PX4-Autopilot/src/lib/CollisionPrevention/CollisionPrevention.cpp

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/**
 * @file CollisionPrevention.cpp
 * CollisionPrevention controller.
 *
 */

#include <CollisionPrevention/CollisionPrevention.hpp>
using namespace matrix;
using namespace time_literals;


CollisionPrevention::CollisionPrevention(ModuleParams *parent) :
	ModuleParams(parent)
{
}

CollisionPrevention::~CollisionPrevention()
{
	//unadvertise publishers
	if (_mavlink_log_pub != nullptr) {
		orb_unadvertise(_mavlink_log_pub);
	}
}

void CollisionPrevention::publishConstrainedSetpoint(const Vector2f &original_setpoint,
		const Vector2f &adapted_setpoint)
{
	collision_constraints_s	constraints{};	/**< collision constraints message */

	//fill in values
	constraints.timestamp = hrt_absolute_time();

	constraints.original_setpoint[0] = original_setpoint(0);
	constraints.original_setpoint[1] = original_setpoint(1);
	constraints.adapted_setpoint[0] = adapted_setpoint(0);
	constraints.adapted_setpoint[1] = adapted_setpoint(1);

	// publish constraints
	if (_constraints_pub != nullptr) {
		orb_publish(ORB_ID(collision_constraints), _constraints_pub, &constraints);

	} else {
		_constraints_pub = orb_advertise(ORB_ID(collision_constraints), &constraints);
	}
}

void CollisionPrevention::publishObstacleDistance(obstacle_distance_s &obstacle)
{
	// publish fused obtacle distance message with data from offboard obstacle_distance and distance sensor
	if (_obstacle_distance_pub != nullptr) {
		orb_publish(ORB_ID(obstacle_distance_fused), _obstacle_distance_pub, &obstacle);

	} else {
		_obstacle_distance_pub = orb_advertise(ORB_ID(obstacle_distance_fused), &obstacle);
	}
}

void CollisionPrevention::updateOffboardObstacleDistance(obstacle_distance_s &obstacle)
{
	_sub_obstacle_distance.update();
	const obstacle_distance_s &obstacle_distance = _sub_obstacle_distance.get();

	// Update with offboard data if the data is not stale
	if (hrt_elapsed_time(&obstacle_distance.timestamp) < RANGE_STREAM_TIMEOUT_US) {
		obstacle = obstacle_distance;
	}
}

void CollisionPrevention::updateDistanceSensor(obstacle_distance_s &obstacle)
{
	for (unsigned i = 0; i < ORB_MULTI_MAX_INSTANCES; i++) {
		// _sub_distance_sensor[i].update();
		// const distance_sensor_s &distance_sensor = _sub_distance_sensor[i].get();
		distance_sensor_s distance_sensor;
		_sub_distance_sensor[i].copy(&distance_sensor);

		// consider only instaces with updated, valid data and orientations useful for collision prevention
		if ((hrt_elapsed_time(&distance_sensor.timestamp) < RANGE_STREAM_TIMEOUT_US) &&
		    (distance_sensor.orientation != distance_sensor_s::ROTATION_DOWNWARD_FACING) &&
		    (distance_sensor.orientation != distance_sensor_s::ROTATION_UPWARD_FACING)) {


			if (obstacle.increment > 0) {
				// data from companion
				obstacle.timestamp = math::min(obstacle.timestamp, distance_sensor.timestamp);
				obstacle.max_distance = math::max((int)obstacle.max_distance,
								  (int)distance_sensor.max_distance * 100);
				obstacle.min_distance = math::min((int)obstacle.min_distance,
								  (int)distance_sensor.min_distance * 100);
				// since the data from the companion are already in the distances data structure,
				// keep the increment that is sent
				obstacle.angle_offset = 0.f; //companion not sending this field (needs mavros update)

			} else {
				obstacle.timestamp = distance_sensor.timestamp;
				obstacle.max_distance = distance_sensor.max_distance * 100; // convert to cm
				obstacle.min_distance = distance_sensor.min_distance * 100; // convert to cm
				memset(&obstacle.distances[0], UINT16_MAX, sizeof(obstacle.distances));
				obstacle.increment = math::degrees(distance_sensor.h_fov);
				obstacle.angle_offset = 0.f;
			}

			if ((distance_sensor.current_distance > distance_sensor.min_distance) &&
			    (distance_sensor.current_distance < distance_sensor.max_distance)) {

				float sensor_yaw_body_rad = sensorOrientationToYawOffset(distance_sensor, obstacle.angle_offset);

				matrix::Quatf attitude = Quatf(_sub_vehicle_attitude.get().q);
				// convert the sensor orientation from body to local frame in the range [0, 360]
				float sensor_yaw_local_deg  = math::degrees(wrap_2pi(Eulerf(attitude).psi() + sensor_yaw_body_rad));

				// calculate the field of view boundary bin indices
				int lower_bound = (int)floor((sensor_yaw_local_deg  - math::degrees(distance_sensor.h_fov / 2.0f)) /
							     obstacle.increment);
				int upper_bound = (int)floor((sensor_yaw_local_deg  + math::degrees(distance_sensor.h_fov / 2.0f)) /
							     obstacle.increment);

				// if increment is lower than 5deg, use an offset
				const int distances_array_size = sizeof(obstacle.distances) / sizeof(obstacle.distances[0]);

				if (((lower_bound < 0 || upper_bound < 0) || (lower_bound >= distances_array_size
						|| upper_bound >= distances_array_size)) && obstacle.increment < 5.f) {
					obstacle.angle_offset = sensor_yaw_local_deg ;
					upper_bound  = abs(upper_bound - lower_bound);
					lower_bound  = 0;
				}

				for (int bin = lower_bound; bin <= upper_bound; ++bin) {
					int wrap_bin = bin;

					if (wrap_bin < 0) {
						// wrap bin index around the array
						wrap_bin = (int)floor(360.f / obstacle.increment) + bin;
					}

					if (wrap_bin >= distances_array_size) {
						// wrap bin index around the array
						wrap_bin = bin - distances_array_size;
					}

					// rotate vehicle attitude into the sensor body frame
					matrix::Quatf attitude_sensor_frame = attitude;
					attitude_sensor_frame.rotate(Vector3f(0.f, 0.f, sensor_yaw_body_rad));

					// compensate measurement for vehicle tilt and convert to cm
					obstacle.distances[wrap_bin] = math::min((int)obstacle.distances[wrap_bin],
								       (int)(100 * distance_sensor.current_distance * cosf(Eulerf(attitude_sensor_frame).theta())));
				}
			}
		}
	}

	publishObstacleDistance(obstacle);
}

void CollisionPrevention::calculateConstrainedSetpoint(Vector2f &setpoint,
		const Vector2f &curr_pos, const Vector2f &curr_vel)
{
	obstacle_distance_s obstacle = {};
	updateOffboardObstacleDistance(obstacle);
	updateDistanceSensor(obstacle);

	//The maximum velocity formula contains a square root, therefore the whole calculation is done with squared norms.
	//that way the root does not have to be calculated for every range bin but once at the end.
	float setpoint_length = setpoint.norm();
	Vector2f setpoint_sqrd = setpoint * setpoint_length;

	//Limit the deviation of the adapted setpoint from the originally given joystick input (slightly less than 90 degrees)
	float max_slide_angle_rad = 0.5f;

	if (hrt_elapsed_time(&obstacle.timestamp) < RANGE_STREAM_TIMEOUT_US) {
		if (setpoint_length > 0.001f) {

			int distances_array_size = sizeof(obstacle.distances) / sizeof(obstacle.distances[0]);

			for (int i = 0; i < distances_array_size; i++) {

				if (obstacle.distances[i] < obstacle.max_distance &&
				    obstacle.distances[i] > obstacle.min_distance && (float)i * obstacle.increment < 360.f) {
					float distance = obstacle.distances[i] / 100.0f; //convert to meters
					float angle = math::radians((float)i * obstacle.increment);

					if (obstacle.angle_offset > 0.f) {
						angle += math::radians(obstacle.angle_offset);
					}

					//split current setpoint into parallel and orthogonal components with respect to the current bin direction
					Vector2f bin_direction = {cos(angle), sin(angle)};
					Vector2f orth_direction = {-bin_direction(1), bin_direction(0)};
					float sp_parallel = setpoint_sqrd.dot(bin_direction);
					float sp_orth = setpoint_sqrd.dot(orth_direction);
					float curr_vel_parallel = math::max(0.f, curr_vel.dot(bin_direction));

					//calculate max allowed velocity with a P-controller (same gain as in the position controller)
					float delay_distance = curr_vel_parallel * _param_mpc_col_prev_dly.get();
					float vel_max_posctrl = math::max(0.f,
									  _param_mpc_xy_p.get() * (distance - _param_mpc_col_prev_d.get() - delay_distance));
					float vel_max_sqrd = vel_max_posctrl * vel_max_posctrl;

					//limit the setpoint to respect vel_max by subtracting from the parallel component
					if (sp_parallel > vel_max_sqrd) {
						Vector2f setpoint_temp = setpoint_sqrd - (sp_parallel - vel_max_sqrd) * bin_direction;
						float setpoint_temp_length = setpoint_temp.norm();

						//limit sliding angle
						float angle_diff_temp_orig = acos(setpoint_temp.dot(setpoint) / (setpoint_temp_length * setpoint_length));
						float angle_diff_temp_bin = acos(setpoint_temp.dot(bin_direction) / setpoint_temp_length);

						if (angle_diff_temp_orig > max_slide_angle_rad && setpoint_temp_length > 0.001f) {
							float angle_temp_bin_cropped = angle_diff_temp_bin - (angle_diff_temp_orig - max_slide_angle_rad);
							float orth_len = vel_max_sqrd * tan(angle_temp_bin_cropped);

							if (sp_orth > 0) {
								setpoint_temp = vel_max_sqrd * bin_direction + orth_len * orth_direction;

							} else {
								setpoint_temp = vel_max_sqrd * bin_direction - orth_len * orth_direction;
							}
						}

						setpoint_sqrd = setpoint_temp;
					}
				}
			}

			//take the squared root
			if (setpoint_sqrd.norm() > 0.001f) {
				setpoint = setpoint_sqrd / std::sqrt(setpoint_sqrd.norm());

			} else {
				setpoint.zero();
			}
		}

	} else if (_last_message + MESSAGE_THROTTLE_US < hrt_absolute_time()) {
		mavlink_log_critical(&_mavlink_log_pub, "No range data received");
		_last_message = hrt_absolute_time();
	}
}

void CollisionPrevention::modifySetpoint(Vector2f &original_setpoint, const float max_speed,
		const Vector2f &curr_pos, const Vector2f &curr_vel)
{
	//calculate movement constraints based on range data
	Vector2f new_setpoint = original_setpoint;
	calculateConstrainedSetpoint(new_setpoint, curr_pos, curr_vel);

	//warn user if collision prevention starts to interfere
	bool currently_interfering = (new_setpoint(0) < original_setpoint(0) - 0.05f * max_speed
				      || new_setpoint(0) > original_setpoint(0) + 0.05f * max_speed
				      || new_setpoint(1) < original_setpoint(1) - 0.05f * max_speed
				      || new_setpoint(1) > original_setpoint(1) + 0.05f * max_speed);

	if (currently_interfering && (currently_interfering != _interfering)) {
		mavlink_log_critical(&_mavlink_log_pub, "Collision Warning");
	}

	_interfering = currently_interfering;
	publishConstrainedSetpoint(original_setpoint, new_setpoint);
	original_setpoint = new_setpoint;
}