SO-101

In the steps below, we explain how to assemble our flagship robot, the SO-101.

Source the parts

Follow this README. It contains the bill of materials, with a link to source the parts, as well as the instructions to 3D print the parts. And advise if it’s your first time printing or if you don’t own a 3D printer.

Install LeRobot 🤗

To install LeRobot, follow our Installation Guide

In addition to these instructions, you need to install the Feetech SDK:

pip install -e ".[feetech]"

Step-by-Step Assembly Instructions

The follower arm uses 6x STS3215 motors with 1/345 gearing. The leader, however, uses three differently geared motors to make sure it can both sustain its own weight and it can be moved without requiring much force. Which motor is needed for which joint is shown in the table below.

Clean Parts

Remove all support material from the 3D-printed parts. The easiest way to do this is using a small screwdriver to get underneath the support material.

Joint 1

• Place the first motor into the base.
• Fasten the motor with 4 M2x6mm screws (smallest screws). Two from the top and two from the bottom.
• Slide over the first motor holder and fasten it using two M2x6mm screws (one on each side).
• Install both motor horns, securing the top horn with a M3x6mm screw.
• Attach the shoulder part.
• Tighten the shoulder part with 4 M3x6mm screws on top and 4 M3x6mm screws on the bottom
• Add the shoulder motor holder.

Joint 2

• Slide the second motor in from the top.
• Fasten the second motor with 4 M2x6mm screws.
• Attach both motor horns to motor 2, again use the M3x6mm horn screw.
• Attach the upper arm with 4 M3x6mm screws on each side.

Joint 3

• Insert motor 3 and fasten using 4 M2x6mm screws
• Attach both motor horns to motor 3 and secure one again with a M3x6mm horn screw.
• Connect the forearm to motor 3 using 4 M3x6mm screws on each side.

Joint 4

• Slide over motor holder 4.
• Slide in motor 4.
• Fasten motor 4 with 4 M2x6mm screws and attach its motor horns, use a M3x6mm horn screw.

Joint 5

• Insert motor 5 into the wrist holder and secure it with 2 M2x6mm front screws.
• Install only one motor horn on the wrist motor and secure it with a M3x6mm horn screw.
• Secure the wrist to motor 4 using 4 M3x6mm screws on both sides.

Gripper / Handle

Configure the motors

1. Find the USB ports associated with each arm

To find the port for each bus servo adapter, run this script:

python lerobot/find_port.py

Finding all available ports for the MotorBus.
['/dev/tty.usbmodem575E0032081', '/dev/tty.usbmodem575E0031751']
Remove the USB cable from your MotorsBus and press Enter when done.

[...Disconnect corresponding leader or follower arm and press Enter...]

The port of this MotorsBus is /dev/tty.usbmodem575E0032081
Reconnect the USB cable.

2. Set the motors ids and baudrates

Each motor is identified by a unique id on the bus. When brand new, motors usually come with a default id of 1. For the communication to work properly between the motors and the controller, we first need to set a unique, different id to each motor. Additionally, the speed at which data is transmitted on the bus is determined by the baudrate. In order to talk to each other, the controller and all the motors need to be configured with the same baudrate.

To that end, we first need to connect to each motor individually with the controller in order to set these. Since we will write these parameters in the non-volatile section of the motors’ internal memory (EEPROM), we’ll only need to do this once.

If you are repurposing motors from another robot, you will probably also need to perform this step as the ids and baudrate likely won’t match.

The video below shows the sequence of steps for setting the motor ids.

Setup motors video

Follower

Connect the usb cable from your computer and the power supply to the follower arm’s controller board. Then, run the following command or run the API example with the port you got from the previous step. You’ll also need to give your leader arm a name with the id parameter.

python -m lerobot.setup_motors \
    --robot.type=so101_follower \
    --robot.port=/dev/tty.usbmodem585A0076841  # <- paste here the port found at previous step

You should see the following instruction

Connect the controller board to the 'gripper' motor only and press enter.

As instructed, plug the gripper’s motor. Make sure it’s the only motor connected to the board, and that the motor itself is not yet daisy-chained to any other motor. As you press [Enter], the script will automatically set the id and baudrate for that motor.

You should then see the following message:

'gripper' motor id set to 6

Followed by the next instruction:

Connect the controller board to the 'wrist_roll' motor only and press enter.

You can disconnect the 3-pin cable from the controller board, but you can leave it connected to the gripper motor on the other end, as it will already be in the right place. Now, plug in another 3-pin cable to the wrist roll motor and connect it to the controller board. As with the previous motor, make sure it is the only motor connected to the board and that the motor itself isn’t connected to any other one.

Repeat the operation for each motor as instructed.

When you are done, the script will simply finish, at which point the motors are ready to be used. You can now plug the 3-pin cable from each motor to the next one, and the cable from the first motor (the ‘shoulder pan’ with id=1) to the controller board, which can now be attached to the base of the arm.

Leader

Do the same steps for the leader arm.

python -m lerobot.setup_motors \
    --teleop.type=so101_leader \
    --teleop.port=/dev/tty.usbmodem575E0031751  # <- paste here the port found at previous step

Calibrate

Next, you’ll need to calibrate your robot to ensure that the leader and follower arms have the same position values when they are in the same physical position. The calibration process is very important because it allows a neural network trained on one robot to work on another.

Follower

Run the following command or API example to calibrate the follower arm:

python -m lerobot.calibrate \
    --robot.type=so101_follower \
    --robot.port=/dev/tty.usbmodem58760431551 \ # <- The port of your robot
    --robot.id=my_awesome_follower_arm # <- Give the robot a unique name

The video below shows how to perform the calibration. First you need to move the robot to the position where all joints are in the middle of their ranges. Then after pressing enter you have to move each joint through its full range of motion.

Calibration video

Leader

Do the same steps to calibrate the leader arm, run the following command or API example:

python -m lerobot.calibrate \
    --teleop.type=so101_leader \
    --teleop.port=/dev/tty.usbmodem58760431551 \ # <- The port of your robot
    --teleop.id=my_awesome_leader_arm # <- Give the robot a unique name

Congrats 🎉, your robot is all set to learn a task on its own. Start training it by following this tutorial: Getting started with real-world robots