Safe Electromagnetic Telecommunications on Vehicle
The SAFETEL Project was set up in the FP6 framework taking into account the Commission Communication for Safe and Intelligent Vehicles COM(2003) 542.
This research was proposed by SYDERA to the FP6 with the purpose of studying the improvement of the robustness of motor vehicles against electro magnetic (EM) disturbances due to both the internal and external EM environment. Its goal is to achieve a higher level of safety than current standards by providing advanced tools for prediction, design and testing.
The project was intended to define a simulation and test strategy, and provide a set of theoretical instruments and design tools to guarantee the proper EMC design of electronic equipment in the presence of vehicle on-board receivers and transmitters.
SAFETEL was aimed at pursuing the objectives as addressed by IST-2002-18.104.22.168: 'eSafety of road and air transports', and was also relevant to the strategic objectives of SUSTDEV-2: 'Sustainable surface transport'.
SAFETEL was aimed at fulfilling the FP6 thematic priority 6 and covered the areas:
- electromagnetic Compatibility (EMC) testing;
- electroMagnetic (EM) environment modelling;
- rapid prototyping;
Finally, a SAFETEL objective within the Thematic Priority Area was to develop a production environment specific to surface transport based on the innovative use of advanced design and manufacturing technologies.
The SAFETEL research Project was specifically focused on the following:
- to improve the robustness of vehicles against electro magnetic (EM) disturbances;
- to increase road safety by achieving levels greater than the existing standards against internal and external EM environment;
- support competition within the European automotive industry.
This is to be achieved by the seven research objectives listed hereafter:
- to define the design electromagnetic environment vehicles are faced with;
- to define immunity safety margins of on board electronic components and equipment;
- to define the EM hardening rules to be applied to the on board equipment design;
- to define advanced test methods and procedures applicable for quantitative measurement of EM threat effects;
- to specify the requirements relevant to a High Intensity Susceptibility Signal (HISS) test setup and facility;
- to specify/design software tools useful to rapid prototyping for vehicles;
- to define a risk assessment model.
The work was based on two lines of research.
The first one was to characterise electronic component behaviour in terms of susceptibility to the electromagnetic environment, and to characterise the EM environment as well, due to sources installed both externally and internally to the vehicles in their operating context. This approach was aimed at defining a design environment to support engineers at an early stage of design with proper solutions to prevent or avoid susceptibility problems. An integrated design environment of this kind constitutes a powerful tool to increase immunity of equipment and systems, to the whole vehicle level, in a pre-prototype phase.
The second line was devoted to the definition/proposition of advanced and enhanced strength test methods, which also come from the approach adopted in the various technological fields (i.e.: medical, avionics). A survey of actual standards and the proposition of their potential update, together with an activity to demonstrate the relevance of methods, was performed as propedeutic activity.
An additional study was devoted to produce a risk assessment model based on a statistical 'sources' and 'victims' approach where sources of EM radiation installed outside the vehicle and constituted by communications equipment were identified, and their potential effect on 'victim' circuitry was considered.
The previously described activities were performed according to the guidelines of eight Work Packages identified in the Project Technical Annex I.
Functional Safety and Safety Margins
These were the key issues of the Project.
Functional Safety represents that part of overall safety which depends on equipment or a system to operate correctly in its entire operational environment to take into account other environmental effects such as vibration, temperature, humidity, and so on. Performance degradation of components and equipment due to ageing and production spread are included in the Functional Safety concept as well.
While introducing the concept of Functional Safety, SAFETEL has shown that the immunity problem cannot be characterised by a simple deterministic approach, but shall be viewed within the wider domain of stochastic processes. In defining the immunity level for equipment we want to answer the question: 'how far are we from upsetting that equipment?' More precisely we want to know what the probability of obtaining a default (or even a malfunction) is; given that we are exposing the equipment to a set level of interference.
With an intended purpose of taking into account all the parameters related to Functional Safety, in both the test and design processes of automotive equipment and systems, engineers shall guarantee a Safety Margin(which is defined as the difference between the correct performance of an equipment system, and its actual performance in the presence of electromagnetic threats). Therefore it becomes compulsory to put the definition of Safety Margin within a framework based upon statistical considerations.
The actual innovative of SAFETEL has been the introduction of the Detection Theory, which is part of the Statistical Signal Processing Theory, for approaching immunity problems in both the design and testing processes. Detection theory is an engineering term for that which the statistician calls hypothesis testing or decision making. The approach is first to take measurements, and then estimate in which of a finite number of states an underlying system resides. The subjective assessment of Equipment Under Test (EUT) immunity made by visual and/or aural monitoring of performance degradation is no longer of sufficient quality.
The approach proposed by SAFETEL attempts to fill the gap that exists between the development of new technologies, and immunity test methods that introduce new processing test result techniques. This is done without increasing the cost impact by avoiding the use of sophisticated test equipment.
Conventional and Unconventional EMC Design
The SAFETEL study paid much attention to immunity problems that, until now, had been limited to the qualitative assessment of susceptibility problems, without taking into account the impact of new technologies on one side, and forgetting that vehicles are becoming more and more full of communication equipment that transmits high power levels in wider frequency ranges on the other. In addition, new electronic technologies aim to design embedded controllers with stronger and more sophisticated system - on - chip integrating functionalities: larger embedded memories and interfacing controls.
In the survey and experimental trials, we have shown that the size reduction of components increases their susceptibility to conducted and radiated interference.
Due to the rapid and complex evolution of electronic devices and systems, the subjective assessment of equipment immunity under visual or aural monitoring test for performance degradation is no longer sufficient. The approach proposed by the SAFETEL project tried to fill the existing gap between the development of new technology and immunity test methods, without increasing the impact of new sophisticated and expensive test equipment. Because safety implications are becoming more and more important, car manufacturers have to respond to market demand which prioritizes an interest in technology, plus safety. SAFETEL demonstrated that the safety assessment of any equipment or system depends on test duration, rather than the creation of a more severe test environment.
A fault of the equipment or system under test can be most easily solved by avoiding catastrophic consequences if the onset is detected on the prototype at the beginning of its production. In order to overcome the difference between the real world and the testing environment, many immunity standards adopt the policy of increasing the frequency range, and in some cases of increasing the test levels too. This creates a disadvantage by making the tests more expensive without giving any warranty of hazard or evaluated risk assessment.
Instead of increasing the amplitudes of the susceptibility signals the approach proposed in the SAFETEL framework is to datamine in the monitored parameters, trying to find the onset of any failure or default. Obviously, the major problem here is that in most cases the susceptibility signal contribution is hidden in noise generated by the monitoring devices, and also by the susceptibility signal generators, which are not stable in amplitude and freque
Because safety implications are becoming more and more important, car manufacturers have to respond to the market demand which holds technology, plus safety as a primary value.
Therefore future developments are recommended to address the following issues:
- to improve the detection algorithms of the start of any failure or malfunction mechanism;
- to improve test signal monitoring techniques by either increasing the number of test parameters of the equipment under test, or by making them more accessible during testing.
In future development, especially with regard to safety devices and equipment, car manufacturers must become aware of the importance of quantitative monitoring parameters with regard to the EMC tests.