International Journal of Powertrains (5 papers in press)

Regular Issues

• Back-stepping Speed Control for Internal Combustion Engines  
  by Munan Hong, Zhenhui Yao, Ling Su, Bo Liu, Anjian Zhou 
  Abstract: Back-stepping technique and Lyapunov theory are employed to design an engine speed controller which can deal with unknown load torque and uncertain model parameters. The nonlinear dynamic system is presented based on a mean value engine model. A back-stepping speed controller is proposed in such a way that the intake pressure is chosen as the virtual control variable. An adaption law is then constructed to estimate the load torque on line. The convergences of the proposed controller and the load torque estimator are obtained through the stability analysis based on Lyapunov theory. Simulations are conducted and the results are shown to demonstrate the controller.
  Keywords: back-stepping;Lyapunov theory;speed control;unknown load.
  
  
• Automotive Powertrain Reliability Modelling Using an Idea Algebra  
  by Andas Amrin, Christos Spitas, Vasileios Spitas, Georgios Vasileiou 
  Abstract: This paper presents a reliability modelling framework for automotive powertrains using a specially developed algebra, where all powertrain components and design and performance parameters are represented as formal computational objects of an Idea class. Unlike previous known frameworks for reliability modelling, such as FMEA, FTA or FBS, the present study constructs the reliability model of a given powertrain topology from the topology only and does not require manual input of constitutive/ performance equations, or the definition of a hierarchy of failure events. This tool is particularly useful in early stages of the design process, where the reliability of several alternative topologies may need to be evaluated a priori but a full-scale FMEA, FTA or FBS analysis would be impractical.
  Keywords: Reliability analysis; Risk assessment; Idea Algebra; FMEA; FTA; FBS.
  
  
• A Review of the Relevance of Driving Condition Mapping and Vehicle Simulation for Energy Management System Design  
  by Lucas Bruck, Ali Emadi, Kavya Divakarla 
  Abstract: With the emerging trend of transportation electrification, energy management strategies have become of significant importance in automotive engineering. Control systems are developed with the objective to increase vehicle efficiency, thus lowering fuel consumption and harmful gas emissions. Both the methodology and tools for powertrain systems design as well as vehicle performance assessment are challenging with a constant necessity for improvement. For both aspects, the importance of developing realistic driving scenarios accounting for real and sometimes random driving conditions is irrefutable. This paper provides an overview of the current state-of-the-art technologies in energy management systems (EMS), highlighting how driving conditions and Journey Mapping can influence the performance of these systems. In addition, a review of vehicle simulators is performed emphasizing how such tools could support the system level vehicle development.
  Keywords: Automotive applications; driving cycle; driving condition; driving prediction; electrification; electrified powertrains; energy management systems; journey mapping; Markov chain; vehicle virtual simulator.
  
  
• A new braking strategy based on motor characteristics and vehicle dynamics for unmanned electric vehicles  
  by Wenfei Li, Haiping Du, Weihua Li 
  Abstract: A challenge for electric vehicles is that electric vehicles have a relatively small limit in range. Regenerative braking is one of the most effective ways to extend the endurance of electric vehicles. Traditionally, vehicle braking generally follows the driver's braking intention. It is impossible for the driver to work out the optimal braking trajectory. However, vehicle can be unmanned in the future. The unmanned vehicle can decide when to brake and how to brake. In this paper, we propose a braking scheme for unmanned electric vehicles. It adopts different braking control strategy according to different braking conditions. When the situation is urgent, the vehicle adopts emergency braking. Otherwise, the vehicle adopts normal braking. In the case of emergency braking, the control target is to make the wheel slip ratio track the optimal slip ratio. Then the vehicle can obtain the shortest braking distance. In the case of normal braking, the vehicle can set the optimal braking trajectory and automatically take braking action. The setting of the braking trajectory is based on the characteristics of the motor and initial braking speed. When the vehicle follows the set braking trajectory, the electric vehicles can obtain the maximum braking energy recovery and extend the endurance. In order to validate the effectiveness of the proposed approach, numerical simulations are tested. The results show that the proposed braking method is able to make wheel slip ratio track the optimal slip ratio in case of emergency braking and achieve the maximum braking energy recovery in case of normal braking.
  Keywords: regenerative braking; electric vehicles; unmanned vehicle; intelligent brake system.
  
  

Special Issue on: Advanced Powertrain Technologies for New Energy Vehicles Modelling, Control and Optimisation

• Flash Boiling Hollow Cone Fuel Spray from a Piezoelectric Fuel Injector under Low Ambient Pressure  
  by Zengyang Wu, Libing Wang, Tiegang Fang 
  Abstract: In this study, an experimental study of the spray characteristics under flash boiling conditions from an outwardly opening piezoelectric gasoline direct injection fuel injector was conducted in an optically accessible constant volume chamber (CVC). Distinct spray structure is noticed when the ambient pressure is extended to a lower range (0.01 bar to 0.1 bar) under flash boiling spray regime. While the original hollow-cone structure is still observable, spray deforms from a hollow-cone structure to a diamond-like shape with a long central plume at the downstream of the spray. Liquid signals at the plume region are much weaker than the original hollow-cone shape region. Within this pressure range, a higher ambient pressure leads to a shorter central plume. Spray penetration length is greatly enlarged due to the change in spray structure. Spray under a lower ambient pressure penetrates much longer at the same time step. Fuel injection pressure and fuel injection duration has little effect on spray front penetration length development. Specially, the highest spray front penetration velocity observed at 0.01 bar is expected to approach to the local sound speed. Spray structure, spray penetration length and spray penetration velocity are mainly dominated by ambient pressure conditions in this study. Compared to isooctane fuel, commercial gasoline generates stronger flash boiling due to the wide boiling range, but the spray structures are quite similar.
  Keywords: Flash boiling; Hollow cone spray; Low ambient pressure; Gasoline direct injection; Isooctane.