anchor.diff:  
   * `diff_drive_controller` -- Converts from twist to wheel velocities for motors.
   * `diff_drive_odometry` -- Publishes odometry from wheel encoder data.
  +* `diff_drive_go_to_goal` -- Moves the robot to a goal position.
   * `diff_drive_mock_robot` -- Implements a mock differential drive robot, for testing.
  -* `diff_drive_drive_to_goal` -- Moves the robot to a goal position.
   
   The nodes in this package are designed with these considerations:
   
  
positive.code: must be greater than _K~p~_. To ensure robust convergence, so that the robot never changes direction,
  _K~a~_ - 5/3*_K~b~_ - 2/pi*_K~p~_ must be greater than zero.
  
  === 4. sim_robot
  
  Implements a simulation of perfect differential drive robot hardware. It immediately follows any speed
  commands received with infinite acceleration, and publishes the wheel encoder values and encoder
  
negative.code: 
  == ROS API
  
  === 1. diff_drive_controller
  
  Listens for desired linear and angular velocity, and publishes corresponding wheel velocities, in encoder ticks per second, required to achieve those velocities.
  
  