sequoia_ros

ROS packages for OU's IGVC Self-Drive competition entry.

After cloning into a ROS workspace, run the following the command from the root of the workspace to install the necessary ROS package dependencies to make everything work correctly:

rosdep install --from-paths src --ignore-src -r

Gazebo simulation of Sequoia

Starting the Simulator

roslaunch gazebo_ros empty_world.launch

To load a custom Gazebo world file, pass its file path to the world_name argument:

roslaunch gazebo_ros empty_world.launch world_name:=<complete path to world file here\>

Spawn Sequoia in Gazebo with spawn_sequoia.launch in the sequoia_ros package:

roslaunch sequoia_gazebo spawn_sequoia.launch

Simulating Specific IGVC Tasks

The self_drive_tasks.world file in the self_drive_tasks_gazebo package simulates the specific tasks as described in the official rules document, which can be found [here].

To load the world and spawn the vehicle at the starting point for a particular task, run the corresponding launch file in the self_drive_tasks_gazebo package. For example, to run task F3, the right turn test where the vehicle has to stop at the intersection:

roslaunch self_drive_tasks_gazebo f3_gazebo.launch

Sensor Data Topics

• /fix: GPS position given in latitude and longitude in the form of a sensor_msgs/NavSatFix message

• /camera_sim/image_raw/*: Standard group of image parameters from image_proc

• /laser/scan: LIDAR scan data in the form of a sensor_msgs/LaserScan message

• /vehicle/twist: The current measurement of the vehicle's speed and yaw rate in a geometry_msgs/TwistStamped message. The linear.x field contains the speed in m/s and angular.z contains the yaw rate in rad/s

Controlling the Simulated Vehicle

Gazebo subscribes to the following sensor_msgs/Float64 topics to simulate control inputs to the vehicle:

• /vehicle/throttle_cmd: Throttle percentage (0 to 1)

• /vehicle/brake_cmd: Brake torque in Newton-meters (0 to 1000)

• /vehicle/steering_cmd: Desired steering wheel angle in radians (-9.5 to +9.5)

Instead of directly publishing messages to the above topics, the sequoia_twist_controller package provides a system for performing closed loop speed control and kinematic transformation from yaw rate to steering wheel angle.

To run the twist controller:

roslaunch sequoia_twist_controller sequoia_twist_controller.launch

To use the twist controller, just publish a geometry_msgs/Twist message on the /vehicle/cmd_vel topic, and it will generate the appropriate brake, throttle and steering wheel angle commands to send to the simulator.