- Team Members: Edoardo Fullin (10677606), Daniele Gazzola (10674966)
- src: contains project source code
- srv: contains definition for the reset service
- msg: contains definition for custom messages (in this case Wheel.msg)
- launch: contains launch files for the project
- cfg: contains the python script to generate dynamic reconfigure headers for odometry
Note: Angles are always expressed in radians, except for the debug messages on the console where they are converted in degrees.
We provide two launch files, project_nobag.launch launches without a bag (the bag must be run separately) while project_bag.launch also launches the rosbag play command and the bag specified in the bag argument (which must be present in bags folder and is not included in the submission). project_bag.launch was used for easier debugging and should not be used.
Both launch files also contain the initial position of the robot (by default (0, 0, 0)) as well as the robot geometric parameters that, by default, have been tweaked a little to help match the ground thruth pose provided.
The default (not tweaked) parameters are also present but commented out, and it is possible to switch between the two without recompiling the source.
The name of the parameters are self-explainatory.
How to launch without a bag
$ roslaunch fg_project1 project1_nobag.launchCalculates the linear velocity of the robot by subscribing to to /wheel_states, publishes a TwistStamped message on /cmd_vel with the current speed.
Computes odometry by subscribing to /cmd_vel and publishes a message of type Odometry on /odom Supports dynamic reconfigure and reset service (see below)
Broadcasts tf2 for the entire robot by subscribing to /odom.
Publishes the needed angular speed for the wheels to have the desired linear speed. Subscribes to /cmd_vel and publishes on /wheels_rpm
It is possible to switch between the euler and Runge-Kutta iuntegration method by using dynamic reconfigure, the module is odom and the parameter name is 'odom_int', values are 'euler' for euler and 'rk' for runge-kutta.
$ rosrun dynamic_reconfigure dynparam set /odom odom_int rk # sets integration method to Runge-KuttaWe provide the 'Reset' service to set the current position, it requires 3 parameters for the new X, Y and Theta positions, all three must be of type float64 (double) and must be all specified.
$ rosservive call /odom/reset 0.0 0.0 3.14 # sets current position to (0,0) and current orientation to 180 degreesA custom message has been defined for the speed of the single wheels, as instructed by the specifications.
Header header
float64 rpm_fl
float64 rpm_fr
float64 rpm_rr
float64 rpm_rl
The tf broadcaster is launched by both launch files. It defines a 'world' reference system centered in (0.0) and a dynamic 'base_link' system following the robot (it subscribes to the /odom topic).
The odometry follows pretty closely the ground thruth pose for bag1 and bag3. The same is not true for bag2, especially for the Y coordinate.
We think the problem is related to the fact that the ground thruth orientation is not linear between 36 and 41 seconds but varies in bigger steps. Also, it jumps from 175 degrees to -167 degrees which is not a 360 degrees difference, leaving a 18 degrees delta which our odometry does seem to not account for.