Unlocking the Secrets of HIL Testing: A Comprehensive Interview with an Expert

In the ever-evolving world of automotive technology, Hardware-in-the-Loop (HIL) testing has become an indispensable tool for ensuring the safety, reliability, and efficiency of electronic control units (ECUs) and advanced driver-assistance systems (ADAS). This cutting-edge testing methodology allows engineers to evaluate the performance of these critical components in a simulated environment, streamlining the development process and reducing costs.

To gain a deeper understanding of HIL testing and its applications, we had the privilege of sitting down with Gregory Rousseau, a Product Owner at AVSimulation, a leading provider of simulation solutions for the automotive industry. In this comprehensive interview, Gregory shared his expertise and insights, shedding light on the intricacies of HIL testing and its role in shaping the future of automotive technology.

Demystifying HIL Testing

Q: Can you introduce yourself in a few words?

Gregory Rousseau: My name is Gregory Rousseau, and I’m a Product Owner at AVSimulation. I’ve been with the company for three years, and my primary responsibility is to define the product roadmap, monitor development progress, and anticipate or address the present and future needs of our customers. Additionally, I oversee projects like SERKET, where we integrate software interfaces developed by our team into a simulator for the DGA (French Defense Procurement Agency) developed by RUAG Défense France.

Q: Can you explain the acronym HIL?

Gregory Rousseau: HIL stands for Hardware-in-the-Loop. A HIL device, often referred to as a HIL bench, involves operating a physical element (sensor or actuator) in a simulation loop. Today, all vehicles contain ECUs, which are systems defined by inputs and outputs and incorporate control laws to regulate various systems like ADAS, air conditioning, and lighting.

The idea behind HIL testing is to test an ECU on a bench before installing it in a vehicle. This involves feeding the ECU inputs with virtual measurements from a simulation loop and observing the evolution of its output values. In other words, the ECU receives information from emulated sensors and acts on actuators or provides instructions to other ECUs.

Q: Can you also quickly explain MIL, SIL, and DIL?

Gregory Rousseau: Certainly!

• MIL: Model-in-the-Loop. It’s a test model that is not compiled and doesn’t meet all the constraints of an embedded software system (defined operating frequency, low-level layers, etc.). It’s a raw product that allows for the development and initial testing of the control law algorithm.

• SIL: Software-in-the-Loop. For this type of test, compiled control laws are used, which are homogeneous to what will be in the ECU. These control laws constitute the embedded software, while the rest of the environment, including the hardware part of the embedded software, remains simulated.

• DIL: Driver-in-the-Loop. This test is used when a simulator driven by a human driver is part of the simulation loop. As soon as a physical person controls something during the simulation, we can refer to it as DIL. The objective is to evaluate the driver’s reactions to specific events, such as information displays or warning signals.

HIL Testing: A Necessity in the Modern Automotive Industry

Q: Is there an alternative to HIL test benches? How did engineers approach testing before these existed?

Gregory Rousseau: Before the advent of HIL test benches, automotive engineers primarily relied on mechanical tests and track testing with prototype vehicles. However, as electronics became more prevalent in the automotive industry, alternative methods, such as laboratory tests, were introduced as precursors to HIL benches.

Test benches allowed engineers to isolate specific vehicle components for unit testing by feeding virtual data into the ECU. While track testing was limited by the availability of prototypes, HIL test benches represented an initial investment that quickly became cost-effective and time-efficient, as they could be interfaced with different products for testing and validation.

Q: What types of problems can HIL test benches solve?

Gregory Rousseau: HIL test benches address several key challenges in the automotive industry:

1. Cost: Track testing is particularly expensive, while HIL test benches require an initial investment but are inexpensive to maintain. They can be interfaced with different products for testing and validation, making them highly cost-effective in the long run.

2. Time-saving: HIL test benches save a significant amount of time. For example, if you need to test control laws for a sensor that is still under development, you can use simulation to test it in advance, rather than waiting for the physical component.

3. Repeatability: With HIL test benches, you can repeat the same scenario infinitely without the variations inherent in real-world testing, such as human or material factors.

Integrating HIL Testing into the Development Cycle

Q: Where in the V-cycle are HIL benches located?

Gregory Rousseau: In the V-cycle, we first have the MiL (Model-in-the-Loop) during the design phase. At this stage, we work with models that are not yet well-structured or capable of being compiled, and the focus is on testing the quality of the algorithms.

As the models are improved and industrialized for compilation, we move to the SiL (Software-in-the-Loop) phase, where the compiled models are used as they would be integrated into an ECU.

During the test and validation phase, when we go back up the V-cycle, the HIL comes into play. Here, we connect a real system to a simulation loop to test it.

Finally, the ViL (Vehicle-in-the-Loop) is used to test the vehicle and its sensors in real-time, partially powered by a simulated environment.

HIL Testing with AVSimulation’s SCANeR

Q: What are the features that allow SCANeR to be used in a HIL test bench?

Gregory Rousseau: At AVSimulation, we have developed several products that enable the use of SCANeR in HIL test benches.

First, we have the RTGateway module, which allows us to connect SCANeR to a real-time target and retrieve all the information (such as sensor data) that transits on the SCANeR network.

Additionally, we have created a vehicle dynamics model called CALLAS RT, which can run on a real-time target and be used in a HIL bench.

These products are integrated into the Real Time Targets pack, allowing SCANeR to be connected to a real-time target running the CALLAS RT vehicle dynamics model. This setup can then be interfaced with various systems, such as sensors or actuators, forming a complete HIL bench with SCANeR as the simulation loop.

Q: Can you give us examples of sensors integrated into HIL benches and benches you have built or are working on?

Gregory Rousseau: Certainly! One example of a HIL sensor bench involves using a camera. We project the SCANeR visual onto a screen, which is then filmed by a camera installed in a box (approximately 1 to 2 cubic meters) and adjusted to film the screen. The idea is to emulate a real scene using the SCANeR visual and film it with the camera as if it were installed on a car windshield.

These cameras can detect targets (presence of a vehicle, speed, inter-vehicle distance) and be used for functions like adaptive cruise control (ACC). Connected to a real-time bench itself connected to SCANeR, the camera transmits the detected targets and their speeds, creating a test and validation bench for ADAS functions through simulation.

Another use case involves integrating a radar sensor into a HIL bench. Similar to emulating a real-world image on a screen, we can emulate radar waves reflecting off a simulated scene using a radar bench. Powered by a radar sensor model like SCANeR’s L2 radar model, the radar bench can send waves that are received by a real radar sensor. Using Doppler echo processing, the radar provides the detected targets to an ADAS system. In a fully looped HIL test bench, the ADAS system is connected to a SCANeR vehicle and can be tested to validate its operation in accident scenarios.

In one of our projects, we worked with our partner Conrad to connect a camera test bench to SCANeR. The HIL connection was implemented with a Mobileye camera connected to a real-time target that acquired the video stream and various information sent by the camera.

More recently, in collaboration with Keysight Technologies and with the support of OKTAL SE, we are working on a project to demonstrate the use of an L2 radar in a radar bench application.

Q: A word to finish up?

Gregory Rousseau: ViL (Vehicle-in-the-Loop) and HIL are key elements in our SCANeR Roadmap, which is why we have been working for several years to ensure compatibility with numerous real-time target providers, such as National Instruments and dSpace.

The operation of our CALLAS vehicle model, as we use it in massive simulation, will be the same as when we use it on a real-time target. We are working to converge as closely as possible towards Digital Continuity, ensuring a seamless transition between different stages of the development cycle.

Conclusion

HIL testing has revolutionized the way automotive engineers develop and validate electronic control units and advanced driver-assistance systems. By providing a controlled and repeatable environment for testing physical components in a simulated loop, HIL test benches offer significant advantages in terms of cost-effectiveness, time-saving, and reliability.

As the automotive industry continues to push the boundaries of innovation, the role of HIL testing will become increasingly crucial in ensuring the safety and performance of the vehicles of tomorrow. With companies like AVSimulation at the forefront of this technology, we can look forward to a future where the development of cutting-edge automotive systems is streamlined, efficient, and driven by a commitment to excellence.