bizhang_-obav/src/lib/FlightTasks/tasks/AutoLineSmoothVel/FlightTaskAutoLineSmoothVel.cpp

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/**
 * @file FlightAutoLine.cpp
 */

#include "FlightTaskAutoLineSmoothVel.hpp"
#include <mathlib/mathlib.h>
#include <float.h>

using namespace matrix;

bool FlightTaskAutoLineSmoothVel::activate(vehicle_local_position_setpoint_s state_prev)
{
	bool ret = FlightTaskAutoMapper2::activate(state_prev);

	checkSetpoints(state_prev);
	const Vector3f accel_prev{state_prev.acc_x, state_prev.acc_y, state_prev.acc_z};
	const Vector3f vel_prev = Vector3f(state_prev.vx, state_prev.vy, state_prev.vz);
	const Vector3f pos_prev = Vector3f(state_prev.x, state_prev.y, state_prev.z);

	for (int i = 0; i < 3; ++i) {
		_trajectory[i].reset(accel_prev(i), vel_prev(i), pos_prev(i));
	}

	_yaw_sp_prev = _yaw;
	_updateTrajConstraints();

	return ret;
}

void FlightTaskAutoLineSmoothVel::reActivate()
{
	// On ground, reset acceleration and velocity to zero
	for (int i = 0; i < 2; ++i) {
		_trajectory[i].reset(0.f, 0.f, _position(i));
	}

	_trajectory[2].reset(0.f, 0.7f, _position(2));
}

void FlightTaskAutoLineSmoothVel::_generateSetpoints()
{
	_prepareSetpoints();
	_generateTrajectory();

	if (!PX4_ISFINITE(_yaw_setpoint) && !PX4_ISFINITE(_yawspeed_setpoint)) {
		// no valid heading -> generate heading in this flight task
		_generateHeading();
	}
}

void FlightTaskAutoLineSmoothVel::_generateHeading()
{
	// Generate heading along trajectory if possible, otherwise hold the previous yaw setpoint
	if (!_generateHeadingAlongTraj()) {
		_yaw_setpoint = _yaw_sp_prev;
	}
}

bool FlightTaskAutoLineSmoothVel::_generateHeadingAlongTraj()
{
	bool res = false;
	Vector2f vel_sp_xy(_velocity_setpoint);

	if (vel_sp_xy.length() > .1f) {
		// Generate heading from velocity vector, only if it is long enough
		_compute_heading_from_2D_vector(_yaw_setpoint, vel_sp_xy);
		res = true;
	}

	return res;
}

/* Constrain some value vith a constrain depending on the sign of the constrain
 * Example: 	- if the constrain is -5, the value will be constrained between -5 and 0
 * 		- if the constrain is 5, the value will be constrained between 0 and 5
 */
inline float FlightTaskAutoLineSmoothVel::_constrainOneSide(float val, float constrain)
{
	const float min = (constrain < FLT_EPSILON) ? constrain : 0.f;
	const float max = (constrain > FLT_EPSILON) ? constrain : 0.f;

	return math::constrain(val, min, max);
}

void FlightTaskAutoLineSmoothVel::_checkEkfResetCounters()
{
	// Check if a reset event has happened.
	if (_sub_vehicle_local_position->get().xy_reset_counter != _reset_counters.xy) {
		_trajectory[0].setCurrentPosition(_position(0));
		_trajectory[1].setCurrentPosition(_position(1));
		_reset_counters.xy = _sub_vehicle_local_position->get().xy_reset_counter;
	}

	if (_sub_vehicle_local_position->get().vxy_reset_counter != _reset_counters.vxy) {
		_trajectory[0].setCurrentVelocity(_velocity(0));
		_trajectory[1].setCurrentVelocity(_velocity(1));
		_reset_counters.vxy = _sub_vehicle_local_position->get().vxy_reset_counter;
	}

	if (_sub_vehicle_local_position->get().z_reset_counter != _reset_counters.z) {
		_trajectory[2].setCurrentPosition(_position(2));
		_reset_counters.z = _sub_vehicle_local_position->get().z_reset_counter;
	}

	if (_sub_vehicle_local_position->get().vz_reset_counter != _reset_counters.vz) {
		_trajectory[2].setCurrentVelocity(_velocity(2));
		_reset_counters.vz = _sub_vehicle_local_position->get().vz_reset_counter;
	}
}

void FlightTaskAutoLineSmoothVel::_prepareSetpoints()
{
	// Interface: A valid position setpoint generates a velocity target using a P controller. If a velocity is specified
	// that one is used as a velocity limit.
	// If the position setpoints are set to NAN, the values in the velocity setpoints are used as velocity targets: nothing to do here.

	_checkEkfResetCounters();
	_want_takeoff = false;

	if (_param_mpc_yaw_mode.get() == 4 && !_yaw_sp_aligned) {
		// Wait for the yaw setpoint to be aligned
		_velocity_setpoint.setAll(0.f);

	} else {
		if (PX4_ISFINITE(_position_setpoint(0)) &&
		    PX4_ISFINITE(_position_setpoint(1))) {
			// Use position setpoints to generate velocity setpoints

			// Get various path specific vectors. */
			Vector2f pos_traj;
			pos_traj(0) = _trajectory[0].getCurrentPosition();
			pos_traj(1) = _trajectory[1].getCurrentPosition();
			Vector2f pos_sp_xy(_position_setpoint);
			Vector2f pos_traj_to_dest(pos_sp_xy - pos_traj);
			Vector2f u_prev_to_dest = Vector2f(pos_sp_xy - Vector2f(_prev_wp)).unit_or_zero();
			Vector2f prev_to_pos(pos_traj - Vector2f(_prev_wp));
			Vector2f closest_pt = Vector2f(_prev_wp) + u_prev_to_dest * (prev_to_pos * u_prev_to_dest);
			Vector2f u_pos_traj_to_dest_xy(Vector2f(pos_traj_to_dest).unit_or_zero());

			// Compute the maximum possible velocity on the track given the remaining distance, the maximum acceleration and the maximum jerk.
			// We assume a constant acceleration profile with a delay of 2*accel/jerk (time to reach the desired acceleration from opposite max acceleration)
			// Equation to solve: 0 = vel^2 - 2*acc*(x - vel*2*acc/jerk)
			// To avoid high gain at low distance due to the sqrt, we take the minimum of this velocity and a slope of "traj_p" m/s per meter
			float b = 4.f * _param_mpc_acc_hor.get() * _param_mpc_acc_hor.get() / _param_mpc_jerk_auto.get();
			float c = - 2.f * _param_mpc_acc_hor.get() * pos_traj_to_dest.length();
			float max_speed = 0.5f * (-b + sqrtf(b * b - 4.f * c));
			float speed_sp_track = math::min(max_speed, pos_traj_to_dest.length() * _param_mpc_xy_traj_p.get());
			speed_sp_track = math::constrain(speed_sp_track, 0.0f, _mc_cruise_speed);

			Vector2f vel_sp_xy = u_pos_traj_to_dest_xy * speed_sp_track;

			for (int i = 0; i < 2; i++) {
				// If available, constrain the velocity using _velocity_setpoint(.)
				if (PX4_ISFINITE(_velocity_setpoint(i))) {
					_velocity_setpoint(i) = _constrainOneSide(vel_sp_xy(i), _velocity_setpoint(i));

				} else {
					_velocity_setpoint(i) = vel_sp_xy(i);
				}

				_velocity_setpoint(i) += (closest_pt(i) - _trajectory[i].getCurrentPosition()) *
							 _param_mpc_xy_traj_p.get();  // Along-track setpoint + cross-track P controller
			}

		}

		if (PX4_ISFINITE(_position_setpoint(2))) {
			const float vel_sp_z = (_position_setpoint(2) - _trajectory[2].getCurrentPosition()) *
					       _param_mpc_z_traj_p.get(); // Generate a velocity target for the trajectory using a simple P loop

			// If available, constrain the velocity using _velocity_setpoint(.)
			if (PX4_ISFINITE(_velocity_setpoint(2))) {
				_velocity_setpoint(2) = _constrainOneSide(vel_sp_z, _velocity_setpoint(2));

			} else {
				_velocity_setpoint(2) = vel_sp_z;
			}

			_want_takeoff = _velocity_setpoint(2) < -0.3f;
		}
	}
}

void FlightTaskAutoLineSmoothVel::_updateTrajConstraints()
{
	// Update the constraints of the trajectories
	_trajectory[0].setMaxAccel(_param_mpc_acc_hor.get()); // TODO : Should be computed using heading
	_trajectory[1].setMaxAccel(_param_mpc_acc_hor.get());
	_trajectory[0].setMaxVel(_param_mpc_xy_vel_max.get());
	_trajectory[1].setMaxVel(_param_mpc_xy_vel_max.get());
	_trajectory[0].setMaxJerk(_param_mpc_jerk_auto.get()); // TODO : Should be computed using heading
	_trajectory[1].setMaxJerk(_param_mpc_jerk_auto.get());
	_trajectory[2].setMaxJerk(_param_mpc_jerk_auto.get());

	if (_velocity_setpoint(2) < 0.f) { // up
		_trajectory[2].setMaxAccel(_param_mpc_acc_up_max.get());
		_trajectory[2].setMaxVel(_param_mpc_z_vel_max_up.get());

	} else { // down
		_trajectory[2].setMaxAccel(_param_mpc_acc_down_max.get());
		_trajectory[2].setMaxVel(_param_mpc_z_vel_max_dn.get());
	}
}

void FlightTaskAutoLineSmoothVel::_generateTrajectory()
{
	if (!PX4_ISFINITE(_velocity_setpoint(0)) || !PX4_ISFINITE(_velocity_setpoint(1))
	    || !PX4_ISFINITE(_velocity_setpoint(2))) {
		return;
	}

	/* Slow down the trajectory by decreasing the integration time based on the position error.
	 * This is only performed when the drone is behind the trajectory
	 */
	Vector2f position_trajectory_xy(_trajectory[0].getCurrentPosition(), _trajectory[1].getCurrentPosition());
	Vector2f position_xy(_position);
	Vector2f vel_traj_xy(_trajectory[0].getCurrentVelocity(), _trajectory[1].getCurrentVelocity());
	Vector2f drone_to_trajectory_xy(position_trajectory_xy - position_xy);
	float position_error = drone_to_trajectory_xy.length();

	float time_stretch = 1.f - math::constrain(position_error * 0.5f, 0.f, 1.f);

	// Don't stretch time if the drone is ahead of the position setpoint
	if (drone_to_trajectory_xy.dot(vel_traj_xy) < 0.f) {
		time_stretch = 1.f;
	}

	Vector3f jerk_sp_smooth;
	Vector3f accel_sp_smooth;
	Vector3f vel_sp_smooth;
	Vector3f pos_sp_smooth;

	for (int i = 0; i < 3; ++i) {
		_trajectory[i].integrate(_deltatime, time_stretch, accel_sp_smooth(i), vel_sp_smooth(i), pos_sp_smooth(i));
		jerk_sp_smooth(i) = _trajectory[i].getCurrentJerk();
	}

	_updateTrajConstraints();

	// If the acceleration and velocities are small and that we want to stop, reduce the amplitude of the jerk signal
	// to help the optimizer to converge towards zero
	if (Vector2f(_velocity_setpoint).length() < (0.01f * _param_mpc_xy_traj_p.get())
	    && Vector2f(accel_sp_smooth).length() < 0.2f
	    && Vector2f(vel_sp_smooth).length() < 0.1f) {
		_trajectory[0].setMaxJerk(1.f);
		_trajectory[1].setMaxJerk(1.f);
	}

	for (int i = 0; i < 3; ++i) {
		_trajectory[i].updateDurations(_deltatime, _velocity_setpoint(i));
	}

	VelocitySmoothing::timeSynchronization(_trajectory, 2); // Synchronize x and y only

	_jerk_setpoint = jerk_sp_smooth;
	_acceleration_setpoint = accel_sp_smooth;
	_velocity_setpoint = vel_sp_smooth;
	_position_setpoint = pos_sp_smooth;
}