The advent of digital computers and the availability of ever cheaper and faster micro processors have brought a tremendous amount of control system applications to the automotive industry in the last two decades. From engine and transmission systems, to virtually all chassis subsystems (brakes, suspensions, and steering), some level of computer control is present. Control systems theory is also being applied to comfort systems such as climate control and safety systems such as cruise control or collision mitigation systems.
Statistical Energy Analysis (SEA) is widely used for modeling the vibro-acoustic response of large and complex structures. SEA makes simulations practical thanks to its intrinsic statistical approach and the lower computational cost compared to FE-based techniques. However, SEA still requires underlying models for subsystems and junctions to compute the SEA coefficients which appear in the power balance equations of the coupled system. Classically, such models are based on simplified descriptions of the structures to allow analytical or semi-analytical developments. To overcome this limitation, the authors have proposed a general approach to SEA which only requires the knowledge of impedances of the structures to compute SEA coefficients. Such impedances can always be computed from an accurate FE model of each component of a coupled system.
Extremely uncomfortable levels of bounce and pitch vibrations are produced when a CV moves over an uneven terrain, thereby causing a considerable amount of physical and mental stress to the crew. The present study was carried out to ascertain the vibrational response at the driver’s, commander’s and trooper’s seats. A 23 DOF lumped parameter 3-D model of a combined CV and human body was made. The vehicle had 15 DOF corresponding to bounce, pitch and roll of the hull (sprung mass) and bounce motions of the 12 wheel stations (unsprung masses) on either side. The human body was idealized as having 8 DOF corresponding to bounce motions of the pelvis, abdomen, diaphragm, thorax, torso, back and head. The seat was also assigned a bounce DOF. The lumped masses of the body parts were connected by springs, representing the elastic properties of the connective tissues.
Pass-by noise measurement is mandatory for automotive manufacturers for conformity of production. With evolving of pass-by noise requirements (under 68 dB in 2024), all the stakeholders should be able to comply with this criterion. OEMs, suppliers of passive acoustic treatments, road manufacturers and tire manufacturers are concerned and should deploy efforts to provide solutions for control of exterior noise. In this regard, simulations are preferable over measurement campaigns as they can provide fast feedback on passive exterior treatments for exterior noise control. In the particular case of Lightyear vehicles, the main contributors to pass-by noise are tyres and in-wheel motors. Considering that, a contribution of each of these two sources of noise to pass-by noise will be described. Tyre sources and motor sources will be replaced by simple monopole sources. The results of this simulation will be compared to the pass-by noise measurements.
Vehicle Acoustic Prototyping in the mid to high frequency range is challenging with numerical models only. To overcome this challenge, over the past decade, experimental techniques were developed that allow the engineer to incorporate Test-Based models in the simulation as well. Using Virtual Point Technology these Test-Based models serve well to describe, for example, the complex dynamics of the vehicle body / NTF. Here the high modal density and damping characteristics are simply measured on a mule or prototype vehicle and coupled using Dynamic Substructuring to cover the mid and high frequency ranges as well. As such accurate predictions and / or risk assessments can be made much earlier in the vehicle development stage. While test-based models serve well to describe the coupled vehicle dynamics, loads to compute actual vehicle responses are needed as well. Here so-called Equivalent or Blocked Forces are ideal as they are found to be independent of the vehicle dynamics.
Layered materials are one of the most commonly used acoustical treatments in the automotive industry, and have gained increased attention, especially owing to the popularity of electric vehicles. Here, a method to model and couple layered systems with various layer types (i.e., poro-elastic layers, solid-elastic layers, stiff panels, and fluid layers) is derived that makes it possible to stably predict their acoustical properties. In contrast with most existing methods, in which an equation system is constructed for the whole structure, the present method involves only the topmost layer and corresponding boundary conditions at two interfaces at a time, which are further simplified into an equivalent interface with a new group of boundary conditions. As a result, for a multi-layered system, the proposed method splits a complicated system into several smaller systems and so becomes computationally less expensive.
It is well known today that Biot parameters are the intrinsic material properties of porous media such as foams and fibers. They are to porous media what Young’s modulus is to steel panels. Once these Biot parameters are accurately known, one can trust that a predictive simulation model will yield the corresponding level of accuracy. But how accurate must these Biot parameters be to warrant a safe level of accuracy of the resulting simulation models. This paper analyzes various round-robin tests publications related to measurements of Biot parameters (acoustic and elastic) and uses the reproducibility of measured data from the numerous laboratories involved to evaluate the effect of the observed measured variability on simulation models accuracy when predicting transmission loss, surface absorption and actual SPL response inside a vehicle.
Simulation and testing are often done by different engineers in different departments of a company. This can lead to disconnects and unrealistic predictions, especially if the person doing simulations does not have an experimental background. On the other hand, experimental results can also include errors that result in misleading answers. It is important for the engineer doing either testing or simulation to have a feel for what results are plausible and what results might be suspect. This paper will provide examples where error crept into testing or simulation that could have been caught and corrected early if a good feel for “reasonable” results had been in place. The paper will also make the case for simulation engineers to be provided with some experimental background, so that they have a better physical understanding of the structures or components being simulated. The ideal case is where the same person is responsible for both simulation and experimental validation.
The technology of active sound generation (ASG) for automobiles is one of the most effective methods to flexibly achieve the sound design that meets the expectations of different user groups, and the active sound synthesis algorithms are crucial for the implementation of ASG. In this paper, the Kaiser window function-based the harmonic synthesis algorithm of automobile sound is proposed to achieve the extraction of the order sounds of target automobile. And, the suitable fitting functions are utilized to construct the mathematical model between the engine speed information and the amplitude of the different order sound. Then, a random phase correction algorithm is proposed to ensure the coherence of the synthesized sounds. Finally, the analysis of simulation results verifies that the established method of the extraction and synthesis of order sound can meet the requirements of target sound quality.
HVAC systems are of critical importance in ensuring passengers’ thermal comfort inside the car cabin as well as safety requirements for defogging functions. These systems involve various components and subcomponents as blowers, thermal exchangers, actuators… with a wide range of well-known technologies and also new ones on newly introduced products. Currently, within established electrification trends worldwide, the HVAC system is becoming the most important embedded system that can induce major contribution of noise and vibration. These NVH issues can emerge through different transfer paths inside the car cabin possibly causing significant discomfort to passengers. During developments, the NVH issues are mastered and contained by both suppliers according to internal standards and OEMs according to specifications compliance. However, OEMs specifications are mainly consisting of overall noise levels and improvements over the years consisting of reduction of these specified levels.
With a view to promote mobility electrification, improved comfort and handling with lower cost are crucial factors in next generation of EV and HEV design. In contrast to ICE platform, electrified counterparts displays distinct NVH characteristics that present challenges in terms of weight transfer, steering, motor vibrations, etc. From a holistic perspective, this paper proposes a semi active suspension system serving dual purpose of dynamic damping and power rejuvenation utilizing electric motor as part of the tuned mass damper inertia system. A variable inertance mechanism is developed in form of geartrain while motor vibration itself receives calculated harness through tuned mass damping. Furthermore, suspension deformation undergoes desirable mitigation as a result of effective simulated annealing optimization focused on shifting objective value according to input tradeoff prediction.
NVH (Noise, Vibration and Harshness) of the electric drive axle (EDA) is a key attribute in electric-vehicle development. The NVH level of the EDA directly determines the driving comfort and customer feeling of the vehicle. Especially in pure electric models, the EDA noise is more prominent without the engine noise masking. The paper aimed at the problem of the 380±50Hz resonance band on the commercial EDA and caused abnormal noise inside the vehicle. Adopted modal analysis, MASTA simulation, modulation noise analysis and exchange parts DOE, gradually refined the source of the problem to a single part, and finally locked to the source of gear parameters Rs and Fr. By adjusting the production process of gear and the second shaft, the assembly process error was avoided, and the gear parameter targets are formulated.
Pulse Width Modulation or PWM has been widely used in traction motor control for electric propulsion systems. The associated switching noise has become one of the major NVH concerns of electric vehicles (EV). This paper presents a multi-disciplinary study to analyze and validate current ripple induced switching noise for EV applications. First, the root cause of switching noise is identified as high frequency ripple components superimposed on the sinusoidal three-phase current waveforms, due to PWM switching. Measured phase currents correlate well with predicted current data using a semi-analytical hardware-in-the-loop (HIL) method. Next, the realistic ripple currents are utilized to predict the electro-magnetic dynamic forces at both the motor pole pass orders and the switching frequency plus its harmonics. Special care is taken to ensure sufficient time step resolution to capture the ripple forces at varying motor speed.
This paper describes idle vibration reduction methods using a Stellantis vehicle as a case study. The causes of idle vibration are investigated using the NVH source, path, and receiver method. The torque transfer path into a vehicle has shown to be very important in determining vehicle idle vibration response. New electronic control enablers that affect idle vibration are tested and discussed, including Neutral Idle Control (NIC), Transfer-case Idle Control (TIC,®), and Switchable Engine Mounts (SEM). The Design For Six Sigma (DFSS) analysis method is used to arrive at an optimized result for vehicle idle vibration. In addition, Stellantis has developed a new idle vibration control enabler known as Transfer-case Idle Control (TIC), which was awarded by the US patent Office and will be applied on future vehicles. This paper also discusses the results confirming TIC’s capability of reducing idle vibration on all-wheel drive vehicles.
Current and future EV’s contain significant amounts of complex electrical hardware, including rechargeable energy modules, control units, cooling systems and wiring situated inside the cabin usually below the carpet , seats or trunk trim and below the cabin floor. These items, whilst likely to have a direct impact on transmission loss, are increasingly difficult to evaluate via typical methods of computer based simulation. The packaging space allocated for control units which may require an air gap between the Body in white and the carpet for aspects of heat stabilization can be problematic. These gaps introduce complex noise transmission within the carpet which tend to exclude simulation using transfer matrix method (TMM) NVH lay-up models. Also in the case of battery installations their high bulk mass doesn’t necessarily transpire to a large expected increase in the floor systems transmission loss. The accurate prediction of these systems requires advanced modeling techniques.
Abstract: This paper describes the characteristics and advantages of a coaxial eBeam axle, and in particular, its NVH performance under various noise excitations including eMotor and the gearing system. The NVH CAE model of the eBeam axle is established, and structural vibration and noise radiation of the motor and gearbox are simulated and analysed. The results are used in the design optimization for NVH performance refinement. NVH validation test data is presented and compared with NVH simulation results, showing excellent correlation. Test data shows that the eBeam axle vibration and noise levels are well below the stringent targets.
As automotive industry experiences a significant change in terms of the dynamic behavior of vehicles and an increasing demand for rapid design of products, accurate prediction of product performances in the early stages has become even more vital in the competitive environment. Shim-stack-type hydraulic dampers are widely used in automotive parts for both internal combustion engine (ICE) vehicles and electric vehicles (EV), and EVs are even more sensitive to the damper performance as ICE, a major NVH source is removed. However, the industry still struggles to obtain accurate models of the dampers due to their highly nonlinear hydro-mechanical behaviors. Bleed slits for a shim-stack-type hydraulic damper play a key role in determining the blow-off characteristics of a damper, and, consequently, accurate prediction of the blow-off characteristics is crucial in evaluating the damping performance of a vehicle.
Abstract: As an important vibration damping element in automobile industries, the rubber mount can effectively reduce the vibration transmitted from the engine to the frame. The influence of preload on the static characteristics of rubber mounts and the identification of hyper-elastic material model coefficients were studied. Firstly, a test rig for stiffness test of a mount with preload was designed, and the influence of preload on the static force versus displacement of mounts was studied. Then, the model for estimating force versus displacement of rubber mounts was established, the response surface model for identifying coefficients was established, and the identification method for estimating constitute parameter of rubber materials was proposed the crow search algorithm.