Series Hybrid Electric Vehicle Powertrain Research Articles

Efficiency enhancement strategy implementation in hybrid electric vehicles using sliding mode control

Introduction. Hybrid electric vehicles are offering the most economically viable choices in today's automotive industry, providing best solutions for a very high fuel economy and low rate of emissions. The rapid progress and development of this industry has prompted progress of human beings from primitive level to a very high industrial society where mobility used to be a fundamental need. However, the use of large number of automobiles is causing serious damage to our environment and human life. At present most of the vehicles are relying on burning of hydrocarbons in order to achieve power of propulsion to drive wheels. Therefore, there is a need to employ clean and efficient vehicles like hybrid electric vehicles. Unfortunately, earlier control strategies of series hybrid electric vehicle fail to include load disturbances during the vehicle operation and some of the variations of the nonlinear parameters (e.g. stator’s leakage inductance, resistance of winding etc.). The novelty of the proposed work is based on designing and implementing two robust sliding mode controllers (SMCs) on series hybrid electric vehicle to improve efficiency in terms of both speed and torque respectively. The basic idea is to let the engine operate only when necessary keeping in view the state of charge of battery. Purpose. In proposed scheme, both performance of engine and generator is being controlled, one sliding mode controllers is controlling engine speed and the other one is controlling generator torque, and results are then compared using 1-SMC and 2-SMC’s. Method. The series hybrid electric vehicle powertrain considered in this work consists of a battery bank and an engine-generator set which is referred to as the auxiliary power unit, traction motor, and power electronic circuits to drive the generator and traction motor. The general strategy is based on the operation of the engine in its optimal efficiency region by considering the battery state of charge. Results .Mathematical models of engine and generator were taken into consideration in order to design sliding mode controllers both for engine speed and generator torque control. Vehicle was being tested on standard cycle. Results proved that, instead of using only one controller for engine speed, much better results are achieved by simultaneously using two sliding mode controllers, one controlling engine speed and other controlling generator torque.

Spark-ignition engine speed profile optimization for maximizing the net indicated efficiency and quantitative analysis of the optimal speed profile

To meet the tightened fuel economy or greenhouse gas emission standards in the transportation sector, many studies focus on the vehicle powertrain. Because hydrocarbon-based fuel is mainly used, an increase in the internal combustion engine efficiency is essential to meet the future regulations. This study discusses the improvement of spark-ignition engine efficiency through intracycle speed profile modulation. An intracycle speed profile modulating strategy could be adopted in the series hybrid electric vehicle powertrain architecture because the internal combustion engine shaft is not directly connected to the vehicle driveshaft. Under the wide-open throttle condition, the net indicated efficiency with the optimized profile increases by 1.3 %p compared to the peak efficiency achievable in conventional operation over 1,000–5,000 rpm and increases by 5 %p compared to the conventional operation with the same cycle average speed. This leads to the conclusion that the engine speed modulation in a spark-ignition engine would be largely effective near knock-limited operating conditions of a conventional engine. The efficiency gain is achieved by improving various performance parameters, conventionally in a trade-off relation. Combustion phasing is improved to the level of knock-free operating condition. In the optimal speed profile, the intake and compression process speed profiles are modulated to suppress knocking. The expansion process speed profile is mainly influenced by heat loss, and the gas exchange process speed profile is related to the pumping work. These propositions lay the foundational knowledge for further investigation into the topic in the future, including the hardware implementation.

Dynamical analysis of series hybrid electric vehicle powertrain with torsional vibration: Antimonotonicity and coexisting attractors

In this paper, nonlinear dynamics of the torsional vibrations of the Series Hybrid Electric Vehicle (SHEV) powertrain are explored. The mathematical equation of the SHEV is obtained by considering both internal and external excitations. We examine the effects of rotational speed, load fluctuation, and road fluctuation on the dynamics of the proposed model. Preliminary analysis based on Hamiltonian energy shows that there is sufficient energy to maintain continuous oscillation behaviors. Our study shows that the interaction between internal and external perturbations originates an important set of phenomena, including chaos, when varying system parameters. More interestingly, the exciting phenomenon of multistability is investigated for the first time on the proposed SHEV model. Furthermore, when increasing excitation force amplitude in some specific regions, an interesting scenario of antimonotonicity is found. • Nonlinear dynamics of the torsional vibrations of the Series Hybrid Electric Vehicle (SHEV) powertrain are explored. • Both internal and external excitations are considered in the mathematical model. • The Hamiltonian energy shows that there is sufficient energy to maintain continuous oscillation behaviors. • The exciting phenomenon of multi-stability is investigated on the proposed SHEV model. • Anti-monotonicity and period-doubling bifurcations are also reported when adjusting the excitation force amplitude of the system.

Design and optimization of a modified series hybrid electric vehicle powertrain

Hybrid electric vehicles are emerging technologies that are considered as eco-friendly alternative solutions to internal combustion engine–driven vehicles. This paper proposes a modified hybrid electric vehicle powertrain system that addresses the shortcomings of a series hybrid electric vehicle powertrain. The proposed configuration replaces the conventional generator of a series hybrid electric vehicle with an integrated starter generator that supports the traction motor of the vehicle during acceleration and peak torque requirements and maintains the state of charge of the batteries to provide an extended electric range of the vehicle. The work done in this paper can be categorized into two stages. The first stage is the methodical development of the powertrain in terms of initial parameter matching and sizing of the vehicle components by considering the fundamentals of longitudinal vehicle dynamics. The second stage describes the optimization of the proposed configuration to meet the design objective of maximizing fuel economy subjected to a set of vehicle performance constraints. The performance of the proposed powertrain was evaluated and compared with a series hybrid electric vehicle powertrain for an on-road Indian driving cycle using AVL CRUISE, which is a commercially available software for the study and analysis of road vehicle powertrains. Result analysis during initial parameterization showed a reduction in gross vehicle weight of the proposed configuration by 244 kg (1.5%) and an improvement in the average operating efficiency of the traction motor by around 11%, when compared to a series hybrid electric vehicle. Furthermore, the optimization results for the proposed configuration established an improvement in the fuel economy by 21% while meeting vehicle performance requirements.

Bandwidth-Based Control Strategy for a Series HEV With Light Energy Storage System

The twin goals of maximizing fuel economy (FE) and improving consumer acceptance by reducing the cost of the energy storage system (ESS) in a series hybrid electric vehicle (SHEV) powertrain is addressed here by using energy storage as a means for filtering drive-cycle power demands on the engine, rather than an energy source for supplying an all-electric drive mode. The concept is intended to minimize, if not eliminate, the battery in the SHEV without resorting to full-range proportional control of the engine and generator. An initial optimization study reported for a mid-size SHEV showed that a 4.5-kWh lithium-ion battery pack was still required. In this paper, a sports-car-class SHEV was studied, where the challenge is to reduce the size of the ESS even more because the available space allocation is only one fourth that of the mid-size vehicle. In this paper, a controller is developed, which allows a hybridized SHEV to be realized with a light ESS. The controller includes a duty-cycling feature that manages the engine performance in multiple efficient regions and a bandwidth-limited (BWL) proportional controller feature that limits low-bandwidth battery current. The performance of the controller has been validated for a SHEV powertrain model with an 80- $\text{V}_{\mathrm{dc}}$ 1.125-kWh battery, plus an 80- $\text{V}_{\mathrm{dc}}$ 46.4-F ultracapacitor module using a customized Autonomie vehicle model. The results show that the combined FE of the new design is increased by 13%, compared with the corresponding FE in the equivalent conventional vehicle. Additional FE improvement is possible by reducing the engine size further to reflect the average power demand imposed by real drive cycles.

Active-charging based powertrain control in series hybrid electric vehicles for efficiency improvement and battery lifetime extension

This paper presents a powertrain control strategy for a series hybrid electric vehicle (SHEV) based on the integrated design of an active charging scenario and fixed-boundary-layer sliding mode controllers (FBLSMCs). An optimized charging curve for the battery is predetermined rather than subject to engine output and vehicle power demand, which is a total inverse of normal SHEV powertrain control process. This is aimed to remove surge and high-frequency charge current, keep the battery staying in a high state-of-charge (SOC) region and avoid persistently-high charge power, which are positive factors to battery lifetime extension. Then two robust chattering-free FBLSMCs are designed to locate the engine operation in the optimal efficiency area. One is in charge of engine speed control, and the other is for engine/generator torque control. Consequently, not only fuel economy is improved but also battery life expectancy could be extended. Finally, simulation and experimental results confirm the validity and application feasibility of the proposed strategy.

Integrated Design of Powertrain Controllers in Series Hybrid Electric Vehicles for Efficiency Enhancement and Battery Lifetime Extension

In this study, a control strategy for the series hybrid electric vehicle (SHEV) powertrain, based on the design of fixed-boundary-layer sliding mode controllers (FBLSMCs) and a battery charge scenario, is presented to enhance engine efficiency as well as extend battery cycle life. An appropriate battery charge scenario is designed to remove surge charge current, keep the battery staying in a high state-of-charge (SOC) region and avoid persistently-high charge power, which are positive factors to the battery lifetime extension. To locate the engine operation in the optimal efficiency area, two robust FBLSMCs against uncertain disturbances are configured in the powertrain control system, responsible for engine speed control and engine torque control, respectively. Simulation results are obtained for comparison between the proposed and conventional powertrain control schemes by using the Advanced Vehicle Simulator (ADVISOR). Through these simulations, the effectiveness and superiority of the FBLSMC-based SHEV power train control strategy are validated.