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FPGAs in NI’s FlexRIO cut Subaru XV Crosstrek Hybrid engine test time by 94% by putting hardware in the loop

Xilinx Employee
Xilinx Employee
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By Dave Wilson, Academic Marketing Director, National Instruments


The XV Crosstrek Hybrid is Subaru's first hybrid vehicle. Safety, reliability, and performance requirements complicate passenger vehicle test programs and make them more difficult to engineer. Hybrid engines make testing even more complex. Hybrid ECUs (engine control units) must balance the power delivered by the hybrid vehicle’s internal combustion engine and its electric motor to the drivetrain over a huge range of operating conditions. Ensuring driver and passenger safety and vehicle reliability means testing all parts of the vehicle—including the ECU—in widely varying conditions and severe environments.



Suburu XV Crosstrek Hybrid.jpg



Because the XV Crosstrek Hybrid is Subaru's first hybrid vehicle, the test program had to be extremely comprehensive. Subaru wanted to ensure the vehicle upheld its industry-recognized safety standards. This meant testing under varied conditions including scenarios nearly impossible to create in real-world testing. In icy driving conditions, for example, wheels can experience a sudden loss of traction during acceleration, which can cause a dramatic increase in motor speed and instability in the vehicle. This particular behavior is extremely difficult and expensive to reproduce.


As a result of this complexity, Subaru engineers developed a comprehensive test program that would have required 2300 hours to complete using conventional testing methods—clearly impractical. The solution was to create a virtual test environment so that much of the powertrain testing could occur in the lab before moving to real-world tests. Test engineers developed an HIL (hardware in the loop) simulation based on National Instruments’ (NI) FlexRIO hardware and LabVIEW graphical design environment. NI’s FlexRIO product line is based on Xilinx Virtex FPGAs.



Suburu HIL Testing.jpg



Subaru engineers needed the FPGA’s real-time response to make the HIL simulation work in the real-world test environment. At best, software-based simulations operated the loop in 5 to 15 microseconds. The FPGA-based HIL loop rate is 1.2 microseconds. Because of the HIL capability, test time dropped from the estimated 2300 hours to 118 hours, a 94% reduction and a huge time-to-market advantage for Subaru.


How did it all turn out? Here’s MotorWeek’s extremely positive video review of the Subaru XV Crosstrek Hybrid:





Note: Mr. Tomohiro Morita, FUJI Heavy Industries, Ltd. submitted this project to the NI Engineering Impact Awards 2014 competition. It won in the Transportation category. It also won the Engineering Grand Challenges Award.