What is Hardware-in-the-Loop (HIL) Testing?

The Problem

Vehicles are being controlled by progressively more advanced computers called ECUs (Electronic Control Units). Testing the designs for new ECU hardware and firmware on actual cars, trucks, and airplanes is expensive, cumbersome, and sometimes even destructive.  To speed development and reduce risk, engineers test their ECU designs "virtually" by using software models to simulate various physical components like engines, wheels, and sensors.  However, these "models-in-the-loop" or MILs have limitations.  Would you drive a car or fly in an airplane that had been designed based only on software models?

Executive Summary

To bridge the gap between using MIL (models-in-the-loop or software component models) and actually building a car, truck, or airplane for each test engineering lab, engineers use HIL.  Since an ECU interfaces with a vehicle through analog, digital, and bus (or messaging) inputs and outputs, an ECU can be physically tested by generating and consuming these electrical signals by placing "hardware in the loop" to emulate the vehicle.

HIL enables ECU design teams to work on an engine controller in parallel with the mechanical team creating the engine.

Applications can range from evaluating ECUs that control simple devices like windshield wipers to running firmware regression testing for flight controllers.  You may run into different contexts for the term "HIL" depending on whether there are tight timing requirements like synchronizing automotive start-up sequences and communicating with other ECUs in real-time versus a system that just requires simple stimulus and response like a dashboard light controller.

To best emulate actual vehicle behavior, a sophisticated HIL test controller will be responsible for running models itself as well as measuring and outputting physical signals.  Running models on the test controller can be especially helpful when an engineer wants to intentionally inject faults or alarm conditions and observe how the ECU responds.

Now that you know the basics about HIL, the next time someone mentions it, you can sound informed by asking something like "Does your application require real-time modeling or just simple responses?".


More about Hardware-in-the-Loop

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HIL allows embedded controllers (ECUs) to be tested with actual hardware components (HIL) that simulate real-world conditions, thus facilitating parallel development and faster time-to-market. (Source: Embedded.com)

With today’s HIL technology and the greater availability of controller software models, it’s easier than ever to move from open loop (simple responses) to closed loop test (real-time modeling).  Closed loop testing provides more accurate data and better test coverage, which means a better chance of finding any anomalies earlier in the development cycle when it’s easier (and cheaper) to fix.  Common HIL applications in transportation industries include:

  • Software regression testing:  Whenever a new software (i.e. firmware) feature is added to an ECU, all previously existing functionality must be thoroughly tested again to ensure nothing’s been broken – a very time-consuming but necessary evil.  HIL systems can automate and greatly speed up this process by using ECU simulation models, reusable test scripts, and test-case generation.

  • Real-world hardware simulation:  HIL allows us to put a device under test (DUT, i.e. an ECU) under the rigors of actual hardware signals and loads that represent the real-world transducers found in a vehicle or aircraft.  By providing more accurate environments and scenarios for the DUT, software and hardware can be truly fine-tuned for optimal performance.

We at Genuen strongly believe in using open and modular technology whenever possible.  This is especially true for HIL testers since they often require rapid deployment, customizable software, and reconfigurable hardware for new use cases.  We've found success with HIL systems by using enterprise hardware and software from National Instruments since their platform is open (versus needing to ask the vendor for feature requests or support).

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Standardizing on a modular, flexible platform from National Instruments for your HIL tester can help ensure you have the capability to tackle unconventional or unforeseen testing challenges while controlling the timeline and monetary investment.

 

We are happy to assist however we can.  That can range from offering a helping hand, to surge support, to being your one-stop shop for building entire test cells inclusive of detailed project management, CE certification, and white glove start up.

To learn more, check out our HIL offering, or better yet, set up a time to talk to an experienced engineer about your HIL goals today.

HIL Examples


Here are some custom HIL testers we've deployed for clients:

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Ford Fuel Cell HIL Test System using NI PXI and NI VeriStand

 

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car suspension

 

Automotive HIL Simulation for Complex Active Suspension System

 

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Automotive Battery Management System HIL Test System

 

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About Genuen

Our goal is to improve time to market without compromising product quality or safety standards. With experience in mission-critical applications and regulatory compliance, Genuen creates custom test systems across the product lifecycle, including hardware-in-the-loop (HIL), fluid power test, and electromechanical test. Headquartered near Kansas City, we have offices across the United States and serve clients in aerospace, transportation, national security, and beyond. The company's Quality Management System (QMS) is certified to ISO 9001.