Hardware-in-the-loop (HIL) testing is a technique that is used in the development and testing of complex real-time embedded systems, such as automotive software systems. HIL testing provides an effective and efficient way to simulate real-world scenarios and validate the performance and functionality of the system under test.
In this blog post, we will explain what HIL testing is, how it works, and what are its benefits for the software-defined vehicle industry.
What is HIL testing?
HIL testing is a method of testing and validating complex software systems on specially equipped test benches that receive data inputs from physical devices such as radars and cameras. The test bench contains all of the relevant vehicle components, such as electronic control units (ECUs), sensors, actuators, and communication networks. The test bench also includes a simulator that generates realistic vehicle and environmental inputs for the system under test, causing it to believe that it is reacting to real-world driving conditions on the open road.
The system under test receives signals from the physical devices attached to the test bench and processes them according to its control algorithms. The system under test then outputs actuator control signals that affect the state of the simulator. The simulator monitors the outputs of the system under test and compares them with the expected outputs based on the predefined test scenarios. The simulator also records and analyzes the data from the system under test and provides feedback to the testers.
How does HIL testing work?
HIL testing is part of the continuous development (CD), continuous integration (CI) and continuous testing (CT) process for the software-defined vehicle, where software developers can rapidly develop, integrate, and test new features and functions for the vehicle software systems.
A typical CI/CD/CT sequence consists of defining the requirements of the new software, generating code, performing software-in-the-loop (SIL) simulation testing, integrating the results into the continually evolving code base, and then conducting HIL testing and validation.
SIL testing is a preliminary testing stage where the software code is executed in a virtual environment without any hardware components. SIL testing can verify the basic functionality and logic of the code, but it cannot account for all of the possible interactions and variations that may occur in reality.
HIL testing is a more advanced testing stage where the software code is executed in a real-time environment with actual hardware components. HIL testing can verify not only the functionality and logic of the code, but also its performance, robustness, reliability, safety, and compatibility with other systems.
HIL testing entails simulating vehicle and environmental inputs for the system under test, such as speed, acceleration, braking, steering, road conditions, weather conditions, traffic situations, sensor failures, etc. The system under test has to process these inputs in real time and decide the course of action to take. For example, test scripts can create a scenario in which a vehicle traveling at 60 mph around a curve in the rain encounters an unknown object in the road or an oncoming car swerving across the center line. Cameras and radars attached to the HIL test bench send images to the ECU, and the system under test has to process that data in real time and decide whether to apply brakes, steer away, or warn the driver.
What are the benefits of HIL testing?
HIL testing is an indispensable part of the modern automotive software development process for a variety of reasons:
HIL testing can run through hundreds or thousands of scenarios without the time and costs associated with conducting physical road tests.- HIL testing can accommodate scenarios that would be too dangerous or impractical to test on the road.- HIL tests are repeatable and consistent. The same inputs always produce the same outputs.- The HIL testing process is highly automated and can accommodate multithreading so that multiple tests can occur at the same time, which speeds up the development process.- HIL supports a frequent software release process with known system behavior performance.- HIL enables collaboration and communication among software developers, testers, OEMs, and third parties.
Conclusion on HIL Testing
HIL testing is a technique that is used in the development and testing of complex real-time embedded systems for software-defined vehicles. HIL testing provides an effective and efficient way to simulate real-world scenarios and validate the performance and functionality of the system under test. HIL testing is part of the CI/CD/CT process for automotive software development that enables rapid innovation, cost reduction, quality improvement, and customer satisfaction.