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Automated Diagnostics and Remote Power Controllers In this NASA application,
targeted to Space Systems Power Management, the Diagnostician has been
implemented on a single-chip micro-controller, and performs fault detection,
fault isolation, reconfiguration and recovery functions. This is a totally self-contained diagnostic
capability that manages the dynamic reconfiguration of system resources around
a fault to provide graceful degradation.
In this application, the time from occurrence of the fault to
reconfiguration around the fault was approximately 60 milliseconds. It also includes a communication link to
ground-based maintenance terminals to monitor specific status of all system elements. Some details are provided below. Safety, sustainability and mission criticality
considerations often predicate the requirement for built-in fault tolerance in
aerospace power management systems. Existing approaches to accomplishing fault
tolerance typically focus on "brute-force" hardware redundancy and
extensive, complex control logic developed as a "point solution" to
effect reconfiguration actions. This project applied the Diagnostician as an
innovative design strategy and implementation approach for embedding an
adaptive model-based diagnostic reasoning capability into a Fault Tolerant
Remote Power Controller (FTRPC) to provide rapid fault diagnostics and
reconfiguration of power flow to critical users. Using
"Diagnostician-on-a-Chip (DOC)" technology, the approach is based on
the use of microcontroller technology and an automated Concurrent Engineering
Tool Set (CETS). CETS is comprised of both a development environment, the
Diagnostic Profiler, and rehostable run-time software, the Diagnostician. The Diagnostic Profiler development
environment is used to generate a Diagnostic Knowledge Base (DKB) of the FTRPC. This DKB is subsequently
integrated with the Diagnostician run-time reasoning software within the target
microcontroller. The Diagnostician/DKB integration provides a fault isolation
capability which functions within the context of the FTRPC Fault Detection, Isolation and Recovery (FDIRR) capability. A key aspect of this project
is that a systems engineering approach was used to develop the reasoning
capability that could be embedded in the system to accomplish FDIRR. The system
engineering approach, applied through the CETS tools is generic in nature and
can be applied to any system, as opposed to a "point solution"
developed by intensive engineering efforts.
The extensibility and applicability of the overall approach is a key
aspect of the technological accomplishments of this program. Advanced Technologies Implemented/Integrated Many exciting advanced
technological aspects were integrated and implemented in this program. These
technologies were synergistically combined and were "cascaded"
together to accomplish the dynamic reconfiguration capability. These technologies include: Model‑Based Diagnostic Reasoning Use of a design model to
implement all diagnostic logic Embedded Model‑Based Reasoning Integration of the model with on-line,
embedded performance monitoring and built-in test functions Diagnostician‑on‑a‑Chip Implementation of the
model-based solution on a single-chip microcontroller for integration in an
embedded environment Fault Tolerant System Management Full software support of operational and
failure data supporting extensive operations monitoring and management from an
off-system or remote location Adaptive Model‑Base
The ability of the design-based model to
adapt to a new hardware configuration state and maintain its functional
integrity. Dynamic Reconfigurability
The ability to dynamically reconfigure
hardware resources in real-time to accommodate a failure event and maintain
operations Uninterrupted Power in the The ability to maintain continuous
operations in the Presence of Fault Events presence of a hardware fault. Simultaneous, Multiple
The ability to detect, isolate and reconfigure
around Independent Faults
multiple faults occurring in independent portions of circuitry that transpire simultaneously. Prognostic Capability
Though not fully implemented, the model-base
and software structure enables a prognostic capability by monitoring "rate
of change" of voltage levels to provide an indication of impending failure
events. Process-oriented Solution Implementation of above technologies in a
structured, automated, generic systems engineering approach
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