OpenTorque Actuator

A powerful, compliant actuator for legged robotics.

Simulation

The additive simulation/ package turns the released STEP assembly into a rigid, inspectable solid-node machine. It leaves every original STEP, STL, image, BOM, print instruction, and licence file unchanged.

From this repository, using the LibreSolid Studio workspace environment:

/home/asa/devel/libresolid-studio/.venv/bin/solid build
/home/asa/devel/libresolid-studio/.venv/bin/solid test --faceted simulation/parts.py
/home/asa/devel/libresolid-studio/.venv/bin/solid test --faceted simulation/hardware.py
/home/asa/devel/libresolid-studio/.venv/bin/solid test --faceted simulation/output_stack.py
/home/asa/devel/libresolid-studio/.venv/bin/solid test --faceted simulation/reducer.py
/home/asa/devel/libresolid-studio/.venv/bin/solid test --faceted simulation/actuator.py

Omit --faceted for the slower exact-kernel certification. solid build publishes _build/viewer.json; a solid-node viewer presents the model's one driver and three demonstration buttons.

Controls and demonstration

input_angle is motor/sun rotation about the STEP assembly's +Z axis, in degrees, from -2880 through +2880. The fixed-ring reducer derives carrier and output rotation as input_angle / 8; each planet spins by -7 * input_angle / 24 in its orbiting carrier frame. No independently drivable internal joint can create an impossible pose.

Instruction	Target	Duration
Home	0°	8 s
One Motor Turn	360°	1 s
One Output Turn	2880°	8 s

Useful ground-up models are simulation.output_stack:OutputStackPreview, simulation.reducer:ReducerPreview, and finally the manifest's simulation.actuator:OpenTorqueActuator.

Reproduce the visual evidence

The snapshot-only previews map normalized time 0→1 to one motor turn. They do not add another control to the published actuator. The following commands produce the four reviewed images; generated PNGs are intentionally ignored and not retained in Git.

/home/asa/devel/libresolid-studio/.venv/bin/solid snapshot simulation/actuator.py:ActuatorPosePreview --time 0 -o snapshot-home-iso.png --autocenter --viewall --camera 0,0,26,55,0,35,220 --imgsize 1200x900 --projection ortho --render
/home/asa/devel/libresolid-studio/.venv/bin/solid snapshot simulation/actuator.py:ActuatorPosePreview --time 1 -o snapshot-driven-iso.png --autocenter --viewall --camera 0,0,26,55,0,35,220 --imgsize 1200x900 --projection ortho --render
/home/asa/devel/libresolid-studio/.venv/bin/solid snapshot simulation/reducer.py:ReducerPosePreview --time 0 -o snapshot-home-axial.png --autocenter --viewall --camera 0,0,50,0,0,0,130 --imgsize 900x900 --projection ortho --render
/home/asa/devel/libresolid-studio/.venv/bin/solid snapshot simulation/reducer.py:ReducerPosePreview --time 1 -o snapshot-driven-axial.png --autocenter --viewall --camera 0,0,50,0,0,0,130 --imgsize 900x900 --projection ortho --render

The isometric pair shows one coherent closed actuator and the carrier/output plate advancing 45°. The axial reducer pair exposes the otherwise hidden three planets at 120° spacing and their 45° orbit.

What the model found

• The assembled standard gears measure 18 sun teeth and 54 planet teeth. The implied fixed ring has 126 teeth, producing the 8:1 reduction.
• The source gears are not zero-volume contacts. At home the exact kernel finds about 23.615 mm³ between each planet and the housing ring, and 10.228–10.241 mm³ between each planet and the sun. These are retained as named, bounded overlaps rather than silently repaired.
• The connected bought-hardware envelopes create additional reviewed capture interfaces: the retainer/outer race, both carrier plates/planet bearings, and each planet bearing/gear. simulation/seats.py requires exactly the 16 known pairs and fails for a new, removed, or out-of-range overlap with no global volume epsilon.
• The BOM's Multistar 9235 and X8318S alternative motors have different published envelopes, so the simulation uses the primary 92 mm Multistar can only as a visual stand-in and makes no interchangeability claim.
• The current workspace CLI can scaffold the STEP with solid import-step, but the documented StepAssembly import is absent. Named StepNode selections are used instead.

Detailed source readings, fingerprints, catalogue links, and kernel-specific overlap volumes are in docs/measurements.md. The simulation does not predict torque, compliance, backlash under load, efficiency, bearing life, thermal or electromagnetic behaviour, firmware response, printability, strength, or safety.