Browse Topic: Regenerative braking

Items (162)

Quantitative Analysis of a Hybrid Electric HMMWV for Fuel Economy Improvement

2024-01-3356

4/23/2025

ABSTRACT This paper presents a quantitative analysis and comparison of fuel economy and performance of a series hybrid electric HMMWV (High Mobility Multi-purpose Wheeled Vehicle) military vehicle with a conventional HMMWV of equivalent size. Hybrid vehicle powertrains show improved fuel economy gains due to optimized engine operation and regenerative braking. In this paper, a methodology is presented by which the fuel economy gains due to optimized engine are isolated from the fuel economy gains due to regenerative braking. Validated vehicle models as well as data collected on test tracks are used in the quantitative analysis. The regenerative braking of the hybrid HMMWV is analyzed in terms of efficiency from the kinetic energy at the wheels to the portion of regenerative power which is retrievable by the battery. The engine operation of both the series hybrid and conventional HMMWV are analyzed using a 2-D bin analysis methodology. Finally, the vehicle model is used to make recommendations on improving the fuel economy of the series hybrid as well as the conventional HMMWV.

Nedungadi, Ashok, Masrur, Abul, Khalil, Gus

V4-002 FK test

SAE-PP-009554/26/2022

Heavy vehicles are essential for the modern economy, delivering critical food, supplies, and freight throughout the world. Connected heavy vehicles are also driven by embedded computers that utilize internal communication using common standards. However, some implementations of the standards leave an opening for a malicious actor to abuse the system. One such abuse case is a cyber-attack known as the “Address Claim Attack.” Proposed in 2018, this attack uses a single network message to disable all communication to and from a target electronic control unit, which may have a detrimental effect on operating the vehicle. This article demonstrates the viability of the attack and then describes the implementation of a solution to prevent this attack in real time without requiring any intervention from the manufacturer of the target devices. The defense technique uses a bit-banged Controller Area Network (CAN) filter to detect the attack. Once an attack is discovered, the defender induces a CAN protocol error to remove the malicious message from the network. We discuss our results in terms of their applicability for Address Claim Attacks and possible implications for preventing a variety of network-based attacks in real time.

Mutagaana, Festo

Accurate Pressure Control Based on Driver Braking Intention Identification for a Novel Integrated Braking System

2021-01-01004/6/2021

With the development of intelligent and electric vehicles, higher requirements are put forward for the active braking and regenerative braking ability of the braking system. The traditional braking system equipped with vacuum booster has difficulty meeting the demand, therefore it has gradually been replaced by the integrated braking system. In this paper, a novel Integrated Braking System (IBS) is presented, which mainly contains a pedal feel simulator, a permanent magnet synchronous motor (PMSM), a series of transmission mechanisms, and the hydraulic control unit. As an integrative system of mechanics-electronics-hydraulics, the IBS has complex nonlinear characteristics, which challenge the accurate pressure control. Furthermore, it is a completely decoupled braking system, the pedal force doesn’t participate in pressure-building, so it is necessary to precisely identify driver’s braking intention. To improve the control accuracy of the system, this paper proposed a novel pressure control strategy based on driver braking intention identification. Firstly, the structure and working principle of the novel integrated braking system was introduced. Secondly, the driver's braking intention identification strategy was designed. Thirdly, Considering the nonlinear and dynamic characteristics of the system, a cascade closed-loop control strategy including a pressure loop by the feedforward-feedback method, a position loop by the sliding-mode control method, and current loop with friction compensation was proposed. Finally, based on dSPACE products, a hardware-in-the-loop (HiL) experimental bench was built for algorithm verification. The HiL experiment results show that the pressure control strategy has the advantages of accurate response, the braking system pressure follows the driver's expected pressure well.

Zhu, Bing, Zhang, Yihan, Zhao, Jian, Chen, Zhicheng, Jin, Wanli

Integrated Regenerative Braking System and Anti-Lock Braking System for Hybrid Electric Vehicles & Battery Electric Vehicles

2020-01-08464/14/2020

Yao, Yixin, Zhao, Yanan, Yamazaki, Mark

Modeling, Validation and Control Strategy Development of a Hybrid Super Sport Car Based on Lithium Ion Capacitors

2020-01-0442

4/14/2020

Today, the contribution of the transportation sector on greenhouse gases is evident. The fast consumption of fossil fuels and its impact on the environment have given a strong impetus to the development of vehicles with better fuel economy. Hybrid electric vehicles fit into this context with different targets, starting from the reduction of emissions and fuel consumption, but also for performance and comfort enhancement. Lamborghini has recently invested in the development of a hybrid super sport car, due to performance and comfort reasons. Aventador series gearbox is an Independent Shift Rod gearbox with a single clutch and during gear shifts, as all the single clutch gearbox do, it generates a torque gap. To avoid the additional weight of a Dual Clutch Transmission, a 48V Electric Motor has been connected to the wheels, in a P3 configuration, to fill the torque gap, and to habilitate regenerative braking and electric boost functions. This paper discusses the usage of a control-oriented vehicle and powertrain model to analyze the performance of the first Lithium Ion Capacitor-based hybrid V12 by Automobili Lamborghini. The internal combustion engine, the gearbox, the LiC and the vehicle longitudinal dynamics models have been initially validated through the comparison with experimental data from chassis dynamometer testing, in addition to experimental results from specific components’ testing. As shown in the paper, the validated model has then been used to develop control strategies aimed at increasing comfort and performance, but also to expand the hybrid system capabilities by widening the LiC working range, and to study the possibility of implementing CO2 reduction-oriented control functions.

Franceschi, Alessandro, Cavina, Nicolo, Parenti, Riccardo, Reggiani, Maurizio, Corti, Enrico

Pressure Tracking Control of Electro-Mechanical Brake Booster System

2020-01-02114/14/2020

The Electro-Mechanical Brake Booster system (EMBB) is a kind of novel braking booster system, which integrates active braking, regenerative braking, and other functions. It usually composes of a servo motor and the transmission mechanism. EMBB can greatly meet the development needs of vehicle intelligentization and electrification. During active braking, EMBB is required to respond quickly to the braking request and track the target pressure accurately. However, due to the highly nonlinearity of the hydraulic system and EMBB, traditional control algorithms especially for PID algorithm do not work well for pressure control. And a large amount of calibration work is required when applying PID algorithms to pressure control in engineering. In this paper, a fuzzy adaptive PI pressure control algorithm based on feed-forward is proposed to a novel self-designed EMBB mechanism, which is utilized to overcome the nonlinear pressure control problem when EMBB is in active braking and improve the control effect of PID algorithm. First, the structure of the EMBB system used in the paper and its working principle is presented. Second, this paper designs a two-layer control algorithm to implement the pressure control of EMBB. The upper layer is a pressure control loop using fuzzy PI algorithm based on feedforward, and the lower layer is a motor control loop composed of position loop and current loop. Finally, to verify the proposed control algorithm, a series of pressure tracking tests were performed under multiple operating conditions based on a real vehicle platform equipped with EMBB. The experimental results show that the proposed control algorithm can effectively enhance the accuracy of EMBB pressure control and its response speed during active braking compared with PID algorithm. Therefore, the proposed algorithm can effectively improve the effect of EMBB pressure control.

Yang, Weihong, Wu, Jian, He, Rui, Zhu, Bing, Zhao, Jian, Chen, Zhicheng

Brake Power Availability Led Optimisation of P0 versus P2 48V Hybrid Powertrain Architectures

2020-01-04394/14/2020

Through improving the 48V hybrid vehicle archetype, governmental emission targets could be more easily met without incurring the high costs associated with increasing levels of electrification. The braking energy recovery function of hybrid vehicles is recognised as an effective solution to reduce emissions and fuel consumption in the short to medium term. The aim of this study was to evaluate methods to maximise the braking energy recovery capability of the 48V hybrid electric vehicle over pre-selected drive cycles using appropriately sized electrified components. The strategy adopted was based upon optimising the battery chemistry type via specific power capability, so that overall brake power is equal to the maximum battery charging power in a typical medium-sized passenger car under typical driving. This will maximise the regenerative braking energy whilst providing a larger torque assistance for a lower battery capacity. Dynamic simulation models were developed using GT-DRIVE software, emulating a mid-sized car with a 48V battery, and different turbocharged gasoline engines with motor-generator unit positions along a drivetrain. The 1.3 kWh battery pack was developed using a 14 Ah Lithium Iron Phosphate cell arranged in a 14 series 2 parallel configuration. A fuel economy comparison was produced using the FTP, WLTP, and HEFET drive cycles. When the motor-generator unit was attached via a synchronous belt, a 10-17% fuel saving was achieved in the WLTP drive cycle. Comparatively, when placing the electric machine after the clutch in a “P2” position, a 17-21% fuel saving was attained. The energy loss analysis of both P2 and P0 configurations revealed up to 7% overall reduction in total energy losses for the P2 setup. This was despite an increase in the motor-generator unit and battery losses due to the extended use of both in the electric-only mode capability with the P2 layout.

Alnamasi, Khaled, Terry, Simon, La Rocca, Antonino, Cairns, Alasdair

Conceptualization and Modeling of a Flywheel-Based Regenerative Braking System for a Commercial Electric Bus

02-12-04-001811/19/2019

The following article illustrates the detailed study of the development of a unique flywheel-based regenerative braking system (f-RBS) for achieving regenerative braking in a commercial electric bus. The f-RBS is designed for installation in the front wheels of the bus. The particular data values for modeling the bus are taken from multiple legitimate sources to illustrate the development strategy of the regenerative braking system. Mechanical components used in this system have either been carefully designed and analyzed for avoiding fatigue failure or their market selection strategies are are explained. The positioning of the entire system is decided using MSC Adams View®, hence determining a suitable component placement strategy such that the f-RBS components do not interfere with the bus components. The entire system is modeled on MATLAB Simulink® with sufficient accuracy to get various results that would infer the performance of the system as a whole. The overall efficiency of the developed system in terms of battery consumption is also computed in this study.

Mathur, Kunal, Choudhary, Lalit Kumar, Natu, Aditya Manoj, Srinivas, Krovvidi, Rastogi, Vikas

Cooperative Distribution Strategy of Regenerative Braking and Pneumatic Braking of an Electric Commercial Vehicle

2019-01-503911/4/2019

This paper mainly proposes one type control strategy of the regenerative braking system of an electric commercial vehicle under normal braking condition. With the main goal of recovering as much energy as possible, the braking force distribution strategy based on maximum regenerative braking optimization is studied under the restriction of ECE regulation and state of charge (SOC) of battery. Firstly, the related models of the regenerative braking system and the target vehicle are separately established in MATLAB/Simulink. Then, the distribution strategy of braking force is developed and optimized considering the influence of SOC and vehicle speed respectively. Finally, the braking effects of this control strategy in the typical deceleration process are numerical simulated and analyzed. Simulation results depict that this control strategy can recover more braking energy under the premise of ensuring braking safety and great braking performance compared with the common braking strategies with traditional strategy and without regenerative braking.

Cheng, Qing, Pi, Dawei, Xie, Boyuan, Wang, Hongliang, Wang, Xianhui

Downhill Safety Assistant Driving System for Battery Electric Vehicles on Mountain Roads

2019-01-21299/15/2019

When driving in mountainous areas, vehicles often encounter downhill conditions. To ensure safe driving, it is necessary to control the speed of vehicles. For internal combustion engine vehicles, auxiliary brake such as engine brake can be used to alleviate the thermal load caused by the continuous braking of the friction brake. For battery electric vehicles (BEVs), regenerative braking can be used as auxiliary braking to improve brake safety. And through regenerative braking, energy can be partly converted into electrical energy and stored in accumulators (such as power batteries and supercapacitors), thus extending the mileage. However, the driver's line of sight in the mountains is limited, resulting in a certain degree of blindness in driving, so it is impossible to fully guarantee the safety and energy saving of downhill driving. Therefore, taking a pure electric light truck as an example, the system proposed in this paper first analyzes the driver's driving intention, proposes the system startup and exit strategy, and then combines the geographic information system (GIS) mountain road information, downslope speed limit and vehicle parameters, considering the motor and battery characteristics, establishes mathematical models such as the regenerative braking model and the brake temperature rise model based on vehicle dynamics and the conservation of energy, determines the appropriate braking mode(There are two braking modes)and the slope top safe speed by calculation, and reminds the driver when going uphill and downhill. The main goal is to use more regenerative braking, reduce the use or duration of the main brake, avoid overheating the main brake, improve the safety during continuous braking, and achieve smarter energy management. Finally, simulations are carried out under different conditions of vehicle speed, slope length, slope gradient and battery SOC. The results show that the system has a good energy-saving effect and can significantly improve the safety of BEVs running downhill.

Feng, Jia'ao, Tian, Zhongpeng, Cui, Jian, Zhou, Fangyu, Tan, Gangfeng

Development of Regenerative Brake Control Strategy to Remove Brake Rust

2019-01-21259/15/2019

This study is the development concept of regenerative braking cooperative control to reduce creep groan noise considering fuel efficiency. Creep groan noise is a traditional brake system noise that has been improved with advances in technology such as brake materials, surface treatment and transfer path. However, recently creep groan noise is again an issue in electronic vehicle which applied a drive motor. Generally, creep groan noise frequently occurs when rust occurs on the friction surface of the brake disc and the brake pad is humidified, but it is easily removed by friction braking several times. However, in the case of electric vehicles which applied regenerative braking system, it is hard to remove. In case of electric vehicle, instead of friction braking, most of brake toques are made by motor regenerative braking. Therefore, even if the same conventional brake system and chassis system are applied, the noise level of the electric vehicle is higher than gasoline or diesel vehicle, and the field claim is also higher. To improve the noise, regenerative braking cooperative control logic was developed that detects long-term vehicle parking condition and control the regenerative brake ratio of total driver demand brake toque considering fuel efficiency. Also several tests are proceeded to review the effect of creep groan noise and fuel efficiency.

Jang, Sora, Kim, Gwichul

Target Setting Process for Hybrid Electric Drives Using TPA, Jury Study, and Torque Management

2019-01-14536/5/2019

The idea of improved efficiency without compromising the “fun to drive” aspect has renewed the auto industry’s interest toward electrification and hybridization. Electric drives gain from having multiple gear ratios which can use advantageous operating set points thus increasing range. Furthermore, they benefit significantly from frequent decelerations and stopping as is experienced in city driving conditions. To recuperate as much energy as possible, deceleration is done at high torque. This presents an interesting but serious sound quality issue in the form of highly tonal whine harmonics of rapidly changing gears that do not track with vehicle speed thus being objectionable to the vehicle occupants. This paper presents an NVH target setting process for a hybrid electric transmission being integrated into two existing vehicles, one belonging to the premium segment and another aimed at enthusiasts with off-road applications. The demand for power has shifted from mechanical domain into electrical domain, and as such, the solution to electric drive NVH issues also lay partly, in the way these drive systems are calibrated. A time-domain Transfer Path Analysis (TPA) model was developed for both vehicles, by virtually installing the hybrid transmission into the vehicle, thus predicting interior noise in several gears and simulating the brake regen coast downs at varying torque levels. Road and wind noise masking was added to these predictions taking care that the summations were correctly done at same vehicle speeds for which a program was written using a commercially available numerical computing tool. Extensive jury studies were then conducted to determine NVH no-fly zones and the torque management strategy for the two vehicles during brake regen events. Requirements and strategy for the two vehicles were different since they presented different levels of road and wind noise masking. To validate the NVH targets, another jury compared the finalized strategy with a premium target vehicle fitted with a similar hybrid system. This target-setting approach was useful in getting an upfront idea of the NVH risks without any system modifications. It then circumvented the need of re-developing expensive acoustic package and/or gear optimization that would be otherwise needed to mitigate the risks, with co-operation from calibration teams, while still being able to meet their regenerative braking targets in every gear for the two vehicles.

Singh, Vinod, Parbat, Aniket, Charan, Anil

Parameter Design of a Parallel Hydraulic Hybrid Vehicle Driving System Based on Regenerative Braking Control Strategy

2019-01-03684/2/2019

In this paper, hydraulic driving system parameters of a parallel hydraulic hybrid vehicle are designed based on the regenerative braking requirement. Torque, speed and power demands during typical driving cycles are analyzed. The braking control strategy is designed considering both the braking safety and braking energy recovery efficiency. The hydraulic braking torque is determined by the braking control strategy. The proportional relationship of hydraulic pump/ motor output torque and its working pressure is considered. Through simulation with typical city driving cycles, most braking energy can be recovered by the proposed hydraulic driving system and braking control strategy.

Zhou, Shilei, Walker, Paul, Tian, Yang, Zhang, Nong

Analyzing the Limitations of the Rider and Electric Motorcycle at the Pikes Peak International Hill Climb Race

2019-01-11254/2/2019

This paper describes a post-race analysis of team KOMMIT EVT’s electric motorcycle data collected during the 2016 Pikes Peak International Hill Climb (PPIHC). The motorcycle consumed approximately 4 kWh of battery energy with an average and maximum speed of 107 km/h and 149 km/h, respectively. It was the second fastest electric motorcycle with a finishing time of 11:10.480. Data was logged of the motorcycle’s speed, acceleration, motor speed, power, currents, voltages, temperatures, throttle position, GPS position, rider’s heart rate and the ambient environment (air temperature, pressure and humidity). The data was used to understand the following factors that may have prevented a faster time: physical fitness of the rider, thermal limits of the motor and controller, available battery energy and the sprocket ratio between the motor and rear wheel. Even though the rider’s heart rate implied a vigorous exercise intensity level, throttle values indicated that the rider wanted to go faster ~33% of the time. The motor reached a steady-state temperature that was approximately 30°C below the maximum allowable temperature and thus could have handled more current. By analyzing additional thermal and current data, it was concluded that the motor controller was likely a limiting factor but not the battery capacity since only ~2/3 of the total available battery energy was consumed. A model that estimates the optimal sprocket ratio was derived and validated; It was determined that using the optimal sprocket ratio of 62/12 would have decreased the finishing time by approximately 2 seconds.

Rodgers, Lennon, Jeunnette, Mark, Biffard, Ryan, Möller, Björn, Wu, Eric, Matthys, Koen

Regenerative Braking Pedal Decoupling Control for Hydraulic Brake System Equipped with an Electro-Mechanical Brake Booster

2019-01-11084/2/2019

Electrification and intelligence are the important development directions of vehicle techniques. The Electro-Mechanical Brake Booster (Ebooster) as a brake booster which is powered by a motor, can be used to replace the traditional vacuum booster. Ebooster not only improves the intelligence level of vehicle braking and significantly improves the braking performance, but also adapts to the application in new energy vehicles and facilitates coordinated regenerative braking. However, Ebooster cannot complete pedal decoupling independently. It needs to cooperate with other components to realize pedal decoupling. In this paper, a pedal decoupling control algorithm for regenerative brake, which is based on the coordination control of Ebooster and ESP, is proposed. First, regenerative braking strategy is designed to distribute the hydraulic brake force and regenerative braking force. Then, the coordinated control strategy of Ebooster and ESP is proposed, and the decoupling of brake pedal and brake wheel cylinder is realized. Finally, series of simulations are carried out under regenerative braking condition. The results show that the control algorithm introduced in this paper can achieve the decoupling of brake pedal and brake wheel cylinder.

Zhao, Jian, Hu, Zhiqiang, Zhu, Bing

Modelling and Control of a Hybrid Urban Bus

2019-01-03544/2/2019

This paper describes the development and on-vehicle validation testing of next generation parallel hybrid electric powertrain technology for use in urban buses. A forward-facing MATLAB/Simulink powertrain model was used to develop a rule-based deterministic control system for a post-transmission parallel hybrid urban bus. The control strategy targeted areas where conventional powertrains are typically less efficient, focused on improving fuel economy and emissions without boosting vehicle performance. Stored electrical energy is deployed to assist the IC engine system leading to an overall reduction in fuel consumption while maintaining vehicle performance at a level comparable with baseline conventional IC engine operation. Regenerative braking is integrated with the existing braking systems on the vehicle, and the control system tailored to maximise the amount of energy recuperated during deceleration events and accelerator pedal lift off without adversely impacting on the normal behaviour of the vehicle. The control system was implemented on both prototype single (Streetlite) and double-deck (Streetdeck) vehicle configurations for real vehicle testing with partner Wrightbus. The hybridisation has reduced equivalent CO2 emissions by 34% (single-deck)/ 35% (double-deck) over the conventional Euro VI diesel vehicle on the Low Carbon Vehicle Partnership UK bus cycle (based on London Bus Route 159). These results compare favourably with alternative powertrain technologies currently available with similar certification. Moreover, the next generation hybrid urban bus has several distinct advantages as it is less restricted by infrastructure, range, or terrain issues, and has a comparatively lower purchase price point. Hybrid bus technologies offer the option of maintaining existing service levels without significant modifications to operations or budgets while achieving significant reductions in average fleet emissions.

Murtagh, Martin, Early, Juliana, Stevens, Gary, Cunningham, Geoffrey, Douglas, Roy, Best, Robert

INSIDE E-TRON

19AUTP02_012/1/2019

Insights into the German approach to developing a premium-class EV. Audi has made its ambitious electromobility goals clear, saying it will offer 10 all-electric and 10 plug-in hybrid models by 2025, accounting for at least one-third of its sales. To help achieve this, the company carefully designed the all-new 2019 Audi e-tron luxury SUV to not alienate its core audience. As engineer Anno Mertens, Audi's product manager for electrification put it: “In the end, it's an Audi, it's not an electric car.” Audi's target for the e-tron (yes, the name is all lower case) is the same SUV buyer who might also have shopped for a Q7, Mertens said (the e-tron's wheelbase sits between the Q5 and Q7 in Audi's SUV lineup). To that end, early in the development process, Audi surveyed its customer base to learn just what kind of EV they would use. The questions included how many business trips they take and whether they live in detached homes or in multi-family dwellings.

Blanco, Sebastian

Hyundai Nexo out-spaces Toyota and Honda FCVs

19AUTP01_181/1/2019

The 2019 Hyundai Nexo is a distinctively-styled and luxurious compact SUV based upon Hyundai's first fully dedicated fuel-cell electric vehicle (FCEV) platform. A technological flagship for Hyundai, the front-wheel-drive Nexo is the most refined fuel-cell (FC) offering to date and also trumps the Toyota Mirai and Honda Clarity via a trendier and more practical SUV format. Like its two Japanese competitors, the Korean offering will face the same geographically limited availability until hydrogen refueling infrastructures catch up with these long-range electrified platforms.

Seredynski, Paul

Brake System Design for Dedicated BEV Architectures

2018-01-187010/5/2018

As fossil fuels dwindle and more electric vehicles enter the market, there is an opportunity to reevaluate the standard brake system. This paper will discuss and compare the differences in brake system sizing between a non-regenerative braking internal combustion engine vehicle and a dedicated battery electric vehicle with regenerative braking. It will use a model derived from component dynamometer testing and vehicle test data of a mid-size production vehicle. The model will be modified for the mass and regenerative braking capabilities of a battery electric vehicle. The contribution of regenerative braking energy will be analyzed and compared to show its impact on component sizing, thermal sizing, and lining life. The detailed design study will calculate the parameters for caliper, rotor design, actuation, etc., that are optimized for 100% regen enabled vehicles.

Shenberger, Michael J., Antanaitis, David

Coordinated Control under Transitional Conditions in Hybrid Braking of Electric Vehicle

2018-01-186910/5/2018

In the hybrid brake system of electric vehicle, due to the limitation of the motor braking force when the motor is at high speed and the failure of the regenerative braking force when the motor is at low speed, there are three transitional conditions in hybrid braking: the hydraulic brake system intervenes the braking, the hydraulic brake system withdraws the braking and the regenerative braking force withdraws the braking. Due to the response speed of the hydraulic system is slower than that of the motor, there is a large braking impact (the derivative of braking deceleration) in the transitional conditions of hybrid braking, which deteriorates the smoothness and comfort in braking. Aiming at the impact caused by the poor cooperation between the hydraulic braking force and the motor braking force, a coordinated strategy of double closed-loop feedback and motor force correction is proposed in this paper. The double closed-loop feedback strategy relies on the motor force to compensate the tracking error of hydraulic pressure of the hydraulic brake system. The purpose of the motor force correction strategy is to allow the motor to consistently have the compensation capability under all transitional conditions. Simulation and hardware in-loop test were carried out based on Integrated-electro-hydraulic brake system (I-EHB). The HIL test results show that the proposed strategy can greatly reduce the impact degree when the two kinds of braking force switch. The impact degree of hydraulic braking force intervention decreased from the initial 28.26 m/s3 to 18.39 m/s3, decreased by 34.9%, the impact degree of regenerative braking withdrawal reduced from the initial −60.94 m/s3 to 16.84 m/s3, reduced by 72.3%, which improved the comfort in vehicle braking and provided a reference for the practical application of the strategy.

Yu, Zhuoping, Shi, Biaofei, Xiong, Lu, Han, Wei

Electrode Design Boosts Supercapacitor Performance

TBMG-325128/1/2018

Supercapacitors are rechargeable energy storage devices that deliver more power for their size than similar-sized batteries. They also recharge quickly, and they last for hundreds to thousands of recharging cycles. Today, they are used in hybrid cars’ regenerative braking systems and for other applications. Advances in supercapacitor technology could make their use widespread as a complement to, or even replacement for batteries used in household electronics.

Research on Regenerative Braking Control Strategy of Distributed EV based on Braking Intention

2018-01-13424/3/2018

Focusing on distributed electric vehicles with in-wheel motors, a novel regenerative braking control strategy based on braking intention is proposed. Firstly, a design scheme for the regenerative braking system is described. Four in-wheel motors and an Electro-Hydraulic Braking (EHB) system are respectively designed for regenerative braking and hydraulic braking. Then, Braking intention recognition self-learning libraries are trained based on Hidden Markov Model method, which is validated by driver-in-loop tests. According to three speed states and four braking intentions, the regenerative braking control strategy for multiple brake modes is developed. The coefficient of regenerative braking is defined to describe the intervening time and proportion of motor maximum regenerative braking. Eventually, the co-simulation results show that the proposed strategy can not only significantly improve the energy recovery capability, but also provide the coordinated control of regenerative braking and hydraulic braking, in consistence with the driver braking intention highly.

Pan, Hao, Guo, Xuexun, Pei, Xiaofei, Pan, Jin, Zhang, Jie

Novel Approach to Integration of Turbocompounding, Electrification and Supercharging Through Use of Planetary Gear System

2018-01-08874/3/2018

Technologies that provide potential for significant improvements in engine efficiency include, engine downsizing/downspeeding (enabled by advanced boosting systems such as an electrically driven compressor), waste heat recovery through turbocompounding or organic Rankine cycle and 48 V mild hybridization. FEV’s Integrated Turbocompounding/Waste Heat Recovery (WHR), Electrification and Supercharging (FEV-ITES) is a novel approach for integration of these technologies in a single unit. This approach provides a reduced cost, reduced space claim and an increase in engine efficiency, when compared to the independent integration of each of these technologies. This approach is enabled through the application of a planetary gear system. Specifically, a secondary compressor is connected to the ring gear, a turbocompounding turbine or organic Rankine cycle (ORC) expander is connected to the sun gear, and an electric motor/generator is connected to the carrier gear. The planetary gear system is equipped with a dry clutch and a band brake allowing flexibility in mechanical and electrical integration of the turbocompound turbine, secondary compressor and electric motor/generator to the engine. The system provides the ability to do electrical integration of turbocompound turbine/ORC expander when the turbine power output is low and mechanical/power-split integration when the turbine power output is high. At low engine speeds and high loads, the secondary compressor can provide power from the turbocompound turbine or from the electric motor. Furthermore, the electric motor/generator can be used for regenerative braking as well as to provide torque assist to the engine when possible. The 1D simulation tool GT-Power was used to evaluate the performance of this planetary gear enabled approach against an approach that integrates each of these technologies (a turbocompound turbine, a 48 V belt starter generator and a 48 V e-compressor) independently on a downsized four cylinder diesel engine applied in a medium heavy-duty class 6/7 vocational vehicle. The fuel consumption of both approaches was compared over the engine map and over engine certification test cycles. The simulations demonstrated the ability of the planetary gear coupled system to match the engine performance of the baseline 7.7 L 6 cylinder engine while providing an additional fuel consumption benefit when compared to independent integration of these technologies. Finally, a 3D CAD model of the planetary gear coupled system was developed and the space claim was compared against the baseline 6 cylinder engine.

Joshi, Satyum, Dahodwala, Mufaddel, Koehler, Erik W., Franke, Michael, Tomazic, Dean, Naber, Jeffrey

Development, Performance Analysis and Optimization of Parallel Hydraulic Hybrid System for City Bus Application

2018-01-04194/3/2018

One of the key requisites for a sustained mobility development is to have an efficient public transport system. Fuel efficiency and emission control are extremely important in this respect. By the very nature of city driving, it is obvious that city traffic results in frequent vehicle start and stops; which involves huge waste of vehicle kinetic energy. Every time vehicle moving from idle, needs a bigger input of power and every time the brakes are applied, all energy built up disappears again, wasted in the brake pads as heat. An effort has been taken to recuperate vehicle kinetic energy, hydraulically during braking events and utilize it to assist the vehicle during acceleration. Hydraulic based hybrid vehicle working on the principle of regenerative braking is one of the most fuel-efficient technologies for city application. Parallel hydraulic hybrid vehicle has been developed and optimized for fuel efficiency gain at vehicle level. Objective of this paper is to study behavior, performance and optimization of hydraulic hybrid vehicle in city application. This paper deals with evaluation of simulation, integration, calibration and performance tests carried out at real world usage conditions. As a final proof of concept and performance, the hydraulic hybrid bus was tested back to back with conventional city bus of same configuration and results were analyzed and compared. This paper also deals on the scope of engine downsizing and major challenges faced in developing hydraulic hybrid system for extremely hot weather conditions such as South Asian countries.

Yaser, K U Syed Taj, Bakatwar, Rupesh, Bhargava, Aashish, Tiwari, Sanjay

Simulation Based Control Strategy Design of All Wheel Drive Electric Vehicle Regenerative Braking System

2018-01-04114/3/2018

Bao, Ran, Griggs, Philip, Baxter, James

Process Turns Carbon Dioxide into 3D Graphene with Microporous Surface

TBMG-281561/1/2018

The conversion of carbon dioxide to useful materials usually requires high energy input due to its ultrahigh stability. A heat-releasing reaction between carbon dioxide and sodium was developed to take carbon dioxide and turn it into 3D graphene with micropores across its surface.

Simulation of Advanced Regenerative Braking Strategies in a Series Plug-in Hybrid Electric Vehicle

2017-01-246610/8/2017

Regenerative braking is an important factor in improving hybrid electric vehicle efficiency. This paper proposes a new regenerative braking strategy that activates preemptively during a distracted driving scenario, before service brakes are utilized. The strategy uses onboard advanced driver assistance systems, such as forward facing radar, to detect when an object is approaching fast enough to enable regenerative braking in response. The proposed strategy is simulated on a full-vehicle model of a series plug-in hybrid electric vehicle. A driver model is developed to mimic the behavior of a distracted driver through delayed response time to the changing speed of a lead vehicle. Multiple trials are simulated using different combinations of existing regenerative braking strategies along with the proposed strategy. Results show that a preventative regenerative braking control strategy can recuperate significant amounts of energy while also improving vehicle safety. Coupling the proposed strategy with an existing brake pedal regeneration strategy returns energy recuperation results that are higher than a system consisting of brake pedal regeneration coupled with coast regeneration.

Arnold, Graham

Study of Difference in Friction Behavior of Brake Disc Rotor with Various Surface Textures during Running-In by Using Simple Model

2017-01-25119/17/2017

The most fundamental function of an automobile brake system is assuring stable braking effectiveness under various conditions. In a previous paper (2004-01-2765), the author et al. confirmed that the friction behavior of disc brakes during running-in depends on both the friction materials and discs’ friction-surface textures. Various friction pairs were tested by combining discs finished with roller-burnishing and grinding and five friction materials including NAO and low-steel. Some NAO material exhibited large effects on the difference in friction behaviors between the discs’ surface textures. A disc finished with roller-burnishing needed a longer running-in period than that with grinding. In another paper (2011-01-2382), a further experiment was conducted by combining eight surface textures (finished under four turning conditions with and without additional roller-burnishing), two NAO materials, and two rotational directions. Notable phenomena were observed, e.g., the coefficients of friction had a peak at the early stage of testing and there was a difference in those at the final stage between surface textures. These behaviors were determined to be due to the contribution of aggressiveness and adhesiveness to friction by comparing the coefficients of friction and discs’ surface textures and wear. Friction behaviors at the early stage of use have become more significant since the running-in period has been extended due to the application of large discs for better braking performance and the increase in the number of hybrid and electric vehicles equipped with regenerative braking. In this study, therefore, simplified linear (2D) and areal (3D) roughness models with various surface textures were introduced, and their behaviors of wear and roughness were numerically simulated. The change in discs’ surface textures along with increasing wear depended on their initial textures. These models and simulation confirmed the effects of surface textures on friction during running-in, which were experimentally observed in the previous studies.

Okamura, Toshikazu

A Comparison of Braking Behavior between an IC Engine and Pure Electric Vehicle in Los Angeles City Driving Conditions

2017-01-25189/17/2017

The Los Angeles City Traffic Brake Test Schedule has been an established procedure used almost universally for generations by vehicle manufacturers to evaluate and validate braking systems for the attributes of NVH and brake wear behavior. The Los Angeles driving route, commonly known as the Los Angeles City Traffic Test (LACT), has long been considered an effective and “quasi” extreme set of real world driving conditions representative of the US passenger vehicle market and have been covered in other analysis including SAE Technical Paper 2002-01-2600 [1] The performance of a vehicle, relative to braking, in LACT conditions is typically influenced by basic vehicle and brake system attributes including the ratios of vehicle mass to brake sizing attributes, friction material selection, and the acceleration, drag, and cooling behavior of the vehicle. The general character of the LACT Route and typical driving behavior establishes an energy input to the braking system that must be managed by the chosen set of brake components overlaid to a set of vehicle attributes. Brake system sizing has generally converged on typical sizing choices based on market forces and the typicality of vehicles in their associated segment. As a result, the general sizing of brakes systems tends to revert to a mean within a segment. Tradeoffs between, noise, wear, dust and other performance attributes are made with the selection of the friction material. Where, by example, a brake designer may tradeoff the attributes of higher dust, lower lining and rotor life in LACT for higher performance in extreme fade testing to achieve a desired market differentiation. The need for the work presented is motivated by the relatively recent entry to the market of pure electric vehicles. Many of the Pure EV’s offer significant capability to employ regenerative braking, which allows the conversion of vehicle kinetic energy to electrical energy. Therefore, the potential exists to significantly affect the amount of energy input to a vehicle’s friction braking system. As the performance in a LACT is highly dependent on the energy input the brake system must manage, it is important to objectively understand how this may change with the contribution of regenerative braking. If it is determined that the energy input to the friction brake system is significantly different in pure EV’s, then the potential exists to design fundamental brake system attributes differently with the potential to realize an improved totality of associated metrics by altering many of the traditional tradeoff balances commonly constraining brake system designers. This paper will provide an analysis by comparison between an exemplar IC engine based vehicle and a pure electric vehicle during a typical “day in Los Angeles”. The paper will provide an assessment of how regenerative braking influences the energy the brake system must manage, as well as any changes to the usage profile of the brake system in these driving conditions. Finally, this paper will offer some thoughts on how this could affect future design of brake systems of pure electric vehicles

Hall, Thomas J.

Traditional and Electronic Solutions to Mitigate Electrified Vehicle Driveline Noises

2017-01-17556/5/2017

Hybrid powertrain vehicles inherently create discontinuous sounds during operation. The discontinuous noise created from the electrical motors during transition states are undesirable since they can create tones that do not correlate with the dynamics of the vehicle. The audible level of these motor whines and discontinuous tones can be reduced via common noise abatement techniques or reducing the amount of regeneration braking. One electronic solution which does not affect mass or fuel economy is Masking Sound Enhancement (MSE). MSE is an algorithm that uses the infotainment system to mask the naturally occurring discontinuous hybrid drive unit and driveline tones. MSE enables a variety of benefits, such as more aggressive regenerative braking strategies which yield higher levels of fuel economy and results in a more pleasing interior vehicle powertrain sound. This paper will discuss the techniques and signals used to implement MSE in a hybrid powertrain equipped vehicle. MSE utilizes powertrain signals from the vehicle bus to determine which harmonics need to be veiled and at what output level. By enhancing and complementing the naturally occurring electric propulsion sounds, it’s possible to create a more continuous and rich hybrid powertrain sound through the hybrid transition states. As MSE is adding noise to improve the overall sound in the vehicle, this feature can also be utilized to make the vehicle sound heartier and more refined for acceleration or deceleration events while simultaneously masking unwanted tones. The MSE concepts discussed in this paper are covered under US patent 9237399.

Valeri, Frank C., Lagodzinski, James T., Reilly, Scott M., Miller, John P.

Exploring the Opportunity Space For High-Power Li-Ion Batteries in Next-Generation 48V Mild Hybrid Electric Vehicles

2017-01-11973/28/2017

48V battery packs, with rated power capabilities on the order of 8-16kW, are rapidly becoming a new standard in the automotive industry. Improving on their 12V counterparts (2-5kW), 48V Mild Hybrid Electric Vehicles (MHEV) allow for extended start-stop and regenerative braking functionalities, providing fuel economy benefits of up to 10-15% in standard passenger vehicles. New and relatively unexplored opportunities exist to further increase the fuel economy and performance of 48V systems. Improvement in battery power (to ~25kW) would further enable hybridization to near-HEV levels as well as engine downsizing, thus paving the way to fuel economy improvements beyond the current 10-15% MHEV limit. Additionally, new electrified features may be added, such as electric turbo/supercharging, electric traction, electric power steering, electric suspension and electric air conditioning. Vehicle electrification topology and strategy are investigated with respect to their impact on sizing, including a fuel-economy-oriented strategy based on a belt-integrated starter generator, a P4 “through-road” hybrid, and a 48V variant with electrified accessories. In this paper, we explore the various opportunities for novel, advanced 48V systems and link these capabilities with requirements at the battery level. We conclude that future-looking vehicle features and high levels of fuel economy benefit require the development of 48V battery packs with a high power-to-energy ratio. 48V batteries with strong power (up to ~25kW) and HEV-level energy capabilities (<200Wh for most scenarios) are needed to enable the technologies explored in this work, demanding batteries with power-to-energy ratios between 30 and 160. To serve these power and energy needs, we present a high-power, lithium-iron-phosphate chemistry with excellent rate capabilities. Our conclusions suggest that a family of batteries based on high-power lithium-iron-phosphate (LFP) can meet the needs of advanced 48V architectures, providing new features to consumers and excellent fuel economy.

Abdellahi, Aziz, Khaleghi Rahimian, Saeed, Blizanac, Berislav, Sisk, Brian

Economy Mode for Electrified Vehicles

2017-01-11593/28/2017

Hybrid and Electric vehicles present special challenges when developing a customer-selectable Economy Mode, as the vehicles are already energy-efficient by design. This paper analyzes the sources of sub-optimal fuel economy in: energy generation, vehicle usage, and customer usage. The paper first reviews the effects on customer acceptance from other implementations of Economy Mode, using “Things Gone Wrong” data from customer surveys on competitive vehicles. This information was used as lessons learned for the new design. The paper then discusses which changes to vehicle functionality could be implemented to improve fuel economy while maintaining acceptable vehicle performance, along with acceptable noise, vibration, and harshness objectives. The vehicle parameters studied in this paper include: 12 V loads, engine operating commands of torque and speed, EV operating limits, customer demand inputs, regenerative braking, cruise control operation, and climate control function. Measures of the fuel economy improvements were developed, as were tests to represent real-world driving conditions. The final package of potential fuel economy changes was tested on several Ford Hybrid vehicles with results demonstrating the net improvement to vehicle fuel economy. The Economy Mode functionality was deemed to be effective and it entered vehicle production during the 2016 model year on the Ford Fusion Hybrid, Ford C-MAX Hybrid, and Lincoln MKZ Hybrid vehicles under the name of EcoSelect.

Treharne, William D., Badger, Charles, Martin, Douglas, Mansour, Mohamed, Smith, Mark

Methods of Measuring Regenerative Braking Efficiency in a Test Cycle

2017-01-11683/28/2017

In Hybrid Electric Vehicles, Regenerative Braking is an essential function to convert vehicle kinetic energy into electrical energy, which charges the battery during a braking event to make a portion of captured kinetic energy available for use later. In comparison, conventional vehicles use friction brakes only and kinetic energy is dissipated as heat and not made available for later use. This paper introduces methods of evaluating Regenerative Braking Efficiency, including multiple efficiency definitions that lead to different attributes. The paper proposes regenerative brake event definitions during the FTP cycle and how they are used for control strategy and calibration updates. Also, we apply the efficiency metrics to four different vehicles from four automotive manufacturers for comparison. The paper presents a sample comparison result. Finally, we compare our efficiency metrics with the Environmental Protection Agency (U.S.EPA) official Brake Energy Recovery efficiency evaluation process.

Liu, Zheng, Ortmann, Walter J., Nefcy, Bernard, Colvin, Dan, Connolly, Francis

Regenerative Braking Control Development for P2 Parallel Hybrid Electric Vehicles

2017-01-11493/28/2017

Regenerative braking in hybrid electric vehicles is an essential feature to achieve the maximum fuel economy benefit of hybridization. During vehicle braking, the regenerative braking recuperates its kinetic energy, otherwise dissipated into heat due to friction brake, into electrical energy to charge the battery. The recuperation is realized by the driven wheels propelling, through the drivetrain, the electric motor as a generator to provide braking while generating electricity. “Rigid” connection between the driven wheels and the motor is critical to regenerative braking; otherwise the motor could drive the input of the transmission to a halt or even rotating in reverse direction, resulting in no hydraulic pressure for transmission controls due to the loss of transmission mechanical oil pump flow. Because of the potential open or slipping torque converter and the multiple step ratios in the drivetrain, and the gear shifting transients in P2 parallel hybrid electric vehicles, special challenges for regenerative braking emerge. The challenges are primarily the torque converter clutch capacity controls, shift scheduling and shift controls, and the coordination between regenerative braking and friction brake controls. This paper describes the control challenges encountered during the regenerative braking development work and presents the design considerations to address these challenges. Finally, the experimental results are presented to demonstrate the performance of the developed regenerative brake controls.

Zhao, Yanan, Kuang, Ming, Nefcy, Bernard, Colvin, Dan, Ford, Stuart, Liu, Zheng

Research on Vehicle Stability Control Strategy Based on Integrated-Electro-Hydraulic Brake System

2017-01-15653/28/2017

A vehicle dynamics stability control system based on integrated-electro-hydraulic brake (I-EHB) system with hierarchical control architecture and nonlinear control method is designed to improve the vehicle dynamics stability under extreme conditions in this paper. The I-EHB system is a novel brake-by-wire system, and is suitable to the development demands of intelligent vehicle technology and new energy vehicle technology. Four inlet valves and four outlet valves are added to the layout of a conventional four-channel hydraulic control unit. A permanent-magnet synchronous motor (PMSM) provides a stabilized high-pressure source in the master cylinder, and the four-channel hydraulic control unit ensures that the pressures in each wheel cylinder can be modulated separately at a high precision. Besides, the functions of Anti-lock Braking System, Traction Control System and Regenerative Braking System, Autonomous Emergency Braking can be integrated in this brake-by-wire system. A sliding mode variable structure vehicle dynamics stability controller based on hierarchical control framework is built in MATLAB/Simulink. The I-EHB actuator model and vehicle dynamic model with 15 degrees of freedom are built in simulation package AMESim through a parameterized and modularized method. Simulations are conducted via co-simulation platform using MATLAB/Simulink and AMESim under scenarios of the typical braking and NHTSA FMVSS 126 standard-Sine With Dwell. Simulation results show that hydraulic braking forces are coordinated well during typical braking process, verifying the feasibility and effectiveness of the models built and the control strategy proposed. Under Sine With Dwell maneuver, compared with the base systems equipped without/with the conventional ESP, the proposed stability control system has a good improvement on the vehicle dynamics.

He, Xiangkun, Yang, Kaiming, Ji, Xuewu, Liu, Yahui, Deng, Weiwen

Switching Frequency Optimization of Boost Converter for HEV Applications

2017-01-12363/28/2017

A hybrid electric vehicle (HEV) can utilize the electromechanical path to optimize the ICE operation and implement the regenerative brake, the fuel economy of a vehicle therefore gets improved significantly. Bi-directional Boost converter is usually used in an electric drive system to boost the high voltage (HV) battery voltage to a higher dc-link voltage. The main advantages for a system with Boost converter is that the traction inverter is de-coupled from battery voltage variations causing it to be over-sized. When designing this Boost converter, the switching frequency is a key parameter for the converter design. Higher switching frequency will lead to higher switching loss of power device (IGBT +diode), moreover, it has significant impact on inductor ripple current, HV battery ripple current and input capacitor current. Therefore, the switching frequency is one of the most important parameters for the design and selection of both active and passive components. This paper investigated the switching frequency optimization with consideration of ripple current of input battery, ripple current and thermal stress of input capacitor, inductor and whole converter efficiency. Both the analysis and test results are provided in this paper, which verified that Boost converter with optimized switching frequency could achieve better tradeoff between converter size, cost, and system efficiency.

Yang, Shuitao, Chen, Lihua, Alam, Mohammed Khorshed, Xu, Fan, Zhou, Yan

Model-Based Pressure Control for an Electro Hydraulic Brake System on RCP Test Environment

2016-01-19549/18/2016

In this paper a new pressure control method of a modified accumulator-type Electro-hydraulic Braking System (EHB) is proposed. The system is composed of a hydraulic motor pump, an accumulator, an integrated master cylinder, a pedal feel simulator, valves and pipelines. Two pressurizing modes are switched between by-motor and by-accumulator to adapt different pressure boost demands. A differentiator filtering raw sensor signal and calculating pedal speed is designed. By using the pedal feel simulator, the relationship between wheel pressures and brake force is decoupled. The relationships among pedal displacement, pedal force and wheel pressure are calibrated by experiments. A model-based PI controller with predictor is designed to lower the influences caused by delay. Moreover, a self-tuning regulator is introduced to deal with the parameter’s time-varying caused by temperature, brake pads wearing and delay variation. To verify the controller validity, a Rapid Control Prototype (RCP) test environment based on dSPACE is built. Self-designed HCU and pedal feel simulator are installed in test bench. The close loop test results of pressure tracking are plotted and analyzed by contrasting normal PI controller and proposed controller. The conclusion indicates that the proposed controller can reach a balance of rapidity and accuracy, meanwhile the operating time and energy consumption are also reduced.

Xiong, Zhe, Pei, Xiaofei, Guo, Xuexun, Zhang, Chengcai

Ankle Exoskeleton Aids or Enhances Mobility

TBMG-253949/1/2016

Clutches can be used to enhance the functionality of springs or actuators in robotic devices. A research team headed up by Steve Collins, an associate professor of mechanical engineering at Carnegie Mellon University, created a lightweight, low-power clutch used to control spring engagement in an ankle exoskeleton.

Solid-State Ultracapacitor

TBMG-249477/1/2016

NASA’s Marshall Space Flight Center has developed a solid-state ultracapacitor utilizing a novel nanocomposite dielectric material. The material’s design is based on the internal barrier layer capacitance (IBLC) concept, and it uses novel dielectric and metallic conductive ink formulations.

An Investigation Into New ABS Control Strategies

2016-01-16394/5/2016

An investigation into two new control strategies for the vehicle Anti-lock Braking System (ABS) are made for a possible replacement of current non-optimal slip control methods. This paper applies two techniques in order to maximize the braking force without any wheel locking. The first considers the power dissipated by the brake actuator. This power method does not use slip to construct its reference signal for control. A heuristic approach is taken with this algorithm where one searches for the maximum power dissipated. This can open up easier implementation of regenerative braking concurrently with ABS on an electro-hydraulic braking system. Parameter scheduling is explored in this algorithm. The second algorithm employs the use of perturbation based Extremum Seeking Control (ESC) to provide a reference slip and a Youla controller in a negative feedback loop.

Loyola, Jonathan, Assadian, Francis

Development of New Electronically Controlled Hydraulic Unit for Various Applications

2016-01-16604/5/2016

The use of hybrid, fuel cell electric, and pure electric vehicles is on the increase as part of measures to help reduce exhaust gas emissions and to help resolve energy issues. These vehicles use regenerative-friction brake coordination technology, which requires a braking system that can accurately control the hydraulic brakes in response to small changes in regenerative braking. At the same time, the spread of collision avoidance support technology is progressing at a rapid pace along with a growing awareness of vehicle safety. This technology requires braking systems that can apply a large braking force in a short time. Although brake systems that have both accurate hydraulic control and large braking force have been developed in the past, simplification is required to promote further adoption. This paper describes the following three items: (1) an examination of the brake system functions that realize the regenerative-friction brake coordination and collision avoidance support functions, (2) considerations and a proposal for a brake system that achieves the functions described in item (1) with a simple structure, and (3) development of core technology for controlling the wheel cylinder pressure in a brake system equipped with a hydraulic regulator.

Okano, Takahiro, Sakai, Akira, Kamiya, Yusuke, Masuda, Yoshio, Yamaguchi, Tomoyuki

Research on Electric Vehicle Braking Force Distribution for Maximizing Energy Regeneration

2016-01-16764/5/2016

The driving range of the electric vehicle (EV) greatly restricts the development of EVs. The vehicles waste plenty of energy on account of automobiles frequently braking under the city cycle. The regenerative braking system can convert the braking kinetic energy into the electrical energy and then returns to the battery, so the energy regeneration could prolong theregenerative braking system. According to the characteristics of robustness in regenerative braking, both regenerative braking and friction braking based on fuzzy logic are assigned after the front-rear axle’s braking force is distributed to meet the requirement of braking security and high-efficient braking energy regeneration. Among the model, the vehicle model and the mechanical braking system is built by the CRUISE software. The paper applies the MATLAB/SIMULINK to establish a regenerative braking model, and then selects the UEDC city cycle for model co-simulation analysis. Finally, the feasibility of the proposed control strategy is demonstrated by the simulation results. It shows that the driving range of the EV could be effectively increased on the premise of satisfying the demand of the driver braking force.

Liu, Wenchao, Chen, Guoying, Zong, Changfu, Li, Chunshan

Development of an Electronically Controlled Brake System for Fuel-efficient Vehicles

2016-01-16644/5/2016

To solve various environmental problems, fuel-efficient vehicles that reduce CO2 emissions as well as exhaust gas emissions have been developed. In such vehicles, a regenerative brake is used to further reduce fuel consumption. Because the market size for such vehicles is expanding, a brake system is required that can be used in a wide range of vehicles extending from internal combustion engine vehicles (ICEVs) to electric vehicles (EVs). In addition, issues such as deceleration fluctuation and brake pedal fluctuation arise because the regenerative brake force is dependent on the vehicle speed. This paper presents a brake system configuration and its element technologies that can replace existing brake systems in different vehicles ranging from ICEVs to EVs. The proposed system can realize a regenerative cooperative brake not only by replacing the brake booster unit but also without replacing the modulator. The advantages of this system are the maximization of regenerative efficiency, assurance of system reliability, and better brake feel.

Masuda, Yoshio, Yamasoe, Yosuke, Kuki, Yosuke, Okano, Takahiro, Uchida, Kiyoyuki

Fault-Tolerant Control of Brake-by-Wire Systems Based on Control Allocation

2016-01-01324/5/2016

Brake-by-wire (BBW) system has drawn a great attention in recent years as driven by rapidly increasing demands on both active brake controls for intelligent vehicles and regenerative braking controls for electric vehicles. However, unlike conversional brake systems, the reliability of the brake-by-wire systems remains to be challenging due to its lack of physical connection in case of system failure. There are various causes for the failure of a BBW system, such as failure of brake controller, loss of sensor signals, failure of communication or even power supply, to name a few. This paper presents a fault-tolerant control under novel control architecture. The proposed control architecture includes a driver command interpreter module, a command integration module, a control allocation module, a fault diagnosis module and state observers. The fault-tolerant control is designed based on a quadratic optimal control method with consideration of actuator constraints. Then a simulation platform has been established and extensive simulations have been conducted. The results have demonstrated the validity and effectiveness of the proposed control architecture and method.

Liu, Haizhen, Deng, Weiwen, He, Rui, Wu, Jian, Zhu, Bing

An Integrated-Electro-Hydraulic Brake System for Active Safety

2016-01-16404/5/2016

An integrated-electro-hydraulic brake system (I-EHB) is presented to fulfill the requirements of active safety. Because I-EHB can control the brake pressure accurately and fast. Furthermore I-EHB is a decoupled system, so it could make the maximum regenerative braking while offers the same brake pedal feeling and also good for ADAS and unmanned driving application. Based on the analysis of current electrohydraulic brake systems, regulation requirements and the requirements for brake system, the operating mode requirements of I-EHB are formed. Furthermore, system topological structure and a conceptual design are proposed. After the selection of key components, the parameter design is accomplished by modeling the system. According to the above-mentioned design method, an I-EHB prototype and test rig is made. Through the test rig, characteristics of the system are tested. Results show that this I-EHB system responded rapidly. Upon the experimental results, increasing pressure response time (T90) of I-EHB is 53% shorter than that of conventional brake system and reducing pressure response time (T10) of I-EHB is 70% shorter than that of conventional brake system. The tracking performance of I-EHB is accurate enough. The RMS (root mean square) of tracking error are 1.99 bar and 1.43 bar according to different aim signals. The experimental results proved that I-EHB fulfills the requirements of active safety.

Yu, Zhuoping, Xu, Songyun, Xiong, Lu, Han, Wei

High Efficiency Electromagnetic Torque Converter for Hybrid Electric Vehicles

2016-01-11624/5/2016

A new concept of an electromagnetic torque converter for hybrid electric vehicles is proposed. The electromagnetic torque converter, which is an electric system comprised of a set of double rotors and a stator, works as a high-efficiency transmission in the driving conditions of low gear ratio including a vehicle moving-off and as a starting device for an internal combustion engine. Moreover, it can be used for an electric vehicle driving as well as for a regenerative braking. In this concept, a high-efficiency drivetrain system for hybrid electric vehicles is constructed by replacing a fluid-type torque converter with the electromagnetic torque converter in the automatic transmission of a conventional vehicle. In this paper, we present the newly developed electromagnetic torque converter with a compact structure that enables mounting on a vehicle, and we evaluate its transmission efficiency by experiment. Furthermore, using the experimental results and finite element analysis of the electric machine, we clarify the system loss of the electromagnetic torque converter.

Watanabe, Takao, Tsuchiya, Eiji, Ebina, Masaki, Osada, Yasumitsu, Toyama, Tomoyuki, Murakami, Akira

Design and Optimisation of the Propulsion Control Strategy for a Pneumatic Hybrid City Bus

2016-01-11754/5/2016

A control strategy has been designed for a city bus equipped with a pneumatic hybrid propulsion system. The control system design is based on the precise management of energy flows during both energy storage and regeneration. Energy recovered from the braking process is stored in the form of compressed air that is redeployed for engine start and to supplement the engine air supply during vehicle acceleration. Operation modes are changed dynamically and the energy distribution is controlled to realize three principal functions: Stop-Start, Boost and Regenerative Braking. A forward facing simulation model facilitates an analysis of the vehicle dynamic performance, engine transient response, fuel economy and energy usage. To identify respectively (1) the maximum overall fuel economy, (2) the maximum amount of air and energy recovered during the braking and (3) the minimum loss of available energy during acceleration, a number of variables in the control strategy are selected in an optimisation process. Three optimisation algorithms are compared in different aspects of the control strategy: (1) using the Pattern Search to optimise the initial air tank pressure for every stop-start event in order to maximize the pressure increment in the air tanks; (2) conducting the Genetic Algorithm optimisation to find out the best gear change strategy during braking in order to maximize the energy recovery to the air tanks; and (3) implementing the multiobjective optimisation to simultaneously minimize the fuel consumption and the loss of available energy in the air flow during acceleration. The rationale for the choice of optimisation methods is explained and recommendations made for the development of energy management strategies in which a variety of different vehicle functions contribute to an overall fuel economy benefit.

Bao, Ran, Stobart, Richard

CO ₂ Emissions Reduction via 48V Active Engine-Off Coasting

2016-01-11524/5/2016

Global CO2 reduction by 2021, according to some projections, will be comprised of multiple vehicle technologies with 7% represented by hybrid and electric vehicles (2% in 2014) [1]. Other low cost hybrid methods are necessary in order to achieve widespread CO2 reduction. One such method is engine-off coasting and regenerative braking (or recuperation) using a conventional internal combustion engine (ICE). This paper will show that a 48V power system, compared to a 12V system with energy storage module for vehicle segments B, D and E during WLTP and NEDC, is much more efficient at reducing CO2. Passive engine-off coasting using 12V energy storage shows a CO2 benefit for practical real world driving, but, during NEDC, multiple sources of friction slow the vehicle down to the extent that the maximum benefit is not achieved. By adding active engine-off coasting at the 48V level the CO2 emissions for NEDC are improved by decreasing the rate of deceleration with a 48V electric motor for propulsion. Also important, which will be explored in more detail, are the necessary power dimensions for the major components for different electrical load profiles.

Brown, Alan, Nalbach, Marc, Kahnt, Sebastian, Korner, André

Delphi says 48-volt mild-hybrid systems could offer 15% CO2 reductions

15MEIP12_1312/1/2015

Delphi believes that 48-volt mild hybrids could offer significant CO2 reductions and driver benefits for cars in the future. Speaking at the IAA 2015 (Frankfurt Motor Show), Christian Schäfer, Global Director of Advanced Electrical and Electronic Architectures at Delphi, told Automotive Engineering that there are several drivers for the technology that were not present 15 years ago. “The main driver is the carbon dioxide threshold of 95 g/km fleet average in 2021 across the European Union,” he said. “The idea is that we have a mild hybrid, so we don't need high-voltage on all cars because it is too expensive to implement. We would have 48-volts, especially in the low segment, up to C-segment cars. Then we could have a belt-driven starter/alternator and can use it as an e-boost if you don't have a rear drive unit, so the alternator is an electrical machine to boost the combustion engine.”

Kendall, John

Isolated Bidirectional DC Converters for Distributed Battery Energy Applications

TBMG-23242

11/1/2015

Power systems are the core heartbeat of any advanced vehicle. Reliability and flexibility of these systems are of the highest priority. This innovation is a highly efficient and modular isolated bidirectional DC converter for battery energy applications that has been translated into high-priority NASA power system applications, demonstrating transferability, robustness, and scalability.

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