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Foundation ::
Reliability Analysis ::
ARAM
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ARAM
Automated Reliability/Availability/Maintainability, Version 2.0
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Moderators:
Adopt This Application!
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SOURCE CODE AVAILABLE
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The Automated Reliability/Availability/Maintainability program, ARAM, is one of the tools designed to assess candidate Space Station Data Management System architectures. It evaluates the reliability, availability, and maintainability characteristics of the system concepts. ARAM uses the data representing the system architecture redundancy characteristics (redundancy diagram), the system maintainability characteristics, and the hardware component reliability parameters.
Reliability is the probability that a function performs without interruptions within a given time interval. For any unit, the time between failures is assumed to have an exponential probability distribution defined by its mean time between failures. Maintainability is the probability that a function is restored within a given time interval. Parameters include repair service priority, mean time to repair, and availability of spares. Maintainability includes global parameters such as spare parts replenishment period and number of repairmen.
The ARAM design is based upon the simulation of failures and the possible subsequent repairs of each hardware unit included in the system. It analyzes the effects of failures and repairs on the system and maintains statistics of the system behavior from which the simulation results are obtained. During a typical ARAM simulation, when the clock advances to a failure event, the program assess whether any group fails because of the unit failure. It then propagates the failure event to all affected groups. Next, ARAM generates a unit repair event for the repairable unit. Other choices include on-line or off-line backup units. The simulation can be repeated a specified number of times for each one of the seeds specified for the random number generator, or can be timed. At the end of a simulation, the program computes the average statistics.
ARAM is delivered as a package of files that include the model generation and simulation program and the model data base template. A data base conversion program enables the users of the previous Version 1.0 to convert their model Version 1.0 data bases to the Version 2.0 format.
ARAM carries the NASA case number LAR-13997. It was originally released as part of the COSMIC collection.
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