fastgripper-lerobot

FastGripper — a worm-gear-driven, compliant parallel gripper for the SO-101 arm, shipped as a turnkey LeRobot plugin. High grip force, zero-power holding (the worm self-locks), and a multi-turn drive that the plugin makes invisible: teleop, datasets, and policies see a standard 0–100 gripper.

Install

pip install lerobot lerobot_robot_fastgripper

LeRobot auto-discovers any installed lerobot_robot_* package — no fork, no config. The robot type is fastgripper_follower.

Quick start

New to the SO-101 entirely? Follow the step-by-step quickstart guide (box → teleop in ~30 min). Full docs — tutorials, command reference, internals — live in docs/site/. The short version:

# one-time (gripper ships closed; the worm holds it there in transit)
fastgripper setup --follower-port /dev/tty.usbmodemXXXX --follower-id follower_1 \
                  --leader-port /dev/tty.usbmodemYYYY --leader-id leader_1
fastgripper calibrate            # standard SO-101 arm calibration (once)

# daily
fastgripper teleop

Every session ends with the gripper parking itself closed and starts with a verified zero-motion restore — the worm cannot backdrive while unpowered, so the parked position is trustworthy across power cycles. If the mechanism is ever moved by hand while off, the next start detects the mismatch and tells you exactly what to do.

Commands

Plain LeRobot commands work too (lerobot-record, lerobot-train, …) with --robot.type=fastgripper_follower.

Why a plugin is needed at all

The gripper's stroke spans ~4.8 servo revolutions, but the STS3215's encoder is absolute only within one revolution. This package runs the servo in its (undocumented) absolute multi-turn mode and manages the volatile turn counter across power cycles — plus tuned motion/protection profiles for driving a worm stage. Design details and all bench findings: docs/multiturn-gripper-notes.md.

Development

uv venv --python 3.12 .venv
uv pip install -p .venv/bin/python -e ".[dev]"
.venv/bin/pytest tests            # simulated-hardware suite, no robot needed

License: Apache-2.0.