Robot control Introducion

The Robot motion controller consists of a very important component in a robotic infrastructure. The flexibility is more and more needed to allow fastness in development and adaptation from one robot to another. At the laboratory of robotic systems of the Ecole Polytechnique Fédérale de Lausanne (LSRO-EPFL), different PhD thesis has been carried out in order to go ahead with the flexibility of the robot control [1] [2] [3].
Indeed since the appearance of the delta robot in 1985 [4], the exigency on the motion controller has been more relevant.

We actually need a control with:

  • Very small sampling rates from 100us.
  • Flexibility with respect to :
  • the robot kinematics,
  • the environment,
  • the needed application

Dr Alain Codourey and Dr Laurent Rey ([1], [2]) has developed a very powerful controller based on a distributed architecture. They start with the Motorola 68000 processor and moved on to the T800 transputers programmed with OCCAM. The Delta robot available at the LSRO is still controlled with such controller at 1 ms sampling period. From 1997 to 2000, we have developed a robot controller based on the real time operating system VxWorks around a VME based Mototorola target. This has been the step made from multi processor distributed architectures to one processor platform with a multitasking architecture. To have more flexibility on developing the applications and to decrease the training cost for the members of the LSRO, we had go on with a PC based architecture running Microsoft Windows adding a real-time extension RTX from Ardence [5].
The flexibility of this control has been proven with the different applications that run based on the same control kernel. With easiness and fastness different field buses have been implemented (Firewire, Profibus and now USB). This section will present the different topics of robot controllers and related works carried out at the LSRO.

[1] Laurent Edouard Rey, Environnement pour la conception de commandes de robots. Thèse EPFL, no 1663 (1997).

[2] Alain Codourey, Contribution à la commande des robots rapides et précis : application au robot delta à entraînement direct. Thèse EPFL, no 922 (1991).

[3] Boris Siaka Stevens, Control characterisation and optimisation of fast industrial robots (an application to the direct drive DELTA parallel robot ). Thèse EPFL, no 1362 (1995).

[4] Reymond Clavel, Conception d’un robot parallèle rapide à 4 degrés de liberté. Thèse EPFL, no 925 (1991).

[5] M. Bouri and R. Clavel, A Windows PC based robot controller: an open architecture,” Internation Symposium on Robotics, Tokyo, 2005

Robot control elements