step.arm.preset

ArmPreset — named arm positions with pre-solved servo angles.

Named positions are resolved at codegen time (on the dev machine) via the raccoon-cli ArmChain generator. At runtime the Wombat only performs a dict lookup and issues existing servo steps — no IK library required.

Instances are generated from raccoon.project.yml into defs.py:

definitions:
  arm:
    type: ArmChain
    joints:
      - servo: shoulder_servo
        length_cm: 12.5
        joint_range_deg: [0, 90]
        servo_range_deg: [10, 130]
    positions:
      grab_cone: {x: 18, y: 0, z: 5}

Generated usage:

from src.hardware.defs import Defs

Defs.arm.grab_cone()  # instant — all joints move in parallel
Defs.arm.grab_cone(speed=60)  # eased at 60 deg/s per joint

Classes

ArmPreset

Named arm positions backed by pre-solved servo angles.

Module Contents

class step.arm.preset.ArmPreset(joints: list[raccoon.hal.Servo], positions: dict[str, list[float]])

Named arm positions backed by pre-solved servo angles.

Each position becomes a callable attribute that returns a Step. All joints move simultaneously via parallel().

Calling without speed issues instant servo() commands. Calling with speed uses SlowServo on every joint.

Parameters:

• joints – Servo hardware devices in kinematic order (base → tip).

• positions – Mapping of position name to pre-solved servo angles in degrees (one angle per joint, same order as joints).

property joints: list[raccoon.hal.Servo]

The underlying servo hardware devices in kinematic order.

to(x: float, y: float, z: float = 0.0, speed: float | None = None) → raccoon.step.Step

Move the arm to a Cartesian position via runtime IK.

Requires ikpy to be installed (pip install ikpy). For competition use, prefer named positions — they are pre-solved at codegen time and carry zero runtime overhead.

Parameters:

• x – Target x in cm (forward from the first joint origin).

• y – Target y in cm (lateral).

• z – Target z in cm (vertical). Defaults to 0.

• speed – Optional speed in deg/s for eased motion.