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Advance CAE Methods for NVH Development of High Speed Electric Axle

AVL LIST GmbH-Mehdi Mehrgou, Julian Pohn, Bernhard Graf, Christoph Priestner
AVL Software and Functions Gmbh-Mathias Deiml
  • Technical Paper
  • 2020-01-1501
To be published on 2020-06-03 by SAE International in United States
By developing more electric vehicles more and more focus are to the noise and vibration from Electric Drive unit. Here a high-speed E-axle for premium class vehicle is being developed up to 30,000 rpm, with high power density and lightweight design which introduce new challenges. Benchmarking of different E-axle and vehicles lead to targets which can be used at the begin of development as subsystem targets. This paper shows first how these targets like tonal noise can be simulated. Then the CAE method is used to optimize the source and structure to improve the NVH. Different aspects like torque ripple, electric whine, gears whine and mounting are discussed.
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Root Cause Analysis and Structural Optimization of E-Drive Transmission

AVL LIST GmbH-Thomas Resch
AVL-AST d.o.o.-Borislav Klarin, Ivan Grozdanovic, Denis Pevec
  • Technical Paper
  • 2020-01-1578
To be published on 2020-06-03 by SAE International in United States
We face a growing demand for so-called eAxles (electric axle drive) in vehicle development. An eAxle is a compact electric drive solution for full electric vehicles (and P4 hybrids) with integrated electric machine and transmission. The transmission can be rather simple using fixed gear with cylindrical gear steps but increasing demands on power and speed range as well as efficiency increase its complexity with planetary stages or switchable gear steps. Such an electro-mechanic system has different behavior than the classical ICE-driven powertrains, for example regarding NVH, where high frequency and tonal noise from gear whining and electro-magnetic excitation is an important comfort issue that needs to be understood and controlled. As knowledge base for such drives is currently low, development needs to be supported by methodologies, which are not only on high predictive level for NVH responses, but also allow a detailed understanding and insight into the causes and reasons of a certain behavior to identify noise effects and to accelerate learning for such systems. In addition, such methods should lead to the possibility to…
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Multi-domain NVH Model for the Complete Electro-mechanical Power Unit

Goethe-Universität-Lars Hedrich
Robert Bosch GmbH-Yashwant Kolluru, Rolando Doelling
  • Technical Paper
  • 2020-01-1584
To be published on 2020-06-03 by SAE International in United States
Multi-domain NVH Model for the Complete Electro-mechanical Power Unit Yashwant Kolluru, Rolando Doelling eBike Department Robert Bosch GmbH Kusterdingen, Germany yashwant.kolluru@de.bosch.com rolando.doelling@de.bosch.com Lars Hedrich Institute of Informatics Goethe University Frankfurt Frankfurt, Germany hedrich@em.informatik.uni-frankfurt.de Acoustics and vibrations are amongst the foremost indicators in perceiving the quality of power units. Analyzing these factors is vital to improve the performances of electro-mechanical systems. This paper deals with development of a generic simulation method enabling the multi-domain vibro-acoustic modelling for the drive trains. Excitation's for these systems majorly arise from the electric motor and mechanical gears. The paper initially depicts a flexible gear model for gear whining, which are generated for reasons like gear tooth bending. The forces generated from gear mesh (lumped parameter model) to gear components (multi-body model and nonlinear static model) and the excitations resulting from motor model are coupled for the frequency domain analysis of complete drive train. Additionally, paper discusses the influences of these forces on bearings (dynamic implicit model) and effect of bearing deformations on the harmonics of drive unit. Furthermore, velocities on…
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Analytical Rotordynamic Study of a High-Speed Gear Transmission System for Race Applications

Loughborough Univ-Stephanos Theodossiades, Mahdi Mohammadpour
Loughborough Univ.-Brett Friskney
  • Technical Paper
  • 2020-01-1502
To be published on 2020-06-03 by SAE International in United States
In motorsport power transmission systems, high-speed operation can be associated with significant rotordynamic effects. Changes in the natural frequencies of lateral (bending) vibrational modes as a function of spin speed are brought about by gyroscopic action linked to flexible shafts and mounted gear components. In the investigation of high-speed systems, it is important that these effects are included in the analysis in order to accurately predict the critical speeds encountered due to the action of the gear mesh and other sources of excitation. The rotordynamic behaviour of the system can interact with crucial physical parameters of the transmission, such as the stiffnesses of the gear mesh and rolling element-to-raceway contact in the bearings. In addition, the presence of the gear mesh acts to couple the lateral and torsional vibration modes of a dual-shaft transmission through which a torque flows. The relative interactions and effects of bearing and gear components can be captured in the form of modal analysis with parametric studies of key stiffness elements, such as mean value as a linear representation of stiffness.…
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Numerical Analysis of the Influences of Wear on the Vibrations of Power Units

Goethe-Universität-Lars Hedrich
Robert Bosch GmbH-Yashwant Kolluru, Rolando Doelling
  • Technical Paper
  • 2020-01-1506
To be published on 2020-06-03 by SAE International in United States
Numerical Analysis of the Influences of Wear on the Vibrations of Power Units Yashwant Kolluru, Rolando Doelling eBike Department Robert Bosch GmbH Kusterdingen, Germany yashwant.kolluru@de.bosch.com rolando.doelling@de.bosch.com Lars Hedrich Institute of Informatics Goethe University Frankfurt Frankfurt, Germany hedrich@em.informatik.uni-frankfurt.de The prime factor, which influences vibrations of electro-mechanical drives, is wear at the components. This paper discusses the numerical methods developed for abrasion, vibration calculations and the coupling between wear and NVH models of drive unit. Wear is a complex process and understanding it is essential for vibro-acoustics. The paper initially depicts finite element static model used for wear calculations. The special subroutines developed, aids in coupling the wear equations, various contact and friction formulations to the numerical model. The vibration domain model initially, focuses on calculations of mechanical excitation's at the gear shafts, which are generated via a nonlinear dynamic model. Furthermore, the bearings are studied for the influences on its stiffness and eventually its impact on harmonics of the drive trains. Later, free and forced vibrations of the complete drive train are simulated via steady-state dynamic…
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Experimental Rattle Source Characterization Using Matrix Inversion on a Reception Plate

Virtual Vehicle-Eugene Nijman, Bernhard Zeller
Virtual Vehicle Research Center-Josef Girstmair
  • Technical Paper
  • 2020-01-1541
To be published on 2020-06-03 by SAE International in United States
Minimising rattle noises is becoming increasingly important for hybrid and electrical vehicles as masking from the IC engine is missing and in view of the functional requirements of the office-like interiors of next generation automated vehicles. Rattle shall therefore be considered in the design phase of component systems. One hurdle is the modelling of the excitation mechanisms and its experimental validation. In this work we focus on excitation by loose parts having functional clearances such as gear systems or ball sensors in safety belt retractors. These parts are excited by relatively large low frequency displacements such as road-induced movements of the car body or low order rigid body engine vibrations generating multiple impacts with broad band frequency content. Direct measurement of the impact forces is in many cases not possible. An experimental procedure to measure the multi-DOF rattle impact forces in component systems is presented based on a reception plate transfer matrix inversion. The investigated component is mounted on the reception plate and rattle is induced by direct low frequency rigid body excitation of the…
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Gear Shift Pattern Optimization for Best Fuel Economy, Performance and Emissions

Chidhanand S.
Mahindra & Mahindra, Ltd.-Lemuel Paulraj, Saravanan Muthiah
  • Technical Paper
  • 2020-01-1280
To be published on 2020-04-14 by SAE International in United States
As the FTP-75 drive cycle does not have a prescribed gear shift pattern, automotive OEMs have the flexibility to design. Conventionally, gear shift pattern was formulated based on trial and error method, typically with 10 to 12 iterations on chassis dynamometer. It was a time consuming (i.e. ~ 3 to 4 months) and expensive process. This approach led to declaring poor fuel economy (FE). A simulation procedure was required to generate a gear shift pattern that gives optimal trade-off amongst conflicting objectives (FE, performance and emissions). As a result, a simulation tool was developed in MATLAB to generate an optimum gear shift pattern. Three different SUV/UV models were used as test vehicles in this study. Chassis dyno testing was conducted, and data was collected using the base and optimized gear shift patterns. Dyno test results with optimized gear shift pattern showed FE improvement of ~ 4 to 5% while retaining the NOx margin well above engineering targets. This labeling FE improvement method did not require any hardware or software changes, thus, involved no additional expense.…
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Rolling Element Bearings - Advanced Modeling for Multibody Simulations

Ghent University - Soete-Dieter Fauconnier
Siemens DI Software NV-Pavel Jiranek
  • Technical Paper
  • 2020-01-0508
To be published on 2020-04-14 by SAE International in United States
The electrification of vehicles, together with the ever-increasing need for more lightweight and durable designs, is putting the NVH performances of the transmission in the spotlight since the generated noises are not masked by the internal combustion engine. To correctly estimate the performances of the transmission while still in the design-phase, predictive models for the main components of the gearbox are of paramount importance. This paper focuses on the modeling of rolling element bearings, a key component that is responsible of transmitting the vibrations from the gear pairs to the surrounding structure while introducing additional excitation frequencies. The modeling techniques use the relative displacement of the rings to compute the corresponding reaction forces by calculating the equilibrium of each rolling element. To do so, the interaction between the rolling elements and the raceways can be modeled employing two different contact models depending on the level of accuracy required. The contact models are, respectively, a Hertz-Based approach that allows for fast computations, and an EHL (Elasto-Hydrodynamic Lubricated) contact model which accounts for the effects of lubrication.…
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Active and Passive Control of Torsional Vibration in Vehicle Hybrid Powertrain System

Tongji University-Lijun Zhang, Shijuan Zhang, Dejian Meng, Jie Xu
  • Technical Paper
  • 2020-01-0408
To be published on 2020-04-14 by SAE International in United States
The vibration characteristics of hybrid vehicles are very different from that of traditional fuel vehicles. In this paper, the active and passive control schemes are used to inhibit the vibration issues in vehicle hybrid powertrain system. Firstly the torsional vibration mechanical model including engine, motor and planetary gear subsystems is established. Then the transient vibration responses of typical working condition are analyzed through power control strategy. Consequently the active and passive control of torsional vibration in hybrid powertrain system is proposed. The active control of the motor and generator torque is designed and the vehicle longitudinal vibration is reduced. The vibration of the planetary gear system is ameliorated with passive control method by adding torsional vibration absorbers to power units. The vibration characteristics in vehicle hybrid powertrain system are effectively improved through the active and passive control.
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A Gear Shifting Indication Strategy of Eco-driving Vehicle

Jiangsu University-Nannan Hu
Jiangsu University-Ren He
  • Technical Paper
  • 2020-01-0966
To be published on 2020-04-14 by SAE International in United States
The current indication strategy of gear shifting indication system for manual transmission vehicles is developed based on the gear shifting strategy of the automatic transmission. In this paper, the driving data of several automatic transmission and manual transmission vehicles are collected. It is found that the shifting frequency of automatic transmission vehicles is significantly higher than that of manual transmission vehicles, which increases the fatigue of drivers. Aiming at this problem, an interval algorithm of gear shifting indication strategy is proposed based on the fuel consumption rate of engine in this paper. The strategy uses genetic algorithm to process the data of fuel consumption rate, finding the maximum and minimum values in the interval of torque and engine speed, and then the interval algorithm is adopted to transform the search of least fuel consumption value into the seeking of optimal interval to avoid the shifting busyness caused by the sudden change of the data of fuel consumption rate. The model of gear shifting indication strategy is established in Matlab/Simulink. Gear shifting tolerance is defined and…