Paul Parkinson

EGNOS Satellite Navigation System Safety Certification

In case you missed it, yesterday Wind River announced that VxWorks has been selected for the European Geostationary Navigation Overlay Service (EGNOS), and has been chosen to run the Integrity Processing Facility (IPF) check set.

The IPF, developed and delivered by Logica, is the crucial element that validates the information broadcast by the satellites to safety-critical users such as aircraft in flight or ships navigating through narrow channels. This is essential, because satellite navigation systems alone do not provide sufficient positional accuracy to be used in safety-critical applications.

The IPF is really good example of a critical system which needs to consistently provide hard real-time performance and total reliability, and this posed some interesting challenges for development and safety certification to the joint avionics software safety standards RTCA DO-178B and EUROCAE ED-12B at Level B.

Logica and the European Space Agency (ESA) have kindly allowed us to produce a case study which discusses the development and certification challenges and how they were successfully overcome, and this has just been published on the Electronics Weekly website. (Update: the case study can now also be downloaded in PDF from the Wind River website)

I hope you'll find this interesting, and the next time you are on a European flight on a landing approach in very poor visibility conditions, you'll know how VxWorks is helping to guide the aircraft to a safe landing.

The Open Group: Real-Time Embedded Systems Forum, Rome

Last week, I attended the The Open Group, Rome 2010 conference, specifically the Real-Time Embedded Systems Forum track (agenda), in order to participate in the MILS API standardization working group sessions.

The goal of the working group is to produce a standardized API for a Minimal Runtime (MRT) environment which is suitable for High Assurance systems, which will enable portability of middleware between MILS platforms and aid interoperability. The working group wrestled with some fundamental aspects of the MRT, including goals/objectives, characteristics and implementation architecture, but these were productive sessions. There's still a long way to go, but these were important steps in the right direction. Watch this space for further developments!

It was also useful to have the opportunity to attend the RTES Forum presentations. Some of the highlights for me were Ed Roberts of Elparazim's presentations on AADL, Olaf Tetteo of Brightsight's presentation on 'Certification & Mutual Recognition above EAL-4 in Europe', and my colleague Alex Wilson's presentation on 'Challenges of Multicore, potential impact on Safety Critical and High Assurance Security Environments'. Open Group members can download the proceedings from here (login required).

With such a packed agenda, I was worried that we might not have an opportunity to see the delights of Rome, but fortunately for the Tuesday evening, The Open Group had arranged a tour of the stunning Capitoline Museum followed by the conference dinner on the rooftop terrace which had a spectacular view of the city skyline.

Police Drone: Episode 2

On Thursday last week, I read that an unmanned air vehicle (UAV) had been recently used by the UK's Merseyside Police in the tracking and arrest of two suspected car thieves (BBC News:'Merseyside police drone tracks car theft suspects').

A quick Google search revealed some additional details in the Liverpool Echo ('Merseyside police make UK's first ever flying drone arrest'), specifically that the UAV had been used in thick fog.

I was really surprised when I read this, because this type of UAV is remotely-piloted, requiring line-of-sight operation, and does not have autonomous 'see and avoid' capabilities (unlike some more sophisticated autonomous military UAVs). So how could it be remotely-piloted safely in poor visibility conditions and in an urban environment?

I was struggling to reconcile this with the fact that the UK Civil Aviation Authority is carefully researching the integration of UAVs into civil airspace, and there are still a number of safety issues to be addressed. I had even discussed some of these, urban environments in particular, in the blog post 'Police Drone' in May 2007 when the media had been reporting the Merseyside Police's UAV trials (BBC News: 'Pilotless Police Drone Takes Off').

However, things began to make more sense when I read about more recent developments of the story, which were reported earlier this week (BBC News: 'Unlicensed Merseyside Police drone grounded' and Guardian: 'Eye in the sky arrest could land Police in the dock'). These reveal that the UAV was being flown by Merseyside Police without a CAA license, and this breach of regulations could lead to prosecution.

So Merseyside Police could be involved in a different type of UAV trial soon...

Case study: Ultra Datel safety-critical avionics upgrade using COTS

I recently had the privilege of working with one of our partners, LDRA, and one of our customers, Ultra Datel, on writing a case study of their experiences of a mid-life upgrade of an existing avionics system.

What caught my attention was the fact that the existing system was uncertified, and the upgrade involved migrating the existing system to a commercial-off-the-shelf (COTS) and undertaking DO-178B Level B safety certification.

As a result, the project faced a number of development challenges because the pre-existing software and device drivers were not developed with safety certification in mind, and the code needed to be re-engineered and modified to meet safety certification requirements.

In the case study, we discuss the following development challenges and how they were overcome using the LDRA Tool Suite during the development of the safety-critical VxWorks application running on a GE Intelligent Platforms ruggedised PowerPC platform:

1. Porting to the VxWorks DO-178B safety-critical subset
2. Reduction of high cyclomatic complexity
3. Programming language subset compliance
4. Code coverage to meet DO-178B Level B objectives

The case study has now been published on the Wind River website on the Aerospace & Defence customers page (and the PDF file can be accessed directly here).

First flight of the Boeing 787

Today, the Boeing 787 Dreamliner made its first flight from Everett, Washington. One of our Wind River colleagues, Chip Downing, was able to attend this historic event in person, and shot the following video:

This is the culmination of years of development of a completely new aircraft which uses many state-of-the-art technologies to significantly improve efficiency, operating range and passenger comfort.

For instance, the 787 employs an Integrated Modular Avionics (IMA) architecture using VxWorks 653, Wind River's world-class ARINC 653 compliant RTOS. This approach which drastically reduces the amount of space, weight and power (SWaP) required for the aircraft's on-board avionics systems. The reduction in weight of avionics systems and cabling results in a reduced fuel load requirement, or increased range for the same fuel load, and of course reduced CO₂ emissions. Similarly, the reduction in the space required for the avionics systems can increase the space available for passengers, luggage and cargo.

(If you want to know more about the 787 development and DO-178B safety certification approach, read Alex Wilson's recent blog, and for details of VxWorks 653, there's a white paper available for download here).

In addition, the composite fuselage not only helps to make the aircraft lighter (improving fuel consumption further), but also enables higher cabin pressures to be used, which will result in passengers feeling more relaxed and less fatigued. When coupled with the advanced air-conditioning systems and state-of-the-art Rolls-Royce Trent 1000 jet engines and noise-reductions technologies, this provides the promise of greater passenger comfort on long haul flights.

This is of course, just the start, as the 787 will continue to evolve through its operational lifetime, just as the 747 has done over the last forty years. So, I wonder what other technologies will appear in the future?

In the meantime, I'm looking forward to seeing the 787 grace the skies above the Farnborough Air Show and taking a flight on one with British Airways in the near future. Congratulations, Boeing!

Ada & C mixed language development

Last week, I downloaded AdaCore's GNAT Pro 6.2.2 and the latest GNATbench 2.3.1 release (which was announced yesterday), as I wanted to port an Ada & C mixed-language application to VxWorks 6.7.

I wanted to do this to show a customer how they can develop new Ada applications (as well as reusing existing intellectual property) and integrate them with network protocol stacks, graphics libraries and other middleware which are often implemented in C or C++.

Whilst the Ada 95 and Ada 2005 language standards provide inter-language compatibility with C and C++ respectively, close integration between the development tools is needed in order to really exploit these capabilities fully, for example being able to debug communication modules and/or tasks implemented in different languages.

My mixed language application consists of two VxWorks tasks (written in C), and two Ada tasks. One of the VxWorks tasks sends messages to an Ada task via a VxWorks message queue, and I wanted to step through the sending and receiving of the messages in a debugger to confirm that individual messages were sent and received correctly. This would not be a very user-friendly activity if I had to use two different debuggers to debug the Ada and C code separately. In addition, I also wanted to check that the inter-language calls that I had made (C function calling an Ada procedure and vice versa) had passed parameters using the correct language types and the data values were interpreted correctly.

Workbench provides an open and extensible framework based on Eclipse, so this has enabled AdaCore to integrate capabilities of GNAT Pro seamlessly through the GNATbench plugin. This enabled me to develop and run my mixed language application in Workbench. I was able concurrently debug multiple tasks in mixed languages (see below), and set task specific breakpoints on the Ada and C tasks individually and step over the calls to msgQSend() and msgQReceive() respectively, and confirm that the messages were passed correctly; and I was able to walk up and down the stackframes in the Workbench Debug View and confirm that parameters had been passed correctly between C function and Ada procedure and vice versa.

I also used Workbench's analysis tools System Viewer, Memory Analyser and Performance Profiler to verify the behaviour of Ada & C tasks at system level, and monitor memory & CPU utilisation of each of the Ada procedures and C functions in the mixed language application.

Even after many years working with these technologies, I am still excited by advances in capabilities which make the complex tasks of embedded software development easier. I just wish I was able to spend more time in Workbench and less time in PowerPoint!

nEUROn UCAV programme

In case you missed the news, the article 'COTS for unmanned flights' (Electronic Product Design, 22nd April 2008) describes how the nEUROn UCAV programme (Airforce Technology) has standardized on the VxWorks 653 RTOS.

nEUROn is a technology demonstrator programme involving five European companies, which in itself is not unusual, but it does have a significant objective - to demonstrate the maturity of technologies by producing modular safety-critical avionics systems running on COTS-based on-board computers. The development of avionics systems for a UCAV are in some ways even more challenging than for a military fast jet, given that it will provide a similar level of capability, but yet has less Space, Weight and Power (SWaP) available. This is one of the driving factors behind the ARINC 653 software architecture, enabling multiple applications to be hosted on a common computing platform (see 'ARINC 653 software weighs less' for background).

However, this advance results in a further challenge, that of being able to support modular and incremental certification of the IMA platform. This is necessary because of the very significant costs of safety certification under RTCA/DO-178B and EUROCAE ED-12B, especially at the higher software integrity levels (SIL). If an avionics platform comprising, say ten applications and several million source lines of code (SLOC) has been developed, and one of the applications undergoes an upgrade, it would be very time-consuming and prohibitively expensive to re-certify the whole platform. Alex Wilson covers these issues in more depth in his webcast 'Towards Incremental Certification with ARINC653'.

Fortunately, the experiences gained on recent IMA programmes in conjunction with the evolution of ARINC 653 standard has resulted in the mature VxWorks 653 implementation which fulfills these requirements and will provide a critical foundation for the objectives of the nEUROn programme.

I'll look forward to the nEUROn taking off in 2010.

Managing Software Obsolescence

Yesterday, I attended the Component Obsolescence Group (COG) quarterly meeting, which was held at the Imperial War Museum, Duxford.  I was standing in for my colleague Alex Wilson, who wasn't able to attend, and I gave his presentation 'Managing Software Obsolescence through Standards'.

The presentation was about how open standards and software abstraction can provide isolation from underlying hardware architectures, and can assist processor architecture migration as part of a technology refresh cycle. This is important in many A&D programmes, given in the increasing in-service lifetimes of some systems, but the principle also applies to other vertical markets too. The presentation also highlighted how the RTCA/DO-297 standard provides guidance on the development of Integrated Modular Avionics (IMA) platforms to enable modular and incremental certification of safety-critical systems, but this actually provides a side-benefit which can help address obsolescence. This is because it advocates a role-based approach, and advocates separation of the configuration data based on role and activities. 

This approach can be used in conjunction with a MILS (Multiple Independent Levels of Security) separation kernel, which is designed for hosting applications of multiple security classifications on the same processors, but can also be used as a framework for software isolation to assist in managing obsolescence.

Some approaches to hardware obsolescence were also discussed during the meeting, and I was interested to hear how hardware & software emulation of a legacy processor are being used to extend the lifetime of a safety-related industrial system. I was struck that there's more similarity between the challenges of some A&D programmes and other markets than I had first thought.

I also took the opportunity to wander around Duxford's new AirSpace exhibition with some of the other delegates during the lunch break. If you haven't been yet, it's well worth a visit.

Drive by Ethernet?

I read last week that BMW has been researching the use of the Internet Protocol (IP) over standard Ethernet (Cisco) to network automotive controllers ('BMW brings Internet protocol under the hood', EETimes).

The motivation for the research is that at present, a number of different networking technologies (including CAN, LIN, MOST and FlexRay) are used in automotive applications, and these are optimized for different types of application, but the lack of standardization results in complexity and cost.

So, I was expecting the article to say that BMW had found Ethernet to be suitable for non-critical applications, but not well-suited to critical systems. Sure enough, the article mentioned that the network had included a multimedia server and a camera (presumably for assisting reversing rather than videophone calls), but I was surprised that the BMW research group had found that:

'IP could well suit the real-time requirements even of safety-critical applications...Our experiments with prototypes demonstrated, that the real-time behaviour far exceeded the requirements — even when we ran multimedia applications across the same network'

Why was I surprised? Well, Ethernet, following its invention at Xerox PARC in the early '70s has become extremely widely used due to an ongoing favourable performance to price ratio, but it does suffer from latency and determinism problems to a certain extent, and while this has been acceptable for many uses including even some A&D mission-critical systems, safety-critical systems which require predictable latency and guaranteed delivery have often used profiled Ethernet implementations (such as ARINC 664) instead, sometimes with the additional expense of AFDX dual-redundant networking.

So, the BMW research engineers must have found away around the automotive problem? According to the article, they used Quality of Service (QOS) and traffic-shaping (wikipedia) techniques to achieve the real-time performance requirement, but unfortunately it doesn't go into details. I'm curious to know if the network profiling requirements for automotive applications have any similarities with avionics networks, or if there are major differences in terms of latencies and traffic characteristics. Maybe there's scope for more technology transfer between the two sectors (as I mentioned in my previous blog)?

There is potentially another interesting parallel between automotive and A&D - the use of multiple networks. In aircraft, multiple on-board networks are used for avionics systems, crew information systems and passenger infotainment systems, separated by firewalls for reasons of safety and security. (This also has the added benefit of reducing the safety certification burden of systems because they are not connected to the avionics network). In a car, I would expect that the automotive control systems would be on a separate network from the infotainment systems (for safety and security reasons).

According to the EETimes article, BMW doesn't have any current plans to put this technology into a production model yet, new technologies often appear in manufacturer's new high-end models, and then the technologies tend to trickle down to other model ranges.

So, unfortunately I might have to wait a while to do a back-to-back test of Ethernet-driven and conventional versions of BMW's awesome new V8-powered M3 to compare the latencies of the Dynamic Stability Control (DSC)...

Military Aerospace & Electronics Show

Yesterday, I attended the UK's Military Aerospace & Electronics technical conference and exhibition, which was held at the Heritage Motor Centre. The technical conference was split into three technical tracks, which were broadly related to avionics, land systems and technologies; and as is sometimes the case at these conferences I found that I wanted to attend some presentations which were running concurrently!

At a high-level, there were recurring themes amongst the presentations relating to modularisation, reconfigurability and of course, security. Some of the presentations discussed these issues in the context of the Future Rapid Effects System (FRES) programme, which is broadly speaking the UK equivalent of the US Future Combat System (FCS) programme. It was interesting to hear how future upgradeability through planned obsolescence and technology insertion prior to deployment, and the recognition that standards-based open architectures could facilitate this requirement.

Michael Morua of Atkins Defence Systems (MOD-appointed Systems House for FRES) gave a technical presentation on how the FRES Electronic Architecture (EA) is being implemented using a service oriented architecture, and even explained how reconfigurability would be achieved through open interface standards, and interfaces to external systems could be implemented through common data exchange middleware.

I always appreciate the opportunity to learn about emerging technologies at these conferences, so I was glad that I attended Peter Allsopp of GE Aviation's (formerly Smiths Aerospace) technical presentation 'Networked Aerospace Systems - Future Data Network Technologies'. It was interesting to hear how as data throughput requirements for avionics networks increase, the determinism, latency and availability requirements become harder to maintain with current avionics networking technologies. It appears that FlexRay, an open standard for time-triggered field bus technology may provide the way forward.

FlexRay was originally developed for safety-critical automotive applications, so it's encouraging to see that avionics can potentially benefit from the more widespread deployment of technologies in the automotive sector. This suggests that there can be cross-fertilisation between aerospace and automotive in both directions (blog: Can Automotive learn from Avionics Safety?).