Integrated vehicle health management
NASA[3] was one of the first organisations to use the name IVHM to describe how they wanted to approach maintenance of spacecraft in the future.
NRTEs were isolated to the GPS satellites after mission operations support personnel replayed the real-time satellite telemetry ruling out RF and land-line noise caused from poor Eb/No or S/N and data acquisition and display system processing problems.
Another milestone was the creation of health and usage monitoring systems(HUMS) for helicopters operating in support of the Oil rigs in the North Sea.
For example, if an aircraft was experiencing frequent heavy landings the maintenance schedule for the undercarriage could be changed to ensure that they are not wearing too fast under the increased load.
The load carried by the aircraft could be lessened in future or operators could be given additional training to improve the quality of the landings.
The growing nature of this field led Boeing[7] to set up an IVHM centre with Cranfield University in 2008 to act as a world leading research hub.
IVHM is a concept for the complete maintenance life cycle of a vehicle (or machine plant installation).
It makes extensive use of embedded sensors and self-monitoring equipment combined with prognostics and diagnostic reasoning.
The remaining useful life is used to plan replacement or repair of the part at some convenient time prior to failure.
The inconvenience of taking the vehicle out of service is balanced against the cost of unscheduled maintenance to ensure that the part is replaced at the optimum point prior to failure.
This allows the reduction in waste component life caused by replacing the part too early and also reducing cost incurred by unscheduled maintenance.
Communications between the vehicle and the maintenance organisation are crucial to fixing faults in a timely manner.
This yields a time advantage as they know some of the parts and personnel required to fix the fault before the aircraft has landed.
However the communication link does cost money and has a limited bandwidth so the worth of this health & usage data must be judged carefully with consideration given as to whether it should be transmitted or merely downloaded during the next maintenance or as part of the operator shutdown process.
