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Characterisation of Brake Creep Groan Vibrations

Graz University of Technology-Peter Fischer, Manuel Pürscher, Severin Huemer-Kals
University of Ljubljana-Jurij Prezelj
  • Technical Paper
  • 2020-01-1505
To be published on 2020-06-03 by SAE International in United States
Creep Groan is an impulsive brake noise at very low velocities of the vehicle. Generally, stick-slip between brake disc and brake pads is assumed as the most dominating vibration mechanism of creep groan. This contribution will show by sophisticated measurement techniques, that stick-slip and speed dependent friction is an important trigger of this annoying vehicle noise. However, the overall vibration is much more complex than common stick-slip vibration models. It turns out, that in typical brake systems of passenger vehicles creep groan occurs around 15-20 Hz and 70-90 Hz. The mechanism at 15-20 Hz is an impulsive noise. Transitions between stick and slip phases trigger complex nonlinear vibrations of the complete brake and suspension system. At 70-90 Hz, the vibrations show a more harmonic-like behaviour, caused primarily by speed-dependent friction characteristics. Flexibilities in the suspension bushings, elastic deformations of suspension parts, wheel and tyre support the growth of instable self excited vibrations. In practical vehicle operation, the range of 70-90 Hz is the most relevant one. In many cases, the 15-20 Hz vibrations are not…
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Tire NVH Optimization for Future Mobility

CEAT Ltd-Rahul R. Sanghani, Thomas Cherian, Subramaniam Loganathan, Kamal Suhalka, Juban Thomas
  • Technical Paper
  • 2020-01-1520
To be published on 2020-06-03 by SAE International in United States
Vehicle NVH (Noise, Vibration and Harshness) is one of the most critical customer touchpoints which may lead to buying decisions. The importance of Noise inside the cabin is increasing day by day because of the new era of E-mobility and autonomous driving. Noise source could be the engine, powertrain, tyre, suspension components, brake system, etc. depending on driving conditions. Among these, tire noise is being identified as biggest contributor at constant mid-speed driving where engine and powertrain operate at minimum noise and wind noise is also at a moderate level. This driving condition becomes very significant for electric vehicles where engine noise is replaced by motor noise which is a tonal noise at very high frequency. This makes the improvement of tire noise levels quintessential for good cabin acoustic feel. This demands a proactive approach to develop low noise tire platforms for future mobility by leveraging research tools and best practices in the industry. With a greater emphasis on ride and comfort in passenger car vehicles, tyre manufacturers will be challenged to meet stringent harshness…
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Heavy Vehicles Kinematics of Automatic Emergency Braking Test Track Scenarios

NHTSA-Devin Elsasser
Transportation Research Center Inc.-M. Kamel Salaani, Christopher Boday
  • Technical Paper
  • 2020-01-0995
To be published on 2020-04-14 by SAE International in United States
This paper presents the test track scenario design and analysis used to estimate the performances of heavy vehicles equipped with forward collision warning and automatic emergency braking systems in rear-end crash scenarios. The first part of this design and analysis study was to develop parameters for brake inputs in test track scenarios simulating a driver that has insufficiently applied the brakes to avoid a rear-end collision. In the second part of this study, the deceleration limits imposed by heavy vehicles mechanics and brake systems are used to estimate automatic emergency braking performance benefits with respect to minimum stopping distance requirements set by Federal Motor Vehicle Safety Standards. The results of this study were used to complete the test track procedures and show that all heavy vehicles meeting regulatory stopping distance requirements have the braking capacity to demonstrate rear-end crash avoidance improvements in the developed tests.
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NHTSA's 2018 Heavy Vehicle Automatic Emergency Braking Test Track Research Results

NHTSA-Devin Elsasser
Transportation Research Center Inc.-M. Kamel Salaani, Christopher Boday
  • Technical Paper
  • 2020-01-1001
To be published on 2020-04-14 by SAE International in United States
This paper presents National Highway Traffic Safety Administration’s 2017 and 2018 test track research results with heavy vehicles equipped with forward collision warning and automatic emergency braking systems. Newly developed objective test procedures were used to perform and collect performance data with three single-unit trucks equipped with the crash avoidance systems. The results of this research show that the test procedures are applicable to many heavy vehicles and indicate that performance improvements in heavy vehicles equipped with these safety systems can be objectively measured.
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Super-Twisting Second-Order Sliding Mode Control for Automated Drifting of Distributed Electric Vehicles

Tsinghua University-Xiaohui Hou, Junzhi Zhang, Weilong Liu, Yuan Ji
  • Technical Paper
  • 2020-01-0209
To be published on 2020-04-14 by SAE International in United States
Studying drifting dynamics and control could extend the usable state-space beyond handling limits and maximize the potential safety benefits of autonomous vehicles. Distributed electric vehicles provide more possibilities for drifting control with better grip and larger maximum drift angle. Under the state of drifting, the distributed electric vehicle is a typical nonlinear over-actuated system with actuator redundancy, and the coupling of input vectors impedes the direct use of control algorithm of upper. This paper proposes a novel automated drifting controller for the distributed electric vehicle. First, the nonlinear over-actuated system, comprised of driving system, braking system and steering system, is formulated and transformed to a square system through proposed integrative recombination method of control channel, making general nonlinear control algorithms suitable for this system. On this basis, a super-twisting second-order sliding mode controller is designed to generate the desired virtual control input, pushing the vehicle to the performance and operating limits while keeping in the quasi-equilibrium state. Finally, an online control allocation is designed to translate the virtual control input to the longitudinal and lateral…
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Modeling and Identification of an Electric Vehicle Braking System: Thermal and Tribology Phenomena Assessment

Siemens Industry Software NV-Thomas D’hondt, Bart Forrier, Mathieu Sarrazin
Università degli Studi di Firenze-Tommaso Favilli, Luca Pugi, Lorenzo Berzi, Riccardo Viviani, Marco Pierini
  • Technical Paper
  • 2020-01-1094
To be published on 2020-04-14 by SAE International in United States
A rapidly shifting market and increasingly stringent environmental regulations require the automotive industry to produce more efficient low-emission Electric Vehicles (EVs). Regenerative braking has proven to be a major contributor to both objectives, enabling the charging of the batteries during braking and a reduction of the load and wear of the brake pads. The optimal sizing of such systems requires the availability of good simulation models to improve their performance and reliability at all stages of the vehicle design. This enables the designer to study both the integration of the braking system with the full vehicle equipment and the interactions between electrical and mechanical braking strategies. This paper presents a generic simulation framework for the identification of thermal and wear behaviour of a mechanical braking system, based on a lumped parameter approach. The thermal behaviour of the system is coupled back to the friction coefficient between the pad and the disk to assess its effect on braking performance. Additionally, the effect of wear and temperature on the generation of airborne particles is investigated. Subsequently, experimental…
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Simulation of the Combined Braking Control System for Hybrid Electric Vehicles

Kharkiv National Automobile and Highway University-Serhii Shuklynov, Mykhailo Kholodov, Leonid Ryzhykh
VN Karazin Kharkiv National University-Victor Verbitskiy
  • Technical Paper
  • 2020-01-0217
To be published on 2020-04-14 by SAE International in United States
Simulation model of the combined braking control system for hybrid electric vehicles is proposed. The model shows working processes of the braking system with actuating friction mechanisms and an electro-hydraulic drive and regenerative braking system with an electrodynamic mechanism. The electrodynamic mechanism of regenerative braking is formed by switching the traction motor to the generator operating mode. At the same time braking effect is transmitted through the transmission to the drive wheels. The combined control of two brake systems of an electric vehicle is carried out by the driver when acting on one common control element - the brake pedal. Pushing on the braking pedal, driver generates the given control signal- desirable level of electric vehicle deceleration. In accordance with the given control signal, the law of control can be selected in the simulation model - the control function (electric vehicle deceleration) is proportional to the pedal effort or the control function is proportional to the set value of deceleration. In this case, the control system is adaptive and corrects the control signal in accordance…
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Modelling of a combined system of hydraulic magnetorheological fluid damper with braking-by-wire system

Tsinghua University-Cenbo Xiong, Liangyao Yu, Zhenchuan Li, Zhenghong Lu, Abi Lanie
  • Technical Paper
  • 2020-01-0988
To be published on 2020-04-14 by SAE International in United States
A hydraulic chamber is embedded in serial with the accumulator of a normal mono-tube magnetorheological fluid damper (MRFD). The damper stiffness can be adjusted by changing the initial accumulator volume with the hydraulic chamber. This hydraulic chamber is connected to an electric pump and controlled by the braking-by-wire system. Some signals and control parameters of the braking system are shared with the suspension system. A modified bi-viscosity magnetorheological fluid (MRF) model that explicitly includes the parameter of control current is adopted to determine the viscous forces of the damper. A dynamic model of this hydraulic MRFD is subsequently set up based on the hydro dynamic system and the MRF model. In this scheme, both the MRF viscosity and the damper stiffness can be continuously adjusted at the same time. A theoretical model combining the vehicle dynamics, the braking-by-wire system and the hydraulic MRFD is established based on which the control principles of the hydraulic MRFD according to the braking intensity are revealed. Simulations are carried out to study the parametric influences of this combined braking…
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Research on AEB Collision Avoidance Strategy Based on Characteristics of Driver-Vehicle-Road

Jiangsu University-Ren He, Dong Zhang
  • Technical Paper
  • 2020-01-1213
To be published on 2020-04-14 by SAE International in United States
With the rise of intelligent transportation systems around the world, research on automobile active safety technology has gained widespread attention. Autonomous Emergency Braking (AEB) which can avoid or mitigate collision by active braking has become a hot research topic in the field of automobile. However, there are some limitations in the present AEB collision avoidance strategy, including lack of effective identification of road adhesion conditions, mismatch of active braking system parameters and imperfection of target vehicle motion information, which leads to poor collision avoidance performance on low adhesion coefficient road surface and intervention with the normal driving operation of the driver. A new collision avoidance strategy for AEB is proposed in this paper. Firstly, a new safe distance collision avoidance model is established based on the peak adhesion coefficient in real time, the performance parameters of the active braking system and the motion information of the target vehicle. Secondly, under the premise of not interfering with the driver's normal collision avoidance operation, an AEB collision avoidance strategy that can balance vehicle safety and intervention comfort…
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Model-Based Design of Service-Oriented Architectures for Reliable Dynamic Reconfiguration

BMW Group-Florian Oszwald, Philipp Obergfell
FZI Research Center for Information Technology-Bo Liu, Victor Pazmino Betancourt
  • Technical Paper
  • 2020-01-1364
To be published on 2020-04-14 by SAE International in United States
Service-oriented architectures (SOAs) are well-established solutions in the IT industry. Their use in the automotive domain is still on the way. Up to now, the automotive domain has taken advantage of service-oriented architectures only in the area of infotainment and not for systems with hard real-time requirements. However, applying SOA to such systems has just started but is missing suitable design and verification methodologies. In this context, we target to include the notion of model-based design to address fail-operational systems. As a result, a model-based approach for the development of fail-operational systems based on dynamic reconfiguration using a service-oriented architecture is illustrated. For the evaluation, we consider an example function of an automatically controlled braking system and analyze the reconfiguration time when the function fails. The reconfiguration time, together with the worst-case execution time (WCET), was determined by a model-based calculation and by simulation. In summary, the proposed approach applied to dynamically reconfigurable systems can meet the design requirements of the ISO 26262.