Mission strategies¶

This workspace ships three behaviour-tree missions. They share the same control substrate (goto, cluster_tf, the search builders in shared_trees/) but they exist at very different levels of sophistication.

Read these before the per-mission pages¶

Concepts: if "behaviour tree", "TF", "anchor frame", or "cluster_tf" are not yet vocabulary, start here.
Architecture: the layered pipeline every mission rides on top of.
Conventions: frame, sign and naming rules. Mission code is much less cryptic once you've internalised these.
Primitives: goto, LocomotionActionServer, the search builders. Every mission page below uses these as vocabulary.

The three missions at a glance¶

Mission	What the robot is trying to do	Search behaviour	Fallback if everything fails
Square	Drive a 2 m × 2 m closed square in body frame. No perception.	None (open-loop).	None. Fail-stop on action timeout.
Bin drop	Find a bin on the pool floor, identify which of two templates it matches, line up the dropper, release three weights into it.	Layered downward "square scan" until enough YOLO detections cluster tightly.	Fire all three droppers blindly from the coarse approach pose.
Torpedo	Find two torpedo panels on the pool wall, pick the correct hole on each (fish vs shark), align each shooter to its hole, fire two torpedoes.	Front-camera yaw scan (±30°, 15° steps).	Fire both torpedoes blindly.

Choosing what to read first¶

Brand-new to robotics or BTs? Start with Square. It's intentionally the simplest mission. No perception, no recovery, no cluster_tf, no anchor-frame trickery. If you can read square.py end-to-end and follow what each leg does, you can read every other mission too.
Comfortable with ROS but new to mission BTs? Read Primitives next, then any mission page. The primitives are the vocabulary the missions are written in.
Already shipped a RoboSub mission once? Skim Square, then jump to Bin or Torpedo for the actually-interesting patterns (cluster_tf integration, anchor-frame swaps, template selection, blind fallbacks).

What all three missions have in common¶

Arm + GUIDED mode
    ↓
Drive to a "vicinity" pose. Coarse approach in the map frame
    ↓
Search if perception isn't seeing the target yet
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Cluster the noisy detections into a stable TF
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Switch anchor frame to whichever part of the robot needs to land on the target
    ↓
Final approach. Tight thresholds, retries on failure
    ↓
Actuate (drop / fire / nothing)
    ↓
(if main sequence fails anywhere). Blind fallback so we still score points

The bin and torpedo pages walk this structure in detail. The square mission is a smoke test that runs only the first two and last two of those phases (no perception, no actuation), giving you a clean way to verify the whole control pipeline before adding vision on top.

Every mission ends with a fallback

The competition rule is unforgiving: a perception failure that drops your score to zero is worse than a half-blind drop that still scores a few points. Both bin and torpedo wrap their main sequence in a Selector(memory=True) whose right child is a "fire-blindly" sequence. When you read the trees, the fallback is a literal sibling of the main plan, not an error-handler bolted on.