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final_writeup.md

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Progress

  1. Finished waypoint_updater.py, validate by seeing green dots representing waypoints: alt text
  2. Finished twist_controller, car is able to follow waypoints in autonomous mode. ##TOOD
  3. But still wandering out of lane sometimes
  4. how to use dbw_test.py?
  5. Car is running in lane if camera off, but way out of lane if camera on?

simulator has two test tracks:

A highway test track with traffic lights the first track has a toggle button for camera data. Many students have experienced latency when running the simulator together with a virtual machine, and leaving the camera data off as you develop the car's controllers will help with this issue. A testing lot test track similar to where we will run Carla To use the second test lot, you will need to update your code to specify a new set of waypoints. We'll discuss how to do this in a later lesson.

units

the simulator displays vehicle velocity in units of mph. However, all values used within the project code are use the metric system (m or m/s), including current velocity data coming from the simulator.

team size

Note that we'd like a minimum team size of 4

components

traffic light detection

  • package source: ros/src/tl_detector/
  • /current_pose topic : provides the vehicle's current position
  • /base_waypoints topic: provides a complete list of waypoints the car will be following.
  • tl_classfier.py: tl_detector/light_classification_model/tl_classfier.py
  • tl_detector.py : tl_detector/tl_detector.py
node subscribed to publish to
tl_detector.py (3) /image_color (3) /traffic_waypoint
/current_pose
/base_waypoints
tl_classfier.py
waypoint_updater.py (4) /current_pose (1) /final_waypoints (1)
/base_waypoints (1)
/obstacle_waypoint
/traffic_waypoint
dbw_node.py (2) /current_velocity /vehicle/throttle_cmd
/twist_cmd /vehicle/brake_cmd
/vehicle/dbw_enabled /vehicle/steering_cmd
twist_controller.py
top message type description
/base_waypoints styx_msgs/Lane Waypoints as provided by a static .csv file.
/current_pose geometry_msgs/PoseStamped Current position of the vehicle, provided by the simulator or localization.
/final_waypoints styx_msgs/Lane This is a subset of /base_waypoints. The first waypoint is the one in /base_waypoints which is closest to the car.

waypoint updater

  • package source: ros/src/waypoint_updater/
  • purpose: to update the target velocity property of each waypoint based on traffic light and obstacle detection data

twist_controller

Suggested Order of Project Development

  1. Waypoint Updater Node (Partial): Complete a partial waypoint updater which subscribes to /base_waypoints and /current_pose and publishes to /final_waypoints.
  2. DBW Node: Once your waypoint updater is publishing /final_waypoints, the waypoint_follower node will start publishing messages to the/twist_cmd topic. At this point, you have everything needed to build the dbw_node. After completing this step, the car should drive in the simulator, ignoring the traffic lights.
  3. Traffic Light Detection: This can be split into 2 parts:
    • Detection: Detect the traffic light and its color from the /image_color. The topic /vehicle/traffic_lights contains the exact location and status of all traffic lights in simulator, so you can test your output.
    • Waypoint publishing: Once you have correctly identified the traffic light and determined its position, you can convert it to a waypoint index and publish it.
  4. Waypoint Updater (Full): Use /traffic_waypoint to change the waypoint target velocities before publishing to /final_waypoints. Your car should now stop at red traffic lights and move when they are green.

learning ROS

# Standard metadata for higher-level stamped data types.
# This is generally used to communicate timestamped data
# in a particular coordinate frame.
#
# sequence ID: consecutively increasing ID
uint32 seq
#Two-integer timestamp that is expressed as:
# * stamp.sec: seconds (stamp_secs) since epoch (in Python the variable is called 'secs')
# * stamp.nsec: nanoseconds since stamp_secs (in Python the variable is called 'nsecs')
# time-handling sugar is provided by the client library
time stamp
#Frame this data is associated with
# 0: no frame
# 1: global frame
string frame_id

common commands

rostopic list
rostopic info /final_waypoints
rosmsg info styx_msgs/Lane

msg

x direction linear velocity of the first waypoint:

my_lane_msg[0].twist.twist.linear.x

errors encountered

No module named terminal_color

pip install --upgrade catkin_pkg
python<x> -m pip install <package>

ERROR: Unable to communicate with master!

cd ros
catkin_make; source devel/setup.sh; roslaunch launch/styx.launch