Toward More Electric Powertrains in Aircraft:Technical Challenges and Advancements

The main purpose of this article is to provide an instructive review of the technological challenges hindering the road toward more electric powertrains in aircraft.Hybrid,all-electric,and turboelectric powertrain architectures are discussed as possible fuel consumption and weight reduction solutions.Among these architectures,the short-term implementation of hybrid and all-electric architectures is limited,particularly for large-capacity aircraft due to the low energy/power density levels achievable by state-of-the-art electrical energy storage systems.Conversely,turboelectric architectures with advanced distributed propulsion and boundary layer ingestion are set to lead the efforts toward more electric powertrains.At the center of this transition,power converters and high-power density electric machines,i.e.,electric motors and generators,and their corresponding thermal management systems are analyzed as the key devices enabling the more electric powertrain.Moreover,to further increase the fuel efficiency and power density of the aircraft,the benefits and challenges of implementing higher voltage powertrains are described.Lastly,based on the findings collected in this article,the projected roadmap toward more electric aircraft powertrains is presented.Herein,the individual targets for each technology,i.e.,batteries,electric machines,and power converters,and how they translate to future aircraft prototypes are illustrated.

Fuel Saving and Control for Hybrid Electric Powertrains

This paper focuses on comparing the performance of the embedded control of a hybrid powertrain with the original and downsized engine. The main idea is to store the normally wasted mechanical regenerative energy in energy storage devices for later usage. The regenerative energy recovery opportunity exists in any condition where the speed of motion is in the opposite direction to the applied force or torque. A rule based optimal robust control algorithm is developed and is tuned for different work cycles. A comparison of the fuel savings using the hybrid system with the original and downsized engines is performed.

Calculation of the Losses of Series-Hybrid Powertrains

Regarding mobile machinery, particularly agricultural tractors, there is an ongoing competition for the most suitable technology to achieve optimum functionality with maximum efficiency. In this competition, the efficiency of electric series-hybrid powertrains （ESHPs） is often depicted as worse than the efficiency of mechanical-hydraulic power-split powertrains （MHPSPs）. On closer inspection of these statements, however, systematic errors, such as unequal balance limits, neglected size effects and nonlinearities, non-observance of recent technical developments and standards, or erroneous application of research results regarding MHPSPs on ESHPs are often evident. For verification （and under avoidance of the systematic errors mentioned above）, the losses of an ESHP of 150 kW power are for example calculated and compared with the losses of a typical MHPSP of the same power. The comparison of the losses shows that the ESHP clearly exceeds the efficiency of the comparative MHPSP in the main working range and that there is still potential for improvement.

Multi-Criteria Decision Analysis for Usage Based Optimization of Powertrains

The electrification of powertrains leads to an increasing diversification of powertrain configurations. Each single configuration has its specific advantages which appear depending on the usage profile. To find the usage based optimal powertrain in consideration of a variety of evaluation criteria, the powertrains have to be optimized for the usage profile and characteristics have to be extracted from the usage profile. The carbon dioxide emissions of the optimized powertrains and usage based criteria are used in a multi-criteria decision analysis to determine the optimal powertrain for a specific usage profile. The description of characteristic maps forms the objective function of a minimization problem. The determined carbon dioxide emissions are one criterion in a multi-criteria decision process. All considered criteria are at least partly objective so that subjective ratings are eliminated as far as possible. The result is an optimized powertrain for a desired usage under the consideration of objective criteria that are extracted from the usage profile.

Robust control for electric vehicle powertrains

This paper considers the application of robust control methods(μ-and H∞-synthesis)to the speed and acceleration control problem encountered in electric vehicle powertrains.To this end,we consider a two degree of freedom control structure with a reference model.The underlying powertrain model is derived and combined into the corresponding interconnected system required forμ-and H∞-synthesis.The closed-loop performance of the resulting controllers are compared in a detailed simulation analysis that includes nonlinear effects.It is observed that theμ-controller offers performance advantages in particular for the acceleration control problem,but at the price of a high-order controller.

Review and Development of Electric Motor Systems and Electric Powertrains for New Energy Vehicles

This paper presents a review on the recent research and technical progress of electric motor systems and electric powertrains for new energy vehicles.Through the analysis and comparison of direct current motor,induction motor,and synchronous motor,it is found that permanent magnet synchronous motor has better overall performance;by comparison with converters with Si-based IGBTs,it is found converters with SiC MOSFETs show significantly higher efficiency and increase driving mileage per charge.In addition,the pros and cons of different control strategies and algorithms are demonstrated.Next,by comparing series,parallel,and power split hybrid powertrains,the series-parallel compound hybrid powertrains are found to provide better fuel economy.Different electric powertrains,hybrid powertrains,and range-extended electric systems are also detailed,and their advantages and disadvantages are described.Finally,the technology roadmap over the next 15 years is proposed regarding traction motor,power electronic converter and electric powertrain as well as the key materials and components at each time frame.

Characterization of a Powertrain Test Bed in the Context of Virtual Validation of Drivability

Technological trends in the automotive industry toward a software-defined and autonomous vehicle require a reassessment of today’s vehicle development process.The validation process soaringly shapes after starting with hardware-in-the-loop testing of control units and reproducing real-world maneuvers and physical interaction chains.Here,the road-to-rig approach offers a vast potential to reduce validation time and costs significantly.The present research study investigates the maneuver reproduction of drivability phenomena at a powertrain test bed.Although drivability phenomena occur in the frequency range of most up to 30∙Hz,the design and characteristics substantially impact the test setup’s validity.By utilization of modal analysis,the influence of the test bed on the mechanical characteristic is shown.Furthermore,the sensitivity of the natural modes of each component,from either specimen or test bed site,is determined.In contrast,the uncertainty of the deployed measurement equipment also affects the validity.Instead of an accuracy class indication,we apply the ISO/IEC Guide 98 to the measurement equipment and the test bed setup to increase the fidelity of the validation task.In conclusion,the present paper contributes to a traceable validity determination of the road-to-rig approach by providing objective metrics and methods.

An adaptive fuel cell hybrid vehicle propulsion sizing model

As we enter the age of electrochemical propulsion,there is an increasing tendency to discuss the viability or otherwise of different electrochemical propulsion systems in zero-sum terms.These discussions are often grounded in a specific use case;however,given the need to electrify the wider transport sector it is evident that we must consider systems in a holistic fashion.When designed adequately,the hybridisation of power sources within automotive applications has been demonstrated to positively impact fuel cell efficiency,durability,and cost,while having potential benefits for the safety of vehicles.In this paper,the impact of the fuel cell to battery hybridisation degree is explored through the key design parameter of system mass.Different fuel cell electric hybrid vehicle(FCHEV)scenarios of various hydridisation degrees,including light-duty vehicles(LDVs),Class 8 heavy goods vehicles(HGVs),and buses are modelled to enable the appropriate sizing of the proton exchange membrane(PEMFC)stack and lithium-ion battery(LiB)pack and additional balance of plant.The operating conditions of the modelled PEMFC stack and battery pack are then varied under a range of relevant drive cycles to identify the relative performance of the systems.By extending the model further and incorporating a feedback loop,we are able to remove the need to include estimated vehicle masses a priori enabling improving the speed and accuracy of the model as an analysis tool for vehicle mass and performance estimation.

Powertrain Torque Control Based on Torque Observer

To reduce shock during transmission gear shift, a transmission torque feedback closed loop control system is proposed based on the powertrain system model and a torque observer. The ignition time of engine was delayed to reduce transmission output shaft torque during gear shift. In contrast to traditional control method, the closed loop control system based on torque observer can obviously reduce the transmission output shaft torque during gear shift. It can be concluded that by way of torque feedback closed loop control, transmission shift shock can be reduced.

汽车的自动驾驶、电池管理、动力传动系以及充电桩的相关技术导向

本文从ADAS(高级驾驶辅助系统)、M电池管理、M Powertrain(动力传动系)以及充电桩四个方面分Y析了当下传统Y汽车和新能源汽车的相关技术的发展情况,并邀CM请专业技术专CM MY MY家探讨了汽车行业的技术变革的挑战和发展思路。CY

Power-balancing Instantaneous Optimization Energy Management for a Novel Series-parallel Hybrid Electric Bus

Energy management（EM） is a core technique of hybrid electric bus（HEB） in order to advance fuel economy performance optimization and is unique for the corresponding configuration. There are existing algorithms of control strategy seldom take battery power management into account with international combustion engine power management. In this paper, a type of power-balancing instantaneous optimization（PBIO） energy management control strategy is proposed for a novel series-parallel hybrid electric bus. According to the characteristic of the novel series-parallel architecture, the switching boundary condition between series and parallel mode as well as the control rules of the power-balancing strategy are developed. The equivalent fuel model of battery is implemented and combined with the fuel of engine to constitute the objective function which is to minimize the fuel consumption at each sampled time and to coordinate the power distribution in real-time between the engine and battery. To validate the proposed strategy effective and reasonable, a forward model is built based on Matlab/Simulink for the simulation and the dSPACE autobox is applied to act as a controller for hardware in-the-loop integrated with bench test. Both the results of simulation and hardware-in-the-loop demonstrate that the proposed strategy not only enable to sustain the battery SOC within its operational range and keep the engine operation point locating the peak efficiency region, but also the fuel economy of series-parallel hybrid electric bus（SPHEB） dramatically advanced up to 30.73% via comparing with the prototype bus and a similar improvement for PBIO strategy relative to rule-based strategy, the reduction of fuel consumption is up to 12.38%. The proposed research ensures the algorithm of PBIO is real-time applicability, improves the efficiency of SPHEB system, as well as suite to complicated configuration perfectly.

OPTIMIZATION APPROACH FOR HYBRID ELECTRIC VEHICLE POWERTRAIN DESIGN

According to bench test results of fuel economy and engine emission for thereal power-train system of EQ7200HEV car. a 3-D performance map oriented quasi-linear model isdeveloped for the configuration of the powertrain components such as internal combustion engine,traction electric motor, transmission, main retarder and energy storage unit. A genetic algorithmbased on optimization procedure is proposed and applied for parametric optimization of the keycomponents by consideration of requirements of some driving cycles. Through comparison of numericalresults obtained by the genetic algorithm with those by traditional optimization methods, it isshown that the present approach is quite effective and efficient in emission reduction and fueleconomy for the design of the hybrid electric car powertrain.

Method of Electric Powertrain Matching for Battery-powered Electric Cars

The current match method of electric powertrain still makes use of longitudinal dynamics, which can’t realize maximum capacity for on-board energy storage unit and can’t reach lowest equivalent fuel consumption as well. Another match method focuses on improving available space considering reasonable layout of vehicle to enlarge rated energy capacity for on-board energy storage unit, which can keep the longitudinal dynamics performance almost unchanged but can’t reach lowest fuel consumption. Considering the characteristics of driving motor, method of electric powertrain matching utilizing conventional longitudinal dynamics for driving system and cut-and-try method for energy storage system is proposed for passenger cars converted from traditional ones. Through combining the utilization of vehicle space which contributes to the on-board energy amount, vehicle longitudinal performance requirements, vehicle equivalent fuel consumption level, passive safety requirements and maximum driving range requirement together, a comprehensive optimal match method of electric powertrain for battery-powered electric vehicle is raised. In simulation, the vehicle model and match method is built in Matlab/simulink, and the Environmental Protection Agency (EPA) Urban Dynamometer Driving Schedule (UDDS) is chosen as a test condition. The simulation results show that 2.62% of regenerative energy and 2% of energy storage efficiency are increased relative to the traditional method. The research conclusions provide theoretical and practical solutions for electric powertrain matching for modern battery-powered electric vehicles especially for those converted from traditional ones, and further enhance dynamics of electric vehicles.

ENERGY MANAGEMENT STRATEGY FOR PARALLEL HYBRID ELECTRIC VEHICLES

Energy management strategy (EMS) is the core of the real-time controlalgorithm of the hybrid electric vehicle (HEV). A novel EMS using the logic threshold approach withincorporation of a stand-by optimization algorithm is proposed. The aim of it is to minimize theengine fuel consumption and maintain the battery state of charge (SOC) in its operation range, whilesatisfying the vehicle performance and drivability requirements. The hybrid powertrain bench testis carried out to collect data of the engine, motor and battery pack, which are used in the EMS tocontrol the powertrain. Computer simulation model of the HEV is established in the MATLAB/Simulinkenvironment according to the bench test results. Simulation results are presented for behaviors ofthe engine, motor and battery. The proposed EMS is implemented for a real parallel hybrid carcontrol system and validated by vehicle field tests.

Parameters matching and optimization of parallel hybrid electric vehicle powertrain

Aiming at the development of parallel hybrid electric vehicle （PHEV） powertrain, parameter matching and optimization are presented, According to the performance of PHEV, the optimization range of engine, motor, driveline gear ratio and battery parameters are determined. And then a two-level optimization problem is formulated based on analytical target cascading （ATC）. At the system level, the optimization of the whole vehicle fuel economy is carried out, while the tractive performance is defined as the constraints. The optimized parameters are cascaded to the subsystem as the optimization targets. At the subsystem level, the final drive and transmission design are optimized to make the ratios as close to the targets as possible. The optimization result shows that the fuel economy had improved significantly, while the tractive performance maintains the former level.

Optimal tracking control for automatic transmission shift process

In order to improve the shift quality, a linear quadratic optimal tracking control algorithm for automatic transmission shift process is proposed. The dynamic equations of the shift process are derived using a Lagrange method. And a powertrain model is built in the Matlab/Simulink and veri- fied by the measurements. Considering the shift jerk and friction loss during the shift process, the tracking trajectories of the turbine speed and output shaft speed are defined. Furthermore, the linear quadratic optimal tracking control performance index is proposed. Based on the Pontryagin＇ s mini- mum principle, the optimal control law of the shift process is presented. Finally, the simulation study of the 1 - 2 upshift process under different load conditions is carried out with the powertrain model. The simulation results demonstrate that the shift jerk and friction loss can be significantly re- duced by applying the proposed optimal tracking control method.

City-Bus-Route Demand-based Efficient Coupling Driving Control for Parallel Plug-in Hybrid Electric Bus

Recently,plug?in hybrid electric bus has been one of the energy?e cient solutions for urban transportation. However,the current vehicle e ciency is far from optimum,because the unpredicted external driving conditions are di cult to be obtained in advance. How to further explore its fuel?saving potential under the complicated city bus driving cycles through an e cient control strategy is still a hot research issue in both academic and engineering area. To realize an e cient coupling driving operation of the hybrid powertrain,a novel coupling driving control strategy for plug?in hybrid electric bus is presented. Combined with the typical feature of a city?bus?route,the fuzzy logic inference is employed to quantify the driving intention,and then to determine the coupling driving mode and the gear?shifting strategy. Considering the response deviation problem in the execution layer,an adaptive robust controller for electric machine is designed to respond to the transient torque demand,and instantaneously compensate the response delay and the engine torque fluctuation. The simulations and hard?in?loop tests with the actual data of two typical driving conditions from the real?world city?bus?route are carried out,and the results demonstrate that the pro?posed method could guarantee the hybrid powertrain to track the actual torque demand with 10.4% fuel economy improvement. The optimal fuel economy can be obtained through the optimal combination of working modes. The fuel economy of plug?in hybrid electric bus can be significantly improved by the proposed control scheme without loss of drivability.

THROTTLE CONTROL STRATEGIES IN THE PROCESS OF INTEGRATED POWERTRAIN CONTROL

Combining with the development of automated manual transmission （AMT）, the various throttle control demands are analyzed under different working conditions of AMT such as tracking acceleration pedal, start, shift and so on. Based on simulation, the responding throttle control strategies are proposed, and a simple but effective throttle control method is presented. The testing results have proved that the strategies are effective for improving the pedal tracking precision and the qualities of start and shift.

Analysis of vehicle powertrain dynamic performance

To study the vehicle dynamic characteristics under typical cycle conditions, a steady-state simulation model of the engine in GT-Power is established and verified with engine bench test data. A dynamic model of the engine is then established. A co-simulation with the engine dynamic model in GT-Power and the vehicle transmission model in AMESim is conducted based on the technology of HLA/RTI. The parameter changes of vehicle powertrain in the accelerating process of 0 - 32 km/h, and vehicle typical cycle conditions are studied. The influence laws of the typical parameters influen- cing vehicle dynamic characteristics are obtained, and a new approach of improving vehicle dynamic characteristics is proposed. The results show that the vehicle powertrain dynamic model can simu- late, analyze and predict dynamic changes of vehicle in actual operating conditions and guide power- train matching and optimization.

Powertrain Fuel Consumption Modeling and Benchmark Analysis of a Parallel P4 Hybrid Electric Vehicle Using Dynamic Programming

The goal of this work is to develop a hybrid electric vehicle model that is suitable for use in a dynamic programming algorithm that provides the benchmark for optimal control of the hybrid powertrain. The benchmark analysis employs dynamic programming by backward induction to determine the globally optimal solution by solving the energy management problem starting at the final timestep and proceeding backwards in time. This method requires the development of a backwards facing model that propagates the wheel speed of the vehicle for the given drive cycle through the driveline components to determine the operating points of the powertrain. Although dynamic programming only searches the solution space within the feasible regions of operation, the benchmarking model must be solved for every admissible state at every timestep leading to strict requirements for runtime and memory. The backward facing model employs the quasi-static assumption of powertrain operation to reduce the fidelity of the model to accommodate these requirements. Verification and validation testing of the dynamic programming algorithm is conducted to ensure successful operation of the algorithm and to assess the validity of the determined control policy against a high-fidelity forward-facing vehicle model with a percent difference of fuel consumption of 1.2%. The benchmark analysis is conducted over multiple drive cycles to determine the optimal control policy that provides a benchmark for real-time algorithm development and determines control trends that can be used to improve existing algorithms. The optimal combined charge sustaining fuel economy of the vehicle is determined by the dynamic programming algorithm to be 32.99 MPG, a 52.6% increase over the stock 3.6 L 2019 Chevrolet Blazer.