Engine-in-the-loop Research Articles

Engine-in-the-Loop in practical application: A sensitivity study toward the influence of test bench parameters

The complexity of automobile powertrains continues to increase, leading to increased development time and effort. One method to address this challenge is to shift vehicle calibration and testing tasks to simulations with Engine-in-the-Loop (EiL) test setups. This increases the efficiency of the development process through high flexibility, low prototype costs, an early starting point, and a high degree of automation. EiL emulates the dynamic interactions between the internal combustion engine and other powertrain components by closed-loop coupling to real-time simulation models. The coupling quality strongly depends on the interface properties, the hardware layout, and the control functionality of the dynamometer test bench. This paper analyzes an existing test bench and presents the impact of altered test bench parameters on different EiL quality aspects. Thereto, the setup is analyzed and a Simulink based grey box test bench model is derived. The latter is parametrized with a full factorial approach in comparison to real test bench measurements. The test bench model is then used for simulative investigations considering different test bench parameters: Two different use cases of Model-in-the-Loop (MiL) supported EiL are investigated. First, a simulative improvement of the test bench control quality by altering the PI based dyno speed controller parameters is investigated. The virtually calibrated controller parameters are applied to the real EiL system and compared to vehicle measurements. Second, sensitivity studies are shown with respect to dynamometer inertia and system dead time in terms of control quality and energy. As a major outcome, a compromise of control accuracy and stability for different speed controller parameters, dyno inertia, and system dead time is shown. Furthermore, it is demonstrated that EiL has only a small deviation in terms of energy compared to a full vehicle, making it a valid approach when considering CO2 emissions.

Real driving emissions evaluation for a heavy duty vehicle based on engine-in-the-loop methodology

In this paper, the engine-in-the-loop (EIL) methodology was used to study real driving emissions of a heavy-duty vehicle on an engine test bed. The virtual vehicle was combined with the actual engine to establish an EIL test platform. The result of the vehicle speed followability shows that the difference between the EIL simulated vehicle speed and the actual vehicle speed is within ±2 km/h, indicating that the vehicle cycle can be well reproduced on the engine test bed by EIL method. The EIL method shows high coincidence of engine operating points. Compared with real driving, the CO2, NOx and PN of EIL is 3.6%, 72.3% and 40% lower for this vehicle, respectively. Analysis shows that equipment difference is the key influencing factor for PN test accuracy of EIL, while the control of exhaust temperature and intercooler temperature play important roles in NOx test accuracy of EIL.

Pollutant emission and CO2 emission at various vehicle loading for a heavy-duty commercial vehicle by EIL methodology

Pollutants and carbon dioxide (CO2) under different vehicle loading were investigated on a dump truck with a maximum designed total mass of 18000 kg. An engine-in-the-loop (EIL) methodology was applied to achieve the test consistency because EIL can use the same road, driver and vehicle model. The results show that the total CO2 emission increases while the brake specific CO2 emission decrease as the vehicle loading increases. Both the total and specific emissions of PN increase when vehicle loading increases. The effect regularity of increasing vehicle loading on NOx, THC and CO is not significant. It is necessary to comprehensively consider the changes in the raw exhaust due to the engine operation points changes and in the SCR catalytic efficiency derived from the SCR inlet temperature variation. The DPF generation is also need to be concerned because the CO2, PN and NOx emissions will rapidly increase during this period.

Real Driving Emissions Evaluation for A Heavy Duty Diesel Vehicle based on Engine-in-the-loop Methodology

Real driving emissions of a heavy-duty vehicle with a maximum total mass of 18000 kg were investigated by the engine-in-the-loop (EIL) methodology. Virtual vehicle model, driver model and real road model was established, then to combined with the actual engine and emission test equipment to fulfill the vehicle emission evaluation on engine test bed. The results indicate the road driving can be well reproduced on engine laboratory with good vehicle speed followability, engine speed and torque consistence. However, the emission results show a larger difference with a 3.6 gap for CO2, a 72.3% gap for NOx and a 40% gap for PN., respectively. Analysis shows that the intercooler temperature, the exhaust temperature and equipment difference has a combined effect on the emission accuracy.

In-Vehicle Validation of Heavy-Duty Vehicle Fuel Savings via a Hierarchical Predictive Online Controller

<div class="section abstract"><div class="htmlview paragraph">This paper presents the evolution of a series of connected, automated vehicle technologies from simulation to in-vehicle validation for the purposes of minimizing the fuel usage of a class-8 heavy duty truck. The results reveal that an online, hierarchical model-predictive control scheme, implemented via the use of extended horizon driver advisories for velocity and gear, achieves fuel savings comparable to predictions from software-in-the-loop (SiL) simulations and engine-in-the-loop (EiL) studies that operated with a greater degree of powertrain and chassis automation. The work of this paper builds on prior work that presented in detail this predictive control scheme that successively optimizes vehicle routing, arrival and departure at signalized intersections, speed trajectory planning, platooning, predictive gear shifting, and engine demand torque shaping. This paper begins by outlining the controller development progression from a previously published engine-in-the-loop study to the in-vehicle driver-in-the-loop testing highlighted in this work. The purpose of this field testing is to quantify the level of agreement between field data and prior results, particularly noting the influence of noise, disturbances and unmodeled dynamics. Also detailed are the steps to effectively implement the predictive horizons in experimentation with human rather than automated driver inputs by replacing the conventional speedometer with an augmented driver display. The driver display seeks to maintain driver awareness and route preview simultaneously. Additional features of the instrumented truck testing protocol include detailed route maps on speed limits, intersections, traffic and road grade; highly accurate fuel flowrate measurements calibrated via gravimetric methods; and closed-loop control between the predictive controller, driver, and vehicle controller area network (CAN). These combined capabilities allow for model validation, investigation of the effects of human-in-the-loop on controller performance, and identification of unmodeled dynamics and disturbances. The results show that the driver advisory implementation matches fuel consumption predictions from software-in-the-loop simulations and engine-in-the-loop studies to within 2-9%. Following the study of in-vehicle performance and variability, these results also validate, using real road tests, the up to 21% fuel savings achieved by using the hierarchical control scheme with a combination of multiple chassis and powertrain optimization technologies.</div></div>

Fuel Consumption and Emissions at China Automotive Test Cycle for A Heavy Duty Vehicle based on Engine-in-the-loop Methodology

In this paper, the engine-in-the-loop (EIL) method was used to study the fuel consumption and emission characteristics of heavy-duty trucks at China Automotive Test Cycle (CHTC-HT) and world transient vehicle cycle (C-WTVC) on an engine test bed. The result of the vehicle speed followability shows that the difference between the actual vehicle speed and the target vehicle speed is within ±2 km/h, indicating that the vehicle cycle can be well reproduced on the engine test bed by EIL method. The consistency results of fuel consumption and emissions indicate that the fuel consumption error is 0.89%, the NOx error is 1.02%, and the particle number (PN) error is 5.04%. For this vehicle, the fuel consumption per 100 kilometers at CHTC-HT is 21.33L, which is 2% higher than that of C-WTVC; while NOx emissions of CHTC-HT are 59.2% higher than that of C-WTVC. It is more difficult for enterprises to meet the fuel consumption and NOx emission standards under China Automotive Test Cycle.

Powertrain test cell and its test procedure development for greenhouse gas emission measurements

The Environmental Protection Agency (EPA) and the Department of Transportation's National Highway Traffic Safety Administration (NHTSA) announced a first-ever program to reduce greenhouse gas (GHG) emissions and improve fuel efficiency of heavy-duty trucks and buses in 2011. The rule was the first phase of the multi-phase GHG reduction approach. The agencies, working together with industry stakeholders, are currently developing different concepts that could be considered for determining compliance with any future phase of GHG and fuel efficiency regulations. The agencies are evaluating a wide array of options, including full vehicle simulation, engine-in-the-loop (EIL) testing, powertrain-in-the-loop (powertrain) testing, and chassis dynamometer testing. Each method has advantages and disadvantages. Full vehicle simulation is ideal for repeatability and managing a large number of vehicle configurations, but it is generally accepted that high-accuracy simulation of the thermal, chemical, and fluid dynamic processes in the engine and aftertreatment is very difficult to achieve. EPA and SwRI have developed a powertrain test cell for the purposes of evaluating powertrain test correlation with chassis testing and simulation results, and validating simulation models. This paper describes the sizing of a powertrain test cell, modifications required to a standard engine test cell for powertrain testing, and a comparison to chassis dynamometer results.

Fuel Displacement Potential of a Thermoelectric Generator in a Conventional Vehicle

This paper evaluates the fuel displacement potential of a Thermoelectric Generator (TEG) device in a conventional gasoline vehicle using vehicle simulation and engine in the loop. A TEG device was modelled in Simulink, to exhibit the thermal and electrical characteristics of such a device. This TEG model was integrated into the vehicle simulation software, Autonomie and evaluated in a real engine – virtual vehicle scenario using Engine in the loop (EIL) technique. The EIL approach was used to evaluate the fuel consumption benefit of TEG under cold and hot conditions. The complete vehicle model was then validated and used to evaluate the impact of the current TEG system on additional drive cycles as well as future TEG systems (i.e. no device temperature limits). EIL evaluation shows a fuel economy gain within the current device of 1% on the US06 cycle. The simulation study will quantify the impact of driving cycles and TEG design on fuel displacement potential.

Hydraulic Hybrid Propulsion for Heavy Vehicles: Combining the Simulation and Engine-In-the-Loop Techniques to Maximize the Fuel Economy and Emission Benefits

The global energy situation, the dependence of the transportation sector on fossil fuels, and a need for a rapid response to the global warming challenge, provide a strong impetus for development of fuel efficient vehicle propulsion. The task is particularly challenging in the case of trucks due to severe weight/size constraints. Hybridization is the only approach offering significant breakthroughs in near and mid-term. In particular, the series configuration decouples the engine from the wheels and allows full flexibility in controlling the engine operation, while the hydraulic energy conversion and storage provides exceptional power density and efficiency. The challenge stems from a relatively low energy density of the hydraulic accumulator. This places particular emphasis on development of the supervisory controller. The conventional wisdom is to operate the engine at the “sweet spot”, but the aggressive pursuit of engine efficiency as the sole objective can lead to frequent and rapid diesel engine transients, thus causing an adverse affect on the soot emissions and driver feel. Therefore, we propose a comprehensive methodology for considering a combined hybrid system fuel-economy and emissions objective. The fuel economy is addressed with the simulation-based approach, while investigating the impact of engine transients on particulate emission relies on the Engine-In-the-loop (EIL) capability. The EIL study confirms advantages of a modulated state-of-charge control over the thermostatic approach, and demonstrates the ability of the Series Hydraulic Hybrid to improve the fuel economy of the medium truck by 72%, while reducing the particulate emission by 74% compared to the conventional baseline over the city driving schedule.

A procedure to reduce pollutant gases from Diesel combustion during European MVEG-A cycle by using electrical intake air-heaters

While intake air heating is a widespread technology used in heavy duty diesel engines, it rarely appears in the field of HSDI diesel engines. Nevertheless, intake air heating is currently under study as a possible alternative to glow plugs for cold start assistance in HSDI diesel engines. Since the use of intake air heaters involves a cylinder-head simplification, this solution presents both economical and combustion advantages. Despite of the negative impact of the high intake temperatures on NO x emissions, intake air heating reduces significantly HC and CO emissions during warm up due to combustion improvement. While the potential of intake air heating technology to assist cold start is proved, the present paper is devoted to the evaluation of the intake air heating technology potential to reduce pollutant emissions from Diesel combustion. To deal with this objective a deep analysis of both glow plug and intake air heating technology behaviour during the MVEG-A cycle is done. Experimental tests are carried out on a small turbocharged direct injection Diesel engine in an engine-in-the-loop (EIL) approach. Results prove that an optimal intake air heating strategy together with an adapted air loop control calibration can improve HC, CO and NO x emissions with only a scarce PM increase.

Engine-in-the-loop study of the stochastic dynamic programming optimal control design for a hybrid electric HMMWV

This paper presents a Stochastic Dynamic Programming (SDP) methodology for automatic generation of an implementable hybrid control strategy, and addresses engine soot emissions during controller development by using an advanced Engine-In-the-Loop (EIL) setup. Coupling the real engine with the virtual driveline/vehicle enables application of fast analysers to characterise the impact of transients on engine emissions. The benefits of using the EIL for establishing driveability and soot emissions constraints, and subsequent application of the constraints for refining the SDP strategy is demonstrated through a study of a virtual parallel-hybrid system for the High-Mobility Multipurpose Wheeled Vehicle with a V8 6L engine.