Browse Publications Technical Papers 2019-26-0252
2019-01-19

Improving Calibration Quality by Virtual Testing Approach for Upcoming BS VI Emission Norms 2019-26-0252

BS-VI or equivalent development will call for tremendous efforts in concept investigation, calibration for engine out, aftertreatment, diagnostic checks & off-cycle emissions, field performance, component safety etc. Achieving calibration quality for all these tasks will be very challenging considering development time and cost aspects if, conventional physical testing approach is followed. Therefore, a new way of virtual testing based calibration provides significant advantage in addressing all these challenges and thus reducing the time to market. In virtual calibration methodology, semi physical Real Time (RT) engine and aftertreatment models are integrated with engine hardware like Engine Control Unit (ECU) and actuators such as injectors, Exhaust Throttle Valve (ETV), EGR valves, Urea injector etc. The calibration is moved from physical testbed to Hardware-in-loop (HiL) based environment and thus can be started well in advance before the proto is built. In this methodology, as early as in the concept phase, the semi physical engine model is coupled with the vehicle model and the performance and emissions behavior under legislative cycles such as WHSC, WHTC is simulated in a "Model-in-the-Loop" environment. Present article focuses on the new virtual testing and calibration approach. To prove and validate the new approach a six cylinder heavy duty diesel engine is selected and it is configured on HiL environment. The engine plant model is built offline and validated with base engine data at steady state and transient operating points. In parallel, load drawer is prepared which includes actuators such as injectors, metering unit etc. Sensors like boost pressure, rail pressure, and temperature sensors were simulated and their characteristics is filled and integrated with ECU hardware. Engine model is converted into real time models and interfaced with ECU. Calibration is then carried out in virtual environment and results are analysed at steady state and transient operating points. Though plant models were built without test data corrections, reasonable accuracy was achieved at all performance and emission points except for soot emissions, which is sufficient coarse ECU calibration. At next level a short measurement campaign is run to generate relevant data for plant model corrections. More accurate and real time plant models are then used for evaluating different calibration strategies on virtual test bed environment. The performance and emission results including soot then matched with very good accuracy and therefore calibration can be carried out for legislative cycle requirements such as WHSC, Hot and cold WHTC, non-standard ambient conditions etc. This methodology has benefited to a great extent in reduction in calibration time and efforts, ease of calibration for nonstandard ambient conditions, screening of various hardware options, very fast calibration of engine derivatives for various applications and most importantly without any change in the calibration toolchain platform. Virtual calibration methodology has huge potential to handle complexity and efforts in calibration desired for upcoming real driving emission norms.

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