近日，奧迪（Audi）公司發(fā)布了全新款A(yù)8旗艦款車型，該車最大的特點(diǎn)是可完全調(diào)控的機(jī)電混合懸掛系統(tǒng)。汽車的前置攝像頭會探測路況的各種變化，然后指示主動懸掛系統(tǒng)提前做出反應(yīng)，以適應(yīng)最新路況。每個輪子都配有一臺電機(jī)，由48-V的主電力系統(tǒng)提供能源。懸掛的其他部件還包括傳動輪、一根內(nèi)置鈦金屬扭力桿的旋管（rotary tube），和一根通過連接桿操控高達(dá)1100牛頓·米（811磅·英尺）力矩的控制桿。為此，SAE在英國記者Ian Adcock采訪到了負(fù)責(zé)奧迪A8可變懸掛的懸掛系統(tǒng)研發(fā)部門主管Thomas Muller，并帶來了這篇獨(dú)家專題報道。
SAE：在這一懸掛新技術(shù)問世后，用戶將從中獲益什么？
Thomas: 48V電動力引進(jìn)后，其他很多新技術(shù)也隨之而來，像電動增壓器，或是這款機(jī)電混合可變懸掛系統(tǒng)等。這一懸掛系統(tǒng)不必采用液壓技術(shù)來輔助空氣懸掛系統(tǒng)的運(yùn)作、支撐車體，就可使每個車輪都可以分別上下微調(diào)。
這一懸掛同時提升了車輛的乘員舒適度、動力性能以及安全性。我們把底盤這一“大腦”放在一個模塊中進(jìn)行重點(diǎn)研究，而在另一控制模塊里，則包括了空氣懸掛的信號測定和演算、減震控制、四輪驅(qū)動下的后差速器，以及奧迪的主動集成轉(zhuǎn)向系統(tǒng)（active integrated steering system）。如果你想在車?yán)镒檬娣?，這一模塊就相當(dāng)重要。
奧迪的主動轉(zhuǎn)向系統(tǒng)（active steering）也是一大突破，將轉(zhuǎn)向齒條、動態(tài)轉(zhuǎn)向桿和后橋轉(zhuǎn)向系統(tǒng)整合到同一系統(tǒng)內(nèi)。同可變懸掛一樣，我們相信這一技術(shù)也將帶來很多駕駛的樂趣。
SAE：所以說這套動態(tài)的全輪轉(zhuǎn)向系統(tǒng)也是一項(xiàng)新成果嗎？
Thomas: 不錯。這一系統(tǒng)讓A8的過彎半徑縮短到了37.4英尺（11.4米），甚至比A4的38英尺（11.6米）都要短，使汽車在繁忙的都市交通中更顯游刃有余。為達(dá)成這一目標(biāo)，我們把后輪的轉(zhuǎn)向調(diào)整了5度，這個數(shù)字是其它所有競爭對手的兩倍。再加上主動懸掛技術(shù)，這輛車開起來會讓人感覺既舒適，又容易操控——比如汽車變道時，汽車的俯仰振動與翻滾振動明顯減少。
全輪驅(qū)動改變了之前的后輪必須進(jìn)一步向后旋轉(zhuǎn)才能減少后排乘客頭部橫向移動幅度的觀點(diǎn)。而有了可變懸掛后，后排乘客將會感覺更舒適。
SAE：主動懸掛系統(tǒng)是如何操控的？
Thomas: 駕駛員輔助系統(tǒng)配有Mobileye單目攝像機(jī)，我們用它獲取路面的縱向信息，分辨率為1.2到6英寸（約3到16厘米），然后系統(tǒng)會指示底盤控制器，調(diào)高或降低懸掛，以應(yīng)對即將到來的各種路況變化，如：路面車輛減速帶或路面坑洼等。
在過彎G力很大時，主動懸掛系統(tǒng)可以使車身側(cè)傾減半，否則車內(nèi)乘員就會有很明顯的感覺。正是這種主動式動態(tài)系統(tǒng)的采用，使車輛具備了更高的敏捷性和更好的平衡效果，過去即使是在A8這樣的高端車型上，也無法體驗(yàn)到這種效果。這一系統(tǒng)還和車上的預(yù)警式側(cè)向傳感器相連，對側(cè)面沖擊造成的車身高度忽然升高做出及時反應(yīng)，使車輛在發(fā)生碰撞時，由車窗框吸收沖撞能量，而非車門。這樣可以使沖擊力減少至一半。
SAE：這一系統(tǒng)的反應(yīng)速度有多快？相關(guān)的能量和力有哪集中？
Thomas: 如果看車輪層面的受力，前輪有3.7千牛（832磅力），后輪3.3千牛（742磅力）。不過最重要的一個數(shù)據(jù)則是每秒每個輪子都可能承受16千牛（3597磅力）的梯度變化。這個力對單個車輪而言非常大，而結(jié)合0到6赫茲的信號帶寬，意味著每15毫秒就可實(shí)現(xiàn)一次產(chǎn)生減震方面的調(diào)整。
這個系統(tǒng)同時也很高效。當(dāng)沒有任何能耗時，默認(rèn)設(shè)置會調(diào)到空氣懸掛系統(tǒng)上；只有當(dāng)需要進(jìn)行懸掛調(diào)整時，力才會產(chǎn)生。研究表明，在城市駕駛環(huán)境中，系統(tǒng)能耗為40到60瓦，在高速公路上則更少，只有10到20瓦，而當(dāng)遇到路面不平時，能耗為250瓦。即使是在德國紐博格林賽道（Nürburgring），單圈耗能也只有400瓦。這方面的計量并不容易，但這一可變系統(tǒng)的效率應(yīng)該是液壓系統(tǒng)的兩到三倍，且梯度更大，帶寬更高。
SAE：這一系統(tǒng)是如何安裝的呢？
Thomas: 汽車四個角上各有一臺2千瓦的電機(jī)，通過皮帶和OvaloStrain Wave傳動輪相連。傳動輪的傳動比很高，為1:80，通過扭力軸和扭力桿連接到轉(zhuǎn)向節(jié)。后輪的情況有所不同，因?yàn)楹筝啛o法通過與差速器相連的萬向軸。另外，車的前后部都還有功率為48-V的發(fā)動機(jī)控制單元（ECU），分別和底盤中央控制器相連。
每隔5毫秒，系統(tǒng)生成的信息就會以圖片形式顯示出路況，并指示如何控制底盤動態(tài)起動機(jī)構(gòu)。ADAS系統(tǒng)的前向攝像頭（鏡頭與行駛方向相同）可以解讀車輛前方16到65英尺（5到20米）的道路表面數(shù)據(jù)，然后底盤控制器ECU會對這些數(shù)據(jù)進(jìn)行分析，再根據(jù)前方道路表面的情況對懸掛系統(tǒng)進(jìn)行預(yù)設(shè)。不過即便沒有攝像頭，整套系統(tǒng)也能運(yùn)轉(zhuǎn)良好。
SAE：這一技術(shù)運(yùn)用到其他奧迪車型的前景如何？
Thomas: 目前，我們討論的都是新款A(yù)8的情況。不過我覺得這一主動懸掛系統(tǒng)前景一片光明，尤其是在手動駕駛以及“輔助”駕駛的情況下。如果一輛車行駛中沒有橫向和縱向力，乘員就可以舒服地工作或休息，感覺就像是在一輛高速列車上，這顯然是極大的優(yōu)勢。
駕駛的樂趣一直是用戶想要的，而舒適感和競速體驗(yàn)，并非魚與熊掌不可兼得。讓你從繁忙的道路行駛中得到解脫，這正是我們的與眾不同之處。
SAE：駕駛員可選的設(shè)置有哪些？
Thomas: 奧迪駕駛模式選項(xiàng)（Audi Drive Select）提供了三種設(shè)置選項(xiàng)——“舒適”、“自動”和“活力”，分別對應(yīng)對可變懸掛、全輪轉(zhuǎn)向和四輪驅(qū)動的設(shè)置。
SAE：奧迪在技術(shù)上的合作伙伴是誰？
Thomas: 奧迪沒有特定的技術(shù)供應(yīng)商。研發(fā)前的工作和概念設(shè)想都是由奧迪內(nèi)部人員完成的，我們也會維護(hù)這個階段的知識產(chǎn)權(quán)。之后我們會把工作拆分，找到各環(huán)節(jié)合適的供應(yīng)商，一同合作。像Ovalo是轉(zhuǎn)彎模塊硬件的主要供應(yīng)商，大陸集團(tuán)（Continental）則負(fù)責(zé)電子硬件方面的供應(yīng)。
Audi recently unveiled its all-new A8 flagship which now features a fully active, electromechanical suspension system. A front camera detects road irregularities and signals a predictive adjustment of the active suspension to suit the road conditions. Each wheel is fitted with an electric motor powered by the 48-V main electrical system. Additional components include gears, a rotary tube together with internal titanium torsion bar and a lever which exerts up to 1100 N·m (811.3 lb·ft) on the suspension via a coupling rod. In an SAE exclusive, U.K.-based contributor Ian Adcock interviewed Thomas Muller, Audi's head of suspension development on the A8 active suspension.
Q: What are the benefits that customers will experience with this new suspension technology?
With the introduction of 48V it has enabled us to introduce new technologies like the e-Booster and, now, electro-mechanical active suspension with no hydraulics integrated into the system that complements the air-suspension which gives the freedom to raise and lower each wheel independently.
It’s about improving comfort and dynamics and safety. We centralize the chassis ‘brain’ into one module; the signal computing and calculations for the air suspension, damper control, quattro sport rear differential and Audi active integrated steering system are all fed into one control module which is essential if you want to have a smooth interaction with the car.
The Audi active steering is very innovative, integrating the steering rack, the dynamic steering column and the rear axle steering into one system. Together with the active suspension we believe this will deliver a lot of driving pleasure.
Q: The dynamic all-wheel steering system is a new development as well?
Yes. It reduces the A8’s turning circle to less than that of an A4, 38 ft (11.6 m) compared to 37.4 ft (11.4 m), making it easy to maneuver in tight urban confines. We achieve that by turning the rear steering by 5° which is twice that of any rival. Combine that with the active suspension and you have a car that is both very comfortable and maneuverable during lane changing, for example, reducing pitch and roll.
The all-wheel steering shifts the point of rotation further back reducing the rear seat passengers lateral head movement, resulting in a more composed ride when combined with the active suspension.
Q: How is the active suspension system controlled?
We use a Mobileye mono camera from the driver assistance system that generates the vertical information from the road with a resolution of 1.2 to 6 in (3 to 16 cm), signaling to the chassis controller to raise or lower the suspension accordingly when countering upcoming imperfections such as sleeping policemen or pot holes.
Once you get into higher G-forces under cornering, body roll is halved; otherwise it feels very artificial. It’s the combination of the active dynamic systems that result in a level of agility and balance you wouldn’t expect from a luxury sedan like the A8. It is also linked into pre-sense side sensors for side impacts instantly raising the body height, so the sill takes the collision and not the door, reducing the impact by up to 50%.
Q: How fast is the system’s reaction time and what sort of energy and forces are involved?
The forces that we have at wheel level are 3.7 kN (832 lbf) front and 3.3 kN (742 lbf) rear. But the really important figures is that we have a gradient at each wheel of 16 kN (3597 lbf) per second. This is a huge force we can apply at each wheel and, combined with the bandwidth of 0 to 6 Hz, means the damper is being altered every 15 ms.
It’s also an efficient system. Its default setting is on the air suspension system when no energy is consumed; force is only generated when active movement is required. Studies show that in a city environment it consumes 40-60 W, on highways it is even less, 10-20 W, rising to 250 W on rough roads. And even lapping the Nürburgring it’s only 400 W. It’s difficult to quantify but that’s two-to-three times more efficient than hydraulic systems with a higher gradient and bandwidth as well.
Q: How is it set up?
There are 2-kW electric motors at each corner, connected by belt to an Ovalo Strain Wave Gear, that delivers a very high transmission ratio of 1:80 transmitted through a torsion shaft and bar to a link into the steering knuckle. It’s different at the rear because it couldn’t go through the Cardan shaft connected to the differential. Additionally there are 48-V power ECUs front and back networked to the central chassis controller.
Information is generated every five milliseconds to create a picture of what is happening and what needs to be done in controlling the chassis dynamic actuators. Data from the road surface, restricted to 16–65 ft (5-20 m) ahead of the car, is read by the forward-facing ADAS camera and analyzed by the chassis controller ECU to preset the suspension ahead of encountering damaged road surfaces, although it works very well without the camera.
Q: What are the prospects of this technology appearing in other Audi products?
Currently we’re only talking about the new A8. But I think that active suspension will have a bright future, especially the combination of manual and what you might call ‘piloted’ driving. Providing a car that eliminates lateral and longitudinal forces so you can work or relax, like a high-speed train, is a huge benefit.
Driving pleasure is something our customers want: comfort or sporty, it’s not either-or. Allowing you to decouple yourself from the road is a big differentiator for us.
Q: How many driver settings are there?
We have three settings with Audi Drive Select, comfort, auto and dynamic that includes the active suspension, all-wheel dynamic settings and quattro sport.
Q: Who are your technology partners?
We don’t have one technology supplier; pre-development and concept phase was done internally and we keep the IP for that. Then we broke it down and generated a network of suppliers working with us. Ovalo is a main supplier for the corner module hardware and Continental for electronic hardware.
Author: Ian Adcock
Source: SAE Automotive Engineering Magazine
奧迪改用48-V電氣系統(tǒng)的舉措，被視為是邁向主動懸架之路的關(guān)鍵一步。圖為前懸架。
2018款奧迪A8的主動后懸架。
