Jonathan Newell visits HORIBA MIRA to speak to EMC Chief Engineer Anthony Martin about the EMC landscape in modern connected vehicles and how they are tested.
Housed in smart, modern buildings in the heart of the sprawling test centre at HORIBA MIRA’s Warwickshire proving grounds, the EMC test facilities are an expanding element of the historic automotive industry consultancy and testing specialist company.
Since its establishment 70 years ago, the former Motor Industry Research Association, now HORIBA MIRA, has had the mission of making its considerable levels of engineering expertise available to the automotive industry. A lot has changed within the industry since that post-war period, most notably in low carbon technology and connectivity.
Growth in electronic content
Consumers have become so used to living in a connected world with ever-present WiFi access and instant availability of entertainment on demand, as well as personalised internet content, that they want that connectivity on the move as well.
The delivery of relevant content is perhaps even more useful when travelling. Knowledge of the nearest petrol station, fast food outlet or place of interest along with prices and opening times is something today’s consumers expect as being the norm rather than a novelty.
As a result, automotive manufacturers and “infotainment” system suppliers as well as app developers and mobile platform companies are all striving to provide these services to car occupants safely and conveniently, along with mapping and navigation data.
Not only is the car becoming more connected, it is also benefitting from increased automation with the objective of improving fuel efficiency, creating safer roads and ultimately bringing prolonged mobility to more elderly people who would otherwise have to give up driving completely.
Autonomy depends on multiple sensors connected to on-board computer systems that monitor the driving environment and intervene in the vehicle’s control. Such systems need to operate in a highly reliable and predictable way. And so there is no room for any risk of radio frequency interference. EMC testing therefore takes on a new level of importance in vehicle design.
Testing modern vehicles
At the HORIBA MIRA EMC test facility, I spoke to the company’s EMC Chief Engineer, Anthony Martin, about these new trends and what their implications are.
Being one of the most capable EMC test facilities in Europe with high capabilities and working three shifts, there are three full vehicle chambers up to 22m long and able to do vehicles of most sizes, including large military vehicles plus an open-air facility and seven component testing laboratories.
According to Martin, there are three issues that are examined: electromagnetic susceptibility where the vehicle is struck with RF to see how it copes; emissions to test what RF is emanating from the vehicle; and internal interference between the components.
It is this internal interference that begins to gain in significance as more componentry is crammed into the limited space available within the vehicle. In this respect, the larger automotive manufacturers are in a better position since they have the commercial scale needed to be able to demand compatibility testing and modifications at the component level from the electronics suppliers. Other manufacturers do not have this luxury and are faced with greater compatibility problems.
Generally, the challenges that manufacturers face relate to:
1 – The number of standard off the shelf and legacy devices which can’t be changed.
2 – The high cost of repackaging as a means of overcoming RFI
3 – New positions for antennas in glass or plastic components
4 – The limited configuration options that stem from trying to pack more functionality into smaller spaces.
All of these functions that consumers are demanding cannot encroach into spaces where they would be noticed. And as a consequence, the EMC “bullies” are being crammed into the same space as the victims.
With no options for bringing these bullies under control through the manufacturer, other means are needed in order to reduce their influence through reconfiguration to remove the coupling mechanism to the victim device.
In some cases, these problems are overcome through the use of standard component combinations, where known compatible groups of components are used together. Such combinations are sometimes known to testing organisations. An example which Martin explained was between components from two different suppliers, which are often combined in remote control applications such as proximity detectors, keyless ignition and gesture recognition for opening the boot.
All of these operate at the rear of the car and must work together and function correctly without interfering or reducing the performance of each operation. For example, interference from proximity detection should not reduce the distance at which the keyless ignition device works.
In such a functionally complex environment, there are countless variables that could be subject to testing and I asked Martin how the company copes with this level of uncertainty. “Nothing is uncertain,” he told me. “We work to standards, regulatory conformance and homologation requirements as well as functional specifications supplied to us by the manufacturers. All of these form the basis of the testing that we do.”
Mainstream vehicle manufacturers are already very adept at generating the specification needed to perform comprehensive functional tests but HORIBA MIRA is very proactive in its approach to improvements in vehicle engineering and will work with suppliers on improving specifications, pointing out shortfalls and making sure that nothing important is omitted from their scrutiny.
For modern, connected and increasingly automated vehicles, EMC testing is much more than measuring emissions and determining levels of interference, it’s also about preserving functionality at the edges of the envelope.
The example of the effect of proximity detection on keyless ignition is one instance, but there are many safety-critical functions in autonomous control that need to operate correctly in all circumstances. Functional testing at HORIBA MIRA is designed to test these envelopes and ensure that such increasingly common equipment as Autonomous Emergency Braking works to specification, regardless of the RF environment, an environment that can change depending on what other equipment is in use at the time.
Recognising these changes in the scope of the work done on functional envelope testing at HORIBA MIRA, Martin and his team have developed a new reporting structure that makes test results clearer in terms of their functional effect.
These reports complement the very complex reports supplied to manufacturers but also have another use for the wider base of consumers. The reports use metrics to create easy to understand charts that provide comparative data and enable consumers to make informed choices in “Which?”-style comparisons.
Martin illustrated this with a radio test output report that showed the performance of the radio at the limits of reception area with engine off and on. Those of an age which makes them familiar with the electrical noise from the radio in old cars when the wipers were switched on mistakenly believe that radio interference from other electrical equipment in the car results in noise.
The days of that intrusive noise are gone but the interference has not. Instead, it reduces the range of the radio reception. The report Martin showed me demonstrated a difference in limits of 88% versus 23% when the engine was switched off and on. This was due to interference caused by the wiring loom routed over the tailgate next to the aerial.
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