dxl_6d_input

ROS package for a 6-d input device based on dynamixels.

The end effector of the device is a 6-DOF manipulator with 2 MX-64 and 5 MX-28 Dynamixels. The device is controlled by a ROS node that reads the position of the end effector and publishes it to a topic as also the position of the gripper. The node also subscribes to a topic to receive the actual position of the robot end effector to compensate the initial position of the device.

Topics

Publishers

• /dxl_6d_input/pos_{side} - Publishes the position of the end effector.
• /dxl_6d_input/gripper_{side} - Publishes the position of the gripper.

Subscribers

• /cartesian/gripper_{side}_grasping_frame/current_reference - Subscribes to the position of the robot end effector.
• /streamdeck/teleoperation_mode - Subscribes to the teleoperation mode of the device.
• /joy - Subscribes to the joystick input.

Parameters

• ~urdf_filename - The URDF file of the device.
• ~ids - The IDs of the Dynamixels.
• ~devicename - The name of the port where the USB2Dynamixel is connected.
• ~baudrate - The baudrate of the USB2Dynamixel.
• ~protocol_version - The protocol version of the USB2Dynamixel.
• ~addr_present_position - The address of the present position register.
• ~len_present_position - The length of the present position register.
• ~debuginfo - Flag to enable the debug information.
• ~arm_side - The side of the arm.
• ~position_topic - The topic where the position of the robot end effector is published.
• ~gripper_topic - The topic where the position of the gripper is published.
• ~robot_position_topic - The topic where the position of the robot end effector is subscribed.
• ~space_scalar - The scalar to convert the position of the robot end effector to the device.

Get Started

3D Design	3D Design

Hardware

For the hardware setup, the package is designed to work with the 2 Dynamixel MX-64 and 5 Dynamixel MX-28 actuators. All the 3D parts can be found in the dxl_6d_input/armd_design folder where you will find the FreeCad files and the STL files for 3D printing. To assemble the device, you can follow the next steps:

Shopping List

• 2 Dynamixel MX-64.
• 5 Dynamixel MX-28.
• 2 FR07 - H101K
• 4 FR07 - S101K
• Dynamixel cables.
• 1 USB2Dynamixel.
• 3D printed parts - PLA.
• Screws and nuts (M2, M3, M4, M5).
• 1 aluminum profile (10x10 mm) - 100 mm.

Assembly

• Print the parts in the dxl_6d_input/armd_design folder. All the parts are designed to be printed with a 0.4mm nozzle and 0.2mm layer height, with 40% infill and supports enabled using PLA.
  • The files finger_1.stl, finger_2.stl, griper_axis.stl, griper_axis_1.stl, griper_axis_1.stl should be mirrored to print the left arm.
  • Once the parts are printed, you can start the assembly.
• The 2 Dynamixel MX-64 should be mounted on the base of the device, while the 5 Dynamixel MX-28 should be mounted on the arm.
• Be aware of the orientation of the Dynamixels:
  • First calibrate each motor to the zero position using the Dynamixel Wizard2.
  • Mount each motor following the joints directions. For a beter understanding of the joints, you can check the URDF file in the dxl_6d_input/src folder and view it with any URDF viewer.
• The aluminum profile should be mounted as a guide for the gripper. You can see it on the images above.
• We strongly recommend to assemble from the bottom to the top.
• For more information about the assembly, check assembly instructions

Installation

From Docker

The easiest way to get started is to use the provided Docker image. You can find the Dockerfile in the docker folder. To build the image, run the following command:

sh build.sh

The run the command below to start the container (inside the docker folder):

sh run_docker.sh

Usage

Prepare the Dynamixels

Before starting the node, make sure that the Dynamixels are connected to the computer and that the USB2Dynamixel is connected to the computer. Also check the following:

• The protocol version is set to 2.0 for each Dynamixel.
• The baudrate is set to 1Mbps for each Dynamixel.
• The left arm it's connected to /dev/ttyUSB0 and the right arm to /dev/ttyUSB1.
• The Dynamixels are connected in the following order:

Left Arm	Right Arm
MX-64 - ID 1	MX-64 - ID 11
MX-64 - ID 2	MX-64 - ID 12
MX-28 - ID 3	MX-28 - ID 13
MX-28 - ID 4	MX-28 - ID 14
MX-28 - ID 5	MX-28 - ID 15
MX-28 - ID 6	MX-28 - ID 16
MX-28 - ID 7	MX-28 - ID 17

Start the Node

Once the Dynamixels are connected, you can start the node running the following command:

roslaunch dxl_6d_input dxl_6d_input.launch