LAN-Cruising

The wheel hasn’t changed much over time apart from the addition of a tyre, and it’s this that most seriously affects its efficiency: a 10 per cent drop in optimum tyre pressure can easily add 10 per cent to the fuel consumption of the engine driving them.

So critical is tyre performance to road transport costs that engineers at Volvo Truck have developed an RF transmitter for each tyre on its massive trucks to send constant information to an in-dash display to warn drivers when any of up to 50 tyres are at anything other than perfect pressure.

A quarter of truck breakdowns are caused by tyre failure, starting as slow leaks and sometimes ending in explosion but certainly adding to rolling resistance and reduced life of expensive rubber.

The matchbox-sized transmitters are fixed next to the valve and connected by a tiny tube to send a burst of eight readings every 15 minutes to a receiver and processor bolted to the chassis.

The processor sifts reports from each wheel to find the most accurate average, signalling an errant tyre on a schematic of the wheel configuration on an LCD screen in the dash.

The system’s CPU is one of 25 in the vehicle, together providing far more computing firepower than for the Apollo 13 landings.

They control pretty well every function in the vehicle other than driving it: engine performance, brake pressure, gear changes and transmission management, air conditioning, and GPS-enabled locators.

While on-board computers have been increasingly gaining new tasks in trucks for nearly a decade, wireless networking has steadily replaced complex wiring looms to get information to the driver’s cab and beyond.

Already 30 per cent of the cost of a new car is in the electronics: the chips, wires and networks that support features ranging from automatic door locks to anti-lock brakes to airbag deployment.

As automotive electronics become more complex, car manufacturers are borrowing a page from the network industry, relying on shared networks and standard protocols to support internal communications between control systems. They’re also turning to industry standards such as Bluetooth and Wi-Fi to support links to external systems that provide traffic, weather, entertainment and other information.

Today’s cars have half a dozen different proprietary networks that carry messages from control systems to the devices being operated. Until recently, each car manufacturer and car model had its own network parts. These are hardened, automotive-specific networks with ultra-reliable electronic components that can withstand vibration and operate in extreme heat and cold.

The latest trend is toward standardisation so car manufacturers can save money on components and software development.

Companies are converging on several standards for internal networks that address different speed requirements. At the same time carmakers are looking to extend the use of those networks to replace the spaghetti of wire used to support functions such as turning on the engine and operating lights.

More carmakers are going wireless to support a host of new navigation and safety services.

Bluetooth is the technology of choice to support mobile phones. The car industry is developing a special profile of the Bluetooth standard - dubbed Bluetooth Handsfree 2.0 - that will link a built-in microphone in the car to any mobile phone without requiring a docking station, allowing for hands-free calling.

Longer term, car manufacturers plan to use Bluetooth to support services such as remote vehicle diagnostics, advanced safety features and vehicle-to-vehicle communications.

But Bluetooth is only one of the technologies that are emerging to connect the computer-based car to the outside world. The rising demand for in-vehicle entertainment services has carmakers looking at everything from satellite links to Dedicated Short Range Communications (DSRC) and Wi-Fi.

On the horizon are real-time news, information and entertainment services that are integrated with in-vehicle entertainment systems. The most promising way to deliver these services is digital satellite radio. With improvements in compression techniques and smaller antennas, digital satellite also could deliver streaming video.

Another technology that could bring high-speed, two-way communications to automobiles is DSRC. DSRC was designed specifically for the transportation industry to complement cellular communications, supporting 6 to 54Mbit/sec wireless data transfer rates. Mercedes-Benz has started shipping cars with DSRC support in Germany.

Further out on the horizon is in-vehicle support for Wi-Fi technology. By around 2006, some car manufacturers will be looking to install self-contained Wi-Fi to allow users to load music and files into the car. Users could download files and other content to the car such as traffic reports or news.

But use of Wi-Fi for Internet access while cars are in motion is still just a pipe dream today. You’d need to have Wi-Fi hot spots along the highway. That won’t happen anytime soon.

局域網(wǎng)巡航

車輪自增加了輪胎以來沒有多大的變化，正是輪胎對(汽車)效率影響最大：如果輪胎壓力比最佳壓力低10%，消耗驅(qū)動輪子轉(zhuǎn)動的燃油就增加10%。

輪胎性能對道路運輸?shù)某杀痉浅ｊP(guān)鍵，所以Volve卡車公司的工程師們給其重型卡車的每個輪胎開發(fā)了射頻發(fā)射機，不斷向儀表顯示板發(fā)送信息，當輪胎(最多50個輪胎)不在最佳壓力時，給司機報警。

四分之一的卡車故障是由輪胎的毛病引起的，從慢撒氣開始到有時輪胎爆炸為止，都會增加輪子滾動阻力，降低昂貴的橡膠(輪胎)的壽命。

火柴盒大小的發(fā)射機緊挨閥門安裝，并用一根細管連接，每15分鐘向固定在底盤上的接收機和處理器發(fā)送8個讀數(shù)的脈沖串。

處理器審查每個輪子送來的報告，算出最精確的平均壓力，在儀表板LCD顯示屏的輪子配置示意圖上指示出有問題的輪胎。

此系統(tǒng)的CPU是車上25個CPU中的1個，它們一起提供的計算能力遠遠超過當年阿波羅 13登月的計算能力。

它們精確地控制著除駕駛以外的一切功能：引擎性能、剎車壓力、擋位變化和傳動管理、空調(diào)以及GPS精確定位器等。

近十年來在車載計算機完成的任務越來越多的同時，無線網(wǎng)絡穩(wěn)步地替代了復雜的連線系統(tǒng)，由它們向駕駛室和其他地方提供信息。

新車成本中30%是電子設(shè)備：芯片、連線和網(wǎng)絡，它們支持從自動門鎖到防抱死剎車和氣囊張開等功能。

由于汽車電子設(shè)備變得越來越復雜，汽車制造商借鑒網(wǎng)絡行業(yè)，依靠共享的網(wǎng)絡和標準協(xié)議來支持控制系統(tǒng)之間的內(nèi)部通信。他們也轉(zhuǎn)向行業(yè)標準，如藍牙和Wi-Fi，支持與提供交通、氣象、娛樂和其他信息的外部系統(tǒng)的連接。

今天的汽車擁有近半打的專有網(wǎng)絡，將信息從控制系統(tǒng)傳送到受它們控制的設(shè)備。直至最近，每家汽車制造商和每個汽車型號都有自己的網(wǎng)絡部件。它們是加固的、特定汽車的網(wǎng)絡，擁有極可靠的電子元器件，能經(jīng)受住震動和在極端熱與冷的環(huán)境中工作。

最新的趨勢是標準化，從而讓汽車制造商可以節(jié)省元器件和軟件的開發(fā)費用。

在要解決不同速度要求的內(nèi)部網(wǎng)絡方面，各公司已集中到幾個標準上。同時，汽車制造商期待著擴大這些網(wǎng)絡的應用，替代那些支持諸如引擎發(fā)動和開燈等功能的橫七豎八的連線。

更多的汽車制造商想用無線技術(shù)，支持導航、安全服務等多種新功能。

藍牙是一項支持移動電話的技術(shù)選擇。汽車行業(yè)正在開發(fā)一項特別的藍牙標準——藍牙Handsfree 2.0，將汽車的內(nèi)裝式麥克風在不需要機座的情況下與任何移動電話相連，允許不用手就能打電話。

從更長遠看，汽車制造商計劃利用藍牙支持諸如遠程車輛診斷、高級安全特性和車與車通信等服務。

但是，藍牙僅是連接基于計算機的汽車與外部世界多種新興技術(shù)中的一項。車內(nèi)娛樂服務需求的高漲，使汽車制造商關(guān)注從衛(wèi)星鏈路到專用短距離通信(RSRC)和Wi-Fi的所有技術(shù)。

即將來到的是實時的新聞、信息和娛樂服務，它們與車內(nèi)娛樂系統(tǒng)合為一體。提供這些服務最有希望的方法是數(shù)字衛(wèi)星無線電。隨著壓縮技術(shù)和更小天線的改進，數(shù)字衛(wèi)星無線電還能提供流式視頻。

另一項將能給汽車帶來高速雙向通信能力的技術(shù)是DSRC。DSRC是專門為運輸業(yè)