THE CHALLENGES OF HIL TESTING
TYPICAL HIL ARCHITECTURE analysis. The ADAS makes safety-critical interventions only if all this information is consistent. When testing ADAS functions within HIL regimes, there can be a variety of UUTs and interfaces. For example, a single ECU might be tested while it runs core emergency functions such as a radar-based emergency brake-assist. Or a dedicated ADAS ECU might receive sensor information from other control units. Depending on the setup, multiple real ECUs may be part of the test bench and connected via automotive network systems like CAN, FlexRay, or Automotive Ethernet. software interface, so establishing the connection In a HIL test bench there can be several points may take some work. Additionally, the fact that at which virtual data is added. One option is feeding simulated data data may no longer come from the physical to physical sensors. Of course, real ADAS have multiple sensors so this sensor can force some software and hardware strategy entails simultaneous generation of multiple signals. In the case of modifications of the UUT. cameras, for example, engineers might show each camera a sequence of images of actual scenery via a screen or projector. For radar returns, the PLATFORM-BASED APPROACH TO HIL HIL system needn’t generate the radar output, just simulated echoes Manufacturers such as National Instruments offer coming back. a platform-based approach to HIL testing. Key One advantage of using physical sensors in HIL testing is that there’s features of NI’s HIL test approach include a tight no need to modify the UUT for testing purposes – the simulated signals synchronization among numerous PXI instruments come via the same physical interfaces as found in real vehicles. Among to enable simulations of driving scenarios and the biggest challenges is assuring the quality of the injected signals. For sensors. Particularly important in ADAS and example, images projected on a screen might not represent the dynamic autonomous driving applications is NI’s FPGA range a camera would see in real life. The classic example is that of a car technology. FPGA technology enables engineers driving straight into a blazing sunset, then descending a hill and plunged to design HIL test systems with extremely fast loop into dusk. All in all, the injection of data into a physical sensor involves few rates for quick decision making. modifications of the UUT, but the accurate representation of scenarios can One recent example of an HIL test system be quite demanding and not currently possible for all sensors. using the platform-based approach to sensor Consequently, engineers sometimes inject virtual data after digitization fusion testing was demonstrated by a consortium as, say, injecting data after the ADC stage of a radar, or by providing called ADAS Innovations in Test. This group is a electrical stimulation of a camera’s imager. This approach is quite productcollaboration between NI alliance partners S.E.T., specific – there is no such thing as a standard radar or camera hardware/
A typical test configuration for an ADAS HIL simulation depicts the different methods of simulating sensor data. Test equipment can inject digital data into the sensor channel to simulate sensor inputs. Alternatively, test equipment can develop sensor inputs in the form of images for cameras or echo patterns for radars to simulate actual sensed data. There are advantages and drawbacks to each approach.
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national instrument article — automotive handbook 8-17.indd 15
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8/3/17 11:11 AM