大眾汽車公司“排放門(mén)”事件曝光后，美國(guó)環(huán)保署修改了相關(guān)的測(cè)試項(xiàng)目，而該事件給汽車制造商帶來(lái)的影響遠(yuǎn)遠(yuǎn)不止這些。
專家指出，傳動(dòng)系統(tǒng)的控制策略，包括利用售后市場(chǎng)設(shè)備來(lái)調(diào)整發(fā)動(dòng)機(jī)的思路，都將可能進(jìn)行修改。他們還希望歐美政府加強(qiáng)現(xiàn)有法規(guī)的執(zhí)行、嚴(yán)整排放測(cè)試協(xié)議、縮小實(shí)驗(yàn)室測(cè)試與路上測(cè)試之間的差距，并在新車型上市后抽樣檢查排放超標(biāo)的情況。
總而言之，在經(jīng)歷這場(chǎng)“排放門(mén)”之后，汽車行業(yè)的工程師們將在測(cè)試和驗(yàn)證方面受到更為嚴(yán)苛的監(jiān)督。
美國(guó)環(huán)保署表示大眾在功率計(jì)校驗(yàn)測(cè)試中使用違法的發(fā)動(dòng)機(jī)控制軟件來(lái)減少尾氣管柴油排放之后不久，就宣布即將實(shí)施道路測(cè)試。這也是美國(guó)環(huán)保署對(duì)大眾CEO辭職、調(diào)查啟動(dòng)、車主訴訟蜂擁而至、公司股價(jià)大跌等一系列連鎖事件做出的迅速回應(yīng)。
大眾事件近日甚囂塵上，但這不是歷史上第一起同類事件。1998年，美國(guó)環(huán)保署曾對(duì)7家重型柴油發(fā)動(dòng)機(jī)生產(chǎn)商開(kāi)出了11億美元的罰單，這是史上因違反環(huán)境法而作出的最嚴(yán)重處罰，因?yàn)樗麄冊(cè)诎l(fā)動(dòng)機(jī)控制器中了使用一種“致勝裝置”。當(dāng)年，這種軟件在130萬(wàn)輛卡車上更改燃油噴射正時(shí)裝置并提高燃油效率，同時(shí)非法地規(guī)避了排放控制設(shè)備的使用。
一些業(yè)內(nèi)人士透露，這種專為測(cè)試而開(kāi)發(fā)的控制圖，曾經(jīng)一度流行于柴油車和汽油車市場(chǎng)。包括福特、通用、本田在內(nèi)的整車廠都曾因作弊而受罰。
實(shí)況測(cè)試與實(shí)驗(yàn)室測(cè)試的比較：氮氧化物含量高出4倍
在測(cè)試與實(shí)際駕駛中使用不同的發(fā)動(dòng)機(jī)控制軟件的做法被稱作“雙圖法”。在排放測(cè)試中，發(fā)動(dòng)機(jī)運(yùn)行而方向盤(pán)不動(dòng)，專為測(cè)試而開(kāi)發(fā)的標(biāo)準(zhǔn)圖正是在這個(gè)時(shí)候使用的。
“90年代估計(jì)很多公司都干過(guò)類似的事，但大多數(shù)在90年代后期就停了，”一家不愿透露姓名的頂尖半導(dǎo)體公司的技術(shù)專家匿名評(píng)論道。與許多行業(yè)高層一樣，他非常猶豫是否在《汽車工程雜志》上公開(kāi)評(píng)論四面楚歌的大眾公司。
這位專家稱，目前的作弊主要集中于柴油機(jī)，“因?yàn)槟芸刂频膮?shù)更多了”。“柴油是一陣接一陣燃燒的，這將決定你怎樣管理機(jī)內(nèi)的元素，比如未燃燒的柴油在汽缸內(nèi)翻滾的狀態(tài)。管理不當(dāng)，你的柴油顆粒數(shù)量就會(huì)飆升。”
法規(guī)制定者發(fā)現(xiàn)，要對(duì)排放進(jìn)行綜合且持續(xù)的監(jiān)控實(shí)屬不易。美國(guó)在幾年前改善了測(cè)試，好讓實(shí)驗(yàn)室的測(cè)試條件接近于實(shí)況測(cè)試，但相對(duì)來(lái)說(shuō)，歐洲的測(cè)試要溫和不少。英國(guó)的道路排放測(cè)試公司EmissionsAnalytics的專家表示，歐洲柴油車的公路測(cè)試結(jié)果至今都與實(shí)驗(yàn)室結(jié)果相距甚遠(yuǎn)。
“在歐洲700輛車的實(shí)況測(cè)試中，我們發(fā)現(xiàn)氮氧化物的水平比政府測(cè)試標(biāo)準(zhǔn)高出4倍，二氧化碳高了31%左右，而燃油經(jīng)濟(jì)性低了24%，” Emissions Analytics的首席執(zhí)行官Nick Molden表示。“但在歐洲，這些數(shù)據(jù)可能都算合法，這說(shuō)明歐洲測(cè)試還不夠到位。”
他指出，目前的歐洲測(cè)試沒(méi)有坡道、急加速或冷啟動(dòng)等美國(guó)測(cè)試中使用的內(nèi)容。許多觀察家認(rèn)為，環(huán)保署宣布即將開(kāi)展的高速公路測(cè)試僅僅是大眾“排放門(mén)”事件之后將要改變的眾多內(nèi)容之一。
“這可能對(duì)售后市場(chǎng)和安全領(lǐng)域造成巨大影響，”這位半導(dǎo)體專家說(shuō)。“車主在購(gòu)買車輛后可以輕易地使用現(xiàn)成工具來(lái)調(diào)整發(fā)動(dòng)機(jī)，而汽車制造商并沒(méi)有加以阻止。但是未來(lái)他們可能不想看到這樣的事發(fā)生，因?yàn)槿桥O(jiān)管人員的代價(jià)是非常巨大的。”
功率計(jì)測(cè)試與實(shí)況測(cè)試之爭(zhēng)，以及對(duì)政府標(biāo)準(zhǔn)協(xié)議的批評(píng)促使人們思考各種解決方案，以縮小二者間的差距。詳見(jiàn)下文http://articles.sae.org/12610/ 和 http://articles.sae.org/7094/。
發(fā)動(dòng)機(jī)控制策略有望得到修改
專家指出，汽車制造商還有可能修改發(fā)動(dòng)機(jī)控制策略。如果新軟件可以集合當(dāng)今微型控制器的所有優(yōu)勢(shì)，那么開(kāi)發(fā)控制系統(tǒng)的任務(wù)就會(huì)變得更簡(jiǎn)單。當(dāng)然，這個(gè)系統(tǒng)必須在確保性能的同時(shí)也滿足排放與燃油經(jīng)濟(jì)性法規(guī)要求。這是密歇根州安娜堡市Simu Quest有限公司首席執(zhí)行官John Mills的觀點(diǎn)，然而這一愿景恐怕不會(huì)立刻實(shí)現(xiàn)。
“公司可以使用能夠更真實(shí)地呈現(xiàn)物理狀態(tài)的軟件，并推行更多的參數(shù)化發(fā)展（即基于模型的發(fā)動(dòng)機(jī)控制系統(tǒng)優(yōu)化），”他表示。“但許多公司都害怕改變傳統(tǒng)策略，因?yàn)樗麄冎涝摬呗允怯杏玫摹?/span>”
法規(guī)要求新發(fā)動(dòng)機(jī)里程必須超過(guò)15萬(wàn)英里，這是汽車公司不愿舍棄久經(jīng)考驗(yàn)的軟件的原因之一。另外一個(gè)原因則是控制一臺(tái)發(fā)動(dòng)機(jī)需要使用大量的軟件。
“代碼的數(shù)量因公司而異。某些OEM對(duì)所有發(fā)動(dòng)機(jī)都使用一套代碼庫(kù)，但每輛車只使用其中的一段，” Mills表示。“另一些則為不同發(fā)動(dòng)機(jī)開(kāi)發(fā)不同策略。某些甚至有幾十萬(wàn)行代碼。其中一大部分都是冗余，但仍有上萬(wàn)條異常關(guān)鍵。”
微控制器的性能不斷提升，是發(fā)動(dòng)機(jī)開(kāi)發(fā)人員能夠?yàn)榕欧艤y(cè)試與普通運(yùn)行分別開(kāi)發(fā)程序的原因之一，專家解釋道。目前的發(fā)動(dòng)機(jī)控制程序只需要做一件事——調(diào)節(jié)發(fā)動(dòng)機(jī)參數(shù)，因此它的處理速度和記憶要求遠(yuǎn)低于手機(jī)、平板電腦等消費(fèi)者電子產(chǎn)品。
“低端發(fā)動(dòng)機(jī)控制單元的處理器的最低頻率目前為100兆赫茲左右，未來(lái)將上升至300兆赫茲左右，”這位半導(dǎo)體技術(shù)專家表示。“處理器將升至6MB。不久的將來(lái)將升至7或8，升至16MB。”
發(fā)動(dòng)機(jī)控制系統(tǒng)的復(fù)雜性，及其保證汽車性能與燃油經(jīng)濟(jì)性的重要性，意味著軟件必然受到密切關(guān)注。有些觀察家相信，正因?yàn)檫@樣，大眾汽車的工程管理團(tuán)隊(duì)（也許還有高層主管）很可能認(rèn)為監(jiān)管機(jī)構(gòu)對(duì)使用額外軟件誤導(dǎo)測(cè)試機(jī)構(gòu)的做法早已心照不宣。
“這就說(shuō)不清了，”一名一線工程師表示。“有人說(shuō)這是一小部分人干的，但這件事可不是整個(gè)團(tuán)隊(duì)都會(huì)看漏的小事，而且整個(gè)集團(tuán)完全沒(méi)有注意到這些行為，也是不可能的。”
作者：Terry Costlow
來(lái)源：SAE《汽車工程雜志》
翻譯：SAE 上海辦公室
VW emissions scandal will impact future engine controls, testing
A change in the U.S. Environmental Protection Agency’s testing programs won’t be the only consequence for automakers in the wake of the Volkswagen emissions-cheating scandal.
Powertrain control strategies, including the ability to adjust engines with aftermarket devices, may also be revised, experts note. They also expect government regulators in the U.S. and Europe to more strictly enforce existing rules and tighten emission-testing protocols, close gaps between laboratory and real-world testing, and perform more spot checks that can catch abuse after new vehicle models are approved for sale.
Overall, industry engineers should expect greater oversight over automotive testing and validation in the aftermath of what some are calling “TDI-gate.”
Shortly after the EPA said VW was using illegal engine-control software that reduced diesel tailpipe emissions during dynamometer calibration testing, the agency announced it would begin performing on-road tests. That quick response came as VW’s CEO resigned, investigations began, lawsuits by vehicle owners flooded in, and the company’s market value plummeted.
While VW’s deception may be the largest such event, it’s far from the first. In 1998 EPA levied a $1.1 billion fine on seven heavy-duty diesel engine makers—the largest civil penalty ever imposed for violations of an environmental law—for using "defeat devices" in the engines’ controllers. This software altered injection timing and boosted fuel efficiency while illegally bypassing the emission control equipment on 1.3 million trucks.
Some industry insiders, speaking on background only, said that such strategies using a control map created just for testing, were once fairly common for both diesels and gasoline engines. Other OEMs, including Ford, GM, and Honda, have also been fined for cheating.
Real-world vs. lab: 4x higher NOx levels
The practice of using different engine-control software for testing and actual driving, is known as “dual mapping.” The control map written solely for emissions tests usually kicks in when the engine’s running but the steering wheel isn’t moving.
“A lot of companies probably did similar things with gasoline engines in the 1990s, but most of them stopped in the late ‘90s,” said a technologist at a leading semiconductor company who requested anonymity for this article. Like many industry executives, he was reluctant to talk with Automotive Engineering publicly about the embattled OEM.
He said the trickery is now conducted primarily in diesels “because you’ve got more parameters to control,” he continued. “Diesel fuel burns in bursts, depending how you manage things like tumbling as unburned fuel moves in the cylinder; you can end up with way more particulates.”
Regulators have found it difficult to monitor emissions comprehensively and consistently. The U.S. upgraded its tests a few years ago to make lab tests closer to real-world driving conditions, but in Europe tests are comparably benign. European diesel vehicles’ highway performance is nowhere near the levels found in regulatory labs, according to experts at Emissions Analytics, a U.K. company that performs on-road emissions tests.
“In real world tests of about 700 cars in Europe, we found NOx levels four times above the government test levels, CO2 was 31% above official levels, and fuel economy was 24% worse,” said Nick Molden, Emissions Analytics' CEO. “The twist is that in Europe, that’s probably all legal, it’s more a factor of inadequate testing in Europe.”
He noted that current European tests don’t have hills, rapid acceleration or tests used in the U.S. including cold starts. Many observers feel that the EPA’s announcement that it would begin running on-highway tests is only one of the changes that will occur in response to the VW scandal.
“This may have a big impact on the aftermarket and security,” the semiconductor expert said. “Car buyers can fairly easily use off-the-shelf tools to adjust the engine; carmakers haven’t gone out of their way to prevent this. Going forward they may not want to let these things happen. This could also impact who’s able to reflash the controller.”
The ongoing controversy over dynamometer vs. real-world testing, and criticisms of government standards protocols, have spawned various solutions aimed at closing the gaps. See http://articles.sae.org/12610/ and http://articles.sae.org/7094/.
Control strategy revisions expected
Experts noted that it’s also possible that automakers will revise their engine control strategies. If new software took advantage of everything that today’s microcontrollers can do, it would be simpler to create controls that meet emissions and fuel economy mandates while still delivering performance, according to John Mills, CEO at SimuQuest Inc., an Ann Arbor, MI, software development company. However, that may not happen soon.
“Companies could move to use a better representation of physics and start adopting more parameterization [model-based optimization of engine controls],” he said. “But a lot of companies have legacy strategies that they’re afraid to change because they know it works.”
Demands that new engines must reliably exceed 150,000 miles is one reason for this reluctance to change from software that’s been proven on the road. Another factor is the large volume of software needed to control an engine.
“The amount of code varies widely; some OEMs have one code base used for every engine, using only a segment of it for each vehicle,” Mills said. “Other OEMs have separate strategies for different engines. Some have hundreds of thousands of lines of code. A lot of that is fairly verbose, but there are tens of thousands of lines of code that are critically important.”
The rising capability of microcontrollers is among the reasons that engine developers can create separate programs for emissions tests and normal operations, experts explained. Engine control programs only do one thing, adjusting engine parameters, so the processing speeds and memory requirements of engine controllers are small compared to consumer devices like phones and laptops.
“The low-end engine control units have processors that run at about 100 MHz at the low end, going up to around 300 MHz,” the semiconductor technologist said. “The processors have up to six Mbytes. In the fairly near future, that will go up to seven or eight, maybe even 16 Mbytes.”
The complexity of engine controls, along with their importance in providing reliable vehicles with good performance and fuel economy, means that software gets close attention. Some observers believe that because of this, VW’s engineering management, and perhaps higher level executives, likely knew that regulators knew that additional software was being used to mislead those who tested the vehicles.
“This is quite troubling,” observed a Tier 1 engineer. “Some people say that this might be the work of a few people. But these aren’t the type of metrics the full team would miss—nor are they activities that the group would not observe.”
新工具可以在汽車正常運(yùn)行過(guò)程中收集大量排放與燃耗數(shù)據(jù)，其工作原理與實(shí)驗(yàn)室測(cè)試或底盤(pán)功率測(cè)試非常相似。圖中裝在福特?？怂管嚿砩系摹翱蓴y帶汽車測(cè)量系統(tǒng)（PEMS）”便是其中之一。自2013年起，英國(guó)的米爾布魯克測(cè)試場(chǎng)便開(kāi)始使用PEMS。