Tapping into boundary scan resources for vehicle health management

Abstract

Design for testability (DFT) should go beyond simply assisting manufacturing test or even beyond fielded unit troubleshooting. Boundary scanned components can be controlled to collect real time snapshots of signals capable of assessing circuit health in situ without interfering with normal operation or flight. Vehicle Health Management (VHM) frameworks can utilize the information gained from SAMPLE instructions gathered by JTAG/IEEE-1149.1 boundary scan compatible ICs using Boeing On-Line Diagnostic Reporting (BOLDR®) techniques to enable this data collection for assessing what maintenance actions should be taken. Boundary scan data at or around the time that failures take place can be collected as historical information and retained as “evidence” during a call for line replaceable unit (LRU) maintenance actions. First, it can help assess whether built-in test (BIT) or embedded test indications are persistent, continuous for certain operational modes, intermittent, or simply spurious. In other words, it can help determine false alarms (FAs). Second, once LRUs are in the repair facility and a No Fault Found (NFF) situation is encountered, the historical evidence can help determine the root cause and direct repair actions. Distributed and Centralized BIT for VHM data acquisition can be enhanced by the information boundary scan data provides. Many LRUs that already have boundary scan hardware can utilize embedded software updates coupled with BOLDR® VHM techniques with minimal if any hardware changes to take advantage of this added information source. This paper details how SAMPLE and BOLDR® can be used without major changes in legacy or new avionics.