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LeKiwi Mobile Manipulator Documentation

repository·main·Indexed 23 days ago

https://github.com/sigrobotics-uiuc/lekiwi

An open-source, low-cost mobile manipulator designed for robotics research and integration with the LeRobot ecosystem. It features a 3-wheel holonomic (Kiwi) drive, a SO-ARM101 robot arm, and Raspberry Pi 5 compute. Documentation includes detailed build guides for 5V, 12V, and Wired versions, 3D printing specifications, assembly instructions, and configuration for Dynamixel teleoperation.

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What's inside LeKiwi

  1. Overview of LeKiwi Low-Cost Mobile Manipulator

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    LeKiwi is a low-cost mobile manipulator (Version 1) designed for robotics research and development. It features a 3-wheel holonomic (Kiwi) drive using omni wheels and integrates a SO-ARM101 robot arm. The system is designed to support teleoperation via controller or laptop (WASD + leader arm), data collection pipelines, and streaming of joint angles and camera feeds.

  2. Bill of Materials for Dynamixel LeKiwi

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    The Bill of Materials (BOM) provides a comprehensive list of parts required to build the Dynamixel LeKiwi mobile manipulator. The project can be built as a complete mobile manipulator or as a base-only version.

    Estimated Costs:

    • Dynamixel LeKiwi (Full): ~$770.47 USD / €1021.60 / ¥6074
    • Base only: ~$339.47 USD / €378.60 / ¥2127.28

    Note: Prices and availability vary by location and time of purchase.

  3. Hardware Specifications and Configuration Options

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    LeKiwi can be configured in different power and drive modes depending on your experience and requirements:

    Power Options

    • 5V Version: Uses a 65W Laptop power bank. Recommended for beginners as it is easier to assemble.
    • 12V Version: Uses a 12V 5A Li-ion battery. Recommended for experienced users who need to lift heavier objects.
    • Wired Version: The most cost-effective option.

    Core Hardware

    • Drive: 3-wheel Kiwi (holonomic) drive with omni wheels.
    • Compute: Raspberry Pi 5 (with capability to stream to a laptop).
    • Robot Arm: SO-ARM101.
    • Sensors: Workspace RGB camera and a Wrist RGB camera.
    • Base Plates: Standardized stacked base plates with 3.5mm diameter holes spaced 20mm apart (inspired by the open robotic platform).

  4. Print the LeKiwi 3D parts

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    To manufacture the LeKiwi robot, use generic PLA filament on a consumer-grade FDM printer. The project provides ready-to-print STL files.

    Recommended Slicer Settings

    When slicing the files, use the following settings for consistent results:

    • Infill Density: 15%
    • Layer Height: 0.2 mm
    • Printing Speed: 150 mm/s

    Printing Workflow

    1. Setup: Calibrate/level the printer, clean the bed, and load filament.
    2. Slicing: Upload STL files to your slicing software. Use auto-rotate and auto-arrange. Crucially, enable supports where specified in the parts list.
    3. Printing: Upload the G-code to the printer and start the print.
    4. Post-Processing: Remove parts from the printer, clean the bed, and remove any supports.
    Infill Density: 15%
Layer Height: 0.2 mm
Printing Speed: 150 mm/s

  5. Perform Final Assembly

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    1. Wiring Pass-through: Feed the servo controller USB-C to USB-A cable, the 5V USB-C power cable, and the SO-101 servo wires through the hole in the top base plate.
    2. Plate Attachment: Mount the top base plate onto the motor mounts using 4 m3x12 machine screws.

  6. Assemble the Top Plate

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    1. Raspberry Pi 5: Place the Pi 5 into the Pi case bottom and snap on the top part of the case.
    2. Pi to Plate: Attach the Pi case to the top base plate using 2 m3x12 machine screws.
    3. Arm Mounting: Mount the SO-101 arm using 4 m3x20 machine screws. The plate supports both the original and the modified SO-101 base.
    4. Wired Version Cable Management:
      • Print 3DPrintMeshes/wired_specific/cable_holder v0.stl and 3DPrintMeshes/wired_specific/usb_connector_case v1.stl.
      • CRITICAL: When plugging in the USB-C cable, ensure the UGreen logo is on the same side as the 20GBS, 240W logo. The 20GBS, 240W side must face up into your laptop. If the USB-C extension cable fails to find the camera or motor controller, flip the orientation 180 degrees.

  7. Assemble the LeKiwi Bottom Plate

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    Follow these steps to construct the base of the robot:

    1. Plate Construction: Attach the 3D-printed triangular insert to the TB3 plate. Align the outer holes and secure the insert using six M3x8 machine screws and matching nuts.
    2. Motor Mounts: Screw each drive motor mount onto the bottom plate using 2 m3x12 machine screws in the front and 2 m2.5x12 machine screws in the back.
    3. Mounts and Wiring:
      • Connect motor wires in series.
      • Insert 2 m3 nuts into the slots on both the battery mount and the base camera mount.
      • Attach the battery mount to the bottom plate using two m3x12mm machine screws.
      • Secure the camera mount to the plate using two m3x16mm machine screws.
    4. Electronics Wiring:
      • Use Wago lever connectors to connect the ground and power battery wire leads to the leads of the 12v->5v converter and the DC barrel plug adapter.
      • Mount the 12V to 5V converter to the bottom plate using two m4x16mm machine screws and two m4 nuts.
      • Connect the unconnected motor wire, the USB cable, and the power wires to the U2D2 power hub board.
      • Attach standoffs to the U2D2 board and secure it to the base plate using three m3x16mm machine screws.

  8. Build and Setup Guide for LeKiwi

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    To build and initialize a LeKiwi robot, follow these sequential steps:

    1. Review Bill of Materials: Check BOM.md for required components.
    2. 3D Printing: Prepare parts using the instructions in 3DPrinting.md.
    3. Assembly: Follow the physical assembly guide in Assembly.md.
    4. Software Setup: Get started with the software stack by following the LeRobot documentation.

  9. Assemble the Bottom Plate

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    1. Mounts: Insert m3 nuts into the mounts for the servo controller and battery mounts. Secure both to the bottom base plate using 4 m3x12 machine screws.
    2. Servo Driver: Add the servo driver and connect wires to the 3 drive servos.
    3. Electronics Wiring:
      • 12V Version: Use Wago lever connectors to connect the ground and power battery wire leads to the 12v->5v converter and the DC barrel plug adapter. Secure the 12v to 5v converter to the bottom base plate using 2 m3x16 machine screws and 2 m3 nuts.
      • 5V Version: Mount a powerbank in the back on the lower plate using the 3DPrintMeshes/5v_specific/5v_power_bank_holder.stl holder.

  10. Use modified LeRobot code for Dynamixel teleoperation

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    The Dynamixel version of LeKiwi uses a modified version of the original LeRobot code to support teleoperation.

    Important: When using this modified code, you must update the configuration to match your specific hardware setup, including:

    • Communication ports
    • IP addresses
    • Other hardware-specific identifiers

    The specific changes made to the original LeRobot codebase can be found in this commit: Dynamixel Teleop.

  11. Choose a LeKiwi build version

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    LeKiwi offers three main configuration options for motors and electronics. Choose based on your experience level and performance requirements:

    • 5V Version: Recommended for first-time builders as it is easier to assemble.
    • 12V Version: Recommended for experienced builders who need to lift heavier objects.
    • Wired Version: The most cost-effective option, but lacks battery mobility.

    Note that the Mobile Base Structure, Sensors, and Compute components are identical across all versions.

  12. Assemble the LeKiwi Top Plate

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    Follow these steps to prepare the upper section of the robot:

    1. Raspberry Pi Setup: Place the Raspberry Pi 5 into the bottom half of the Pi case and snap on the top cover.
    2. Arm and Camera: Ensure you have a modified Koch arm base and modified static gripper. Attach the webcam as shown in the assembly diagrams.
    3. Mounting:
      • Mount the Raspberry Pi to the top plate using two M2x12 machine screws and nuts.
      • Secure the Koch arm using four M3x12 machine screws and nuts.