anchor.diff:  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
  +=== 4. diff_drive_mock_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
  
positive.code: `~timeout_ticks` (int, default: 2)::
  The number of velocity target messages that will be published after the last twist message is received.
  
  === 2. wheels_to_odometry
  
  Listens for wheel movement and rates and publishes the transform between the odom frame and the robot frame.
  
  
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.
  
  