About Health-Ready Components and Systems (HRCS)
The recommended best practices and guidance provided in SAE JA6268 are advisory in nature and are suggested for use in concert with other IVHM recommended practices and the relevant organization’s engineering design practices. There will be situations where good design requires that these guidelines be extended or modified to maximize use of the component, subsystem, system or the vehicle’s inherent (health-ready) design functions and to optimize the benefits of the IVHM system solution.
It is important to note that this document provides recommendations for the integration of both the design-time data and the run-time messages. A supplier may choose to achieve a “Health-Ready” designation for its components through a process that relies primarily on providing additional design-time data, additional run-time messages or a combination of both.
JA6268 seeks to provide uniform requirements, practices, and methods to address the sharing of critical component/subsystem design-time information. This will facilitate real-time platform level communication and the implementation of supplemental IVHM functions. In the past, component suppliers were primarily operating in the diagnosis-only paradigm in which the focus was to facilitate the detection and identification of the root cause(s) once a failure had occurred.
In the new IVHM or prognostics paradigm, the supplier must also facilitate health monitoring and tracking of system degradation severity to prevent a given component from experiencing an unreported degradation to the point where it goes outside its operational performance envelope. Health-ready components are accompanied by descriptive data that produce a coherent picture of the overall health status of the asset and an estimate of the cost/benefit associated with the implementation or enhancement of the component/subsystem health-ready functionality.
A very important selling point of prognostics is that they have a significant impact on perceived reliability from the end-user’s point of view. Consider the fact that if the vehicle health system can reliably predict 90% of a component’s actual field failure incidents, this implies that only 10% of the expected faults would occur without warning. These high coverage rates may be somewhat easier to attain in the automotive space but recent aerospace programs have had the stated goal of reaching as high as 95-99% coverage. Note that from the end-user’s point of view, achieving a 90% prediction rate is analogous to a ten-fold improvement in raw reliability because 90% of the expected field failures would be transformed into simple maintenance events and never actually allowed to become a failure. Of course, 90% coverage may be difficult to achieve in all cases since some failures are not associated with wear-out mechanisms and can be difficult or even impossible to predict—the attainable level is application-specific.
It is nevertheless still extremely important for design engineers to do all that is practical to make a component’s true reliability be as high as possible. But, no matter what level of reliability is achieved through the application of good design practices, the added opportunity for a significant improvement from the customer’s point of view should be carefully considered. Care must also be taken that false alarm rates are not allowed to go up alongside detection rates.
This recommended practice allows for maximum flexibility for the supplier to determine the best way to provide the required IVHM functionality. In some cases, the supplier will implement nearly all the functionality, but only be required to provide structured data to inform the larger IVHM system how to interact with these functions and use their results. In other cases, the supplier may decide that it is better to provide additional design data to allow the integrator or a third party to implement the required functionality.
In either case, or with a combination of them, the recommended practice calls for the supplier to provide their data in a machine-readable format that this document will reference as a “model.” It is important to note that the “model” includes a series of interface definitions, information to interpret results or data provided by the supplier, and possibly, information required to allow a third party to implement the required IVHM functionality.
The SAE’s IVHM Standards Committee has defined a progression of IVHM Capability Levels as shown in Figure 1. These levels offer a harmonized classification system which:
- Identifies six levels of IVHM system capability from essentially “no automation” at level 0 to “self-adaptive health management” at level 5.
- Provides definitions and levels based on functional aspects of the technology.
- Describes representative categorical distinctions for a step-wise progression through the levels.
- Is consistent with current industry practice and future directions.
- Reduces confusion and is useful across numerous disciplines (engineering, legal, media and public discourse).
- Helps educate the wider community by clarifying for each level the role maintenance technicians have in performing vehicle repairs.
A major transition occurs between levels 2 and 3, where prognostics and predictive analytics are brought to bear. These can significantly enhance the capabilities of the system. These levels as shown in the chart are intended to be generally descriptive and not precise — they hopefully provide a general picture for managers and journalists that captures performance evolution over time along with key distinctions between the levels. They imply no particular order of market introduction. Elements indicate minimum rather than maximum system capabilities for each level. A system may, in fact, have multiple IVHM features which could operate at different capability levels depending upon the feature(s) that are engaged.
Figure – General IVHM capability levels for aerospace and automotive applications
Benefit 1: A Win-Win-Win Strategic Goal
OEMs and suppliers share a common goal of producing the best possible vehicles which ultimately satisfy the needs of the customer. This in turn drives more business to the OEM and to the suppliers in the long term. This common bond creates the basis for a win-win-win situation. First, the OEM achieves a more capable and efficient process to create a higher quality product with built-in IVHM. Second, the supplier has one basic approach whereby it produces the needed information for all its OEM customers. Lastly, the end customer gets a better product that is more reliable, less costly to maintain, and/or better meets their needs.
Benefit 2: Supports Emerging Paradigm Shift from Diagnosis to Prognosis
Throughout the history of the automobile and aerospace industries, OEMs have designed increasingly reliable products built on top of increasingly reliable components and subsystems. The introduction of electronics and computer-based control resulted in the need for more sophisticated diagnostic systems because traditional maintenance approaches were no longer adequate. This happened in part because service technicians could no longer directly observe how various components were performing. For the purpose of JA6268, diagnosis is defined as the process to identify the root cause of a failure once a problem has occurred—specifically, what part or parts require replacement and/or what repair action (e.g., reseating a controller board) is required. The diagnosis paradigm has served these industries well for many decades. However, an argument can be made that the current diagnosis paradigm increasingly suffers from unacceptable rates of No Fault Found (NFF) or No Trouble Found (NTF) incidents. The advent of the prognosis paradigm offers the means to reduce NFF/NTF occurrences since knowing more about the component’s state of health may prevent or reduce unnecessary component replacements.
In today’s world, systems are being designed with ever higher levels of electronics and computer-based control. There is a continuing shift toward electrification of various subsystems, with electronic or electromechanical devices supplanting traditional mechanical solutions. This has created an increased need for health monitoring to mitigate the inherent risks of increased usage of electronics, controls, and software which tend to drive both problem incidents in general and intermittent failures in particular. Similarly, increased usage of certain advanced materials may necessitate new forms of health monitoring. These design innovations in electronics and advanced materials have proven to be a highly effective in meeting the demanding requirements of governmental regulations related to safety, emissions, fuel efficiency, etc. This, in turn, is driving the need for migrating from the diagnosis paradigm to the prognosis paradigm. The goal of prognosis is to track degrading aspects of the overall design to predict deviation. Generally, a prognostic system is defined as capable of computing remaining useful life (RUL), performance life remaining (PLR) or state of health (SOH) with sufficient fidelity and sufficient advance notice to allow a maintenance action well before an operational failure. It is important to note that from the customer or end user point of view, detecting and then correcting problems before they result in loss of function essentially eliminates the impending field failures and replaces them with preventive maintenance actions instead.
Benefit 3: Provides for Better Logical Abstractions of Physical Systems
One critical aspect of more effectively designing and applying health-ready components has to do with the establishment of clear and precise logical abstractions which align well with the represented physical systems. This allows improved design and better communication between the OEM and its suppliers. It becomes the essential underpinning for building good models of these systems and how they behave. In the physical world, there are a multitude of failure modes which lead to performance degradation and ultimately to failure of the given component or subsystem. For example, physical seals can leak and contamination can occur or a fault may be caused by an open circuit or a short circuit. Creating logical abstractions for all these physical systems allows practitioners to understand them, model them and describe their operation. These functional models can incorporate diagnostics as well. In some cases, suppliers provide Failure Mode and Effect Analysis (FMEA) information or possibly a Fault Tree Analysis (FTA). This information correlates symptoms of a failure to the corresponding failure and its root cause, which then facilitates fault isolation and reduced “Could Not Duplicate” (CND) situations. The FTA can provide a method to evaluate the effects (and the probabilities) of failures of the components on the vehicle system as a whole. The FMEA will always be valuable and some of its content will clearly be required for health-ready components. In fact, the FMEA process itself could be enhanced to better meet the needs of IHVM and prognostics by identifying relevant parameters and relationships that could be used to detect the onset of all known failure modes.
Benefit 4: Facilitates Sharing of Semantic (Underlying Meaning) Data from Suppliers
To implement a health-ready component/subsystem into the IVHM system integration strategy, it is important for the supplier to identify and specify the health state data parameters, messages and their meaning (i.e., semantics) which must be provided for the component/subsystem to provide the critical IVHM interfaces. If the supplier does not wish to implement all of the recommended functionality, the supplier may instead choose to provide additional design data to allow the integrator to do so.
Suppliers should provide understandable, machine readable formulae to permit the translation of raw sensor outputs into specific, appropriate engineering units. The machine readable aspect is very important because simple textual descriptions are highly error prone and frequently complicate the use of the information or, worse yet, lead to incorrect conclusions as the data is used.
Benefit 5: Offer Enhanced Methods for Model-Based Engineering
The cost of obtaining equipment-specific IVHM design characteristics could be greatly reduced if the suppliers of the equipment provided more of their design data in a machine readable format. The increasing use of model-based design engineering tools across the industry will facilitate the exchange.
It is worth noting that the presence of these models goes well beyond just defining the interface between the component and the higher level system which is going to access the data. It must also provide insight into what is happening within the component or subsystem. Specifically, it should allow the data to be properly interpreted at the vehicle level. Ideally, these models will become more comprehensive and useful as time progresses. In the interim, a less demanding alternative is to share just the relationships between provided parameters which are deemed important by the designer in terms of detecting degradation. For example, a supplier could identify the critical parameters (along with their normal ranges and the relationships or ratios involving those parameters) that are best used to warn of the onset of specific failure modes.
Are there SAE standards for Health-Ready Components and Systems?
Yes. On April 2, 2018, SAE published “JA6268: Design & Run-Time Information Exchange for Health-Ready Components.” This document is designed to help reduce existing barriers to the successful implementation of Integrated Vehicle Health Management (IVHM) technology into the aerospace and automotive sectors by introducing the concept of “health-ready components.”
What is a health-ready component?
Health-ready components are supplier-provided components or subsystems which have been augmented to monitor and report their own health or, alternatively, those where the supplier provides the integrator sufficient information to accurately assess the component’s health via a higher-level system already on the vehicle.
Why is JA6268 important?
The principal motivation behind JA6268 is to facilitate the integration of the IVHM functionality in supplier-provided components to meet the needs and objectives of vehicle OEMs, end users, and government regulators in a cost-effective manner. Underlying this motivation is the assumption that market forces will drive the need to achieve industry-wide application of IVHM technology across the aerospace and automotive sectors, which will in turn drive new health-ready requirements that suppliers must ultimately meet.
What are the objectives of JA6268?
The recommended practices contained in JA6268 have two primary objectives:
(1) to encourage the introduction of a much greater degree of IVHM functionality in future vehicles at a much lower cost
(2) to address legitimate intellectual property concerns by providing recommended IVHM design-time and run-time data specification and information exchange alternatives
Why is industry awareness important?
IVHM technology has the potential to provide significant business benefits in terms of performance, availability, and safety. To date, the level of deployment in aerospace and automotive domains has been limited with respect to higher end functionality such as predictive analytics or prognostics. One of the key barriers is the lack of uniform information sharing methods between OEMs and their suppliers.
Why is now the right time for HRCS?
There is a window of opportunity to move proactively to accelerate IVHM implementations and avoid unnecessary proliferation of different approaches which would be costly and counterproductive. JA6268 is a recommended practice designed to capture this opportunity now. The SAE HM-1 committee established the consortium of OEMs and suppliers, Health Ready Components & Systems, to steer the JA6268 implementation path and positively impact IVHM industry-wide practices.