Heavy-duty Vehicle Applications Research Articles

Stochastic power management approach for a hybrid solid oxide fuel cell/battery auxiliary power unit for heavy duty vehicle applications

The present paper aims to develop an innovative real-time power management strategy dedicated to the efficient operation of an auxiliary power unit (APU) in a heavy-duty vehicle. Specifically, the APU comprises a Solid Oxide Fuel Cell (SOFC) system and a Lead-Acid battery pack. The power management strategy envisages optimal power sharing between the APU elements and it is defined based on Simultaneous Perturbation Stochastic Approximation (SPSA) principle, pursuing SOFC power profile smoothing in real-time. The SPSA-based algorithm introduced here overcomes real-time operation issues remarked in other implementations (fuzzy logic, genetic algorithms), accounting for a robust and less complex formulation. The power management strategy is implemented in a dynamic model developed in Matlab/Simulink, simulating SOFC-based APU behavior. Simulation outcomes highlight that the proposed strategy allows a global energy saving over 6% if compared to a conventional power management, based on power split control. Moreover, comparing the power profiles corresponding to the battery and the SOFC, it is remarked as SOFC power oscillations evaluated over 1 s timeframe are halved, achieving values lower than 4.5 W/s for more than 80% of the operation time.

Design space exploration for waste heat recovery system in automotive application under driving cycle

Organic Rankine Cycle (ORC) systems have been recently considered for the promising application to Waste Heat Recovery (WHR) in automotive application. However, the design of ORC systems for highly transient operations typical of heavy-duty vehicles faces several challenges. This work extends the method of Design Space Exploration (DSE) to optimize the design of an ORC system for heavy-duty vehicle applications. The goal is to match the size of ORC system with the feature areas of driving cycle. Starting from drive cycle data, the feature areas are identified to represent the driving cycle. Then, a Weighted Least Square method is adopted to determine the initial design condition from feature areas, and based on the design condition, the initial ORC model is built for the further optimization. Particle Swarm Optimization (PSO) with parallel computation is adopted to optimize the performance of nonlinear ORC system with coupled constraints. The result shows that the optimal system can output 6.87% more power than the initial system and 20.08% more power than the inferior system over the feature areas of WHTC test. The analysis shown in this work also includes general design guidelines for optimizing the system architecture and optimally sizing the heat exchangers to improve the ORC thermal efficiency.

Energy Consumption and Cost Savings of Truck Electrification for Heavy-Duty Vehicle Applications

An evaluation was made of the application of battery electric vehicles (BEVs) and GenSet plug-in hybrid electric vehicles (PHEVs) to Class-7 local delivery trucks and GenSet PHEV for Class-8 utility bucket trucks over widely real-world driving data performed by conventional heavy-duty trucks. GenSet refers to a PHEV range extension mode in which the PHEV engine is used only to generate electricity and charge the battery if the PHEV battery is out of electrical energy. A simulation tool based on vehicle tractive energy methodology and component efficiency for addressing component and system performance was developed to evaluate the energy consumption and performance of the trucks. As part of this analysis, various battery sizes combined with different charging powers on the e-trucks for local delivery, and utility bucket applications were investigated. The results show that the e-truck applications not only reduce energy consumption but also achieve significant energy cost savings. For delivery e-trucks, periodic stops at delivery sites provide sufficient time for battery charging, and for this reason, a high-power charger is not necessary. For utility bucket PHEV trucks, energy consumption per mile of bucket truck operation is typically higher because of longer idling times and extra high idling load associated with heavy utility work. The availability of en route charging is typically lacking at the worksites of bucket trucks; thus, the battery size of these trucks is somewhat larger than that of the delivery trucks studied.

Method for Dimensioning Battery and Thermal Management Systems for Heavy-Duty Vehicle Applications Using Aged Battery Experimental Data and Advanced Modelling Techniques

During the life of a Li-Ion battery, capacity and power capability fade. Despite this degradation, an electric vehicle battery needs to deliver designed power performance until battery end-of-life. Comprehension of battery performance degradation is required to design sufficient margin for power capability and thermal management. This paper proposes battery laboratory testing combined with advanced modelling techniques to obtain design parameters based on aged batteries. Laboratory cell aging and characterization tests are performed to parametrise models, which are used to verify electric city bus battery performance at various lifetime levels. The modelling gives an indication on the level of margin that needs to be designed for power capability and thermal management. The results obtained indicate that from performance point of view, the battery that was studied can be utilized well beyond 80% capacity point while still retaining power capability and low cell level power losses.

Method for Dimensioning Battery and Thermal Management Systems for Heavy-Duty Vehicle Applications Using Aged Battery Experimental Data and Advanced Modelling Techniques

When a battery degrades, capacity and power capability fade while losses in battery cells increase. Despite from fading capacity, an electric vehicle battery needs to deliver designed performance until battery end-of-life. To dimension sufficient margin for battery power capability and thermal management, comprehension of battery performance degradation is required. This paper proposes battery cell and module level laboratory testing combined with advanced modelling techniques to obtain design specifications from aged batteries. Extensive laboratory cell aging and characterization tests are performed to parametrise customised Simulink based dynamic electrical battery models with aged battery data at different degradation levels. Furthermore, a finite element thermal model implemented with COMSOL Multiphysics is used to model heat transfer in battery pack structure and thermal management system. This model is validated using experimental data from a prototype battery module. The Simulink model is used to check and validate electrical performance using measured drive cycle data and to provide data on battery losses as an input for the COMSOL model. The latter model is then used to check the performance of a thermal management system. This paper provides an example of this design approach by dimensioning a battery for an opportunity charged electric city bus. The dimensioning is made by using real drive cycle and energy consumption data from an electric bus operating in the city of Espoo, Finland. The chosen cells are then characterized and aged to near end-of-life. Simulations on electrical and thermal performance are then conducted using Simulink and COMSOL with parametrisations representing fresh and aged cells at different levels of degradation. These results are then compared with each other. This gives an indication on how much margin should be designed for power capability and thermal management and tells the performance based end-of-life criteria for the battery system. The results are discussed and recommendations made on battery dimensioning using specifications of aged batteries.

Clutch fill control of an automatic transmission for heavy-duty vehicle applications

In this paper an integrated clutch filling phase control for gearshifts on wet clutch transmissions is developed. In a clutch-to-clutch shift of an automatic transmission, in order to obtain smooth gearshift, it should synchronize the oncoming clutch and the off-going clutch timely as well as precise pressure control for the engagement of the oncoming clutch. However, before the oncoming clutch pressure starts to increase, the initial cavity of the clutch chamber has to be filled first. The filling time and stability of the fill phase are very important for the clutch control. In order to improve the shift quality of the automatic transmission which is equipped on heavy-duty vehicles, the electro-hydraulic clutch actuation system is analysed and modelled. A new fill phase control strategy is proposed based on the system analysis as well as the control parameters are optimized according to the variation of the oil temperature and engine speed. The designed strategy is validated by a simulation work. The results demonstrate that the proposed control strategy and parameters modified method can transit the shift process from the fill phase to the torque phase effectively.

Design of an energy management scheme for a series-hybrid powertrain in heavy-duty vehicle applications

This paper presents a systematic and efficient design method for an energy management scheme of a series–hybrid powertrain. Different fuel–cell powertrain topologies are briefly introduced and their advantages as well as disadvantages discussed in perspective of heavy–duty vehicle applications. Plant models and energy management algorithms for a modern powertrain sizing approach are described with mathematical descriptions and aid of an energetic macroscopic representation, because of a need for detailed alternative powertrain design descriptions to educate new engineers to electrify vehicle systems in upcoming decades. Therefore, the paper illustrates a design space of the powertrain with a fuel–cell system buffered by passive battery and active ultracapacitor packs. Furthermore, a time–domain simulation and input parameter sensitivity analysis of the energy management scheme is presented, specifically - for interest of practising powertrain engineers aiming for series–hybrid powertrain adoption in demanding applications.

Experimental analysis on the performance of a turbocharger compressor in the unstable operating region and close to the surge limit

To make simulation models able to accurately predict engine performance, a better understanding of compressor behavior over an extended range can be accomplished by using a specialized test facility and measuring equipment. Besides, the correct surge line position is another important aspect to be considered to optimize engine-turbocharger matching calculation. In the paper the results of an experimental investigation developed on a turbocharger compressor for heavy duty vehicle application is presented. The study was focused on the definition of surge line position adopting different methods and on the evaluation of compressor performance over an extended range, taking into account compressor behavior both in the stable and unstable operating region.

PCDD/F Formation in an Iron/Potassium-Catalyzed Diesel Particle Filter

Catalytic diesel particle filters (DPFs) have evolved to a powerful environmental technology. Several metal-based, fuel soluble catalysts, so-called fuel-borne catalysts (FBCs), were developed to catalyze soot combustion and support filter regeneration. Mainly iron- and cerium-based FBCs have been commercialized for passenger cars and heavy-duty vehicle applications. We investigated a new iron/potassium-based FBC used in combination with an uncoated silicon carbide filter and report effects on emissions of polychlorinated dibenzodioxins/furans (PCDD/Fs). The PCDD/F formation potential was assessed under best and worst case conditions, as required for filter approval under the VERT protocol. TEQ-weighted PCDD/F emissions remained low when using the Fe/K catalyst (37/7.5 μg/g) with the filter and commercial, low-sulfur fuel. The addition of chlorine (10 μg/g) immediately led to an intense PCDD/F formation in the Fe/K-DPF. TEQ-based emissions increased 51-fold from engine-out levels of 95 to 4800 pg I-TEQ/L after the DPF. Emissions of 2,3,7,8-TCDD, the most toxic congener (TEF = 1.0), increased 320-fold, those of 2,3,7,8-TCDF (TEF = 0.1) even 540-fold. Remarkable pattern changes were noticed, indicating a preferential formation of tetrachlorinated dibenzofurans. It has been shown that potassium acts as a structural promoter inducing the formation of magnetite (Fe3O4) rather than hematite (Fe2O3). This may alter the catalytic properties of iron. But the chemical nature of this new catalyst is yet unknown, and we are far from an established mechanism for this new pathway to PCDD/Fs. In conclusion, the iron/potassium-catalyzed DPF has a high PCDD/F formation potential, similar to the ones of copper-catalyzed filters, the latter are prohibited by Swiss legislation.

A novel monitoring method of wet friction clutches based on the post-lockup torsional vibration signal

Wet friction clutches play a critical role in vehicles equipped with automatic transmissions, power shift transmissions and limited slip differentials. An unexpected failure occurring in these components can therefore lead to an unexpected total breakdown of the vehicle. This undesirable situation can put human safety at risk, possibly cause long-term vehicle down times, and result in high maintenance costs. In order to minimize the negative impacts caused by the unexpected breakdown, an optimal maintenance scheme driven by accurate condition monitoring and prognostics therefore needs to be developed and implemented for wet friction clutches. In this paper, the development of a condition monitoring system that can serve as a basis for health prognostics of wet friction clutches with a focus in heavy duty vehicle applications is presented. The developed method is based on monitoring the dominant modal parameters extracted from the torsional vibration response occurring in the post-lockup phase, i.e. just after the clutch is fully engaged. These modal parameters, namely the damped torsional natural frequency fd and the decay factor σ, are computed based on the pre-filtered Hankel Total Least Squares (HTLS) method which has an excellent performance in estimating the parameters of transient signals with a relatively short duration. In order to experimentally validate the proposed monitoring method, accelerated life tests were carried out on five different paper-based wet friction clutches using a fully instrumented SAE#2 test setup. The dominant modal parameters extracted from the post-lockup velocity signals are then plotted in function of the service life (duty cycle) of the tested clutches. All the plots exhibit distinct trends that can be associated with the progression of the clutch degradation. Therefore, the proposed quantities can be seen as relevant features that may enable us to monitor and assess the condition of wet friction clutches. Since velocity sensor(s) is typically available in a transmission, the proposed monitoring method allows for the practical implementation.