Estimator Base

Overview

The estimator base implements the basic ROS interfaces for the estimator. This includes setting up subscribers, publishers and initializing parameter management. The idea of the base class, is that all interfacing with ROS and shared resources across all inheritance levels happens or are contained in this class.

ROS Interfaces

The estimator has the following ROS interfaces.

Figure 1: Estimator's ROS interactions.

The estimator has several ROS interfaces that are tracked as member variables of the estimator_base class. They are summarized in the table below:

ROS Interface	Topic	Explanation	Message Type
vehicle_state_pub_	/estimated_state	Publishes the estimated state of the vehicle.	State.msg
gnss_fix_sub_	/navsat_compat/fix	Subcribes to the GNSS position information.	NavSatFix.msg
gnss_vel_sub_	/navsat_compat/vel	Subcribes to the GNSS velocity information.	TwistStamped.msg
imu_sub_	/imu/data	Subcribes to the IMU data (both Gyro and Accel).	Imu.msg
baro_sub_	/baro	Subcribes to the barometer pressure information.	Barometer.msg
airspeed_sub_	/airspeed	Subcribes to the differential pressure information.	Airspeed.msg
status_sub_	/status	Subcribes to the aircraft status information.	Status.msg

Note

The NavSatFix, TwistStamped and Imu messages are from standard ROS message packages. Barometer, Airspeed and Status messages are from rosflight_msgs.

Parameters

Parameter	Explanation	Type	Range
rho	The density of the air.	double	~1.225 $\frac{kg}{m^3}$
gravity	The acceleration due to gravity.	double	~9.81 $\frac{m}{s^2}$
estimator_update_frequency	The frequency that the estimator will run estimations.	double	$\geq 100$ Hz
gps_ground_speed_threshold	This determines when the aircraft is moving fast enough to get a course estimate.	double	$\geq$ 0.3 $\frac{m}{s}$
baro_measurement_gate	The maximum allowable instantaneous change in barometer pressure measurement.	double	~1 meter
airspeed_measurement_gate	The maximum allowable instantaneous change in differential pressure measurement.	double	~5 $\frac{m}{s}$
baro_calibration_count	The number of barometer measurements used to do calibration.	int	$\geq 100$

Modifying the Estimator

Update when full state estimator and continuous-discrete are both implemented and a swap between them works.