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Journal of Information Science and Engineering, Vol. 26 No. 3, pp. 1121-1136


Weighted Characteristic P-vector and Deadlock Control of WS3PR

DANIEL YUH CHAO
Department of Management and Information Science 
National Chengchi University 
Taipei, 116 Taiwan

    Current deadlock control approaches for S3PGR2 (systems of simple sequential processes with general resources requirement) suffer from incorrect or restricted liveness characterization based on the concept of deadly marked siphons (DMS) and max-controlled siphons. Dead transitions may exist when there are no DMS and the net model is in livelock states. A new liveness condition is developed based on the so-called max*- controlled siphons to replace that of the restrictive max-controlled siphons. A deadlock control policy is further proposed for WS3PR (weighted S3PR (systems of simple sequential processes with resources)) by adding control nodes and arcs for elementary siphons only, reducing significantly the number of monitors compared with existing methods. A counter example is shown to indicate that Li's characteristic P-vector must be weighted. The controlled model for WS3PR is proposed and its liveness property is proved.

Keywords: flexible manufacturing systems, deadlock control, Petri nets, siphons, elementary siphons

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