z));
attitude_target_quat = attitude_vehicle_quat * thrust_vec_correction_quat * yaw_vec_correction_quat;
}
}
// thrust_vector_rotation_angles - calculates two ordered rotations to move the attitude_vehicle_quat quaternion to the attitude_target_quat quaternion.
// The first rotation corrects the thrust vector and the second rotation corrects the heading vector.
void AC_AttitudeControl::thrust_vector_rotation_angles(const Quaternion& attitude_target_quat, const Quaternion& attitude_vehicle_quat, Quaternion& thrust_vec_correction_quat, Vector3f& attitude_error_vector, float& thrust_angle, float& thrust_error_angle)
{
Matrix3f att_target_rot_matrix; // rotation from the inertial frame to the target body frame.
attitude_target_quat.rotation_matrix(att_target_rot_matrix);
Vector3f att_target_thrust_vec = att_target_rot_matrix * Vector3f(0.0f, 0.0f, -1.0f); // target thrust vector
Matrix3f att_vehicle_rot_matrix; // rotation from the inertial frame to the vehicle body frame.
attitude_vehicle_quat.rotation_matrix(att_vehicle_rot_matrix);
Vector3f att_vehicle_thrust_vec = att_vehicle_rot_matrix * Vector3f(0.0f, 0.0f, -1.0f); // current thrust vector
// the dot product is used to calculate the current lean angle for use of external functions
_thrust_angle = acosf(constrain_float(Vector3f(0.0f,0.0f,1.0f) * att_from_thrust_vec,-1.0f,1.0f));
thrust_angle = acosf(constrain_float(Vector3f(0.0f,0.0f,1.0f) * att_vehicle_thrust_vec,-1.0f,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;
Vector3f thrust_vec_cross = att_vehicle_thrust_vec % att_target_thrust_vec;
// the dot product is used to calculate the angle between the target and desired thrust vectors
thrust_error_angle = acosf(constrain_float(att_from_thrust_vec * att_to_thrust_vec, -1.0f, 1.0f));
thrust_error_angle = acosf(constrain_float(att_vehicle_thrust_vec * att_target_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_error_angle)) {
thrust_vec_cross = Vector3f(0, 0, 1);
thrust_error_angle = 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_error_angle);
// Rotate thrust_vec_correction_quat to the att_from frame
// Rotate thrust_vec_correction_quat to the att_vehicle frame
thrust_vec_correction_quat = attitude_vehicle_quat.inverse() * thrust_vec_correction_quat * attitude_vehicle_quat;
// calculate the remaining rotation required after thrust vector is rotated transformed to the att_from frame
Quaternion yaw_vec_correction_quat = thrust_vec_correction_quat.inverse() * attitude_vehicle_quat.inverse() * attitude_target_quat;
// calculate the angle error in x and y.
Vector3f rotation;
thrust_vec_correction_quat.to_axis_angle(rotation);
attitude_error_vector.x = rotation.x;
attitude_error_vector.y = rotation.y;
// calculate the remaining rotation required after thrust vector is rotated transformed to the att_vehicle frame
Quaternion heading_vec_correction_quat = thrust_vec_correction_quat.inverse() * attitude_vehicle_quat.inverse() * attitude_target_quat;
// calculate the angle error in z (x and y should be zero here).
yaw_vec_correction_quat.to_axis_angle(rotation);
heading_vec_correction_quat.to_axis_angle(rotation);
attitude_error_vector.z = rotation.z;
// Todo: Limit roll an pitch error based on output saturation and maximum error.
// Limit Yaw Error based on maximum acceleration - Update to include output saturation and maximum error.
// Currently the limit is based on the maximum acceleration using the linear part of the SQRT controller.
// This should be updated to be based on an angle limit, saturation, or unlimited based on user defined parameters.
if (!is_zero(_p_angle_yaw.kP()) && fabsf(attitude_error_vector.z) > AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS / _p_angle_yaw.kP()) {
attitude_error_vector.z = constrain_float(wrap_PI(attitude_error_vector.z), -AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS / _p_angle_yaw.kP(), AC_ATTITUDE_ACCEL_Y_CONTROLLER_MAX_RADSS / _p_angle_yaw.kP());
yaw_vec_correction_quat.from_axis_angle(Vector3f(0.0f, 0.0f, attitude_error_vector.z));
attitude_target_quat = attitude_vehicle_quat * thrust_vec_correction_quat * yaw_vec_correction_quat;
}
}
// calculates the velocity correction from an angle error. The angular velocity has acceleration and

12
libraries/AC_AttitudeControl/AC_AttitudeControl.h
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@ -298,13 +298,17 @@ public:
// translates body frame acceleration limits to the euler axis
Vector3f euler_accel_limit(const Vector3f &euler_rad, const Vector3f &euler_accel);
// 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 thrust_heading_rotation_angles(Quaternion& attitude_target_quat, const Quaternion& attitude_vehicle_quat, Vector3f& attitude_error_vector, float& thrust_error_angle);
// Calculates the body frame angular velocities to follow the target attitude
void attitude_controller_run_quat();
// thrust_heading_rotation_angles - calculates two ordered rotations to move the attitude_vehicle_quat quaternion to the attitude_target_quat quaternion.
// The maximum error in the yaw axis is limited based on the angle yaw P value and acceleration.
void thrust_heading_rotation_angles(Quaternion& attitude_target_quat, const Quaternion& attitude_vehicle_quat, Vector3f& attitude_error_vector, float& thrust_angle, float& thrust_error_angle);
// thrust_vector_rotation_angles - calculates two ordered rotations to move the attitude_vehicle_quat quaternion to the attitude_target_quat quaternion.
// The first rotation corrects the thrust vector and the second rotation corrects the heading vector.
void thrust_vector_rotation_angles(const Quaternion& attitude_target_quat, const Quaternion& attitude_vehicle_quat, Quaternion& thrust_vec_correction_quat, Vector3f& rotation, float& thrust_angle, float& thrust_error_angle);
// sanity check parameters. should be called once before take-off
virtual void parameter_sanity_check() {}