HIL Integrated Simulation

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ECU testing can benefit from integrating Hardware-in-the-Loop testing with DiL simulation

With electronic control units (ECUs) being so crucial to the next generation of automotive models, development labs are working constantly on their testing and validation.

Hardware-in-the-loop (HIL) testing is the final stage of controller development following proof-of-concept work and executable code testing during the software-in-the-loop phase. At every step, there is value in adding experiments with a human driver but especially with HIL (Hardware-in-the-Loop), where testing the interaction between the driver and ECU is an important part of the validation process.

Validating the ECU with all the intrinsic faults and shortcomings of a driver involved is a more robust approach than a pure HIL test without DIL integration, which assumes the driver’s course of action. Drivers are unpredictable, so testing the combination of a driver with the ECU is a more realistic test of whether the car remains safe or not. In extreme cases, if the driver does something that the ECU software engineer did not expect, then the combination of driver and safety-system ECU could make the situation worse rather than better. That makes driver-in-the-loop (DIL) integration highly relevant to the development of safety systems such as electronic stability control (ESC).

For HIL/DIL integration to work, the two simulation environments must share a vehicle dynamics model running in real time on the HIL system, because the ECU under test expects sensor inputs to arrive, always at the same frequency, in real time.

Example sensor inputs being exchanged between the two sides could involve an engine RPM sensor or a wheel-speed sensor. Driving through a virtual world in the Cruden simulator, the vehicle model generates the sensor signals that the ECU uses as inputs. Conversely, the ECU also has outputs back to the vehicle model, which then influence the driver in the simulator.

Of course, ensuring that the driving simulator integrates perfectly with the customer’s vehicle model is a cornerstone of every Cruden implementation.

Data Interface

There are two parts to the integration. The first is to create a data interface to exchange signals and data between Cruden’s Panthera simulator control software and the vehicle model running on the real-time system. Then the vehicle model must be tuned for DIL use, so that the vehicle responds properly to the driver’s inputs and the platform motion, pedal feel and steering-wheel torque enhance the immersive experience. It’s not hard to imagine, for example, that a HIL model used mostly for braking development, has excellent fidelity in longitudinal acceleration and deceleration, but doesn’t perform as well in the lateral domain.

“With a HIL system, you’re often very specific on the elements that you’re testing, and you make sure that your model has what you need to test that element. However, to make a vehicle model feel realistic in a driving simulator, we must make sure that the fidelity is where we want it: in all aspects of vehicle dynamics. That’s where Cruden’s experts come in, working closely with its client engineers,” says Christiaan Koppel of Cruden

Cruden is open to working with whichever HIL system the customer wishes to integrate. Its approach is about adding value to existing, preferred engineering tools by adding a DIL component, rather than prescribing specific products. In addition, the size and flexibility of Cruden’s simulator architecture opens the door to bespoke configurations for specialised user cases, such as adding a wet bench to the top frame for brake simulation, for example. In this way, Cruden integrates with HIL not only at the software level, but also with simulation hardware.

Jonathan Newell
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