FCS 4-DOF Robot Hand

A 4 degree-of-freedom robot hand driven by four Futaba Command Servos, with 3D-printed link parts and ros2_control support.

This repository has no photo of the robot yet.

3D preview converted from github.com/knaga-rgj/fcs4hand2310 at 2f344bc, under Apache-2.0. View the original files from GitHub (1.3 MB) (opens in a new tab)

What it can do

Written by Robotheca from the project's documents.

Drives a four-joint robotic hand (hndj0 to hndj3) using Futaba industrial command-type servos.
Joint angles are commanded through a joint_trajectory_controller and reported back by a joint_state_broadcaster under ros2_control.
Servos can be switched between torque off (inactive) and torque enabled (active) states through ros2_control.
Test and tuning of individual servos is possible with the dicot Python tool over a serial connection.
Tested under ROS 2 Humble.

This repository has no parts list Robotheca can read yet.

The creator's steps, each with its instructions.

The guide appears here as you scroll.

Guide by @knaga-rgj (Readme.md), under Apache-2.0. The English translation is by Robotheca, shared under the same license.

Notes written by Robotheca from the project's documents.

Four Futaba command-type servo modules (RS304MDFF or RS303MRFF for TTL type; RS302CDF3 or RS305CR for RS-485 type).
Futaba TB-RV71EH-7.4V/3W hub (TTL type) or a pair of hubs BA2083/BA2084 with BA2085 (RS-485 type).
Futaba RSC-U485 USB adapter, required together with the hub.
Motor power supply rated 4.8 to 7.2 V; current capacity not documented.
JST EHR-4 connectors (TTL type) or Hirose DF11-4DS-2C connectors (RS-485 type).

TTL type: servos connect to the hub via JST EHR-4 4-pin connectors, and the hub connects to the USB adapter.
RS-485 type: the USB adapter to hub link is RS-485, and a custom 3-core cable runs from EHR-4 to DF11-4 carrying D+, D- and GND.
RS-485 type: a custom 2-core power cable runs from the power supply to the DF11-4 connector, carrying VCC and GND.
Termination resistors may be placed at both ends of the RS-485 line.
Servo IDs must be written to each servo before operation.

Incomplete documentation

How complete the published files are for rebuilding this robot, measured by Robotheca at commit 2f344bc. It isn't a rating of the robot.

3D and CAD files10/20
6 CAD source files.
Add the parts to print (STL or 3MF files).
Robot description0/15
No URDF.
Add a URDF: the robot can then be seen in 3D and tried in the browser.
Parts list0/20
No parts list in the repository or linked.
Most points to gain: Link to your parts list, or add it to the repository (a CSV or a Markdown table) with quantities, prices and where to buy each part.
Software15/15
Code in this repository, instructions to install or run it, built on ros2.
Documentation10/15
README of 7,206 characters with 0 pictures; 6 build steps.
Show the robot and its assembly in pictures in the README.
Simulation0/5
No simulation files.
Add a simulation model (MuJoCo, Gazebo, Webots or Isaac).
Licenses10/10
Hardware: Apache-2.0; software: Apache-2.0.

Written by Robotheca from the project's documents.

Install the hardware_fcs package from its repository so that ros2_control can use the servos.
Add the user account to the dialout group so the serial device can be accessed, then reboot.
Build the package and start it with the launch file launch/fcs4hand2310.launch.py.
Activate the hardware component fcs0 with the set_hardware_component_state service, using the torque_enable.sh script or the equivalent service call.
Send joint positions to the joint trajectory controller, using scripts/set_angles.py or ros2 action send_goal.

Robotheca doesn't review code. Read it before running it.

Every file of the project: code, CAD, electronics, guides, at commit 2f344bc.

Questions and improvements go to the creator's repository.