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SENSORS & SYSTEMS Test & Measurement


Sensors playing key role in electric vehicle development


In a demonstration of the capabilities of electric vehicles, a Brabus Full Electric car is fitted with a Protean Electric in-wheel electric drive system. Key to the development of the Protean Drive were custom built test rigs


unique in-wheel electric drive system for hybrid, plug-in hybrid and battery electric light-duty vehicles, which can improve fuel economy, add torque, increase power and improve vehicle handling of both new and existing vehicles. The system has already been successfully installed in vehicles ranging from small vans to luxury, high performance cars. The integrated motor and


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inverter in the Protean Drive provides all the high power and torque needed for the electrification of vehicles without compromising vehicle performance or cost. It also enables full regenerative braking in normal driving to recapture large amounts of kinetic energy that is subsequently fed back into the batter. And all of this is packaged in-wheel, which saves huge amounts of space in the vehicle for passengers and batteries, and eliminates all external transmission components. In addition, it provides advanced vehicle dynamics through the independent torque control of each wheel. Developing the drive system required a great deal of


careful testing and characterising to cover every performance aspect, and having proved the concept, Protean Electric is now continuing to increase the efficiency of the in-wheel electric motor and regenerative braking capability to further improve performance. Characterisation is performed on in-house


dynamometers and involves the interaction of a number of different systems for control and data acquisition. Both the Protean Drive system and the dynamometers are separately controlled via CAN, and during testing a large amount of data is collected from a wide variety of inputs including


n a business park near Farnham in Surrey, Protean Electric is developing a novel method of providing practical, cost-effective electric power for road vehicles. The Protean Drive is a


(Above) Test rig showing the two in-wheel motors and the Kistler torque measuring flange. (Left) CompactDAQ testing of the drive system. (Inset) Cross section of a wheel with the Protean Drive (Below) The Brabus Full Electric car fitted with the Protean Drive


multiple CAN channels,


temperatures, pressures, volt- ages, currents and digital inputs.


The aim was to automate this testing to help reduce the time Protean’s engineers spend performing characterisation work. Protean’s solution was to use the integrated hardware and


software offered by National Instruments to dramatically reduce both time and costs through automation. Protean’s product validation manager Mark McDonnell says: “LabVIEW was an obvious choice due to its widespread use in the industry and the large range of compatible hardware available both directly from National Instruments and offered by third-party manufacturers.” Protean used LabVIEW to create a fully automated


control program capable of independently controlling both the Protean Drive system and the dynamometer via CAN, as well as providing integrated fault monitoring and data logging. “The automated, integrated system we created using LabVIEW software and NI CompactDAQ hardware revolutionised our product testing,” says McDonnell.


“Testing that used to require up to three weeks can now be completed in just 12 hours, completely unmanned and automated. This has literally saved us months of engineers’ time.” A second test rig designed by Protean engineers uses


two in-wheel motors; one as the power source and the other as the brake. This configuration allows the performance of the motors to be monitored in both drive and regenerative braking modes on the same rig with both torque and speed being measured using a Kistler Type 4504 contactless torque measuring flange. The CoMo Torque control monitor calculates and displays power derived from the torque and speed signals. McDonnell says Protean chose the Kistler system four


years ago because it was easy to use, good value and had the accuracy needed. Over the years, Protean have added additional Kistler torque measuring systems as the development programme has expanded. Already, the in-wheel motor weighing only 31kg


delivers more than 81kW. and 800Nm yet fits easily into a conventional 18- to 24-inch road wheel. With the need to reduce reliance on fossil fuels growing in importance, the suitability of the Protean Drive for easy retro-fitting and as original equipment means that the test rigs will be kept busy well into the future. www.kistler.co.uk www.ni.com


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INDUSTRIAL TECHNOLOGY • July 2012


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