Hardware-in-the-Loop-Based Virtual Calibration Approach to Meet Real Driving Emissions Requirements
Abstract:
The use of state-of-the-art model-based calibration tools generate only limited benefits for seamless validation in powertrain calibration due to the often neglected system-level simulation of a closed-loop vehicle environment. This study presents a Hardware-in-the-Loop (HiL)-based virtual calibration approach to establish an accurate virtual calibration platform using physical plant models. It is based on a customisable real-time HiL simulation environment. The use of physical models to predict the behaviour of a complete powertrain makes the HiL test bench particularly suited for Engine Control Unit (ECU) calibration. With the virtual test rig approach, the calibration for the critical extended driving and ambient conditions of the new Real Driving Emissions (RDE) requirements can efficiently be optimised. This technique offers a clear advantage in terms of reducing calibration time and costs. The physical nature of the plant models permits to extrapolate the behaviour of the system under a wide variety of real driving conditions, e.g. varied ambient conditions (hot, cold, and altitude) with limited initial calibration effort.
The article focuses on the practicality and usability of the virtual calibration approach. It demonstrates extended usage of HiL and optimised performance of the physical engine model including a crank-angle-resolved combustion model. In addition, other real-time capable powertrain models such as driver, transmission, vehicle, and after-treatment system models are implemented into a closed-loop environment with the ECU as the hardware component. After calibration of the plant models, the overall accuracy of the HiL test bench has been validated using steady state and transient cycle measurement data. The investigations focus on the accurate prediction of pressure, temperature, and emissions for different ambient conditions. Also, a strong emphasis was placed on the practical application examples for the air path and emission calibration using the HiL test bench and virtual calibration approach. The obtained calibration dataset has been compared with the calibration of the same development vehicle. Finally, the ECU dataset, generated with the HiL approach, is validated on the reference vehicle under RDE conditions.