大眾汽車公司“排放門”事件曝光后，美國環保署修改了相關的測試項目，而該事件給汽車制造商帶來的影響遠遠不止這些。
專家指出，傳動系統的控制策略，包括利用售后市場設備來調整發動機的思路，都將可能進行修改。他們還希望歐美政府加強現有法規的執行、嚴整排放測試協議、縮小實驗室測試與路上測試之間的差距，并在新車型上市后抽樣檢查排放超標的情況。
總而言之，在經歷這場“排放門”之后，汽車行業的工程師們將在測試和驗證方面受到更為嚴苛的監督。
美國環保署表示大眾在功率計校驗測試中使用違法的發動機控制軟件來減少尾氣管柴油排放之后不久，就宣布即將實施道路測試。這也是美國環保署對大眾CEO辭職、調查啟動、車主訴訟蜂擁而至、公司股價大跌等一系列連鎖事件做出的迅速回應。
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，美國環保署曾對7家重型柴油發動機生產商開出了11億美元的罰單，這是史上因違反環境法而作出的最嚴重處罰，因為他們在發動機控制器中了使用一種“致勝裝置”。當年，這種軟件在130萬輛卡車上更改燃油噴射正時裝置并提高燃油效率，同時非法地規避了排放控制設備的使用。
一些業內人士透露，這種專為測試而開發的控制圖，曾經一度流行于柴油車和汽油車市場。包括福特、通用、本田在內的整車廠都曾因作弊而受罰。
實況測試與實驗室測試的比較：氮氧化物含量高出4倍
在測試與實際駕駛中使用不同的發動機控制軟件的做法被稱作“雙圖法”。在排放測試中，發動機運行而方向盤不動，專為測試而開發的標準圖正是在這個時候使用的。
“90年代估計很多公司都干過類似的事，但大多數在90年代后期就停了，”一家不愿透露姓名的頂尖半導體公司的技術專家匿名評論道。與許多行業高層一樣，他非常猶豫是否在《汽車工程雜志》上公開評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，“因為能控制的參數更多了”。“柴油是一陣接一陣燃燒的，這將決定你怎樣管理機內的元素，比如未燃燒的柴油在汽缸內翻滾的狀態。管理不當，你的柴油顆粒數量就會飆升。”
法規制定者發現，要對排放進行綜合且持續的監控實屬不易。美國在幾年前改善了測試，好讓實驗室的測試條件接近于實況測試，但相對來說，歐洲的測試要溫和不少。英國的道路排放測試公司EmissionsAnalytics的專家表示，歐洲柴油車的公路測試結果至今都與實驗室結果相距甚遠。
“在歐洲700輛車的實況測試中，我們發現氮氧化物的水平比政府測試標準高出4倍，二氧化碳高了31%左右，而燃油經濟性低了24%，” Emissions Analytics的首席執行官Nick Molden表示。“但在歐洲，這些數據可能都算合法，這說明歐洲測試還不夠到位。”
他指出，目前的歐洲測試沒有坡道、急加速或冷啟動等美國測試中使用的內容。許多觀察家認為，環保署宣布即將開展的高速公路測試僅僅是大眾“排放門”事件之后將要改變的眾多內容之一。
“這可能對售后市場和安全領域造成巨大影響，”這位半導體專家說。“車主在購買車輛后可以輕易地使用現成工具來調整發動機，而汽車制造商并沒有加以阻止。但是未來他們可能不想看到這樣的事發生，因為惹怒監管人員的代價是非常巨大的。”
功率計測試與實況測試之爭，以及對政府標準協議的批評促使人們思考各種解決方案，以縮小二者間的差距。詳見下文http://articles.sae.org/12610/ 和 http://articles.sae.org/7094/。
發動機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動機控制策略。如果新軟件可以集合當今微型控制器的所有優勢，那么開發控制系統的任務就會變得更簡單。當然，這個系統必須在確保性能的同時也滿足排放與燃油經濟性法規要求。這是密歇根州安娜堡市Simu Quest有限公司首席執行官John Mills的觀點，然而這一愿景恐怕不會立刻實現。
“公司可以使用能夠更真實地呈現物理狀態的軟件，并推行更多的參數化發展（即基于模型的發動機控制系統優化），”他表示。“但許多公司都害怕改變傳統策略，因為他們知道該策略是有用的。”
法規要求新發動機里程必須超過15萬英里，這是汽車公司不愿舍棄久經考驗的軟件的原因之一。另外一個原因則是控制一臺發動機需要使用大量的軟件。
“代碼的數量因公司而異。某些OEM對所有發動機都使用一套代碼庫，但每輛車只使用其中的一段，” Mills表示。“另一些則為不同發動機開發不同策略。某些甚至有幾十萬行代碼。其中一大部分都是冗余，但仍有上萬條異常關鍵。”
微控制器的性能不斷提升，是發動機開發人員能夠為排放測試與普通運行分別開發程序的原因之一，專家解釋道。目前的發動機控制程序只需要做一件事——調節發動機參數，因此它的處理速度和記憶要求遠低于手機、平板電腦等消費者電子產品。
“低端發動機控制單元的處理器的最低頻率目前為100兆赫茲左右，未來將上升至300兆赫茲左右，”這位半導體技術專家表示。“處理器將升至6MB。不久的將來將升至7或8，升至16MB。”
發動機控制系統的復雜性，及其保證汽車性能與燃油經濟性的重要性，意味著軟件必然受到密切關注。有些觀察家相信，正因為這樣，大眾汽車的工程管理團隊（也許還有高層主管）很可能認為監管機構對使用額外軟件誤導測試機構的做法早已心照不宣。
“這就說不清了，”一名一線工程師表示。“有人說這是一小部分人干的，但這件事可不是整個團隊都會看漏的小事，而且整個集團完全沒有注意到這些行為，也是不可能的。”
作者：Terry Costlow
來源：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行過程中收集大量排放與燃耗數據，其工作原理與實驗室測試或底盤功率測試非常相似。圖中裝在福特福克斯車身上的“可攜帶汽車測量系統（PEMS）”便是其中之一。自2013年起，英國的米爾布魯克測試場便開始使用PEMS。