Stretch

Gripper Assembly and Prep

Follow this guide to assemble the gripper: Assembly Guide

Have the following materials ready:

• Download and print the gripper mount

• 4 M2.5 x 10mm Screws

• The Dynamixel Starter Set, which includes parts 2-6 in the photo below:

1. Connect the Dynamixel Motor to the U2D2 Power Hub. You will hear a clicking sound when connected:

1. Connect the Power Hub to the U2D2 Board

1. Connect the U2D2 and your computer with the USB cable. A red light will turn on.

1. Plug the 12V 5A power supply into the U2D2 Power Hub board and switch on the power. A red LED should turn on.

Go to the robot-server directory and run this script to initialize the gripper:

cd robot-server
python gripper_init.py

Gripper Setup

1. Attach mount to the assembled gripper using M2.5 x 10 mm screws

1. Slide the mount onto the stretch

1. Connect motor to wrist joint

1. Set up the iPhone on the robot:

   • Slide the iPhone into the gripper mount until the camera block hits the mount, then tighten the knob (snug, not over-tight).

1. Connect the iPhone to the robot via USB.

1. In Record3D app settings: set RGBD Streaming mode to USB and FPS to 30.

1. Press Record to enter “stream-ready” mode.

Operating the Stretch Robot

1. Turn on the robot and set the charger to 12V supply mode (use 12V AGM mode when turned off).

   • In general, keep the robot charging unless it needs to move untethered.

2. Calibrate the joints (required every power-on).

   • Place the clamp ~one-third from the bottom so the lift doesn’t collide.

   • Remove the gripper during calibration so it doesn’t collide with the arm.

   • Run the joint calibration script:

     stretch_robot_home.py

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General Information

1. Don’t move the robot or any joints unless it’s in “run-stop” mode.

   • There’s a white button on the robot’s head (the “run-stop” button)

• If the light is not flashing → joints can be locked; press once to enter “run-stop” so you can move the robot freely.

• If the light is flashing → the robot is already in “run-stop”; hold the button for a few seconds to exit it (necessary for operation).

1. The “run-stop” button functions as an emergency stop—press it any time the robot is unsafe.

2. If code runs but the robot doesn’t move, check run-stop mode first.

3. When finished:

   • Shut down: sudo shutdown now.

   • Wait a few seconds until the base LiDAR stops spinning.

   • Move the lift down to the clamp.

   • Power off the robot.

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Deploying a Trained Policy

We assume that your robot has a display (a physical monitor, or X11 forwarding, or a remote setup like this documentation).

1. Run conda deactivate until no conda environments are active, not even the base environment, so that Stretch SDK imports work properly.

2. Start the robot server:

   cd robot-server

   First, run the gripper calibration script. The gripper will calibrate itself by watching the blue pixels move, so make sure there are no blue pixels in the background.

   python3 auto_calibrate_gripper.py

   Then, start the robot server:

   python3 start_server.py controller=stretch

   This starts streaming images from the iPhone and the robot begins listening for action commands. If you have missing imports, try pip3 install hydra-core record3d (and any other missing packages).

3. Run the policy in another terminal (requires display):

   cd imitation-in-homes
   conda activate home_robot
   python run.py

4. Head to the Eval Playbook

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