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.

A sophisticated HIL test controller will be responsible for running models itself to best emulate vehicle behavior. 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?".

If you'd like to have a conversation about an application or strategy, there is good news: You can setup a meeting with Todd VanGilder, Executive VP here at Wineman Technology.

  1.  Click here to view Todd’s calendar.
  2. Ask Todd questions; he'll guide the discussion with some of his own.
  3. Take some time to think about whether a custom HIL system makes sense in your lab.


More about Hardware-in-the-Loop

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HIL allows embedded controllers to be tested with actual hardware components 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 to closed loop test. 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 feature is added, 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) 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, the controller software and hardware can be truly fine-tuned for optimal performance.

With years of experience creating test solutions for all types of industries and applications, we at Wineman Technology strongly believe in using open and modular technology whenever possible. This is especially true for HIL testers that require rapid deployment, easily customizable software, and reconfigurable hardware for new use cases. Our proven success with HIL systems comes from our expertise using National Instrument’s complete suite of enterprise class software and high-performance, fully featured hardware.

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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 complicated testing challenges while keeping time and monetary costs down.

Wineman Technology is a one-stop shop for building entire test stands, providing detailed project management, ensuring CE certification as needed, and training users how to use and customize the delivered system. To learn more about HIL, read the whitepaper Smarter Products Need Smarter Testers or talk to an experienced engineer about your HIL needs today.

Read the White Paper