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

Updated: May 21, 2020

One of the first technical terms I was confronted with at my job was Hardware-in-the-Loop (HIL) simulation and testing. Engineers use this workflow to develop and test sophisticated real-time embedded systems. In applying HIL, engineers can test the behavior of control algorithms without having to build physical prototypes. They create a virtual real-time environment which represents the physical system they like to control and validate their control algorithms by deploying it onto the dedicated target controller. Oh, and the plant simulation interacts with the embedded system under test. Confused yet? Well, there are two things you have to keep in mind, when talking about HIL: if the term “plant simulation” pops up and if the plant model runs on the target computer hardware it is HIL!

But what exactly can HIL accomplish? It is widely used across different industries. The use-case I am going to write about in this post is a use-case from the automotive industry. To be more specific, today is tractor day! There are other off-highway vehicle use-cases I could further highlight, I will definitively talk about excavators in an upcoming blog post. But let's get back to the tractor use-case of the day: engineers working for a big agricultural company have created drivetrain and engines models for the next generation of tractors. They optimized control algorithms for the respective model and deployed them onto the target control hardware. They modeled the drivetrain and the engine models with a software package dedicated to multiphysics simulation. Multiphysics simulation means that there are different simultaneously occurring physical fields to attend to, therefore needing different tools and predefined components for the different fields. In developing, applying and deploying the algorithms (remember these three steps, they will reoccur in almost every post), they were able to test the physical parts of the tractor at an earlier stage (remember the plant simulation and the physical system are connected), allowing much quicker changes based on driver feedback which finally led to an improved and optimized tractor.

So, let me summarize the benefits of HIL quickly: it lets engineers implement complete testing solutions, start testing their new designed control algorithms at an early stage therefore accelerating the development process. And as always: stay curious!

  • For more information about how HIL works (like exactly), click here.

  • Would you like to know more about the tractors? Here you go. It features their HIL-setup, which I believe can answer almost every question you might still have. And if not – you have my email!

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