This repository contains the code to control the UMI-RTX robot. The UMI-RTX robot was designed in 1985 for Universal Machine Intelligence Ltd [1] and first released in 1986 [2-3]. It is a robot in SCARA format with extended vertical travel. This robot is designed to work in a cylindrical workspace. With its three axis wrist the UMI-RTX robot has in total 6 degrees of freedom.
The upper arm and lower arm have the same length: AB == BC. This means that you can move the wrist in a straight line outwards from the column - a radial line between the shoulder and wrist spindles - by rotating the two parts of the arm, making sure that angle P is always half angle Q: The gear ratio from the shoulder motor to the upper arm is twice that of the elbow motor to the lower arm. To move the wrist in a radial line, both motors are driven at the same speed but in opposite directions. The benefit of this arrangement is that the robot controller can keep track of the position of the wrist in cylindrical coordinates very easily, by simple calculations based on the motor encoder counts.
In addition, the gripper is automatically pointing along the radial line: This is achieved without needing to drive the yaw motor (angle R): the yaw is not only coupled to its own motor, but also coupled to the elbow motor!
At the University of Amsterdam, the UMI-RTX robot was used to play chess [4], which it still can do (with this code ported to Ubuntu 20.04).
Note that based on this code also a ROS2 interface was build. This code can also be found at github. Details on this implementation can be found in their internship report [5].
The code is tested on two Linux LTS distributions:
The code has a number of dependencies on libraries which are not part of the basic configuration of an Ubuntu distribution. The following dependencies are known:
* sudo apt update
* sudo apt install gcc
* sudo apt install libelf-dev
* sudo apt install libreadline-devThese dependencies can also be installed by running the install-dependency.sh script.
The code is tested with the following build order of the libraries:
* cd src/hostlib; make
* cd src/rtxlib; make
* cd src/armlib; make
* cd src/daemon; make
* cd src/shell; make
* cd src/umi; make
* cd src/matrix; make
* cd src/xml_parser; make
* cd src/inverse; make
* cd src/stub_pp; make
* cd src/pathplan; make
* cd src/gnuchess; make
* cd src/game; make
* cd src/playall; make
The communication with the UMI-RTX robot is possible via one of your USB ports. Under Ubuntu this port is accessible via /dev/ttyUSB0 (or a higher number when you connect multiple times). The communication with the robot is handled by a daemon with runs as a server in the background. Your applications can run as client in the forground.
As first example of such combination is the daemon and a shell.
cd bin; sudo ./rtxd /dev/ttyUSB0
cd bin; sudo ./rtxshOnce you are in the shell, you can simple type 'help'.
Output of the daemon is printed in a log, which you can find in umi-rtx/logs. When corrected working the log should display only the message
(RTXD) Restarting, listening to port ----- on this machineIf you started the daemon without argument, it will try to use the IPC protocol (and fail):
(RTXD) Restarting, listening to port 33849 on nb-ros<br>
/dev/ipc0: No such file or directory
/dev/vme32: No such file or directory
(RTXD) Can not open IPC
(RTXD) 'IPC' should start with '/dev/'
(RTXD) No rtx_ops found for 'IPC'
(RTXD) Can not talk to RTXIf you start the daemon with out super user rights (forget to use sudo), you can get one of these messages:
Current working dir ~/git/umi-rtx
./ports/rtx: Permission deniedWhen you forgot to connect the USB (or the UMI-RTX is not on), you will get:
(RTXD) Couldn't open '/dev/ttyUSB0'
(RTXD) No rtx_ops found for '/dev/ttyUSB0'
(RTXD) Can not talk to RTXIf you try to start the shell with root permisions (forget to use sudo), you will get the following error messages:
RTX command line interface $Revision$
======================= ARM version 8 March 2022
downloadlib has problems connecting to UNIX socket: Permission denied
[armlib:downloadlib] failed
init: Retry the connection
======================= ARM version 8 March 2022
downloadlib has problems connecting to UNIX socket: No such file or directory
[armlib:downloadlib] failed
init: Cannot connect to daemon[1] Tim Jones, Developing a Personal Robot from Concept to Final Product, Personal Robotics Seminar, London, UK, 3rd July 1985.
[2] Universal Machine Intelligence Ltd, Inside RTX, guide to the design, mechanics and electronics, April 1987.
[3] Universal Machine Intelligence Ltd, Maintenance Manual for RTX , August 1987.
[4] Groen, F., der Boer, G., van Inge, A., and Stam, R. (1992). A chess playing robot: lab course in robot sensor integration. In Instrumentation and Measurement Technology Conference, 1992. IMTC ’92., 9th IEEE, pages 261–264
[5] Guillaume Garde and Théo Massa, A ROS 2 Interface for the UMI-RTX robotic arm, internship report, École Nationale Supérieure de Techniques Avancées Bretagne, August 21, 2023.