International Journal of Powertrains (7 papers in press)
Stress Analysis of Self-aligning Automotive Gearing
by I. Beisekenov, C. Spitas, A. Amani, E. Tsolakis, V. Spitas
Abstract: This paper presents an analysis of the contact and bending stresses of certain self-aligning automotive spur gear designs under various degrees of misalignment. The resulting deflection and stress fields are studied and compared for different design variants. The proposed solution not only dispenses to a large extent with the need for crowning and the large associated expenses, but also makes practical the increase of gear width and a corresponding reduction of the gear module, potentially further benefitting gear dynamics and efficiency.
Keywords: Self-aligning gearing; misalignment; stress concentration.
Power-on Gear Downshift of Electric Vehicles using I-AMT with an Overrunning Clutch
by Jinlong Hong, Bingzhao Gao, Hong Chen
Abstract: Torque interruption of automated manual transmission (AMT) electric vehicles can be avoided by introducing a two-speed inverse AMT (I-AMT). An overrunning clutch is designed in this study to replace the traditional gear shift mechanism. The gear shift process of the introduced two-speed I-AMT with overrunning clutch can be divided into inertia and torque phases, and the control performance of the two phases greatly affects the overall shift quality. Unlike gear upshift, power-on gear downshift produces greater vehicle jerk due to its larger torque requirement. Thus, this study introduces the structure of the overrunning clutch and validates its dynamic characteristics. Then, the dynamics and control problems during power-on gear downshift are described in detail. A control scheme is also proposed, wherein optimal trajectory tracking control is used during the inertia phase and linear feedforward control is applied during the torque phase. Lastly, simulation results demonstrate that the seamless gear downshift of the proposed transmission can be realised whilst the shift shock is kept sufficiently small.
Keywords: Power-on gear downshift; Inverse-AMT; Overrunning Clutch; Electric Vehicle.
Fuel Consumption and Emission Reduction by Using a CVT in Series with Conventional Multi-Speed Transmission
by Jack Walker, Isabel Medina-Huerta, Callum Oglieve, Stephen Bewsher, Mahdi Mohammadpour
Abstract: Fuel economy is a growing concern for both manufacturers within the automotive sector and consumers. Increasing government legislation is driving towards greener vehicles with reduced CO2 and NOx emissions and greater fuel economy, especially within urban environments. Manufacturers use new technologies in their powertrain systems to tackle these problems. This paper simulates and evaluates the performance of using a half toroidal CVT in series with a conventional multi-speed transmission, by analysing different shifting strategies to optimise fuel consumption and NOx emissions over the NEDC using this novel approach. The results show an 8.83% increase in fuel economy and up to an 11.34% reduction in NOx emissions is possible using this arrangement. The introduction of CVT adds a further 1.18% increase in fuel economy and 3.59% decrease in NOx emissions. The paper concludes that this novel arrangement should be considered by automotive manufacturers as a solution for improvements to powertrain technology.
Keywords: Toroidal CVT; Optimum Gear Ratio; Fuel consumption; Nitrogen Oxide Emissions; New European Driving Cycle.
Analysis of a Novel Actively Controlled Split Path Automotive Gear Powertrain Topology
by C. Spitas, A. Amani, V. Spitas, A. Akiltayev
Abstract: Automotive powertrains are susceptible to noise and vibration borne from the dynamical excitation of the gear meshes, particularly at partial loads, such as whine and rattling. A novel design has been proposed, based on the subdivision of the power flow into parallel paths via a compact internal gear preloading subsystem. The design allows the real-time control of mesh stiffness, load sharing and backlash, thereby allowing the instantaneous optimisation of the dynamical response of the system and the elimination of rattling and whine at any torque and speed. This paper performs an analysis of the new topology and discusses some of its advantages over conventional and preloaded zero-backlash gear powertrain designs.
Keywords: Automotive gears; torque preloading; mesh stiffness control; backlash control.
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.
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.