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Technical Paper

Vibration Characteristic Analysis and Optimization of the Rear Suspension of Eccentrical Motor Driven Electric Vehicle

2013-03-25
2013-01-0088
To wheel driven electric vehicle, besides road unevenness excitation, the electric motor torque fluctuation has great effects on the whole body vibration (WBV) according to prior research.[1],[2] To evaluate and further reduce the influence of torque fluctuation on the whole body vibration (WBV), vibration characteristic of rear suspension is analyzed thoroughly and finally optimized in this paper. Firstly, based on an existing eccentrical motor driven electric vehicle, a rear twist beam suspension suitable for high frequency analysis is modeled in Adams/View. Secondly, the vibration characteristic is simulated using Adams/Vibration module and verified with natural modal parameters of system. Finally, the vibration characteristic is optimized by adjusting the parameters of bushings using DOE method and proven to be effective to reduce WBV caused by torque fluctuation.
Journal Article

Combination of Test with Simulation Analysis of Brake Groan Phenomenon

2014-04-01
2014-01-0869
During a car launch, the driving torque from driveline acts on brake disk, and may lead the pad to slip against the disk. Especially with slow brake pedal release, there is still brake torque applies on the disk, which will retard the rotation of disk, and under certain conditions, the disk and pad may stick again, so the reciprocated stick and slip can induce the noise and vibration, which can be transmitted to a passenger by both tactile and aural paths, this phenomenon is defined as brake groan. In this paper, we propose a nonlinear dynamics model of brake for bidirectional, and with 7 Degrees of Freedom (DOFs), and phase locus and Lyapunov Second Method are utilized to study the mechanism of groan. Time-frequency analysis method then is adopted to analyze the simulation results, meanwhile a test car is operated under corresponding conditions, and the test signals are sampled and then processed to acquire the features.
Journal Article

Analysis of Friction Induced Stability, Bifurcation, Chaos, Stick-slip Vibration and their Impacts on Wiping Effect of Automotive Wiper System

2014-04-01
2014-01-0021
A 2 DOF nonlinear dynamic model of the automotive wiper system is established. Complex eigenvalues are calculated based on the complex modal theory, and the system stability as well as its dependence on wiping velocity is analyzed. Bifurcation characteristics of frictional self-excited vibration and stick-slip vibration relative to wiping velocity are studied through numerical analysis. Research of nonlinear vibration characteristics under various wiping velocities is conducted by means of phase trajectories, Poincaré map and frequency spectrum. The pervasive stick-slip vibration during wiping is confirmed, and its temporal and spatial distributions are analyzed by way of time history and contour map. Duty ratio of stick vibration and statistics of scraping residual are introduced as quantitative indexes for wiping effect evaluation. Results indicate that the negative slop of frictional-velocity characteristic is the root cause of system instability.
Technical Paper

Analysis of Gear Rattle Noise and Vibration Characteristics Using Relative Approaches

2016-04-05
2016-01-1121
Noise signals of the driver’s right ear include those of engine, environment, chassis dynamometer, loaded gears and unloaded gears when they are recorded in full vehicle on chassis dynamometer in semi-anechoic room. Gear rattle noise signals of the driver’s right ear caused by unloaded gear pairs can’t be identified or quantified directly. To solve the problems, relative approaches are used to identify and quantify the gear rattle noise signals. Firstly, the rattle noise signals of the driver’s right ear are filtered by human ear characteristic functions and steady noise signals are extracted by regression and smoothing processes. The noise signals are regressed at 200ms interval in the hearing critical frequency bands and smoothed in the flanking frequencies. Then, the noise relative approaches are obtained by subtracting the steady noise signals from the filtered noise signals, which are the transient noise signals of the unloaded gear pairs inducing the rattle noise.
Journal Article

Active Noise Equalization of Vehicle Low Frequency Interior Distraction Level and its Optimization

2016-04-05
2016-01-1303
On the study of reducing the disturbance on driver’s attention induced by low frequency vehicle interior stationary noise, a subjective evaluation is firstly carried out by means of rank rating method which introduces Distraction Level (DL) as evaluation index. A visual-finger response test is developed to help evaluating members better recognize the Distraction Level during the evaluation. A non-linear back propagation artificial neural network (BPANN) is then modeled for the prediction of subjective Distraction Level, in which linear sound pressure RMS amplitudes of five Critical Band Rates (CBRs) from 20 to 500Hz are selected as inputs of the model. These inputs comprise an input vector of BPANN. Furthermore, active noise equalization (ANE) on DL is realized based on Filtered-x Least Mean Square (FxLMS) algorithm that controls the gain coefficients of inputs of trained BPANN.
Journal Article

Vibro-Impact Analysis of Manual Transmission Gear Rattle and Its Sound Quality Evaluation

2017-03-28
2017-01-0403
Experimental schemes, frequency characteristics, subjective and objective sound quality evaluation and sound quality prediction model establishment of a certain mass-production SUV (Sport Utility Vehicle, SUV) manual transmission gear rattle phenomenon were analyzed in this paper. Firstly, vehicle experiments, including experiment conditions, vibration acceleration sensor and microphone arrangements and especial considerations in experiments, were described in detail. Secondly, through time-frequency analysis, broadband characteristics of manual transmission gear rattle noise were identified and vibro-impact of gear rattle occurs in the frequency range of 450~4000Hz on the vehicle idle condition and the creeping condition. Thirdly, based on bandwidth filtering processing of gear rattle noise, subjective assessment experiments by a paired comparison method were carried out.
Technical Paper

The Investigation of Self-Balanced Property and Vibration on the Particular Crankshaft System for an Opposed Piston Engine

2016-06-15
2016-01-1768
For an in-line diesel engine with four cylinder operating in four-stroke mode, the second-order reciprocating inertia forces generally cannot be well balanced with direct approach. The unbalanced second-order inertia forces are the main reason to cause vibration and noise in a diesel engine within low frequency range. The more superior tone quality for modern diesel engine has been expected even for bus application all the time, and there are tougher requirements for truck noise in developed countries, i.e. in Europe and USA. In present research a unique crankshaft system configuration was proposed, which including opposed piston, inner and outer connecting rod, and crankshaft but running in two-stroke mode, to eliminate the second-order inertia force considerably rather than by adding an extra balance shaft mechanism.
Technical Paper

Effect of Road-Induced Vibration on Gas-Tightness of Vehicular Fuel Cell Stack

2016-04-05
2016-01-1186
The vehicular fuel cell stack is unavoidably impacted by the vibration in the real-world usage due to the road unevenness. However, effects of vibration on stacks have yet to be completely understood. In this work, the mechanical integrity and gas-tightness of the stack were investigated through a strengthen road vibration test with a duration of 200 h. The excitation signals applied in the vibration test were simulated by the acceleration of the stack, which were previously measured in a vehicle vibration test. The load signals of the vehicle vibration test were iterated through a road simulator from vehicle acceleration signals which were originally sampled in the proving ground. Frequency sweep test was conducted before and after the vibration test. During the vibration test, mechanical structure inspection and pressure maintaining test of the stack were conducted at regular intervals.
Journal Article

A Study on the Bench Test of Friction-Induced Hot Spots in Disc Brake

2015-09-27
2015-01-2694
During light to moderate braking at high speed, the local high temperature phenomenon can be observed on the brake disc surfaces, known as hot spots. The occurrence of hot spots will lead to negative effects such as brake performance fade, thermal judder and local wear, which seriously affect the performance of vehicle NVH. In this paper, based on the bench test of a ventilated disc brake, the basic characteristics of hot spots is obtained and the evolution process of temperature field and disc deformation is analyzed in detail. In temperature field, hot bands appear first and grow, migrate from inner and outer radius to the middle, with the growing temperature fluctuation and finally hot spots appear in the middle radius of the brake disc. The stable SRO waviness forms much earlier than the temperature fluctuation. In the stop brake studied in this paper, the SRO waviness stabilizes in main 7 order state which is lower than the final hot spot order.
Journal Article

Influence Mechanism of Electromechanical Parameters on Transient Vibration of Electric Wheel System

2019-04-02
2019-01-0462
Electric wheel systems of in-wheel motor driven vehicles consist of the motor controller, in-wheel motor and tire-suspension assembly. The coupling between the electromagnetic excitation and elastic structure gives rise to electromechanical dynamic issues. As for the structural layout of the electric wheel system, the driving motor is directly connected to the wheel without torsion dampers or transmission in the driveline, thus making the electric wheel structure a weak damping system. Moreover, the driving torque of electric wheel can change rapidly in various conditions of vehicle. As a result, the transient vibration problem becomes one of the key electromechanical dynamic issues in the electric wheel system. To investigate this problem, the electromechanical coupling model of the electric wheel system is established first. Then the transient responses of the electric wheel under abrupt changes of the driving torque are simulated.
Technical Paper

Transfer Path Analysis and Low-Frequency Vibration Reduction by Locally Resonant Phononic Crystal

2019-04-02
2019-01-0786
The motor has vibration characteristics of order and multi-band in the frequency domain, which is different from the internal combustion engine when it is used as the vehicle’s drive. These characteristics cannot be briefly attenuated by general methods, but make the phononic crystal (PC) an ideal solution to eliminate the vibration transmission of the motor, because the concentrated vibration peak can easily be blocked by the bandgap. In this paper, one dimensional locally resonant phononic crystal (LRPC) which has low-frequency bandgaps are arranged on the automotive subframe to absorbing vibration. The partial coherence analysis is used to analyze the transfer characteristic of vibration on the subframe. Then, 6 main paths are selected from the 18 vibration transmission paths, based on its high ratio of partial coherence coefficient in a certain frequency, and the arranged position, the spring stiffness and the resonator’s mass of the LRPCs are chosen based on this result.
Journal Article

Longitudinal Vibration Analysis of Electric Wheel System in Starting Condition

2017-03-28
2017-01-1126
Due to coupling of in-wheel motor and wheel/tire, the electric wheel system of in-wheel motor driven vehicle is different from tire suspension system of internal combustion engine vehicle both in the excitation source and structural dynamics. Therefore emerging dynamic issues of electric wheel arouse attention. Longitudinal vibration problem of electric wheel system in starting condition is studied in this paper. Vector control system of permanent magnet synchronous hub motor considering dead-time effect of the inverter is primarily built. Then coupled longitudinal-torsional vibration model of electric wheel system is established based on rigid ring model and dynamic tire/road interface. Inherent characteristics of this model are further analyzed. The vibration responses of electric wheel system are simulated by combining electromagnetic torque and the vibration model. The results indicate that abrupt changes of driving torque will cause transient vibration of electric wheel system.
Technical Paper

A Method of Acceleration Order Extraction for Active Engine Mount

2017-03-28
2017-01-1059
The active engine mount (AEM) is developed in automotive industry to improve overall NVH performance. The AEM is designed to reduce major-order signals of engine vibration over a broad frequency range, therefore it is of vital importance to extract major-order signals from vibration before the actuator of the AEM works. This work focuses on a method of real-time extraction of the major-order acceleration signals at the passive side of the AEM. Firstly, the transient engine speed is tracked and calculated, from which the FFT method with a constant sampling rate is used to identify the time-related frequencies as the fundamental frequencies. Then the major-order signals in frequency domain are computed according to the certain multiple relation of the fundamental frequencies. After that, the major-order signals can be reconstructed in time domain, which are proved accurate through offline simulation, compared with the given signals.
Technical Paper

Optimization of EV Mounting System Considering Power Train Torsion Control

2015-06-15
2015-01-2225
Faced on transient vibration of EV, considering the characteristics of the electric drive system, active and passive integrated transient vibration control method of power train mounting system was proposed. Models of power train system and mounting system were established, modal characteristics were grasped by simulation and experiment. A feed-forward controller was constructed from the facet of active control, mounting system transient vibration and power train torsion vibration were reduced. Based on this, further optimization of mounting system was conducted from a passive control perspective. Results show that the active and passive integrated control method can effectively reduce the dynamic reaction force of mounting points, improve the vibration conditions of power train and vehicle body as well.
Technical Paper

Vibration Analysis of Series-parallel Hybrid Powertrain System under Typical Working Condition and Modes

2018-04-03
2018-01-1291
Powertrain system of series-parallel hybrid vehicle contains multiple excitation sources like engine, motor and generator. The reduction of noise and vibration is quite difficult during multiplex working modes or the switch of modes. Aiming at Series-parallel hybrid powertrain system which contains engine, motor and planetary gear subsystems, this paper considered a typical working condition which is based on the power control strategy and established the torsional vibration mechanical model of hybrid powertrain system. The inherent characteristics and transient vibration response of the electric mode, hybrid mode and parking charging mode were studied and it was discovered that the repetitive frequency of the powertrain system under the three working modes is the same which is only related to inertia and meshing stiffness of planetary gear system. The non-repetitive frequency and corresponding vibration modes under the electric mode and parking charging mode are both close.
Technical Paper

Gear Tooth Modification of EV Powertrain for Vibration and Noise Reduction

2018-04-03
2018-01-1289
In order to research the vibration and noise reduction in pure electric vehicle power-train, a comprehensive work is to simulate the power-train incentive of a high-speed pure electric vehicle, and indicates significant impact of gear mesh system on the power-train NVH performance. Therefore, it is necessary to further study the impact of meshing gear system on electric vehicle power-train vibration and noise performance and seek reasonable methods to reduce the vibration and noise. In this paper, a typical pure electric vehicle's powertrain was used to conduct vibration and noise dynamic simulation. Firstly, the power train model was established considering the gear meshing stiffness, transmission errors, bearing factors and shell flexible, then the vibration and sound radiation dynamic response of power-train was simulated. Based on the accuracy of prediction model, a gear tooth modification was carried out for vibration and noise optimization.
Technical Paper

One New Transient Transfer Path Analyses of Vehicle Interior Vibration Excited by Vertical Speed Hump

2018-04-03
2018-01-0687
Vertical excitations from obstacles on public road are typical and likely to increase vehicle interior vibration through major paths of wheel spindle-suspension-body. A new transient transfer path analysis (TTPA) methodology is presented combining the substructure reverse matrix method based on FRFs with operational excitation. Additionally, a new kind of experimental method is applied to solve an engineering problem and also validates the TTPA theory above. There are three steps in all. Firstly, vibration in Z direction of wheel spindle was collected in one proving ground and represented on MTS 320 road simulator bench after many times of iteration of piston signals. This procedure guarantees excitation decoupling in one certain direction so it leads to accurate frequency response functions (FRFs) under transient shocking excitation. Secondly, the new transient transfer path analysis approach was used to calculate vibration contribution of wheel-suspension-body.
Technical Paper

Numeric Study on Torsional Characteristics of Dual Mass Flywheel with Circumferential ARC Spring

2019-04-02
2019-01-0934
The rapid development of automotive technology has promoted the application of higher efficiency engines, while also putting higher requirements on the control of crankshaft torsional vibration. The traditional clutch driven disc torsional vibration damper can no longer meet the current new vibration and noise reduction requirements. Under these circumstances adopting dual mass flywheel (DMF) could be an efficient measure to reduce powertrain torsional fluctuations. For the sake of studying the torsional characteristics of DMF, a dual mass flywheel with circumstance arc spring (DMF-CS) is taken as the research subject. Firstly, According to lumped mass model, a multi-degree of freedom torsional vibration model of DMF-CS is established, which takes the mutual conversion of dry friction and viscous friction into consideration. Then, the overall and partial torsion characteristics of dual mass flywheel are obtained through numerical analysis.
Technical Paper

Optimization of the Finite Hybrid Piezoelectric Phononic Crystal Beam for the Low-Frequency Vibration Attenuation

2020-04-14
2020-01-0913
This paper presents a theoretical study of a finite hybrid piezoelectric phononic crystal (PC) beam with shunting circuits. The vibration transmissibility method (TM) is developed for the finite system. The uniform and non-uniform configurations of the resonators, piezoelectric patches and shunting circuits are respectively considered. The properties of the vibration attenuation of the hybrid PC beam undergoing bending vibration are investigated and quantified. It is shown that the proper relaxation of the periodicity of the PC is conducive to forming a broad vibration attenuation region. The hybrid piezoelectric PC combines the purely mechanical PC with the piezoelectric PC and provides more tunable mechanisms for the target band-gap. Taking the structural and circuit parameters into account, the design of experiments (DOE) method and the multi-objective genetic optimization method are employed to improve the vibration attenuation and meet the lightweight demand of the attachments.
Technical Paper

Active and Passive Control of Torsional Vibration in Vehicle Hybrid Powertrain System

2020-04-14
2020-01-0408
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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