A finite sate machine for driving a mobile robot towards a target. More...

Namespaces
	bug0

Functions
def	bug0.new_random_target ()
	Get a new randomly-chosen target. More...

def	bug0.change_state (state)
	Change the state of the node. More...

def	bug0.normalize_angle (angle)
	Normalize an angle in [-pi, pi]. More...

def	bug0.srv_bug0_switch (data)
	Turn on or off the node. More...

def	bug0.srv_bug0_status (empty)
	Get the status of the service. More...

def	bug0.clbk_odom (msg)
	Get the actual posture. More...

def	bug0.clbk_laser (msg)
	Get the laser measurements. More...

def	bug0.main ()
	The main section of the Bug0 algorithm. More...

def	bug0.cbk_on_shutdown ()
	Called on the shutdown of the node. More...

Variables
string	bug0.node_name = "bug0"
	name of this node More...

string	bug0.name_bug0_switch = "/bug0_switch"
	name of the service 'bug0_switch' More...

string	bug0.name_bug0_status = "/bug0_status"
	name of the service 'bug0_status' More...

string	bug0.name_get_point = "/get_point"
	name of the service 'get_point' More...

	bug0.srv_get_point = None
	call-point of the service 'get_point' More...

bool	bug0.service_active = False
	Is the service active? More...

bool	bug0.only_once = False
	Only_once mode (see bug0_switch service) More...

	bug0.pub = None
	handler for the topic 'cmd_vel' (Publisher) More...

int	bug0.yaw_ = 0
	Actual orientation wrt 'z' axis. More...

	bug0.position_ = Point()
	actual position More...

	bug0.desired_position_ = Point()
	target position More...

	bug0.regions_ = None
	Laser regions. More...

list	bug0.state_desc_ = ['Go to point', 'wall following', 'target reached']
	Status labels. More...

int	bug0.state_ = 0
	Actual status. More...

int	bug0.err_pos = -1
	distance from the target More...

float	bug0.max_tolerance_target = 0.5
	Tolerance on the distance from the target. More...

	bug0.srv_client_go_to_point_ = None
	call-point of the service 'go_to_point_switch' More...

	bug0.srv_client_wall_follower_ = None
	call-point of the service 'wall_follow_switch' More...

	bug0.sub_laser = rospy.Subscriber('/scan', LaserScan, clbk_laser)

	bug0.sub_odom = rospy.Subscriber('/odom', Odometry, clbk_odom)

Detailed Description

A finite sate machine for driving a mobile robot towards a target.

Authors: Prof. Carmine Recchiuto (first version), Francesco Ganci (S4143910) (Service version)

Version: 2.0

Date: 2021-06-25

The node implements a simple planning algorithm, an alternative to move_base. It works under the assumptions that a robot has a good odometry (see SLAM_gmapping) and has laser sensors.
Formally speaking, the node is a finite state machine, reacting to the sensor and to the distance from a given target:

State 0 : the robot goes straight until it finds a wall
State 1 : the robot follows the wall, see wall_follow_service_m.py
State 2 : the robot has "reached" the target (i.e. the robot is close enough to the target position)

The node can be turned on and off, exposing a service interface quite similar (architecturally speaking) to the node reach_random_pos_service.py .
Two behaviours are implemented here:

ask for a random target, then try and reach it
given a target via parameter server, try and reach the target.

When turned off, the service immediately blocks the robot in the actual position.
Note that this node doesn't directly publish the velocity to the simulated environment, rather it uses the nodes wall_follow_service_m.py and go_to_point_service_m.py for the low-level control.

See also: wall_follow_service_m.py the wall follower component; go_to_point_service_m.py the go to point component; reach_random_pos_service.py an alternative service using move_base

Related services:

Definition in file bug0.py.

Namespaces

Functions

Variables

Detailed Description