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This article deals with a novel 2-speed transmission system specifically designed for electric axle applications. The design of this transmission permits seamless gearshifts and is characterized by a simple mechanical layout. The equations governing the overall system dynamics are presented in the paper. The principles of the control system for the seamless gearshifts achievable by the novel transmission prototype - currently under experimental testing at the University of Surrey and on a prototype vehicle - are analytically demonstrated and detailed through advanced simulation tools. The simulation results and sensitivity analyses for the main parameters affecting the overall system dynamics are presented and discussed.

The paper presents linear and non-linear driveline models for Heavy Goods Vehicles (HGVs) in order to evaluate the main parameters for optimal tuning, when considering the drivability. The implemented models consider the linear and non-linear driveline dynamics, including the effect of the engine inertia, the clutch damper, the driveshaft, the half-shafts and the tires. Sensitivity analyses are carried out for each driveline component during tip-in maneuvers. The paper also analyses the overall frequency response using Bode diagrams and natural frequencies. It is demonstrated that the most basic model capable of taking into account the first order dynamics of the driveline must consider the moments of inertia of the engine, the transmission and the wheels, the stiffness and the damping properties of the clutch damper, driveshaft and half-shafts, and the tires (which link the wheel to the equivalent inertia of the vehicle).

E-mobility is a game changer for the automotive domain. It promises significant reduction in terms of complexity and in terms of local emissions. With falling prices and recent technological advances, the second generation of electric vehicles (EVs) that is now in production makes electromobility an affordable and viable option for more and more transport mission (people, freight). Current e-vehicle platforms still present architectural similarities with respect to combustion engine vehicle (e.g., centralized motor). Target of the European project EVC1000 is to introduce corner solutions with in-wheel motors supported by electrified chassis components (brake-by-wire, active suspension) and advanced control strategies for full potential exploitation. Especially, it is expected that this solution will provide more architectural freedom toward “design-for-purpose” vehicles built for dedicated usage models, further providing higher performances.

The previously published equation found on page 492 contains an error which is corrected in the erratum.

The first step toward a braking system ‘by wire’ is Electro-Hydraulic Braking System (EHB). The paper describes a method to evaluate through virtual experimentation the actual improvement in vehicle behaviour, from the point of view of both handling and comfort, including also pedal feeling, due to EHB. The first step consisted in modelling the hydraulic unit, comprehensive of sensors. Then it was conceived a control logic devoted to medium-low intensity braking manoeuvres, without ABS intervention, to determine an optimal braking force distribution and pedal feeling depending on the manoeuvre. A failsafe strategy, complete of on board diagnosis, to prevent dangerous system behaviour in the eventuality of a component failure was carried out and tested. Finally, EHB wheel pressure sensors were used to improve both ABS performance, increasing the adherence estimation, and Vehicle Dynamics Control (VDC) performance, through a more precise actuation.

This paper presents an experimental methodology which can be adopted to measure the friction torque of the bearings in the wheel hubs of passenger vehicles. The first section of the paper highlights the reasons why an experimental device is necessary to have an objective evaluation of the performance of the bearing in terms of friction. In particular, the high level of approximation of the current formulas for the estimation of the friction inside a single bearing is discussed and demonstrated. An analytical methodology for the evaluation of the distribution of the axial load between the two bearings of the wheel hub is presented. However, its practical application for the precise calculation of the distribution of the load has to be checked through experimental tests.

The paper describes Politecnico di Torino braking systems test bench, based on hardware in the loop (HIL). The test bench, consisting of the whole braking system hardware, can be used for: Analysis of passive braking systems, to determine the main characteristics both in semi-stationary and dynamic conditions; Analysis of passive braking systems, to investigate the influence of eventual asymmetries on vehicle behaviour, since a vehicle model runs in real time and receives wheels pressure values by the sensors on the physical device; Analysis of Commercial Anti-lock Braking/Electronic Stability Program (ESP) Systems, both from the point of view of control strategies and hydraulic units performance; Definition of new ABS/ESP control strategies, e.g. considering wheels caliper pressure signals as inputs, using pre-existing commercial hydraulic units.

Firstly, the paper presents Politecnico di Torino Hardware-in-the-Loop (HIL) brake systems test bench. Secondly, it describes in detail all the necessary basic tests to characterize, on the bench, an ESP hydraulic unit: for example, step response of each valve, measurement of pressure limiter valves calibration, step response of motor pump unit. The experimental results are reported. Thirdly, the paper deals with the frequency response of ESP valves, by using Pulse Width Modulation. Pressure gradients and pressure oscillations obtained in the tests are commented in detail. An open loop actuation strategy for ESP is presented, permitting to obtain, in each condition, the desired wheels pressure levels, without having any output pressure sensor in the hydraulic unit. This strategy was conceived by simulation and then successfully tested on the bench. An ESP control strategy, complete of a diagnostic algorithm, was added to the actuation logic described before and tested on the bench.

The paper shortly describes an ABS/ESP Hardware-In-the-Loop (HIL) test bench built by the Vehicle Dynamics Team of the Department of Mechanics of Politecnico di Torino. It consists of a whole brake system, integrated through specific interface (e.g. wheel pressures signals) with a vehicle model running in real time on a dSPACE® board. Different commercial ABS strategies are compared, in a large spectrum of manoeuvres: slow brake apply manoeuvres, panic brake manoeuvres, μ-split brake manoeuvres, brake manoeuvres with a sudden variation of the friction coefficient between tyres and ground. The paper deals with the generation of all the signals required for activating a commercial ESP: steering wheel angle, body yaw rate, body lateral acceleration, engine control, etc… Some of them are transmitted by CAN. Typical handling manoeuvres are used to test the ESP: step steer, double step steer, ramp steer, etc… Several brake manoeuvres are simulated while turning.

Vehicle handling in steady-state and transient conditions can be significantly enhanced with the continuous modulation of the driving and braking torques of each wheel via dedicated torque-vectoring controllers. For fully electric vehicles with multiple electric motor drives, the enhancements can be achieved through a control allocation algorithm for the determination of the wheel torque distribution. This article analyzes alternative cost functions developed for the allocation of the wheel torques for a four-wheel-driven fully electric vehicle with individually controlled motors. Results in terms of wheel torque and tire slip distributions among the four wheels, and of input power to the electric drivetrains as functions of lateral acceleration are presented and discussed in detail. The cost functions based on minimizing tire slip allow better control performance than the functions based on energy efficiency for the case-study vehicle.

The research presented in this paper focuses on the effects of downsizing the electric motor drive of a fully electric vehicle through the adoption of a multiple-speed transmission system. The activity is based on the implementation of a simulation framework in Matlab / Simulink. The paper considers a rear wheel drive case study vehicle, with a baseline drivetrain configuration consisting of a single-speed transmission, which is compared with drivetrains adopting motors with identical peak power but higher base speeds and lower peak torques coupled with multiple-speed transmissions (double and three-speed), to analyze the benefits in terms of energy efficiency and performance. The gear ratios and gearshift maps for each multiple-speed case study are optimized through a procedure developed by the authors consisting of cost functions considering energy efficiency and performance evaluation. The cost functions are explained in the paper along with the models adopted for the research.

The paper describes the advantages due to the adoption of multi-speed transmission systems within fully electric vehicles. In particular, the article compares a conventional single-speed transmission layout, a 2-speed layout based on a novel gearbox architecture capable of seamless gearshifts, and a Continuously Variable Transmission layout. The selection of the optimal gear ratios for the 2-speed system has been based on an optimization procedure, taking into account the efficiency characteristics of the components of the whole vehicle powertrain. The control system for the Continuously Variable Transmission system has been designed with the aim of maximizing the efficiency of the operating points of the electric motor.

The combination of continuously-acting high level controllers and control allocation techniques allows various driving modes to be made available to the driver. The driving modes modify the fundamental vehicle performance characteristics including the understeer characteristic and also enable varying emphasis to be placed on aspects such as tire slip and energy efficiency. In this study, control and wheel torque allocation techniques are used to produce three driving modes. Using simulation of an empirically validated model that incorporates the dynamics of the electric powertrains, the vehicle performance, longitudinal slip and power utilization during straight-ahead driving and cornering maneuvers under the different driving modes are compared.

Electric vehicles with multiple motors permit continuous direct yaw moment control, also called torque-vectoring. This allows to significantly enhance the cornering response, e.g., by extending the linear region of the vehicle understeer characteristic, and by increasing the maximum achievable lateral acceleration. These benefits are well documented for human-driven cars, yet limited information is available for autonomous/driverless vehicles. In particular, over the last few years, steering controllers for automated driving at the cornering limit have considerably advanced, but it is unclear how these controllers should be integrated alongside a torque-vectoring system. This contribution discusses the integration of torque-vectoring control and automated driving, including the design and implementation of the torque-vectoring controller of an autonomous electric vehicle for a novel racing competition. The paper presents the main vehicle characteristics and control architecture.

E-mobility is a game changer for the automotive domain. It promises significant reduction in terms of complexity and in terms of local emissions. With falling prices and recent technological advances, the second generation of electric vehicles (EVs) that is now in production makes electromobility an affordable and viable option for more and more transport mission (people, freight). Still, major challenges for large scale deployment remain. They include higher maturity with respect to performance (e.g., range, interaction with the grid), development efficiency (e.g., time-to-market), or production costs. Additionally, an important market transformation currently occurs with the co-development of automated driving functions, connectivity, mobility-as-a-service. New opportunities arise to customize road transportation systems toward application-driven, user-centric smart mobility solutions.