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Thrusters

Mission planner works internally as follows:

  1. mission_planner.py
    • main() calls listener().
    • listener() creates a new node called mission_planner. The node subscribes to a topic called /zsys and calls the callback().
    • The callback() calls main() where an object called sm of StateMachine is created with 3 outcomes - [‘mission_complete’, ‘mission_failed’, ‘aborted’]
    • sm performs 3 tasks - sink to a certain depth, align to a certain heading, move forward for some seconds.
      Sink (sm, 'SINK1', 515, 'HEADING1')
      Heading(sm, 'HEADING1', 75,'FORWARD1')
      Forward(sm, 'FORWARD1', 6, 'FORWARD2')
      Forward(sm, 'FORWARD2', 12, 'mission_complete')
  2. Sink.py & Depth.py
    Sink (<state machine object>, <name of state>, <pressure>, <next state>)
    • In Sink.py the Sink class’s constructor is called which sets the initial pressure.
    • A substate called sm_sub is created with outcomes as [‘depth_success’, ‘aborted’].
    • sm_sub creates an object called depthTask of the class Depth.
      depthTask = Depth(INITIAL_PRESSURE, 'depth_success')
      The Depth.py’s constructor sets the values of pressure and task variables.
      depthTask.addDepthAction(smach_StateMachine) calls the addDepthAction(self, sm) method of class Depth where a new SimpleActionState DEPTH is added to sm and depthCallback() is called, transitions being ‘succeeded’:self.TASK, ‘preempted’:’DEPTH’, ‘aborted’:’aborted’.
    • In depthCallback(), the depth_setpoint is set to PRESSURE’s value.’
    • From mission_planner.py, execute() is called which creates a SimpleActionClient and sends the PRESSURE as the goal and returns ‘DepthReached’/’aborted’.
  3. Heading.py
    Heading (<state machine object>, <name of state>, <heading>, <next state>)
    • In Heading.py the Heading class’s constructor is called which sets the initial heading.
    • A new SimpleActionState heading1 is added to sm and headingCallback() is called..
    • In headingCallback(), the heading_setpoint is set to HEADING’s value.’
    • From mission_planner.py, execute() is called which creates a SimpleActionClient and sends the HEADING as the goal and returns ‘HeadingReached’/’aborted’.
  4. Forward.py
    Forward (<state machine object>, <name of state>, <time>, <next state>)
    • Creates a SimpleActionState called surgeServer, calls goalCallback() to move the Underwater Vehicle forward for the time sent from mission_planner.py.