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Technical Paper

Development of Lithium-Ion-Battery System for Hybrid System

2011-04-12
2011-01-1372
A battery module structure and a battery management system that is optimal for the structure were developed, in order to facilitate the work of equipping hybrid cars with lithium-ion batteries (LIBs) that are expected to improve vehicle performance. This paper describes the structure of the LIB and the battery management system that is optimal for it. The battery module structure has cells with a sturdy holding structure and a highly efficient cooling system. The structure has enabled the improvement of battery pack system power output by 80% per unit weight and by 20% per unit volume compared to the previous model. The optimal management system prevents battery overcharge by detecting and controlling the state of charge (SOC) of each cell with a high degree of accuracy.
Technical Paper

Detection of Hybrid and Quiet Vehicles by Blind and Visually Impaired Pedestrians

2011-05-17
2011-01-1725
The increased popularity of hybrid electric vehicles has created a growing concern for the safety of blind and visually impaired pedestrians. Accident data published by the National Highway Traffic Safety Administration demonstrates a higher incident rate among hybrid electrics vehicles compared to internal combustion engine vehicles during slow speed movement, like when coming to a stop and leaving/entering a parking spot. The typical lower sound output of hybrid electric vehicles, compared to internal combustion engine vehicles, has been reported as the reason for higher incident rates. Previous studies have focused on the overall sound pressure level of vehicles and the ability for blind pedestrians to detect their approach.
Technical Paper

Model-Based Approach to Estimate Fuel Savings from Series Hydraulic Hybrid Vehicle: Model Development and Validation

2011-09-13
2011-01-2274
A simulation framework with a validated system model capable of estimating fuel consumption is a valuable tool in analysis and design of the hybrid vehicles. In particular, the framework can be used for (1) benchmarking the fuel economy achievable from alternate hybrid powertrain technologies, (2) investigating sensitivity of fuel savings with respect to design parameters (for example, component sizing), and (3) evaluating the performance of various supervisory control algorithms for energy management. This paper describes such a simulation framework that can be used to predict fuel economy of series hydraulic hybrid vehicle for any specified driver demand schedule (drive cycle), developed in MATLAB/Simulink. The key components of the series hydraulic hybrid vehicle are modeled using a combination of first principles and empirical data. A simplified driver model is included to follow the specified drive cycle.
Technical Paper

Hydraulic Hybrid Powertrain-In-the-Loop Integration for Analyzing Real-World Fuel Economy and Emissions Improvements

2011-09-13
2011-01-2275
The paper describes the approach, addresses integration challenges and discusses capabilities of the Hybrid Powertrain-in-the-Loop (H-PIL) facility for the series/hydrostatic hydraulic hybrid system. We describe the simulation of the open-loop and closed-loop hydraulic hybrid systems in H-PIL and its use for concurrent engineering and development of advanced supervisory strategies. The configuration of the hydraulic-hybrid system and details of the hydraulic circuit developed for the H-PIL integration are presented. Next, software and hardware interfaces between the real components and virtual systems are developed, and special attention is given to linking component-level controllers and system-level supervisory control. The H-PIL setup allows imposing realistic dynamic loads on hydraulic pump/motors and accumulator based on vehicle driving schedule.
Technical Paper

Challenges and Opportunities in Adoption of Hybrid Technologies in Medium and Heavy Duty Applications

2011-09-13
2011-01-2251
A key strategy to improving the real-world fuel consumption and emissions of medium and heavy duty vehicles is the hybridization of these applications. Unlike the passenger vehicle market, medium and heavy duty applications are typically comprised of a range of components from a variety of manufacturers. The vocational market diversity and size places considerable demand on fuel efficiency and emission compliance. Medium and heavy duty applications have the ability to be successfully hybridized in ways that are not currently, or would not be practical within a passenger vehicle. This would also drive greater truck and bus vertical integration of the hybrid components. However, medium and heavy duty manufacturers have been prevented from certifying a full vehicle level platform due to the current engine only certification requirements.
Journal Article

Ground Fault Detection for Flexible High Voltage Power Systems

2011-09-13
2011-01-2252
Hybrid Electric Vehicles (HEV) in the consumer and commercial vehicle sectors have seen tremendous technological advancement in the last decade. The commercial vehicle industry in particular has benefited significantly from the hybridization of the propulsion system, and unlike the automotive segment, serves a wide variety of functions. This diversity in vehicle applications drives the necessity for high voltage power systems to be flexible in nature, allowing them to adapt to different vehicle architectures while performing the intended function. As a result, diagnostic modules within the high voltage power system, such as ground fault detection circuits, are being required to operate robustly in a high voltage power system that is exposed to electrical noise and significant variation in common mode impedance characteristics.
Journal Article

Impact of Model-Based Lithium-Ion Battery Control Strategy on Battery Sizing and Fuel Economy in Heavy-Duty HEVs

2011-09-13
2011-01-2253
Electrification and hybridization show great potential for improving fuel economy and reducing emission in heavy-duty vehicles. However, high battery cost is unavoidable due to the requirement for large batteries capable of providing high electric power for propulsion. The battery size and cost can be reduced with advanced battery control strategies ensuring safe and robust operation covering infrequent extreme conditions. In this paper, the impact of such a battery control strategy on battery sizing and fuel economy is investigated under various military and heavy-duty driving cycles. The control strategy uses estimated Li-ion concentration information in the electrodes to prevent battery over-charging and over-discharging under aggressive driving conditions. Excessive battery operation is moderated by adjusting allowable battery power limits through the feedback of electrode-averaged Li-ion concentration estimated by an extended Kalman filter (EKF).
Journal Article

Flexible High Voltage Architecture for Commercial Hybrid Vehicles

2011-09-13
2011-01-2255
Architecting and integrating commercial hybrid electric vehicles (HEV) is a long and labor intensive process which is unique every time. The challenge intensifies when one attempts to create an HEV capable of engine-off operation. In this case, electrical power needs to be supplied to devices which are normally powered by the engine accessory belt. These devices are referred to as e-accessories. To address the issue of time to market and reduce vehicle integration burden, a plug-and-play architecture for connecting e-accessories has been developed. The Flexible High Voltage DC System is analogous to a USB hub on a PC and serves to provide power, control and communication to e-accessories such as electrified power steering, electrified brakes and electrified HVAC.
Technical Paper

Performance Study and Comparison of Representative e-CVT Based Hybrid Powertrains

2011-04-12
2011-01-1442
An electronic continuously variable transmission (e-CVT) with integrated electric machines and planetary gears is widely used in the powertrains of hybrid electric vehicles (HEV). The e-CVT supports various promising hybrid powertrain designs, blending electric and mechanical drives with high efficiency and flexible energy sources. Identifying the peak performance characteristic of an e-CVT design for a given HEV, however, is a challenging task due to the complexity of hybrid propulsion system and the multi-disciplinary nature of hybrid powertrain design. In this work, model-based design and optimization methods are used to identify the peak synergetic performance of hybrid powertrains with an e-CVT. Four popular HEVs platforms have been studied: the Chevy 2-mode, Chevy Volt, Lexus RX450h, and Toyota Prius.
Technical Paper

Design of an Optimal Control Strategy in a Parallel Hybrid Vehicle in Order to Simultaneously Reduce Fuel Consumption and Emissions

2011-04-12
2011-01-0894
In this paper, an optimal control strategy is developed. The control strategy aims to simultaneously reduce fuel consumption and emissions of a parallel hybrid electric vehicle (HEV). A continuously variable transmission (CVT) is implemented in the HEV model. The CVT has a significant role to operate the internal combustion engine (ICE) near its optimal operating points; consequently its proper control will contribute to enhance the fuel economy and emissions. Using a trade-off between the fuel consumption and emission rates, improving the fuel consumption can cause the emission rates to be improved too. First, 5 different modes for the vehicle motion is defined. Afterwards, depending on the state of charge of the battery (SOC) and the requested power from the driver, the best mode, in each time step, is chosen. Knowing the best mode, the control strategy refers to ICE or electric motor (EM) pre-calculated optimal curves, and determines ICE/EM output speed (i.e. input speed to CVT).
Technical Paper

The Application of the Milner CVT as a Novel Power Splitting Transmission for Hybrid Vehicles

2011-04-12
2011-01-0890
Hybrid vehicles are becoming an increasingly popular choice for both consumers and manufacturers due to their potential for superior fuel economy and low emissions compared with conventional vehicle power trains. Traditionally there have been two types of hybrid vehicle configurations; the parallel hybrid configuration takes advantage of power regeneration for short periods of zero emissions operation, whilst the series hybrid configuration acts as a continually variable transmission (CVT) so that increased engine efficiency can be obtained. The recent interest in hybrid vehicles has led to a number of non-traditional configurations, most notably the power-splitting hybrid electric vehicle, which uses an epicyclic gear as the power-splitting device, and can operate as either a series or a parallel hybrid. A further improvement to this configuration is proposed with the use of a Milner CVT (MCVT) to replace the epicyclic gear set.
Technical Paper

Development of an Energy Management Strategy for Plug-in Series Hybrid Electric Vehicle Based on the Prediction of the Future Driving Cycles by ICT Technologies and Optimized Maps

2011-04-12
2011-01-0892
An adaptative energy management strategy for series hybrid electric vehicles based on optimized maps and the SUMO (Simulation of Urban MObility) predictor is presented here. The first step of the investigation is the off line optimization of the control strategy parameters (already developed by the authors) over a series of reference mini driving cycles (duration of 60s) obtained from standard driving cycles (UDDS, EUDC, etc) and realistic driving cycles acquired on the ITAN500 HEV. The optimal variables related to each mini driving cycle are stored in maps that are then implemented on the ITAN500 vehicles. When the vehicle moves, a wireless card is used to exchange information with surrounding vehicle and infrastructure. These information are used by a local instance of the SUMO traffic prediction tool (run on board) to predict the driving conditions of the HEV in the future period of time T=60s.
Technical Paper

Effect of First Cycle Fuel Injection Timing on Performance of a PFI Engine during Quick Start for HEV Application

2011-04-12
2011-01-0886
Idle stopping is one of the most important fuel saving methods for hybrid electric vehicle (HEV). While the enriched injection strategy which was employed to ensure reliable ignition of first cycle will leads to even more fuel film stayed in the intake port, all of the liquid film will evaporate randomly and interfere the mixture air-fuel ratio of the followed cycles. The fuel transport of the first cycle should be enhanced to reduce the residual fuel film, and then the control of the cycle-by-cycle air-fuel ratio will become easier and the combustion and HC emissions will also be better. In this paper the mixture preparation characteristics of the unfired first cycle, as well as the combustion and HC emissions characteristics of the fired first cycle under various injection timing strategies such as close-valve injection, mid-valve injection, and open-valve injection were investigated.
Journal Article

Hybrid Electric Vehicle Powertrain and Control Strategy Optimization to Maximize the Synergy with a Gasoline HCCI Engine

2011-04-12
2011-01-0888
This simulation study explores the potential synergy between the HCCI engine system and three hybrid electric vehicle (HEV) configurations, and proposes the supervisory control strategy that maximizes the benefits of combining these two technologies. HCCI operation significantly improves fuel efficiency at part load, while hybridization aims to reduce low load/low speed operation. Therefore, a key question arises: are the effects of these two technologies additive or overlapping? The HEV configurations include two parallel hybrids with varying degrees of electrification, e.g. with a 5kW integrated starter/motor (“Mild”) and with a 10 kW electric machine (“Medium”), and a power-split hybrid. The engine is a dual-mode, SI-HCCI system and the engine map reflects the impact of HCCI on brake specific fuel consumption.
Technical Paper

Developing an Extensible and Concise Simulink Toolset for Hybrid Vehicle Modeling and Simulation

2011-04-12
2011-01-0755
Today's energy economy holds efficiency at a premium. As engineers it is our job to find and eliminate inefficiencies no matter how big or small-whether a major change to an engine design or a small tweak to a shift schedule is required. Because of the ever-increasing need for these efficiency gains, system-level design is a crucial step in the hybrid vehicle development process. There exist several tools to simulate the behavior and performance of hybrid vehicles, but many of these are prohibitively expensive, too complex for engineers (particularly students) to learn from, or unable to support custom or unusual driveline configurations. This paper will discuss the development of a simple and extensible Simulink toolset which models hybrid vehicle systems and controls.
Technical Paper

Comparison between Rule-Based and Instantaneous Optimization for a Single-Mode, Power-Split HEV

2011-04-12
2011-01-0873
Over the past couple of years, numerous Hybrid Electric Vehicle (HEV) powertrain configurations have been introduced into the marketplace. Currently, the dominant architecture is the power-split configuration, notably the input splits from Toyota Motor Sales and Ford Motor Company. This paper compares two vehicle-level control strategies that have been developed to minimize fuel consumption while maintaining acceptable performance and drive quality. The first control is rules based and was developed on the basis of test data from the Toyota Prius as provided by Argonne National Laboratory's (Argonne's) Advanced Powertrain Research Facility. The second control is based on an instantaneous optimization developed to minimize the system losses at every sample time. This paper describes the algorithms of each control and compares vehicle fuel economy (FE) on several drive cycles.
Journal Article

PHEV Energy Management Strategies at Cold Temperatures with Battery Temperature Rise and Engine Efficiency Improvement Considerations

2011-04-12
2011-01-0872
Limited battery power and poor engine efficiency at cold temperature results in low plug in hybrid vehicle (PHEV) fuel economy and high emissions. Quick rise of battery temperature is not only important to mitigate lithium plating and thus preserve battery life, but also to increase the battery power limits so as to fully achieve fuel economy savings expected from a PHEV. Likewise, it is also important to raise the engine temperature so as to improve engine efficiency (therefore vehicle fuel economy) and to reduce emissions. One method of increasing the temperature of either component is to maximize their usage at cold temperatures thus increasing cumulative heat generating losses. Since both components supply energy to meet road load demand, maximizing the usage of one component would necessarily mean low usage and slow temperature rise of the other component. Thus, a natural trade-off exists between battery and engine warm-up.
Technical Paper

A Study on Fuel Economy and Low Emission Development of LPI HEV (SULEV) to Meet Stringent Emission Regulations

2011-04-12
2011-01-0869
Hybrid vehicles, which have a higher fuel economy and system efficiency than conventional gas only vehicles, has been attracting worldwide attention for its various advantages. These advantages include low emissions of greenhouse gases which mitigates direct or indirect effects on the ozone layer. LPI HEV recently developed by HMC performs with the same output level, torque and fuel economy as conventional gasoline hybrid vehicles by employing the world's first liquid-state-injection system for exclusive use of LPG. In particular, the improved fuel economy of the vehicle is expected to help cope with future regulations relating to environmental protection from exhaust fumes.
Technical Paper

A Novel Air Hybrid Engine Configuration Utilizing Cam-Based Valvetrain

2011-04-12
2011-01-0871
In this work, a new air hybrid engine configuration is introduced in which cam-based valvetrain along with three-way and unidirectional valves make the implementation of different air hybrid engine operational modes possible. This configuration simplifies the air hybrid engine valvetrain significantly and relaxes the necessity of using fully flexible valvetrain in air hybrid engines. Utilizing the proposed configuration allows compression braking (CB), air motor (AM), startup and conventional modes of operation to be realized. The proposed configuration is modeled in GT-Power and the deceleration of a typical vehicle, utilizing only regenerative braking system, is simulated. The efficiency of the system in storing the vehicle's kinetic energy is determined using second law definition for efficiency. The stored energy can be used to either start up the engine or run the off-engine accessories. These two modes are studied and compared.
Technical Paper

Controls Development for Clutch-Assisted Engine Starts in a Parallel Hybrid Electric Vehicle

2011-04-12
2011-01-0870
In a parallel hybrid electric vehicle, higher fuel economy gains are typically achieved if significant electric drive (or engine-off) operation is possible, shifting the engine operating schedule so that it only runs at medium to high load for best efficiency. To enable efficient engine-off driving, a typical configuration will have a disconnect clutch between the engine and the rest of the driveline. In some configurations, when engine-on operation is requested the disconnect clutch is applied in conjunction with the traction motor/generator to crank the engine (i.e., a flying engine start). In this paper we describe the development of a control system for a flying engine start using an engine disconnect clutch. The clutch is located between the engine and electric motor, which is connected to the input of a multispeed transmission. We first describe an initial control algorithm evaluation using a driveline model.
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