Automotive Drivetrains Research Articles

Optimization of High- Impact Efficiency in Automotive Drivetrains

Optimization of High- Impact Efficiency in Automotive Drivetrains

Design and Manufacturing of CV Joint’s Tripod-Cup

Abstract: Constant Velocity Joints (CVJs) are essential components in automotive drivetrains, enabling the transmission of power from the differential to the wheel hub while accommodating varying angles and rotations. This project report provides a comprehensive overview of the design and manufacturing process of Tripod Cup Constant Velocity Joints, highlighting the key steps such as material selection, machining steps, heat treatment, quality control measures for its integration with OEM tripodspider and differential

Real-Time Estimation of Backlash Size in Automotive Drivetrains

The presence of backlash in automotive drivetrains causes the so-called clunk (a.k.a. shunt) phenomenon during reversals in the sign of the actuator torque. This clunk manifests as an audible noise when the gears make contact at the end of the lash traversal, and thus, affects the drive comfort of the vehicle. To mitigate the clunk, automotive OEMs employ a variety of actuator torque shaping strategies, which require knowledge of the size of the backlash in order to be effective. Furthermore, since the size of the drivetrain backlash is expected to vary significantly over the lifetime of the vehicle and/or from vehicle-to-vehicle (due to manufacturing variations), there is a requirement to estimate the backlash size in real-time so as to maintain the effectiveness of these strategies. To this end, the current work develops an innovative Kalman filter-based lash size estimator that uses readily available speed and torque signals from the vehicle CAN bus. As part of the development, we evaluate the efficacy of the proposed estimator using both simulations and test vehicle data. The evaluation also includes a study of the robustness of the estimator to variations in the actuator torque trajectory and the calculated road load torque, presence of CAN jitter in the measured speed signals, and variations in backlash size, driveshaft compliance, and tire-road interaction. Furthermore, we analyze the computational feasibility of the estimator using processor-in-loop simulations in a dSPACE prototype controller. Both the performance and robustness studies prove the effectiveness of the proposed backlash size estimation system.

Automotive dry clutch fully coupled transient tribodynamics

Determining the root causes of Noise, Vibration and Harshness (NVH) phenomena in modern automotive drivetrains is a task of critical importance. This research investigates the stability of dry clutch systems vibrational behaviour during engagement. A fully coupled dry clutch numerical model including the influence of friction is presented and validated using vehicle measurements. The clutch component frictional properties are measured using parts that exhibit aggressive NVH behaviour using representative tribometric experiments. The validated numerical tool highlights the occurrence of instabilities which are caused by modal couplings, particularly between the input shaft bending and clutch disc radial motions. Such a validated transient dynamics model of a dry clutch system has not hitherto been presented in the open literature.

Robust Data-Driven Error Compensation for a Battery Model

Abstract Models of traction batteries are an essential tool throughout the development of automotive drivetrains. Surprisingly, today’s massively collected battery data is not yet used for more accurate and reliable simulations. Primarily, the non-uniform excitation during regular battery operations prevent a consequent utilization of such measurements. Hence, there is a need for methods which enable robust models based on large datasets. For that reason, a data-driven error model is introduced enhancing an existing physically motivated model. A neural network compensates the existing dynamic error and is further limited based on a description of the underlying data. This paper tries to verify the effectiveness and robustness of the general setup and additionally evaluates a one-class support vector machine as the proposed model for the training data distribution. Based on five datasets it is shown, that gradually limiting the data-driven error compensation outside the boundary leads to a similar improvement and an increased overall robustness.

Tire-Slip Start Detection Using Sign of Rotation Jerk on Occurring Resonance of Automotive Drivetrains

Tire-Slip Start Detection Using Sign of Rotation Jerk on Occurring Resonance of Automotive Drivetrains

Comparison of Anti-Jerk Controllers for Electric Vehicles With On-Board Motors

Anti-jerk controllers actively suppress the torsional oscillations of automotive drivetrains, caused by abrupt variations of the traction torque. The main benefits are: i) enhanced passengers’ comfort; and ii) increased component life. Extensive literature deals with the design of anti-jerk controllers for electric powertrains with on-board motors, i.e., in which the electric motor is part of the sprung mass of the vehicle, and transmits torque to the wheels through a transmission, half-shafts and constant velocity joints. Nevertheless, a complete and structured comparison of the performance of the different control options is still missing. This study addresses the gap through the assessment of six anti-jerk controllers – five exemplary formulations from the literature, and one novel formulation based on explicit nonlinear model predictive control (eNMPC). All proposed control structures have the potential to be implemented on production vehicles. A set of objective performance indicators is defined to assess the controllers, which are tuned through an optimization-based routine. Results show that the wheel speed input is critical to enhance controller performance, but may lead to reduced robustness.

Active vibration control of automobile drivetrain with backlash considering time-varying long control period

Active vibration control of automotive drivetrains must be developed to compensate for the backlash of gears because it causes undesired responses. In addition, an engine used as an actuator has a constraint which makes the control periods longer and time-varying, resulting in deterioration of the control performance. The contribution of this study is to cope with all the issues described above, backlash and the control period constraint, simultaneously. First, a basic experimental device, which simplifies an actual vehicle to focus on the effect due to backlash, is demonstrated. In the device, the control period constraint, which is equivalent to that of an engine, is reproduced by a digital signal processor. To reduce an adverse effect due to the extension of the control period, the sampled-data controller, which does not require discretization in its implementation, is employed. In this paper, predictive processing using the servo-type sampled-data controller is proposed to compensate for the phase delay of the control input caused by the time-varying control period. In addition, a control mode switching technique included in the prediction suppresses undesired responses due to backlash. Finally, control experiments verify the effectiveness of the control system.

Experimental Implementation of Power-Split Control Strategies in a Versatile Hardware-in-the-Loop Laboratory Test Bench for Hybrid Electric Vehicles Equipped with Electrical Variable Transmission

The energy management strategy (EMS) or power management strategy (PMS) unit is the core of power sharing control in the hybridization of automotive drivetrains in hybrid electric vehicles (HEVs). Once a new topology and its corresponding EMS are virtually designed, they require undertaking different stages of experimental verifications toward guaranteeing their real-world applicability. The present paper focuses on a new and less-extensively studied topology of such vehicles, HEVs equipped with an electrical variable transmission (EVT) and assessed the controllability validation through hardware-in-the-loop (HiL) implementations versus model-in-the-loop (MiL) simulations. To this end, first, the corresponding modeling of the vehicle components in the presence of optimized control strategies were performed to obtain the MiL simulation results. Subsequently, an innovative versatile HiL test bench including real prototyped components of the topology was introduced and the corresponding experimental implementations were performed. The results obtained from the MiL and HiL examinations were analyzed and statistically compared for a full input driving cycle. The verification results indicate robust and accurate actuation of the components using the applied EMSs under real-time test conditions.

Noise, vibration and harshness during dry clutch engagement oscillations

Determining the root causes of various noise, vibration and harshness phenomena in modern automotive drivetrains is a critical task for industry, since noise, vibration and harshness issues often result in worsened driving experience. The aim of the current research is to investigate the dynamics during dry clutch engagement and the associated – often problematic – oscillations. This paper reports the development and partial validation of numerical models to study dry clutch behaviour. The models are used to investigate the influence of clutch and throttle actuation on the occurrence of unwanted clutch oscillations. The dynamic coefficient of friction between the clutch interacting surfaces was measured using a pin-on-disc rig under different slip speeds and contact pressure conditions, which are representative of a typical clutch engagement manoeuvre. The paper highlights the occurrence of instability issues in clutch dynamics (disc radial mode) as potential generators of aggressive noise, vibration and harshness, particularly during two different clutch pedal actuations. Such analysis has not hitherto been reported in the open literature.

Tire Slip Detection Using Oscillation Frequency of Automotive Drivetrains

Tire Slip Detection Using Oscillation Frequency of Automotive Drivetrains

Identifying in operando changes in membrane hydration in polymer electrolyte membrane fuel cells using synchrotron X-ray radiography

The cost of the polymer electrolyte membrane (PEM) fuel cell must undergo significant reductions before the widespread adoption of PEM fuel cell powered automotive drivetrains can be achieved. Eliminating the need for active anode humidification is one strategy for reducing the cost and system size of the PEM fuel cell. In this study, we investigated the impact of anode gas inlet relative humidity (RH) on membrane hydration and the associated electrochemical performance of the PEM fuel cell. The anode gas inlet RH was varied to study the impact on fuel cell potential, during which simultaneous in operando visualizations were performed using synchrotron X-ray radiography, and electrochemical impedance spectroscopy was used to gain an understanding of the membrane hydration and water dynamics. The thickness of a Nafion® N115 membrane expanded by up to 26 μm (20% of nominal thickness) compared to the manufacturer specification, as a result of changes in membrane hydration. Through this work, we present the utility of synchrotron X-ray radiography for tracking changes in membrane hydration of an operating PEM fuel cell.

A Generic and Modular Modeling Approach for Automotive Drivetrains Using a Coordinate Partitioning Method

Drivetrain models play an important role in state-of-the-art automotive drivetrain and control concept development. Based on a proposed set of elementary drivetrain components, this article contributes a generic straightforward approach to compute state-space models for various geared drivetrain layouts, including complex hybrid multi-mode transmissions. The modular approach follows Lagrange formalism: The free motion of rigid shafts is subsequently constrained, considering connecting elements like spur and planetary gear sets. The generalized coordinates are determined by a coordinate partitioning method, ensuring a physically reasonable coordinate system. The proposed approach features high potential for automation. This enables drivetrain modeling by non-experts in the field of mechanical engineering.

A study on torsional vibration attenuation in automotive drivetrains using absorbers with smooth and non-smooth nonlinearities

The automotive industry is predominantly driven by legislations on stringent emissions. This has led to the introduction of downsized engines, incorporating turbocharging to maintain output power. As downsized engines have higher combustion pressures, the resulting torsional oscillations (engine order vibrations) are of broadband nature with an increasing severity, which affect noise and vibration response of the drive train system. Palliative devices, such as clutch pre-dampers and dual mass flywheel have been used to mitigate the effect of transmitted engine torsional oscillations. Nevertheless, the effectiveness of these palliative measures is confined to a narrow band of response frequencies. The nonlinear targeted energy transfer is a promising approach to study vibration mitigation within a broader range of frequencies, using nonlinear vibration absorbers (or nonlinear energy sinks – NESs). These devices would either redistribute vibration energy within the modal space of the primary structure, thus dissipating the vibrational energy more efficiently through structural damping, or passively absorb and locally dissipate a part of this energy (in a nearly irreversible manner) from the primary structure. The absence of a linear resonance frequency of an NES, enables its broadband operation (in contrast to the narrowband operation of current linear tuned mass dampers). Parametric studies are reported to determine the effectiveness of various smooth or non-smooth nonlinear stiffness characteristics of such absorbers. A reduced drivetrain model, incorporating single and multiple absorber attachments is used and comparison of the predictions to numerical integrations proves its efficacy.

Targeted energy transfer and modal energy redistribution in automotive drivetrains

The new generations of compact high output power-to-weight ratio internal combustion engines generate broadband torsional oscillations, transmitted to lightly damped drivetrain systems. A novel approach to mitigate these untoward vibrations can be the use of nonlinear absorbers. These act as Nonlinear Energy Sinks (NESs). The NES is coupled to the primary (drivetrain) structure, inducing passive irreversible targeted energy transfer (TET) from the drivetrain system to the NES. During this process, the vibration energy is directed from the lower-frequency modes of the structure to the higher ones. Thereafter, vibrations can be either dissipated through structural damping or consumed by the NES. This paper uses a lumped parameter model of an automotive driveline to simulate the effect of TET and the assumed modal energy redistribution. Significant redistribution of vibratory energy is observed through TET. Furthermore, the integrated optimization process highlights the most effective configuration and parametric evaluation for use of NES.

Unilateral contact condition enhanced with squeeze film modelling in automotive differentials

The dynamic behaviour of automotive drivetrains is significantly influenced by contacts occurring between the various parts. In this paper, a three-dimensional formulation is proposed to model unilateral and frictional contact conditions between two rigid planar rings. The magnitude of the contact force is determined by a penalty method. In a second step, a simple squeeze film model is developed to account for the damping effect produced by the lubricating oil filling the gap between the two contacting bodies. The relevance and the accuracy of these models are illustrated through the global multibody modelling of a TORSEN differential.

Theoretical study of structural modification control and analytical model reduction of torsional vibration in FR–type automotive power drivetrain

Problems of analysis and control of torsional vibrations of FR–type automotive power drivetrains are studied in this paper. First, a multi–degree–of–freedom analytical model of torsional vibration of a truck is developed, and its natural vibration characteristics are computationally analysed. Secondly, several possible and practical ways of structural modifications, i.e. modifications to stiffnesses, masses and dampings, for control of vibration and noise are numerically simulated. Thirdly, two special problems about torsional vibration analysis and analytical model reduction are investigated: (i) local vibration modes and their dominant substructures, and (ii) modal symmetry and analytical model simplification of symmetrically branched driving axle substructure.

HIL-simulation as an instrument for elaboration of automotive drivetrains with wheels torques distribution

The paper gives an analysis of the Hardware-in-the-Loop (HIL) simulation applied to development and elaboration of drivetrains with separate drives to individual wheels or axes. First, features and functions of such drivetrains are shortly described. Further, the most difficult tasks emerging during development of these drivetrains are analyzed along with ways that HIL offers to resolve these tasks. For that analysis, the paper gives essential principles of vehicle simulation by means of a test rig and HIL-technique. As examples of pertinent drivetrains and HIL-solutions the paper surveys developments of world-leading companies i.e. LuK, Froude Hofmann and Horiba as well as Russian research organizations: Moscow State University of Mechanical Engineering (MAMI), Central scientific research automobile and automotive engine institute «NAMI» and NAMI-Service.

Unified modeling of hybrid electric vehicle drivetrains

Hybridizing automotive drivetrains, or using more than one type of energy converter, is considered an important step toward very low pollutant emission and high fuel economy. The automotive industry and governments in the United States, Europe, and Japan have formed strategic initiatives with the aim of cooperating in the development of new vehicle technologies. Efforts to meet fuel economy and exhaust emission targets have initiated major advances in hybrid drivetrain system components, including: high-efficiency high-specific power electric motors and controllers; load-leveling devices such as ultracapacitors and fly-wheels; hydrogen and direct-methanol fuel cells; direct injection diesel and Otto cycle engines; and advanced batteries. The design of hybrid electric vehicles is an excellent example of the need for mechatronic system analysis and design methods. If one is to fully realize the potential of using these technologies, a complete vehicle system approach for component selection and optimization over typical driving situations is required. The control problems that arise in connection with hybrid power trains are significant and pose additional challenges to power-train control engineers. The principal aim of the paper is to propose a framework for the analysis, design, and control of optimum hybrid vehicles within the context of energy and power flow analysis. The approaches and results presented in the paper are one step toward the development of a complete toolbox for the analysis and design of hybrid vehicles.

Densification strategies for high endurance PM components : P.Jones et al. (Stackpole Ltd, Mississauga, Canada.) Int. J. Powder Metall., vol 33, no 3, 1997, 37–43

In recent years the use of powder metallurgy (P/M) parts in automotive drivetrains has shown impressive growth. This is forecast to continue in the medium term (1-5 years) with the ongoing adoption of high volume components such as powder forged connecting rods, P/M main bearing caps and P/M transmission sprockets. In the longer term (5-10 years) continued real growth will become increasingly dependent on P/M's ability to displace parts made from heat treated, low alloy wrought steel. Many traditional P/M materials will not meet the durability demands of these components, in part due to strength deficits caused by residual porosity and inappropriate alloying. This review paper focuses on the density requirements for high performance components. By reference to actual parts in production, it is proposed that no single high density process will meet the requirements for every component. A variety of strategies must be developed, keeping in mind from the outset, that any new process must have a sustainable cost advantage if it is to succeed in dislodging long established manufacturing methods.