Mobile ALOHA 🏄: Learning Bimanual Mobile Manipulation with

Low-Cost Whole-Body Teleoperation

Zipeng Fu*     Tony Zhao*     Chelsea Finn

* project co-leads  Stanford University

https://mobile-aloha.github.io/ 

Our CAD: https://a360.co/47Wn6hp 

The robot frame design is also available from Vention: Link. Credit: Robert Shuttleworth

Bill of Materials

3D Printed Parts

For leader and follower end-effectors, follow the original ALOHA tutorial: ALOHA 🏖️ Tutorial

For wheel odometry, below are the required parts (6 pieces in total):

Link to STL/STEP/Fusion360 Files

Hardware Guide

1. Install ALOHA end-effectors

Follow Part 1 of ALOHA 🏖️ Tutorial to install end-effectors for both leaders and follower robots. Also install wrist cameras for both follower robots.

2. Build the robot frame

Follow the CAD files: https://a360.co/47Wn6hp

4040-50 means a 50cm beam

3. Mount the robots and the cameras

Unlike the rest of the frame which has M8 screws, the robot needs to be mounted with M6 (see M6 20mm, M6 T nuts for 4040 in the BOM.)

To mount the front camera, we tape the base of the logitech webcam on top of the beam, then use the hot glue to fix the camera angle.

Optional: Gravity compensation for the leader arms.

The original ALOHA’s gravity comp is too cumbersome for mobile applications. Below is our redesign (partially inspired by GELLO):

4. Cable connections

4.1 Power

Place the battery pack on top of the bottom beams:

To power the ALOHA arms, please refer to ALOHA 🏖️ Tutorial, then plug the power supply directly into the battery pack.

Also, plug in the laptop power supply to the battery pack directly.

4.2 USB connections

To connect the Tracer Base to the laptop, use the USB-CAN bus converter that comes with the base.

We use two USB hubs for this setup:

1. 4 USBs from each robot arm, 1 USB for the Tracer Base, 1 front camera
2. 2 wrist cameras

These two USB hubs are then plugged into the laptop on the left and right sides respectively.

At this point, you should be able to teleoperate both arms! Go to the mobile-aloha repo to complete the software setup, then try out one_side_teleop.py!

5. Wheel Odometry

The wheel odometry is used to collect base velocity information during teleoperated data collection. We cannot use the readings from Tracer wheels directly, because when powered on the wheels are automatically torqued on. Thus unless AgileX (manufacturer of Tracer) updates their software to support pure reading mode from their motors, we need to turn off the base and use this odometry unit for data.

We need to install the unit on both sides of the base. For each side, we need:

1x DYNAMIXEL XL430-W250-T

1x Wheel, 1x Mount, 1x Housing (see Mobile ALOHA 🏄 Tutorial)

Since we use the Dynamixels purely for reading base velocity (just as an encoder but not the motor), the friction of the gear could result in slipping between the ground. To reduce that, we disconnect the shaft from the DC motor inside the Dynamixel.

1. Take out the horn following Dynamixel X-Series Horn Disassembly or brute force.
2. Open up the Dynamixel case following [Do It Yourself] DYNAMIXEL Gear Replacement - AX-Series till 0:41. The motor we used is different from the one shown, but similar in structure.
3. Take out the gear closest to the motor shaft, then put everything back.

To further reduce slipping between the wheels and the ground, we use gripping tape to wrap around the wheels, and add weight on top of the housing.

To connect the motors to the laptop:

1. Connect both motors to the U2D2 Power Hub Board Set with the cable that comes with the motor and the jumper wires.
2. Connect the U2D2 Power Hub Board Set to the U2D2
3. Connect U2D2 to laptop with USB directly
4. Add another 12V DC Cable to the 12V power supply and plug that into the U2D2 Power Hub Board Set

Lastly, setup both motors following the tutorial in Mobile ALOHA repo.

You are now ready to use the Mobile ALOHA 🏄!