Vol.3 No.3 2010
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Research paper : A methodology for improving reliability of complex systems (A. Katoh et al.)−204−Synthesiology - English edition Vol.3 No.3 (2010) integrated control computer which controls the measurement and robot subsystems and a consoleTerm 34 to input work instructions and to check system status. The integrated control subsystem controls the robot subsystem based on the results of measurements by the measurement subsystem.Also, the traceability matrixes for the measurement, robot, and integrated control subsystems are developed for architectural designing.5.2.2 Bridge methodBridge method is applied to the subsystem specifications, the interface specifications among the subsystems, the traceability matrix, and the system specification for the irregular-rigid-body-transport robot system. Here, we discuss the measurement and integrated control subsystems to describe the specific application of the bridge method.First, the specifications related to the cooperative behavior are extracted from the subsystem specifications and the interface specification between subsystems based on the traceability matrix. The specific extraction of the specifications related to the cooperative behavior follows the means described in subchapter 4.2. For the measurement subsystem specification, six items are extracted from 39 specification items, and for the integrated control subsystem, six items are extracted from 78 specification items. For the interface specification between the measurement and integrated control subsystems, 22 items are extracted from 26 specification items.Next, the properties which must be satisfied by the cooperative behavior of the subsystems are extracted based on the traceability matrix and the system specification of the irregular-rigid-body-transport robot system. The specific extraction of the properties which must be satisfied by the cooperative behavior follows the means described in subchapter 4.2. For the measurement and integrated control subsystems, 23 items are extracted as the properties which must be satisfied by the cooperative behavior. Table 1 shows two items from the 23 properties extracted.The attributes of the cooperative behavior are determined based on the extracted specifications related to the cooperative behavior and the properties which must be satisfied by the cooperative behavior. In the cooperative behavior of the measurement and integrated control subsystems, the lacks and variances of the messages which are sent or received between subsystems and processings related to the messages are suspected. There are specifications for the timing of the messages which are sent or received between subsystems and processings related to the messages as well as the temporal limitation within 100 ms. Therefore, the two attributes, (1) and (2), as shown in subchapter 4.2, are determined.Also the model checking tool to be applied is selected based on the identified attributes. For the cooperative behavior by the measurement and integrated control subsystems, it is necessary to verify the temporal limitation and the timing of messages which are sent or received between subsystems and processing related to the messages. Since the measurement and integrated control subsystems behave in parallel, it is necessary to select the model checking tool which can deal with the parallel systems. Therefore, UPPAAL is selected as the model checking tool which satisfies these requirements.5.2.3 Model checkingAs in the previous section, the measurement and integrated control subsystems are discussed in this section to describe the specific application of model checking.First, the specifications related to the cooperative behavior extracted by the bridge method are modeled according to the expression form of the model checking tool. Figures 11 to 13 show the results of modeling the specifications for the cooperative behavior by the measurement and integrated control subsystems using UPPAAL. The developed model is composed of three models for the specifications related to cooperative behavior: the model corresponding to the measurement subsystem (Fig. 11); the model corresponding to the integrated control subsystem (Fig. 12); and the model corresponding to the interface between the measurement and integrated control subsystems (Fig. 13).Next, the formulae for model checking are developed based 9 Irregular-rigid-body-transportrobot systemIntegrated control subsystemConsoleVertical movementmechanism forlaser scannerRobotsubsystemMeasurementsubsystemMeasurementcontrol computerLaserscannerRobot handControllerTeachingpendantRobot armControllerIntegratedcontrol computerInterfaceSubsystemcomponentSubsystemSystemFig. 10 Results of architectural designing for the irregular rigid-body transport robot systemTable 1 Properties to be satisfied for the cooperative behavior by the measurement and integrated control subsystems (2 out of 23 items)The measurement subsystem must stop the measurement processing within 100 ms after the measurement stop request is transmitted by the integrated control subsystem.3-3The integrated control subsystem must receive the result of rigid-body measurement or the failure response of rigid-body measurement from the measurement subsystem, when the rigid-body measurement request is sent to the measurement subsystem.1-5PropertyNo.

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