Vehicle-in-the-Loop Testing

Realistic tests on virtual roads

Why do we perform VIL Tests?

Advanced driver assistance systems (ADAS) offer great potential for improving traffic safety. One example of this is the autonomous emergency braking system (AEBS), with which all newly registered cars must be equipped from July 2024. To ensure that AEBS works reliably, the function, including its associated sensors and actuators, must be verified in the form of an active chain test. Vehicle-in-the-loop (VIL) systems allow reproducible tests in a realistic environment.  

In response to the increasing effort required for validation in the area of autonomous driving functions, the United Nations Economic Commission for Europe (UNECE) has also approved digital procedures as a supplement to the established real test drives for homologation. 

VIL: A Special HIL Use Case

In a VIL test, the entire vehicle is coupled with the real-time simulation of a driving scenario. Ideally, the sensors are stimulated non-invasively over the air (OTA) so that the complete functional chain can be tested. If the OTA approach is not possible, sensor signals can alternatively be simulated and fed into the vehicle’s communication network.

A VIL test stimulates the environmental sensors of a test vehicle and thus enables realistic testing of the entire ADAS functionality from the sensor front end to the reaction of the powertrain and chassis actuators (brakes and steering). In this way, all software and hardware components required for the driving function to be tested, including the onboard network communication, can be evaluated.

Advantages of VIL Simulation

  • Synchronous driving scenario simulation and simulation or stimulation of ADAS-relevant sensors
  • Real driving maneuvers on a chassis dynamometer or on the test track
  • Testing of the complete ADAS function chain (from sensor to vehicle actuators)
  • Efficient and safe testing
  • Reproducibility of tests on the test bench
  • Industry-proven solution
  • Can be used for research and development, homologation, end-of-line testing, and PTI

The Implementation of VIL Tests Using the Chassis Dynamometer as an Example

To check the correct functioning of the environmental sensors and driver assistance systems, the vehicle under test (VUT) is positioned on a chassis dynamometer, for example. The advantage of the VIL test in this case with OTA stimulation is that the vehicle does not have to be manipulated in any way. No data is fed directly into the ECUs and there is no communication with the vehicle via the onboard diagnostic interface. dSPACE has developed its own solution, VERIDRIVE, for this.

Depending on the test scenario, the driver can accelerate, brake, and, thanks to the steerable chassis dynamometer, also steer. The data from the test bench (wheel speeds, steering angles, etc.) is transmitted to the simulation via interfaces so that the behavior of the VUT can be virtualized with its real physical movements. This digital representation of the vehicle and its surroundings is calculated in real time and displayed synchronously.

Additional Validation, Certification, and Verification Tool

The simulation feeds a monitor and radar target simulator to the OTA stimulation of the camera and radar sensors. A monitor and the antennas of the radar target simulator, which are attached to a dynamic gantry system, are integrated into the test track and directly in front of the vehicle to be tested. The monitor stimulates the vehicle’s camera with environment and road scenarios animated by the sensor-realistic simulation solution in the form of a 3D world. This serves to check whether the camera sensor of the VUT recognizes the relevant objects correctly.

VIL simulation with OTA sensor stimulation on a chassis dynamometer enables black-box tests of ADAS/AD functions of an unchanged vehicle. Even critical test scenarios can be carried out reliably and reproducibly. This approach therefore provides an additional validation, certification, and verification tool for the entire vehicle life cycle.

Wide Range of Applications for VIL

This form of validation can be used for periodic technical inspections (PTI), end-of-line (EOL) tests in automotive production, type approval/homologation of ADAS/AD, and in research and development (R&D). 

While for the specific use cases of EoL testing of vehicles and PTI, only non-invasive test methods (such as OTA stimulation) can be considered, another form of feeding simulation data into the vehicle is possible in research and development and, to a certain extent, in homologation. This invasive sensor data feed contains, for example, an intervention in the vehicle’s communication network. A combination of the two techniques is also possible.

Different VIL Tests

There are different methods of testing VIL simulations, each with different advantages. The following options are available:

  • On a chassis dynamometer/drivetrain test bench with OTA stimulation
  • On a chassis dynamometer/drivetrain test bench with invasive sensor data feed 
  • On a test track with OTA stimulation
  • On a test track with invasive sensor data feed

More Information about Vehicle-in-the-Loop Testing

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