Hybrid Powertrain Configurations Research Articles

Configurations and Control Strategies of Hybrid Powertrain Systems

The configuration and control strategy of hybrid powertrain systems are significant for the development of hybrid electric vehicles (HEV) because they significantly affect their comprehensive performance. In this paper, the types, features, and applications of the mainstream hybrid powertrain configurations on the market in recent years are summarized and the effects of different configurations on the comprehensive performance of HEVs are compared. Moreover, the technical routes for each hybrid configuration are highlighted, as configuration optimization methods have become a technical difficulty. In addition, the technological advances in the steady-state energy management strategy and dynamic coordinated control strategy for hybrid powertrain systems are studied. The optimization of the steady-state energy management strategy mainly involves assigning the working point and working range of each power source reasonably. However, with the increase in the complexity of optimization algorithms, real-time control of HEVs still needs to be improved. The optimization of the dynamic coordinated control strategy mainly focuses on the stability and smoothness of the dynamic process involving switching and shifting the working mode. The optimization of the dynamic control process for the system remains to be further improved. It is pointed out that the configurations and strategies should be optimized jointly to obtain a comprehensive improvement in the system performance. This paper provides an informative basis and technical support for the design and optimization of a hybrid powertrain system.

Unified Mode-Based Description of Arbitrary Hybrid and Electric Powertrain Topologies

To find the optimal powertrain design for hybrid and electric vehicles in terms of energy efficiency and performance, automatised optimisation tools are often applied. These require a mathematical model of the powertrain configuration, which is usually done on the level of components, such as planetary gear sets (PGSs), clutches and brakes. This, however, leads to a huge design space with lots of functional redundancy. In fact, each functional powertrain mode can be realised by various component combinations. In this paper, a novel mode-based modelling technique for arbitrary hybrid and electric powertrain configurations with up to one internal combustion engine (ICE) and two electrical machines (EMs) is proposed. This allows to easily analyse multi-mode hybrid and electric powertrains on a purely functional basis. Additionally, it reduces mode describing parameters to the minimum amount required. First, an existing graphical representation of hybrid powertrains with one ICE and one EM is analysed and formalised. Based on that, virtual powertrain nodes are defined. These are used to compose all hybrid and electric powertrain modes. Five of them are presented in detail and plotted within a three-dimensional ratio plot. Using a first case study, it is shown how the ratio plot can be used to analyse arbitrary multi-mode powertrains. Within a second case study, it is demonstrated how optimal parameter sets for single-mode powertrain configurations can be identified using the derived model.

A Software-in-the-Loop Simulation of Vehicle Control Unit Algorithms for a Driverless Railway Vehicle

The realization of the first prototype of a vehicle requires several tests of the algorithms implemented on the electronic control unit (ECU). This represents an important step for conventional vehicles, which becomes fundamental when dealing with unmanned vehicles. Since there is no human supervision, most critical tasks are handled by the control unit, which results in higher complexity for the control algorithms. In this work, a software-in-the-loop (SiL) test bench is used to validate the control algorithms of a vehicle control unit (VCU) for a driverless railway vehicle (DLRV). The VCU manages the control of the traction motors, pneumatic braking systems, and range extender, as well as control of the hybrid powertrain configuration to guarantee a high level of availability via the use of redundant systems. The SiL test bench has been developed in a Simulink real-time environment, where the vehicle model is simulated along with its fundamental subsystems. The model communicates with the VCU through a CAN bus protocol in the same way that it will operate with a real vehicle. The proposed method can be used to simulate many mission profiles for the DLRV, which may last several hours each. Moreover, this kind of test bench ensures a high time resolution, which allows one to find solutions for problems which occur with a time scale that is much smaller than the simulation time scale.

Analysis of experimental results with an active pre-chamber ultra-lean burn SI engine

To ensure that private cars can continue to be used in the future, they must become significantly more efficient and at the same time emit considerably less pollutants. In addition to pure electric drives, further optimized gasoline engines in hybrid powertrain configurations still offer major potentials in this respect. A major step toward increasing efficiency can be achieved by extremely lean burn combustion. If, in addition to low fuel consumption, this operation should also simultaneously reduce NOx raw emissions, lean-burn operation with relative air/fuel ratios of λ≥ 2 must be enabled in wide ranges of the engine operation map. Within the scope of this publication, results of experimental investigations with a lean burn pre-chamber ignition system applied to a small gasoline engine with 75 mm bore and 90.5 mm stroke are presented. In this context, the effects of the pre-chamber design on emissions and fuel consumption are examined. By comparing different pre-chamber enrichments with natural gas and conventional RON98 gasoline, it can be shown that with the direct liquid injection of gasoline into the pre-chamber similar good thermodynamic results as with natural gas can be achieved with the advantage of easier integration of a single fuel system. Due to its significantly improved lean burn capability with relative air/fuel rations of up to λ = 3, combined with low specific indicated NOx raw emissions of less than 0.1 g/kWh, the presented lean-burn combustion system offers excellent conditions for further efficiency improvements of electrified powertrains. WLTP cycle simulations based on measured engine maps for the developed combustion process resulted in a fuel consumption reduction of up to 10%. At the same time, NOx raw emissions below the Euro 6d limit of 60 mg/km can be achieved.

Comparison of four-wheel-drive hybrid powertrain configurations

The stringent fuel economy and emission standards enforce sport sedan and sport utility vehicle employ four-wheel-drive (4WD) hybrid powertrain to achieve better fuel economy and acceleration performance simultaneously. This paper reviews and conducts a comparative study of four 4WD hybrid configuration types: series, series-parallel, power-split and compound-split configurations. To make a fair comparison of fuel economy and acceleration performance, an integrated hierarchical optimization framework is presented, which solves the parameters sizing and energy management problem simultaneously. The pareto-front optimal design of each configuration is derived. According to detailed energy analysis, a novel multi-mode configuration is proposed by adding clutches between planetary gear nodes of compound-split configuration. By combining multiple modes, the proposed configuration achieves better fuel-saving and acceleration performance than initial configuration. Moreover, this comparative study takes into consideration the cost, control complexity and off-road performance. The results show that the power-split one adopting three motor/generators (MGs) shows superior fuel economy and acceleration performance than others, while the proposed multi-mode configuration maintains a competing performance with less MGs. In addition, the series-parallel configuration has great comprehensive potential.

Comparing Fuel Consumption and Emission Levels of Hybrid Powertrain Configurations and a Conventional Powertrain in Varied Drive Cycles and Degree of Hybridization

Hybrid electric powertrains in automotive applications aim to improve emissions and fuel economy with respect to conventional internal combustion engine vehicles. Variety of design scenarios need to be addressed in designing a hybrid electric vehicle to achieve desired design objectives such as fuel consumption and exhaust gas emissions. The work in this paper presents an analysis of the design objectives for an automobile powertrain with respect to different design scenarios, i. e. target drive cycle and degree of hybridization. Toward these ends, four powertrain configuration models (i. e. internal combustion engine, series, parallel and complex hybrid powertrain configurations) of a small vehicle (motorized three wheeler) are developed using Model Advisor software and simulated with varied drive cycles and degrees of hybridization. Firstly, the impact of vehicle power control strategy and operational characteristics of the different powertrain configurations are investigated with respect to exhaust gas emissions and fuel consumption. Secondly, the drive cycles are scaled according to kinetic intensity and the relationship between fuel consumption and drive cycles is assessed. Thirdly, three fuel consumption models are developed so that fuel consumption values for a real-world drive cycle may be predicted in regard to each powertrain configuration. The results show that when compared with a conventional powertrain fuel consumption is lower in hybrid vehicles. This work led to the surprisingly result showing higher CO emission levels with hybrid vehicles. Furthermore, fuel consumption of all four powertrains showed a strong correlation with kinetic intensity values of selected drive cycles. It was found that with varied drive cycles the average fuel advantage for each was: series 23 %, parallel 21 %, and complex hybrids 33 %, compared to an IC engine powertrain. The study reveals that performance of hybrid configurations vary significantly with drive cycle and degree of hybridization. The paper also suggests future areas of study.

Synthesis and analysis method for powertrain configuration of single motor hybrid electric vehicle

Existing hybrid powertrain configuration analysis methods mainly focus on power-split hybrid electric vehicles with multiple planetary gears. However, these methods cannot be applied directly to single motor hybrid electric vehicles with automatic transmission. Hence, an analysis method to optimize the powertrain configuration of single motor hybrid vehicles is proposed to overcome this limitation. In the proposed method, two different adjacency matrices are established to generate all powertrain configurations, and a corresponding matrix analysis method is proposed to analyze their working modes. Subsequently, a set of working modes are established to improve the efficiency of obtaining mathematical models of powertrain configurations. Finally, an energy management strategy based on dynamic programming is developed to analyze the performance of the generated configurations. The proposed method is utilized to analyze the single motor hybrid vehicle with a planetary gear and a continuously variable transmission, and a new configuration is obtained after the analysis for validation. It is observed that the fuel efficiency increases by 12.2% and the 0–100 km/h acceleration time is reduced by 8.7%, in comparison to the existing powertrain configuration.

Optimization Design and Analysis for a Single Motor Hybrid Powertrain Configuration with Dual Planetary Gears

To further improve the comprehensive operating performance of the single motor hybrid electric vehicle, a single motor hybrid powertrain configuration with dual planetary gears (SMHPC-2PG) design is proposed in this paper. By adopting a topology design method that characterizes the constraint relationship between power resource components and planetary gear (PG) nodes, all feasible configuration candidates based on the basic configuration scheme are systematically explored, and dynamic models of configuration candidates are automatically generated. The optimal fuel economy and dynamic performance for configuration candidates are simulated by applying the global optimal control strategy based on dynamic programming (DP). Results of this study demonstrate that SMHPC-2PG with excellent operating performance can be screened out by this method.

Optimization of a Brayton external combustion gas-turbine system for extended range electric vehicles

Significant research efforts are considered in the automotive industry on the use of low-carbon fuels in order to reduce the emissions and improve the fuel economy of vehicles. Some of these fuels, such as the solid fuels for example, are only compatible with external combustion machines. These machines are only suitable for electrified powertrains relying on electric propulsion, in particular the extended-range-electric-vehicles with series hybrid powertrain configuration where fuel consumption strongly relies on the energy converter efficiency and power density. This paper investigates the fuel savings potential of these vehicles using a Brayton external combustion gas-turbine system as energy converter substitute to the conventional internal combustion engine. An exergo-technological explicit analysis is conducted to identify the best system configuration. A downstream-intercooled reheat external combustion gas-turbine (DIRe-ECGT) system is prioritized, offering the highest efficiency among the investigated systems. An extended-range-electric-vehicle model is developed and energy consumption simulations are performed on the worldwide-harmonized light vehicles test cycle. Fuel consumption simulation results are compared to a reference extended-range-electric-vehicle using an engine auxiliary-power-unit. Results show 6%–11.5% of fuel savings with the prioritized DIRe-ECGT auxiliary-power-unit as compared to the reference model, depending on the battery capacity and the trip distance.

Multisource Coordination Energy Management Strategy Based on SOC Consensus for a PEMFC–Battery–Supercapacitor Hybrid Tramway

For the sake of coordinating multiple energy sources appropriately from power demand and guarantee stage of charge (SOC) consensus of the energy storage systems in different operation conditions, a multisource coordination energy management strategy based on self-convergence droop control is proposed for a large-scale and high-power hybrid tramway. A hybrid powertrain configuration that includes multiple proton exchange membrane fuel cell systems, batteries, and supercapacitors is designed for a 100% low-floor light rail vehicle (LF-LRV) tramway. According to the hybrid system model of LF-LRV tramway developed with commercial equipment, this proposed multisource coordination energy management strategy is assessed with a real driving cycle of tramway. The results obtained from RT-LAB platform testify that the proposed strategy is capable of coordinating multiple energy sources, guaranteeing the SOC consensus and improving the efficiency of overall tramway.

THE EFFECT OF DIFFERENT GEAR RATIO SELECTION ALGORITHMS ON THE EFFICIENCY OF CONVENTIONAL AND PARALLEL HYBRID DRIVETRAINS

Road vehicles using electric power sources have become increasingly popular in the last decade. Meanwhile, battery technology is still not mature enough to meet expected vehicle range; thus the transition from ICE vehicle to fully electric vehicle is not imminent. Therefore the concept of hybrid drivetrain technology was introduced. The hybrid powertrain configuration includes at least two different energy converters together with an energy storage medium. In this article, different gear shifting algorithms were introduced to increase ICE efficiency in conventional vehicle. Besides, a parallel hybrid configuration was also introduced to enhance drivetrain efficiency. The Equivalent Energy Minimization Method (ECMS) and Dynamic Programming (DP) algorithms were selected as online and offline implementable optimal control methods for hybrid power sharing management. Totally six different case studies were planned to compare the efficiency of each configuration. Finally, the effect of the gear ratio selection and power split algorithms were compared on conventional and parallel hybrid drivetrains regarding overall efficiency.

Kinetic energy storage using a dual-braking system for an unmanned parallel hybrid electric vehicle

In this paper a novel regenerative dual-braking strategy is proposed for utility and goods delivery unmanned vehicles on public roads, which improves their ability to recover regenerative energy and consequently improves the fuel use of parallel hybrid powertrain configurations for land unmanned vehicles where the priority is not comfort but extension of their range. Furthermore, the analysis takes into account the power-handling ability of the electric motor and the power converters. In previous research, a plethora of regenerative braking strategies have been reported; in this paper, the key contribution is that the vehicle electric regeneration is related to a fixed braking distance in relation to the energy storage capabilities specifically for unmanned utility-type land vehicles where passenger comfort is not a concern but pedestrian safety is of critical importance. Furthermore, the power converter capabilities of the vehicle facilitate the process of extending the braking time by introducing a variable-deceleration profile. The proposed approach has therefore resulted in a regenerative algorithm which improves the energy storage capability of the vehicle without considering the comfort since this analysis is applicable to unmanned vehicles. The algorithm considers the distance as the key parameter, which is associated with safety; therefore, it allows the braking time period to be extended, thus favouring the electric motor generation process while maintaining safety. This method allows the vehicle to brake for longer periods rather than for short bursts, hence resulting in more effective regeneration with reduced use of the dual system (i.e. the caliper–stepper motor brake system). The regeneration method and analysis are addressed in this paper. The simulation results show that the proposed regenerative braking strategy improved the ability of the hybrid powertrain configuration to recover energy significantly. The paper is also supported by experimental data that verify the theoretical development and the simulation results. The two strategies developed and implemented utilize a constant braking torque and a constant braking power. Both methods were limited to a fixed safety-based distance. Overall, the results demonstrate that the constant-braking-torque method results in better energy-based savings.

Drivability-Related Discrete-Time Model Predictive Control of Mode Transition in Pre-Transmission Parallel Hybrid Powertrains

During the mode transition from the pure electric propulsion mode to the hybrid propulsion mode, clutch-based pre-transmission parallel hybrid electric vehicles are subject to drivability issues. These issues originate from the fact that in the clutch-based pre-transmission parallel hybrid powertrain (CPPHP) configuration, the clutch connects the engine and the motor. Without a carefully designed mode transition control that coordinates the engine torque, clutch torque and motor torque, torque sluggishness and surges occur during the mode transition, and residual torque oscillation occurs after the mode transition. In this paper, a discrete-time model predictive control (DMPC)-based controller is proposed to address these drivability-related issues. Modeling improvements and novel drivability-related indices and constraints are all taken into consideration in the design of the discrete-time model predictive controller. Furthermore, by using discrete-time Laguerre functions and introducing the equilibrium state and the ranking of constraints, an explicit solution of the discrete-time model predictive controller is obtained. The calculation results demonstrate that the proposed controller can ensure a smooth and rapidly decaying torque difference during the mode transition, alleviating the residual torque oscillation after the mode transition and guaranteeing that the mode transition is completed within an acceptable duration.

A state machine strategy based on droop control for an energy management system of PEMFC-battery-supercapacitor hybrid tramway

In this paper, a hybrid powertrain configuration which consists of multiple proton exchange membrane fuel cell (PEMFC) systems, batteries and supercapacitors (SCs) is developed for LF-LRV tramway. A state machine strategy based on droop control is proposed to coordinate multiple power sources, avoid the transients and rapid changes of power demand, and achieve high efficiency without degrading the mechanism performance for an energy management system of hybrid tramway. A hybrid system model of tramway is established with commercially available devices, and then the proposed energy management strategy is evaluated with a real driving cycle of tramway from Turkey. The results demonstrate that the proposed strategy is able to coordinate multiple power sources based on their natural characteristics, satisfy rapid changes of the power demand and achieve high efficiency of overall tramway. Hence, the proposed energy management strategy for high-power hybrid tramway will improve the hydrogen consumptions of overall hybrid system and the efficiencies of each power source.

Robust coordinated control for hybrid electric bus with single‐shaft parallel hybrid powertrain

The efficient coupling driving control is a key technique that affects both the fuel economy and drivability of the hybrid electric bus (HEB). However, the uncertainties resulting from the complex driving condition and the powertrain would affect the control performance. To solve this problem, this study proposes a novel control approach, which is elaborately integrated with multi-controllers under the consideration of properties of the city-bus-route and the hybrid powertrain configuration. First, a torque split strategy with the automated mechanical transmission (AMT) gear-shifting strategy is employed to adapt the driving intention quantified by fuzzy logic. Then the coordinated control mechanism is constructed through utilising the electric machine (EM) to compensate the response deviation of engine torque, meanwhile a robust controller is designed to withstand parameter perturbation and external disturbance existing in EM. Simulation results show that the operating points of the engine and EM are adjusted into the high-efficiency areas with the assistance of AMT gear-shifting, and the EM torque tracking performance especially when parameter perturbation and external disturbance appear. Moreover, the strategy adaptively distributed the driving torque in the predefined working modes for different driver's intentions. Thus, the efficient coupling driving of HEB might be implemented by the proposed method.

Development of energy management system based on a power sharing strategy for a fuel cell-battery-supercapacitor hybrid tramway

A hybrid powertrain configuration based on a proton exchange membrane (PEMFC), a battery and a supercapacitor (SC) is designed without grid connection for the LF-LRV tramway. In order to avoid rapid changes of power demand and achieve high efficiency without degrading the mechanism performance, a power sharing strategy based on a combination of fuzzy logic control (FLC) and Haar wavelet transform (Haar-WT) is proposed for an energy management system of the hybrid tramway. The results demonstrate that the proposed energy management system is able to ensure the major positive portion of the low frequency components of power demand can be deals with the PEMFC. The battery can help provide a portion of the positive low frequency components of power demand to reduce the PEMFC burden while the SC bank can supply all the high frequency components which could damage the PEMFC membrane. Therefore, the energy management system of high-power hybrid tramway is able to guarantee a safe operating condition with transient free for the PEMFC and extend the lifetime of each power source. Finally, the comparisons with other control strategies verify that the proposed energy management system can achieve better energy efficiency of the overall hybrid tramway.

Multi-Objective Optimal Design of Parallel Plug-In Hybrid Powertrain Configurations with Respect to Fuel Consumption and Driving Performance

Multi-Objective Optimal Design of Parallel Plug-In Hybrid Powertrain Configurations with Respect to Fuel Consumption and Driving Performance

Simulation environment for the analysis of different hybrid powertrain configurations

A powertrain must fulfil requirements regarding fuel consumption and exhaust emissions and at the same time must be economically viable and meet customer expectations. New concepts with a wide range of topologies are now in the focus of development, thus offering more degrees of freedom but at the same time increasing the time and cost required for analysis. A simulation environment, newly developed by Bertrandt, now makes it possible to analyse different powertrain configurations at an early stage.

Simulation and analysis of powertrain hybridisation for construction equipment

Nowadays simulations are widely used in new systems design, and the same approach is applicable to Hybrid Electric Vehicle (HEV) development. In this paper several hybrid powertrain configurations for a typical construction machine – a backhoe loader – are investigated. Roading and lorry-loading performances of the backhoe loader are analysed by means of simulation studies. The simulation tool used for these studies is LMS Imagine.Lab AMESim. Several parameters are analysed, including the machine's acceleration and top speed, maximum tractive effort, roading performance on a particular test circuit, battery current and state of charge, electric motor and engine power. The results clearly indicate the advantages and disadvantages of each hybrid powertrain configuration.

Hybridization of powertrain and downsizing of IC engine – A way to reduce fuel consumption and pollutant emissions – Part 1

The aim of this two part paper is to present the results of extensive simulation and analytical analysis of the energy conversion efficiency in parallel hybrid powertrains. The simulation approach is based on an accurate and fast forward facing simulation model of a parallel hybrid powertrain and a conventional internal combustion engine powertrain. The model of the ICE is based on a verified dynamic model that provides sufficiently small time steps to model adequately the dynamics of electric systems during transient test cycles. Models of the electrical devices enable computation of the instantaneous energy consumption, production and storage as well as computation of the instantaneous energy losses and component efficiencies. Moreover, the paper offers an analytical approach based on the energy balance in order to analyze and predict the energy conversion efficiency of hybrid powertrains. The analysis covers a broad range of parallel hybrid powertrain configurations from mild to full hybrids. Combined simulation and analytical analysis enables deep insight into the energy conversion phenomena in hybrid powertrains. The paper reveals the conditions and influences that lead to improved fuel economy of hybrid powertrains with the emphasis on determining the optimum hybridization ratio. The theoretical background, simulation program and brief analysis of one test cycle are presented in Part 1, whereas the extensive analysis and parametric study is presented in the companion paper, Part 2.