Safety systems are a major incentive for purchasing new vehicles. In order to ensure customer satisfaction after the purchase, these systems must function reliably. In terms of development, this means that extensive testing is needed. Virtual test driving can be used to supplement real test driving in order to reduce time and costs. Relevant elements, such as vehicle, road, road users and objects, can be virtually simulated using CarMaker, in order to mirror a real test drive.
Feeding Virtual Image Data into Real Components
The simulation offers several options for feeding virtually generated image data into the control unit to be tested.
Monitor HIL is the quickest method and very cost-effective. As the name suggests, the virtual image data are shown on a high resolution monitor and the entire camera system to be tested (optics, image sensor (imager) and ECU) is placed in front of the monitor so that it can capture and process the virtually simulated data. While this method is easy to implement, problems should be expected. Scenarios with significant differences in brightness, such as when approaching oncoming traffic at night or when exiting a tunnel, pose particular difficulties and reach the limits of the monitor HIL method. Precise set up is also a challenge. The method is generally entirely unsuitable for testing camera systems with ultra wide angle lenses (fisheye lenses).
One way of overcoming the challenges of the monitor HIL method is by transmitting the image data directly to the control unit to be tested. That’s why we created the Video Interface Box. This approach involves physically separating the image sensor and optics from the rest of the camera system. A customized hardware interface was developed for this junction. As construction typically requires interfaces in this location, coupling is easy – even with series versions of the control unit. The Sensor Model Extension Package for CarMaker makes it possible to reproduce the remote optical path, which consists of a color filter and lens attached to the sensor. The hardware interface is implemented as an exchangeable add-on board within the Video Interface Box in order to make the test system as flexible as possible. All aspects related to the embedding and timing of data are located on the motherboard as FPGA code. The operator can assign parameters to these aspects and adjust them for specific projects. Parameterization is conducted in IPGMovie. The visualization software IPGMovie is connected to the Video Interface Box via the HDMI output of a standard graphics card, ensuring an efficient and low-latency transmission of image data with exact and reliable timing.
Using the Video Interface Box in the Vehicle-in-the-Loop Vehicle
The Video Interface Box can even be used in the Vehicle-in-the-Loop test vehicle. This enables the testing of camera-based driver assistance systems – the device under test – under real conditions in the complete vehicle. The Vehicle-in-the-Loop method combines the advantages of real test driving and simulation and is typically used near the end of the development process. Unlike real test driving, however, some environmental elements are calculated in the simulation. The advantage of this is that it makes it easy to generate complex scenarios or even adopt scenarios from earlier phases of simulation for completely reproducible implementation.