Simulation testedroller skatev1.0.0Apache-2.0

Classic Swizzle Skating

Symmetric rhythmic swizzle gait on passive roller wheels, generating forward propulsion without lifting feet off the ground.

By Pollen Robotics @pollen-robotics

About this behavior

Emulates human inline skating swizzles (hourglass foot patterns). Uses continuous lateral leg splaying and converging arcs to convert leg extension forces into forward rolling momentum without foot lift-off. Trained in mjlab using full roller wheel contacts.

Runtime contract

61-dimension input · 14 joint targets · 50 Hz

Show details

50 Hz / 4×slot: rollers

Observation vector61 dimensions · normalizer baked in

Proprioception48D

Positions, velocities, previous actions, gravity, and gyro.

Twist command3D

Forward, lateral, and yaw velocity intent.

Head pose4D

Neck and head orientation targets.

Body pose6D

Six-axis torso offset command.

Action targetsscale: 1×

Left leg5 joints

hip yaw · hip roll · hip pitch · knee · ankle

Neck & head4 joints

neck pitch · head pitch · yaw · roll

Right leg5 joints

hip yaw · hip roll · hip pitch · knee · ankle

Actuator model: Dynamixel XL330 (BAM M6 voltage control law). The beak motor is separate from this fixed locomotion action space.

Verification

Status: Simulation tested
Evidence: Verified in MuJoCo Warp / mjlab simulation over 4096 parallel environments with BAM actuator friction physics.
Target hardware: MicroDuck v1 + Roller Skate Accessories
Simulation: mjlab (MuJoCo Warp) at 50 Hz
Note: Targeted for smooth surfaces like wood or polished concrete where passive wheel friction is minimal.

Compatibility

Robot model: microduck-rollers
MJCF model: robot_allcollisions_rollers.xml
Terrain: flat
Required accessories: roller skates

Run it on your duck

Use the canonical model and this policy slot to try the behavior locally.

slot: rollers

Try the simulation first. Hardware testing assumes a matching Microduck, clear space, and a safe surface. uDuck does not guarantee that a community policy is safe to run.

Deployment stepsShow instructions

1 Download the ONNX model swizzle_rollers.onnx

curl -L "https://raw.githubusercontent.com/pollen-robotics/microduck_rl/develop/docs/models/swizzle_rollers.onnx" -o "/opt/robot/policies/swizzle_rollers.onnx"

2 Add the policy to robotd

[policy]
roller_swizzle = "/opt/robot/policies/swizzle_rollers.onnx"

3 Restart the control loop

sudo systemctl restart robotd
robotctl health

⌁ Try it in simulation

uv run play Mjlab-Velocity-Swizzle-MicroDuck

Sources

Upstream repositorypollen-robotics/microduck_rl Training codeMjlab-Velocity-Swizzle-MicroDuck