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3 fill 'Uc> V? Fault tolerant embedded computers and power electronics for nuclear robotics A. Giraud/M. Robiolle LETI (CEA - Advanced Technologies) DEIN - CE/S F91191 Gif-sur-Yvette Cedex - FRANCE tel : (33) fax: (33) e_mail: agiraud@heron. saclay. cea. fr Interest area : The interest session in which work described in this paper would be suitable is : Hostile environment, Hardening and Survivability Technologies. Abstract For requirements of nuclear industries, it is necessary to use robots with embedded rad-tolerant electronics and high-level safety. In this paper, we first describe a computer architecture called MICADO designed for French nuclear industry. We then present ongoing projects on our architecture. A special point is made on power electronics for teleoperated and legged robots.

4 Fault tolerant embedded computers and power electronics for nuclear robotics A. Giraud/M. Robiolle LETI (CEA - Advanced Technologies) DEIN - CE/S F91191 Gif-sur-Yvette Cedex - FRANCE tel : (33) fax: (33) e_mail:agiraud@heron. saclay.cea.fr ABSTRACT For requirements of nuclear industries, it is necessary to use robots with embedded rad-tolerant electronics and highlevel safety. In this paper, we first describe a computer architecture called MICADO designed for French nuclear industry. We then present ongoing projects on our architecture. A special point is made on power electronics for teleoperated and legged robots. I. INTRODUCTION - design of reliable electronic modules and embedded systems. HI. MICADO ARCHITECTURE The architecture shown in figure 1 was studied in order to alternate supplied / unsupplied phases on the most significant and sensitive to radiations components. MICROCONTROLLER OQMMCM powatsumr The use of remote handling robots with rad-hard (7 rays) electronics, high-level safety and availibility for embedded applications is required for the nuclear industry. Studies made by our team have been particularly successful at developing methodologies for characterising standard rad-tolerant CMOS components and specifing the influence of the most significant parameters to increase total dose tolerance (section II). Computer architecture MICADO. using the 68HC05 family, provides an innovative approach to this problem. Two sets of prototypes (section III) have been produced for French nuclear operators. We are developing MICADO_16 (section IV). an evolution of MICADO to meet the short term needs of the (French) nuclear industry. We also made specifications for a new architecture called CADMOS. It will be used for powerful embedded applications in mobile robots. Our work on power electronics will also be discussed. II. METHODOLOGY PROM POWZ* SUPPLY DMICROCONTROLLER PROM rownt SUPPLY MICROCONTROLLER 10 BUS INTERFACE IO BUI INTERFACE CMOS standard technology has been choosen to limit energizing and economical weights in civil nuclear embedded applications. The high sensitivity of CMOS to total dose needs to specify an original methodology to build electronic systems. This methodology [1] is based on three points: - prospecting and selection of components which give best results under radiation - specific architecture design which increases components life-time and applications availibility[2] PROM Figure 1 : MICADO architecture (basic unit Multibus board computer) This originality made on 68HC05 family microcontrollers increases total dose level by a factor of around 20.

5 Targeted embedded applications arc smart multiplexes in remote control moving robots. Total dose expected is up to 10 3 Gy. A. Multibus board computer The central unit, composed of two basic units of 3 microcontrollers, handles analog and digital I/O through a common soft control bus. In normal mode, on each basic unit, only one of the three microcontrollers is supplied and executes tasks. After a one minute run, it questions the bus until it finds a newly supplied microcontroller able to assume continuation of work. If there is one, context and activity are commuted. The power supply of the previous microcontroller is cut off for one minute. If there is a failure on the active microcontroller, fault confinement is achieved through isolation from the bus and cut off of the power supply. The safety position is turned on I/O cards. The application is recovered a few seconds later by doing a cold restart on one of the two last microcontrollers. To maintain a minimum performance level after a second failure, a watch-dog sets a sleeping time after ten minutes work. Degraded operation is preferable to no operation at all. Built to resist to total dose effects, this architecture is fault -tolerant with dynamic reconfiguration and graceful degradation [4]. Global tests under radiation gave correct availibility over 800 Gy (1000 Gy for I/O cards). B. 3 U board computer We have added downloading to update codes or data at initialisation or during long time missions. IV. POWER ELECTRONICS To complete MICADO embedded computers, we have conceived power electronic control cards to drive DC motors (48V. 3A). Standard components are used and withstood a total dose of 10 4 Gy. A new rad-hard design power amplifier VULCAIN[5] has been developped. It can solve motion commands for feedback effort manipulators in cells (60V, 10A). The use of standard or rad-hard CMOS technology will allow the driving of brushless and asynchronous motors (legged robots). IV. CADMOS ARCHITECTURE In the long term, embedded applications will need more computing power to assume larger autonomy than today. We need to go beyond the concepts of MICADO. In figure 2, ypu can see the CADMOS architecture. Mcra processor Sarial b< i (riagnost. in in* Me >. satoty mode) This computer is an optimisation of the previous in volume, modularity and standardization. We made the choice of a 3U size and a 96 pin connector for the bus with the same soft control. Two microcontrollers brought together on a same card represent basic units. The central unit, expanding to 4 basic units, is a good answer to graceful matching with environment, computing power and redundancy. External memory is added for data diagnosis, rollback points and journaling. I/O cards have been rebuilt in 3U size. VMEBUS Supervisor Supervisor handling : CADMOS architecture IV. MIC ADO J6 ARCHITECTURE Short term prospects that we have identified show that there is a need for more embedded computing power and a total dose up to 10 4 Gy. To be easily extended to applications which already use MICADO computer, we decided to change only basic units. We found either in standard technology and in rad-hard technology (up to 10 4 Gy) a pin to pin compatible 80C86 microprocessor. Each basic unit includes one 8086 microprocessor, in standard or rad-hard technology, pin to pin compatible. In that way. with the same card, we are able to answer most parts of the embedded applications. The main features are: - standard VME interconnection bus[6] - supervisor to handle failure detection, failure confinement and reconfiguration (also for alternative supply if used) - standard technology and, if possible, rad-hard technology' 16 or 32 bits microprocessors basic units cards The supervisor has been completely designed. It is composed of a duplex MICADO architecture computer and an original decision modulc[8j. The prototype will be built in 1995.

6 V. CONCLUSION Selection and qualification of industrial components for this architecture were an important point for the design of MIC ADO and MICADOJ6 architectures. We are able to build rad-tolerant electronic systems for remote control in nuclear plants. The development of new components and the evaluation of their characteristics under radiation will have an influence of our next architecture design. Then, we will provide computers for future projects like decommissioning. VI. REFERENCES [1] F. Joflre, J. Buisson, D. Mijuin, "Instrumentation pour l'etude des effete de la dose cumulee sur les composants des systemes microinformatiques H p Actes RADECS 1991 [2] F. Joflfre, "Precede pour la prolongation de la duree de fonctionnement d'un circuit a composants MOS soumis a rayonnement GAMMA", demande de brevet du 12 Juin 1990 au nom du CEA [3] F. Joffre, "Calculateur embarque a tolerance de panne", revue de la societe des ingenieurs de l'ecole Superieure d'electncite no 145 Avnl/Mai 1992 p 38 [4] D. P. Siewiorek, R. S. Swarz "Theory and practice ol" reliable System Design" Digital Presse 1982 [5] A. Basire, M. Marceau "Systemes de commande d'actionneurs a courant continu en electronique de puissance", demande de brevet 93J5564 du 23 Decembre 1993 au nom du CEA. [6] W. D. Peterson "The VME bus handbook : a users's guide to IEEE 1048 and IEC 821 Microcomputer bus" VFEA international Trade Association 1991 [7] R. Galy, "Architecture duplex decisive", demande de brevet du 03 Mai 1994 au nom du CEA