Intelligent Control Lab.
Open Control Architecture for a PUMA 560

The Intelligent Control group at ISR has built a testbed for design, development and test of multi-sensor control algorithms for a PUMA manipulator, based on an open software and hardware architecture. This has already allowed the testing of telemanipulation, vision-based controllers, trajectory planners, as well as centralzed non-linear control algorithms which were not implementable with the original Unimate Mark II controller. In the future, we expect to implement, among others, real-time position and force control algorithms, task planners, and in general manipulator controllers which rely on several different external sensors.

The open control architecture is based on a PC network. Each PC of the network is responsible for a computation module (e.g. position control, image processing, task planning). The communication between PCs requires real-time multi-platform software.

Current Project Status

The original central (LSI-11) board and 1-PID-per-joint (6503) boards were removed and their functions were completely replaced by the TRC004 board, manufactured by Trident Robotics .

All the developed functions are now usable as primitives for future developments, grouped in several appropriate libraries. People at the VA Rehab R&D Center in Palo Alto, California, USA, are using our libraries as a basis for their work using a PUMA 260 arm. We are starting the implementation of a task coordinator based on Petri nets, which will use some of those primitives.

Original Unimate Mark III Controller Architecture


Current TRC004-based Control Architecture

The TRC004 enables the transmission of digital commands (such as arm power-on, release brakes), direct readings of the 6 joint encoder values, a D/A to provide torques to the joint DC motors, and an A/D to read the 6 joint potentiometers for calibration purposes. It communicates with an external Pentium PC by a ribbon cable connected to a TRC006 (ISA-bus). Sampling rates up to 400 Hz were attained for both the motor current analog servo and the trajectory digital servo. Also available is an interface board for VME machines, not used at the moment.

Results of tests based on a cubic polynomial trajectory interpolator are available for:

The sampling rate for both tests was 200 Hz.

This work was developed at ISR by Paulo Alvito, Nuno Martins and Nuno Moreira.

A paper summarizing the conversion from the original to the new architecture is available:

ISR Main Page
ISLab Main Page
Contact
Last modified: 17:30 15-September-2002