> For the complete documentation index, see [llms.txt](https://cap-policy.gitbook.io/guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cap-policy.gitbook.io/guide/stretch.md).

# Stretch

## Gripper Assembly and Prep

Follow this guide to assemble the gripper: [Assembly Guide](https://nyu-gripper.pages.dev/robot-gripper)

Have the following materials ready:

* Download and print the [gripper mount](https://nyu-gripper.pages.dev/cad/Robot%20_Gripper/quick-release-mount.stl)
* 4 M2.5 x 10mm Screws
* The [Dynamixel Starter Set](https://www.robotis.us/dynamixel-starter-set-us/), which includes parts 2-6 in the photo below:

<figure><img src="/files/3yD4fZhHGy3PTt9c9cFL" alt=""><figcaption></figcaption></figure>

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

<figure><img src="/files/5S5DLs5dBH6bD3zvR4OR" alt="" width="563"><figcaption></figcaption></figure>

2. Connect the Power Hub to the U2D2 Board

<figure><img src="/files/ioEy35xD60ROM8kQ1V0X" alt="" width="563"><figcaption></figcaption></figure>

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

<figure><img src="/files/BuGIpAEEK9VqtUSfIYGI" alt="" width="563"><figcaption></figcaption></figure>

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

<figure><img src="/files/GPZAxWm8efyid6GSaJO9" alt="" width="563"><figcaption></figcaption></figure>

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

```bash
cd robot-server
python gripper_init.py
```

## Gripper Setup

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

<figure><img src="/files/56ta8CKRxQzAIGmqBLsm" alt="" width="375"><figcaption></figcaption></figure>

2. **Slide the mount onto the stretch**

<figure><img src="/files/5CvA4uuCrRlxiwPOCoIE" alt="" width="375"><figcaption></figcaption></figure>

3. **Connect motor to wrist joint**

<figure><img src="/files/ivDPEF2kdAjR5oZGmD9c" alt="" width="375"><figcaption></figcaption></figure>

4. **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).

<figure><img src="/files/GMeyJkgH5yX83lgdbszF" alt=""><figcaption></figcaption></figure>

5. Connect the iPhone to the robot via USB.

<figure><img src="/files/HujPQH5SIFhKZiqhgQaY" alt=""><figcaption></figcaption></figure>

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

<figure><img src="/files/ULtWZKVcYHdqnDAzubJe" alt="" width="375"><figcaption></figcaption></figure>

7. 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:

     ```bash
     stretch_robot_home.py
     ```

***

## 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)

<figure><img src="/files/MtOSQmRu46A7NNNUott6" alt=""><figcaption></figcaption></figure>

* 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).

2. The “run-stop” button functions as an **emergency stop**—press it any time the robot is unsafe.
3. If code runs but the robot doesn’t move, **check run-stop mode** first.
4. 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.

***

## 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](https://docs.hello-robot.com/0.3/getting_started/connecting_to_stretch/#untethered-setup)).

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**:

   ```bash
   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.

   ```bash
   python3 auto_calibrate_gripper.py
   ```

   Then, start the robot server:

   ```bash
   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):

   ```bash
   cd imitation-in-homes
   conda activate home_robot
   python run.py
   ```
4. Head to the [Eval Playbook](https://docs.google.com/document/d/1DTy8G2XzWs01yTducmVBbdiEGack96QJm9dK1AOyS4Q/edit?tab=t.0)

### Available Policy Checkpoints

When running `python run.py`, you can select from these preconfigured checkpoints:

* **`run_vqbet_pick`**: default checkpoint for picking task.
* **`run_vqbet_open`**: default checkpoint for opening task.
* **`run_vqbet_close`**: default checkpoint for closing task.
* **`run_vqbet_pick_exp`**: experimental pick checkpoint.

Choose the config that matches your task and substitute it in:

```bash
python run.py --config-name=<one_of_the_above>
```

***