汽車前沿技術(shù) | NVH前沿工程技術(shù)
“乘員不應(yīng)該聽到腳下的電池組和電驅(qū)動(dòng)系統(tǒng)運(yùn)行的聲音，而車外的噪音仍然需要感知到。”Saha斷言：“在某些時(shí)候，這些噪音將成為一項(xiàng)質(zhì)量問題。”
無論是方興未艾的電動(dòng)車，還是燃油發(fā)動(dòng)機(jī)車型，客戶對(duì)產(chǎn)品精致程度的期望從未降低。在內(nèi)燃機(jī)汽車中，大約50%的NVH問題與動(dòng)力系統(tǒng)有關(guān)。另一半主要由路噪和風(fēng)噪產(chǎn)生。在電動(dòng)汽車中，噪聲來源更加平衡；電力驅(qū)動(dòng)裝置（EDU）的噪聲是主要貢獻(xiàn)源，但中低速行使時(shí)的路噪和高速路上的風(fēng)噪“往往占主導(dǎo)地位”，F(xiàn)EV的動(dòng)力系統(tǒng)、電動(dòng)出行和整車產(chǎn)品高級(jí)副總裁Kiran Govindswamy解釋道。
他說：“看待這個(gè)問題的一種角度是，牽引電機(jī)或齒輪傳動(dòng)系統(tǒng)發(fā)出的噪音如果被客戶在車內(nèi)聽到了，那就是問題。路噪和風(fēng)噪可以在一定程度上掩蓋來自EDU(傳動(dòng)系統(tǒng))的噪聲。能被掩蓋自然是好的，但你能寄希望于非常糟糕的[路噪和風(fēng)噪]來掩蓋系統(tǒng)噪聲，畢竟路噪或風(fēng)噪太大，也容易讓客戶覺得這根本不是一輛精致的汽車。”
不斷發(fā)展的仿真試驗(yàn)
Govindswamy指出，更精致的高端電動(dòng)車通常在減少進(jìn)入座艙內(nèi)的路噪和風(fēng)噪方面“做得非常好”，但有時(shí)也是以暴露高轉(zhuǎn)速電機(jī)和齒輪系統(tǒng)的高頻噪音為代價(jià)的。動(dòng)力逆變器也會(huì)表現(xiàn)出10,000赫茲范圍內(nèi)的高頻噪聲。
EDU噪聲有三個(gè)主要來源：包括來自電機(jī)本身的電磁噪聲，它從設(shè)備的外殼上輻射出來；齒輪傳動(dòng)系統(tǒng)噪聲；以及來自軸承、流場(chǎng)和旋轉(zhuǎn)系統(tǒng)運(yùn)行時(shí)的整體機(jī)械噪聲。對(duì)NVH工程師來說，定義噪聲源、傳輸路徑以及確定可接受的水平，幾乎是一個(gè)臨床診斷過程。例如，F(xiàn)EV公司采用了基于仿真的流程來開發(fā)EDU，從而滿足客戶的聲學(xué)目標(biāo)。
“我們使用所謂的‘多體系統(tǒng)仿真’（對(duì)相互關(guān)聯(lián)的多個(gè)運(yùn)動(dòng)部件如何相互作用的動(dòng)態(tài)系統(tǒng)級(jí)分析）和有限元分析的組合，考慮了電磁力以及齒輪傳動(dòng)系統(tǒng)的作用力，從而可預(yù)測(cè)出噪聲水平。FEV正在不斷改進(jìn)其預(yù)測(cè)結(jié)果的置信度和準(zhǔn)確性，以確保能滿足客戶的目標(biāo)。”Govindswamy說：“當(dāng)我們導(dǎo)入第一個(gè)原型進(jìn)入測(cè)試單元時(shí)，我們發(fā)現(xiàn)離我們需要達(dá)到的目標(biāo)并不遙遠(yuǎn)。”
專家斷言，仿真試驗(yàn)正在不斷改進(jìn)，但在關(guān)聯(lián)性方面仍有許多工作要做。“我們卻非常依賴仿真分析，但我認(rèn)為許多新公司（汽車初創(chuàng)公司）有些過于信賴仿真結(jié)果。”Saha認(rèn)為：“他們?cè)陂_發(fā)到較晚階段時(shí)才驗(yàn)證仿真結(jié)果，或者他們的仿真預(yù)測(cè)可能不完全正確。我們已經(jīng)看到了根據(jù)測(cè)量結(jié)果來反調(diào)預(yù)測(cè)的例子。我無法理解他們是如何達(dá)到目標(biāo)的。”
他指出，雖然那些正在進(jìn)入電動(dòng)車領(lǐng)域的傳統(tǒng)主機(jī)廠也在使用預(yù)測(cè)性仿真模擬，但“他們有更強(qiáng)大的測(cè)量經(jīng)驗(yàn)背景”，并在開發(fā)過程中能更早地驗(yàn)證他們的預(yù)測(cè)。
輕量化設(shè)計(jì)和仿真
電動(dòng)卡車、大型公共設(shè)施和高性能電動(dòng)車中的鋰離子電池組有著驚人的載荷，這就需要車身工程師用輕量化材料方案來抵消這些重量，在某些情況下，這也導(dǎo)致了座艙層面的NVH問題。
“為了實(shí)現(xiàn)輕量化設(shè)計(jì)，我們看到鋼材和其他金屬被聚合物材料所取代，屏障解耦器被耗散系統(tǒng)所取代。”Saha指出：“更輕的車身面板帶來了振動(dòng)聲學(xué)相關(guān)問題。乘客希望有一個(gè)更安靜的座艙，而工程團(tuán)隊(duì)則專注于質(zhì)量(重量)效率。這就把新型和不同類型的輕質(zhì)阻尼材料和其他技術(shù)帶入了研發(fā)階段。”
盡可能減少額外的NVH處理裝置和聲學(xué)包的質(zhì)量是一個(gè)重點(diǎn)。“這又回到了從源頭上減少噪聲的重要性。”Govindswamy說：“大量的仿真工作正在進(jìn)行中，這是一個(gè)挑戰(zhàn)。但這也教會(huì)了工程師們能更有效地使用更輕的聲學(xué)材料。”
與汽車開發(fā)的所有領(lǐng)域一樣，仿真試驗(yàn)越來越成為緩解NVH噪聲的組成部分。“我把它看作是一個(gè)金字塔，頂端是目標(biāo)定義簽字，下面是大量的具體工作，以實(shí)現(xiàn)定義目標(biāo)。”VI-grade公司產(chǎn)品管理高級(jí)主管Dave Bogema說。該公司是NVH和車輛動(dòng)力學(xué)工作的仿真工具制造商。NVH分析從桌面開始，工程師們使用最新的、功能越來越強(qiáng)的分析軟件快速處理各種想法并剔除那些不可行的想法。下一步是主觀評(píng)價(jià)，如果想讓決策具有很高的置信度，就必須真正體驗(yàn)一下NVH狀態(tài)。
“你可以從電腦界面上得到一定程度的答案。”Bogema說：“但電腦仿真并不能提供在物理模擬器上體驗(yàn)虛擬原型所帶來的沉浸感和現(xiàn)實(shí)感的全部好處。”
由于物理領(lǐng)域的多樣性和這些領(lǐng)域之間復(fù)雜的相互作用，預(yù)測(cè)由電機(jī)產(chǎn)生的聲學(xué)噪音和振動(dòng)是具有挑戰(zhàn)性的。電磁學(xué)、熱力學(xué)和振動(dòng)聲學(xué)分析需要以耦合的方式對(duì)電機(jī)產(chǎn)生的聲學(xué)噪聲進(jìn)行精確預(yù)測(cè)。根據(jù)Ansys解決方案，準(zhǔn)確預(yù)測(cè)聲學(xué)噪聲有四個(gè)基本要素：需要一個(gè)高保真仿真解決方案來說明所有涉及的物理學(xué)科；一個(gè)耦合所有不同的物理學(xué)元素的平臺(tái)；為每個(gè)涉及的物理學(xué)參數(shù)設(shè)置和優(yōu)化的設(shè)計(jì)能力，以及加速模擬的高性能算力。
還有車輛動(dòng)力學(xué)，在許多方面與NVH密不可分，包括如何影響虛擬樣車的評(píng)估過程和乘員對(duì)車輛精良性的感知等。物理仿真工具也在擴(kuò)大，以滿足電動(dòng)車改進(jìn)的各個(gè)方面。
“當(dāng)你駕駛一輛車時(shí)，你能體會(huì)到周遭的一切。”VI-grade的Bogema說：“如果你在做乘坐舒適性評(píng)價(jià)，這是一種多感官的運(yùn)動(dòng)、振動(dòng)和聲音體驗(yàn)，把NVH和車輛動(dòng)力學(xué)結(jié)合在一起，可以提供很好的重復(fù)性和管控力，這對(duì)提高整體置信度來說至關(guān)重要。”他的公司最近在2023年SAE噪聲和振動(dòng)會(huì)議上推出了新的緊湊型全頻譜模擬器（FSS）。緊湊型FSS能夠進(jìn)行0.5Hz到20kHz的模擬，同時(shí)提供主要和次要驅(qū)動(dòng)運(yùn)動(dòng)、振動(dòng)和異響。雖然不是傳統(tǒng)的六足式模擬器設(shè)計(jì)，但FSS的四條腿使它能夠準(zhǔn)確地再現(xiàn)，在坑洞、鵝卵石或任何其他表面行駛時(shí)發(fā)生的道路狀態(tài)。它的振動(dòng)器通過方向盤和座椅產(chǎn)生高頻振動(dòng)，此外還模擬有來自路面的運(yùn)動(dòng)。
VI-grade還提供了一個(gè)專用的緊湊型NVH駕駛模擬器，使工程師能夠準(zhǔn)確地調(diào)出汽車在NVH方面的感覺。它的座椅結(jié)構(gòu)允許嘗試一系列的虛擬座椅設(shè)計(jì)，而FSS需要改變座椅的物理形式。專用的NVH模擬器“可以立即改變座椅參數(shù)，感受座椅之間的差異”，Bogema指出。“他們是為不同的使用場(chǎng)景而設(shè)計(jì)的。”他說。FSS在很大程度上是針對(duì)乘坐舒適性課題的；而NVH版本則是為了精調(diào)設(shè)計(jì)的。
工程師們也意識(shí)到，他們可以在桌面軟件上進(jìn)行聲音設(shè)計(jì)，相應(yīng)地，模擬出不同的汽車聲效。振動(dòng)也是如此。“你真的需要在聲音設(shè)計(jì)中考慮到車輛的整體運(yùn)動(dòng)嗎？也許不是所有的時(shí)候。”Bogema說。
定制版NVH組件
提高車輛精良性的門檻并不是電動(dòng)汽車的專利。專家們說，電動(dòng)車和混合動(dòng)力車正在推動(dòng)新的設(shè)計(jì)和降低NVH的方法，包括那些仍然由內(nèi)燃發(fā)動(dòng)機(jī)汽車主導(dǎo)的產(chǎn)品領(lǐng)域。然而，他們也注意到，成本壓力會(huì)使復(fù)雜的設(shè)計(jì)變得難以銷售，除非其NVH性能十分出眾。
全球領(lǐng)先的汽車NVH解決方案供應(yīng)商Vibracoustic最近推出的用于空氣懸架供氣裝置（ASU）的新型可調(diào)支架就是一個(gè)注重NVH的例子。簡(jiǎn)單而復(fù)雜的新ASU，如附圖所示，具有一個(gè)塑料底座（以前是鋼），以改善阻尼性能，以及波紋管式橡膠襯套和防撞塊。襯套的特殊材料特性恰好滿足了所需的剛度水平，同時(shí)也對(duì)壓縮機(jī)產(chǎn)生的徑向和軸向振動(dòng)提供避震。
據(jù)Vibracoustic稱，新的安裝支架比傳統(tǒng)支架更輕、更堅(jiān)固，并能在各個(gè)方向上就NVH性能進(jìn)行調(diào)整，這是通常用于此類應(yīng)用的螺旋彈簧所無法做到的。此外，波紋管式襯套設(shè)計(jì)允許在低應(yīng)變水平上實(shí)現(xiàn)高位移，重現(xiàn)了彈簧的性能。該公司工程師稱，橡膠材料還有助于將共振峰值保持在合理的范圍內(nèi)，因?yàn)橄鹉z化合物表現(xiàn)出的動(dòng)態(tài)剛度峰值比螺旋彈簧低60%。
據(jù)FEV的Govindswamy介紹，未來電動(dòng)車NVH技術(shù)和工程的關(guān)鍵是取得一種平衡：在不降低車輛續(xù)航能力的情況下滿足客戶的精細(xì)化期望。“如果你能保證電動(dòng)馬達(dá)的效率并接受稍高的噪音，使其對(duì)客戶的影響最小化，這就是我們正在努力的挑戰(zhàn)，而這要?dú)w結(jié)為系統(tǒng)優(yōu)化。”
NVH軟件模擬解決方案
在幾十家提供NVH仿真軟件工具的供應(yīng)商中，有很多受SAE讀者歡迎的產(chǎn)品：
Actran
作為Hexagon AB的一部分，Actron是一種基于FE(有限元)的工具，用于對(duì)機(jī)械系統(tǒng)和部件的聲學(xué)行為進(jìn)行建模。其被廣泛用于解決中頻（400-1500Hz）范圍內(nèi)的NVH問題，這對(duì)電動(dòng)汽車設(shè)計(jì)至關(guān)重要。作為一個(gè)"開放"的工具，它利用現(xiàn)有的FE和CFD仿真模型，用于研究電動(dòng)汽車的傳動(dòng)和輔助系統(tǒng)（泵、壓縮機(jī)）噪聲源。例如，通用汽車工程師使用Actran來優(yōu)化凱迪拉克Lyric電動(dòng)車的噪音減震處理。
Altair
HyperWorks仿真套件包含廣泛的NVH建模、裝配、診斷、分析和優(yōu)化的解決方案。該套件的可定制NVH Director功能通過整合網(wǎng)格劃分、裝配、載荷設(shè)置和后處理的整個(gè)過程，使NVH分析的任務(wù)自動(dòng)化，以減少整車NVH仿真時(shí)間。
Ansys
在概念設(shè)計(jì)階段的快速NVH工作流程中可比較不同電動(dòng)馬達(dá)設(shè)計(jì)/拓?fù)浣Y(jié)構(gòu)的噪聲水平，以預(yù)測(cè)全速掃描的噪聲。它可以在早期確定電機(jī)噪聲的起因，并幫助在與其他電機(jī)性能目標(biāo)的權(quán)衡中做出相關(guān)的設(shè)計(jì)改變，使NVH、熱和電磁表現(xiàn)同時(shí)得到研究。NVH工作流程集成到了Ansys Motor-CAD中，為設(shè)計(jì)者提供各種力、位移和聲功率的表示方法。然后可以在Ansys Maxwell中生成2D和3D模型，并在Ansys Mechanical中進(jìn)行振動(dòng)聲學(xué)分析。
AVL
X-FEM NVH是一個(gè)4通道采集模塊，適用于所有常見的聲學(xué)傳感器輸出類型，如電壓、電荷和ICP/IEPE。每個(gè)通道可以單獨(dú)配置，原始信號(hào)以高分辨率和時(shí)間同步的格式存儲(chǔ)于壓縮文件中。AVL IndiCom或AVL Concerto的可選NVH工具箱包括最常用的NVH分析工具和在線NVH宏。
Brüel & Kj?r
Desktop NVH、SimSound、Source Path Contribution和VSound使工程師能夠?yàn)槿魏闻渲玫能囕v設(shè)計(jì)和評(píng)估車內(nèi)和車外聲音。Insight+實(shí)現(xiàn)了NVH數(shù)據(jù)的全面體驗(yàn)，直接從CAE模型中創(chuàng)建聲音，NVH工程師可以聆聽體驗(yàn)。CAE模型數(shù)據(jù)可以與測(cè)試數(shù)據(jù)結(jié)合起來，創(chuàng)造一個(gè)身臨其境的真實(shí)環(huán)境。
Dassault
廣泛使用的標(biāo)志性的SIMULIA套件為NVH工作提供了全面的仿真工具集。
Dewesoft
在以NVH為重點(diǎn)的工具中，聲音質(zhì)量測(cè)量工具很好地解決了以往按經(jīng)驗(yàn)評(píng)估不同種類機(jī)器產(chǎn)生的聲音如何被人耳感知的工作。該工具可幫助工程師確定聲音是如何被感知的，并調(diào)校聲音，并使其更容易被客戶接受或更具吸引力。
Hexagon
該公司的Romax Spectrum能夠進(jìn)行機(jī)電動(dòng)力總成NVH仿真，并提供完整的、參數(shù)化的動(dòng)力總成全系統(tǒng)建模，包括齒輪和軸承接觸面。Romax套件提供與第三方CAE工具的接口，包括用于聲學(xué)的Actran; 用于多體仿真的Adams；用于電磁模擬的JMAG和Maxwell; 用于FE建模的Nastran；用于整車NVH和聲音質(zhì)量的VI-grade。
Siemens Digital Industries西門子的Simcenter套件會(huì)繼續(xù)增加NVH分析工具，這些工具受益于數(shù)字孿生法，可準(zhǔn)確預(yù)測(cè)車輛內(nèi)部和外部NVH性能。
Electrification brings new benchmarks, tools, and challenges to the ongoing battle with noise, vibration and harshness. NVH testing at FEV’s Auburn Hills, Michigan, tech center using HEAD Acoustics digital artificial head instruments. With two parallel analog-to-digital converters the HEAD units cover the entire audible dynamic range.
The complex science of analyzing and abating noise, vibration, and harshness has entered a “new frontier” as the industry transitions to electrified vehicles, experts in the NVH field tell SAE Media. New design and engineering challenges at the component, system, and full-vehicle levels continue to emerge as EV offerings expand beyond the initial wave of predominantly premium-spec products. Engineers note that benchmarking activity and the introduction of new analysis and testing tools related to NVH mitigation are at “crazy” levels.
“Our interest in acoustically improved vehicles always is going to accelerate and the NVH technology must always meet customer expectations,” observed Pranab Saha, whose company Kolana & Saha Engineers specializes in acoustics, noise and vibration analysis and testing. He noted that some of the latest EV designs show progress in attacking both NVH sources and their propagation paths. There is less reliance on “patch” materials —urethane foams deployed in body cavities and mastics baked into underbody areas that add mass, cost and complexity. But Saha and other experts do not believe those so-called “Band-Aid”sound dampers will be eliminated entirely.
“Occupants should not hear anything going on underneath them in the battery pack and electric drive system, while outside the vehicle noise remains,” Saha asserted. “At some point, those noises are going to become a quality issue.”
Customer expectations of refinement in EVs versus the incumbent IC-engine vehicles are still evolving. In ICE vehicles, about 50% of NVH issues are related to the powertrain. The other half are generated mainly by road and wind noise. In EVs, the noise sources are more balanced; the electric drive unit (EDU) noise is important but road noise at low- to mid- speeds and wind noise at high speeds “tend to dominate,” explained Kiran Govindswamy, senior VP - Drivetrain, e-Mobility and Vehicle, at FEV.
“One way to look at this is, noise coming from the traction motor or geartrain is only important if the customer hears it in the vehicle,” he said. “Sufficient road and wind noise can, to an extent, mask the noise coming from the EDU. This might be beneficial, but you don’t want it [road and wind noise] to be so bad that the customer feels it’s not a refined vehicle at all.”
Evolving simulation
Govindswamy noted that higher-end EVs that are more refined typically “do a very good job” at reducing the road and wind noise entering the cabin—but sometimes at the expense of exposing the higher-frequency whine of the high-rpm electric machine and geartrain. Power inverters also exhibit high-frequency noise in the range of 10,000 Hz.
Three main sources of EDU noise include electromagnetic noise from the motor itself that radiates off the unit’s housing; geartrain noise, and overall mechanical noise from bearings, fluids and rotating systems. Defining the noise sources, their transmission paths, and establishing acceptable levels, is almost a clinical process for NVH engineers. FEV, for example, employs simulation-based processes that develop EDUs to meet customer acoustic targets.
“We use a combination of what we call ‘multibody systems simulation’ [a dynamic system-level analysis of how interconnected multiple moving parts interact with each other] and finite-element analysis, which consider the electromagnetic forces as well as the geartrain forces, then predicts what the noise levels are.” FEV is continuously improving the fidelity and accuracy of its predictions to ensure it can meet customer targets. “When we come into the test cell with the first prototype, we’re not too far off from where we need to be,” Govindswamy said.
Simulation is evolving and continues to improve, but it’s still a work in progress in terms of correlation, experts assert. “We rely a lot on simulation, but I think many new companies [automotive start-ups] rely on it too much,” Saha opined. “They’re not verifying the simulated results until very late in development, or their simulation predictions may not be totally correct. We’ve seen examples of predictions being adjusted based on what the measurements were telling. I can’t understand how they get to their target.”
He noted that while the established OEMs who are moving into EVs also are using predictive sim, “they have a much stronger measurement background” and verify their predictions much sooner in the development process.
Lightweighting and Simulation
The alarming mass of lithium-ion battery packs in electric trucks, large utilities and high-performance EVs has led body engineers to offset that weight with lightweighting material solutions that, in some cases, have caused NVH issues at the cabin level.
“In the interest of lightweighting we’re seeing steel and other metals being replaced by polymeric materials, and barrier decouplers being replaced by dissipative systems,” noted Saha. “There are vibracoustic issues associated with lighter weight body panels. Passengers want a quieter cabin, while the engineering team is focused on mass efficiency. This is bringing new and different types of lightweight damping materials and other technologies into the picture.”
Reducing the mass of all the additional NVH treatments and acoustic packages is a related focus. “This comes back to the importance of reducing noise at the source,” said Govindswamy. “A lot of simulation work is going into that, and it’s a challenge. But it’s also teaching engineers to use lighter weight acoustical materials more efficiently.”
As with all areas of vehicle development, simulation is increasingly integral to NVH mitigation. “I see it as a pyramid with the sign-off at the top tip and an immense amount of work that goes on underneath it to get to the sign-off point,” observed Dave Bogema, senior director of product management at VI-grade, maker of simulation tools for NVH and vehicle dynamics work. NVH analysis begins at the desktop where engineers using the latest, increasingly capable analysis software rapidly work through various ideas and wee d out those that are unfeasible (see sidebar). The next step is subjective evaluation, where NVH really must be experienced if decisions are to be made with confidence.
“You can get a certain level of answers from the desktop,”Bogema said. “But desktop simulation doesn’t have the full benefit of immersion and reality that experiencing virtual prototypes on physical simulators delivers.”
Predicting acoustic noise and vibration generated by electric machines is challenging due to the variety of physical domains and complex interactions among these domains. Electromagnetics, thermodynamics, and vibro-acoustic analyses are required in a coupled fashion for a precise prediction of acoustic noise generated by electric machines. According to Ansys Solutions, there are four essential elements for accurately predicting acoustic noise: need for a high-fidelity simulation solution to account for all the physics involved; a platform to couple all the different physics elements; ability to parameterize and optimize machine design parameters for each of the physics involved, and high-performance computing capability to accelerate the simulation.
There’s also vehicle dynamics, in many ways inseparable from NVH including how they influence the virtual-prototype evaluation process and the occupant’s perception of vehicle refinement. Physical simulation tools are expanding to meet the many facets of EV refinement.
“When you drive a vehicle, you feel everything at the same time,” VI-grade’s Bogema said. “If you’re doing ride comfort, which is a multi-sensory motion, vibration, and sound experience, putting NVH and vehicle dynamics together delivers the repeatability and control that are vital to overall fidelity.” His company recently launched its new Compact Full-Spectrum Simulator (FSS) at the 2023 SAE Noise and Vibration Conference. Capable of simulations from 0.5Hz to 20kHz, the Compact FSS delivers both primary and secondary driving motion, vibration, and sound, simultaneously. While not a traditional hexapod-type simulator design, the FSS’s four legs enable it to accurately replicate the motion of the road as generated when driving over potholes, cobblestones, or any other surface. Its vibration shakers produce high-frequency vibration through the steering wheel and the seat, in addition to the motion from the road.
VI-grade also offers a dedicated Compact NVH driving simulator that allows engineers to dial in exactly what the car is going to feel like for NVH. Its seat structure allows an array of virtual seat designs to be tried, where the FSS requires a physical seat change. The dedicated NVH simulator “can instantly change the seat parameters and feel the difference between seats,”Bogema noted. “They’re designed for different use cases,” he said—the FSS is very much aimed at ride comfort; the NVH version is for dialing in refinement.”
Engineers also are realizing they can do sound design at the desktop, interactively, and come up with different soundscapes for the car. Vibration plays into that. “Do you really need the whole motion of the car in the sound design? Maybe not all the time,” Bogema said.
Bespoke NVH Components
Raising the thresholds of vehicle refinement is not exclusive to EVs. Experts say EVs and hybrids are driving new designs and NVH-reduction approaches across product segments including those still dominated by IC-engine vehicles. They note, however, that cost pressures can make sophisticated designs a tough sell unless their NVH performance is exceptional.
An example of a new NVH-focused component is a new tunable bracket for air suspension air-supply units (ASU) recently launched by Vibracoustic, a leading global automotive NVH solutions supplier. The simple yet sophisticated new ASU, shown in the accompanying image, features a plastic base (previously steel) for improved damping, and bellow-style rubber bushings and bump stops. The bushings’ special material properties give the required stiffness levels while also damping both radial and axial excitations generated by the compressor.
The new mounting bracket is lighter and more robust than traditional brackets, according to Vibracoustic, and enables NVH tuning in all directions—something not possible with coil springs typically used in such applications, the company claims. Additionally, the bellow-type bushing design allows for high displacement at low strain levels, replicating the performance of springs. The rubber material also helps maintain resonance peaks within a reasonable range, because the rubber compound demonstrates a dynamic stiffness peak that is up to 60% lower than of a coil spring, company engineers claim.
The key to NVH science and engineering in EVs going forward, according to Govindswamy at FEV, is striking a balance: meeting customer refinement expectations without degrading vehicle range. “If you can secure the electric motor’s efficiency and accept a slightly higher noise but improve the traditional vehicle to minimize the effect to the customer—that’s the challenge we’re working on. And it comes down to systems optimization.”
NVH software simulation solutions
Among dozens of suppliers offering NVH simulation software tools are these popular products used by SAE readers:
Actran
Part of Hexagon AB (see below), Actron is an FE-based tool for modeling acoustic behavior of mechanical systems and components. It is widely used to solve NVH problems in the mid-frequency (400-1500Hz) range that are critical for EV design. An ‘open’tool, it leverages existing FE and CFD sim models and is used to study EV transmission and ancillary (pumps, compressors) noise sources. GM engineers used Actran to optimize noise-damping treatments in the Cadillac Lyric EV.
Altair
The HyperWorks simulation suite contains a broad range of solutions for NVH model build, assembly, diagnostics, analysis and optimization. The suite’s customizable NVH Director automates the tasks involved in NVH analysis by integrating the entire process of meshing, assembly, loadcase setup, and post-processing, to reduce full-vehicle NVH simulation time.
Ansys
Rapid NVH workflow for the concept design stage compares noise levels for different e-motor designs/topologies to predict the noise over a full speed sweep. It can identify the cause of motor noise early on and help make relevant design changes in trade-off with other motor performance targets, allowing the NVH, thermal, and electromagnetic behavior to be investigated at the same time. The NVH workflow is integrated into Ansys Motor-CAD to provide designers with various representations of force, displacement, and acoustic power. 2D and 3D models can then be generated in Ansys Maxwell and vibroacoustic analysis performed in Ansys Mechanical.
AVL
The X-FEM NVH is a 4-channel acquisition module suitable for use with all common acoustic sensor output types such as voltage, charge and ICP/IEPE. Each channel can be individually configured and raw signals are stored in a compressed file at high resolution and in time-synchronized formats. An optional NVH TOOLBOX for AVL IndiCom or AVL Concerto includes the most common NVH analysis tools and online NVH macros.
Brüel & Kj?r
Desktop NVH, SimSound, Source Path Contribution, and VSound allow engineers to design and evaluate interior and exterior vehicle sounds for vehicles of any configuration. Insight+ enables the total experience of NVH data – creating sounds directly from CAE models that NVH engineers can listen to and experience. The CAE model data can be combined with test data to create an immersive, realistic environment.
Dassault
The widely used, iconic SIMULIA suite offers a comprehensive simulation toolset for NVH work.
Dewesoft
Among the NVH-focused tools is Sound Quality Measurement, which addresses the need to empirically evaluate how sound produced by different kinds of machines is perceived by the human ear. The tool helps engineers determine how the sound is perceived, tune the sound, and make it appealing to the customer.
Hexagon
The company’s Romax Spectrum enables electro-mechanical powertrain NVH simulation and offers complete, parametric whole-system modelling of the powertrain including gear and bearing contact surfaces. The Romax suite offers interfaces to third-party CAE tools, including Actran for acoustics: Adams for multibody sim; JMAG and Maxwell for electromagnetic simulation Nastran for FE modeling, and VI-grade for vehicle NVH and sound quality.
Siemens Digital Industries
Siemens’ Simcenter suite continues to add NVH analysis tools that benefit from the digital twin approach to accurately predicting vehicle interior and exterior NVH performance.
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