Just as the adrenaline rush of the Le Mans or Sebring races far outpaces a leisurely drive down country lanes, so does the intensity and power expenditure of the engine. Average rev ranges highlight the difference in engine workload between race tracks and public highways. A luxury commercial Aston Martin spends 90 percent of its time below 3,000 rpm at 20 percent throttle. In contrast, its race-ready counterpart spends 90 percent of its time between 5,500 and 7,500 rpm and 70 percent of the race at full throttle. The Le Mans 24 hour race requires the engine to run on this punishing duty cycle for 5,000 km.
Aston Martin Racing
Aston Martin Racing (AMR) has competed in the Le Mans race since 2005 with the DBR9 V12 race car, which won the race in both 2007 and 2008. The DBR9 was superseded by the V12-powered R14 and R16 cars, which proved to be the fastest petrol-powered LMP1 cars at Le Mans in 2009 and 2010. AMR now competes in the latest Grand Touring Endurance (GTE) category with the Aston Martin V8 Vantage, which took home the prize at the opening round of the GTE World Endurance Championship series in 2013 at Silverstone.
The Need for a Specialised Acquisition System
Aston Martin’s standard road car engines provide the baseline for the AMR race engines, but requires significant reengineering to turn them into world-class race engines in terms of power and durability. This transformation is undertaken by the in-house AMR engine engineering team.
To assist with this complex work, the AMR engine group needed a high-speed logging system capable of analysing the torsional behavior of engine crank train and cam drive systems to identify potentially harmful resonances in the engine operating range.
“Significant torsional vibration of any of the rotating engine systems can cause rapid and severe damage. To ensure that these vibrations can be tuned out, it is vital that engine behavior is measured and understood,” said A Shaw, AMR.
AMR asked Computer Controlled Solutions to produce an instrument to facilitate these measurements.
Computer Controlled Solutions
Computer Controlled Solutions (CCS) is a National Instruments Silver Alliance Partner and was recently awarded for 20 years of service with NI. We provide test rigs and data acquisition systems primarily for the auto sport and aerospace sectors. We are based in Warwickshire, at the heart of these industries. Within National Instruments wealth of products, our main area of expertise lies with the NI CompactRIO platform, enabling us to provide real-time processing and advanced FPGA solutions to a wide range of problems.
At CCS, we have a history of working in the noise, vibration and harshness (NVH) field. In a previous project, we replaced expensive, aging instruments that performed vibration analysis on helicopter rotor blades at speeds up to 60,000 rpm. Our cost-effective solution, based on NI products, was more extensible and easier to maintain than the original fixed-functionality system. The NVH techniques we learned during the rotor blade project became the solid foundation for the AMR torsional vibration measurement and analysis system.
Architecting the System
Under-the-hood of the AMR measurement system, we used a CompactRIO real-time, embedded controller connected to an 8-slot FPGA backplane with I/O modules to accommodate the acquisition of digital, analogue and controller area network (CAN) signals. We wired this to a robust flight case, complete with simple front-end connectivity. The low power requirements of the CompactRIO were ideal, as we were able to power the system and surrounding peripherals with a 12 V power supply unit or by the car’s own battery. Critically, we also used a temporary battery backup system to maintain acquisition during the power loss experienced when the ignition key is turned.
Upon boot up, the CompactRIO system begins headless data acquisition, analysis and logging. We also built a WiFi router into the flight case, allowing a laptop to cleanly connect to the CompactRIO for remote configuration and monitoring of the tests. This meant the entire system could be wired to car-mounted transducers and operated from a laptop in the passenger seat. Equally, the system could be connected to a dyno engine then configured with a laptop in the dynamotor viewing room, all while making real-time adjustments to the engine control unit (ECU).
We accelerated the development and testing of the AMR system by using the NI LabVIEW software 3D graphing tools and the NI Sound and Vibration Toolkit, a LabVIEW add-on that provides a prebuilt library of functions to perform key measurements like swept sine analysis, frequency response measurements and transient analysis.
Our solution also performed batch data processing, which exported crunched data from LabVIEW into formats that could be directly imported into NI DIAdem data analysis software and third-party vibration analysis software. We implemented permanent data storage by streaming directly to the onboard memory of the CompactRIO controller, or alternatively, to an external USB memory stick.
The Power of Software-Defined Instrumentation
Compared to alternative approaches based on other programming languages and hardware, the NI solution was a clear winner. Not only is the CompactRIO-based Aston Martin Racing measurement system reliable and high-precision, it was deployed at a significantly lower cost than other fixed-functionality systems on the market. CompactRIO features, such as small-footprint, rugged build and high-precision I/O made it ideal for mounting within the racecar. This was vital in correlating dyno development work with live, in-vehicle test-track measurements.
Furthermore, the NI graphical system design approach offered a straightforward and seamless hardware integration that helped us reduce our development time from months to weeks. The resulting solution also simplified system maintenance, allowing us to perform future system servicing and upgrades with commercially available hardware at an attractive price for AMR.
Since adopting the system, AMR found the data that was collated and analysed from the track and dynamometer rig to be consistent and reliable in pinpointing resonant frequencies of critical engine components such as the crankshaft. AMR used this information to perform mechanical adjustments and ECU mapping to ultimately improve engine longevity.
The Future of Our System on the NI Platform
By its very nature, a software-defined instrument coupled with modular hardware lends itself to endless scalability. When AMR approached us to adapt its hardware, the system extensibility provided a clear approach to accommodating synchronised acquisition of up to 300 high-speed CAN channels.
Looking forward, the opportunities for this system seem endless. We look forward to furthering our work with Aston Martin and National Instruments, and continuing to be a front-runner in the NVH field.
Computer Controlled Solutions Ltd
F12a Holly Farm Business Park
Kenilworth CV8 1NP
Tel: 01926 485532