计算机专业时文选读(989)

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.

局域网巡航

车轮自增加了轮胎以来没有多大的变化，正是轮胎对(汽车)效率影响最大：如果轮胎压力比最佳压力低10%，消耗驱动轮子转动的燃油就增加10%。

轮胎性能对道路运输的成本非常关键，所以Volve卡车公司的工程师们给其重型卡车的每个轮胎开发了射频发射机，不断向仪表显示板发送信息，当轮胎(最多50个轮胎)不在最佳压力时，给司机报警。

四分之一的卡车故障是由轮胎的毛病引起的，从慢撒气开始到有时轮胎爆炸为止，都会增加轮子滚动阻力，降低昂贵的橡胶(轮胎)的寿命。

火柴盒大小的发射机紧挨阀门安装，并用一根细管连接，每15分钟向固定在底盘上的接收机和处理器发送8个读数的脉冲串。

处理器审查每个轮子送来的报告，算出最精确的平均压力，在仪表板LCD显示屏的轮子配置示意图上指示出有问题的轮胎。

此系统的CPU是车上25个CPU中的1个，它们一起提供的计算能力远远超过当年阿波罗 13登月的计算能力。

它们精确地控制着除驾驶以外的一切功能：引擎性能、刹车压力、挡位变化和传动管理、空调以及GPS精确定位器等。

近十年来在车载计算机完成的任务越来越多的同时，无线网络稳步地替代了复杂的连线系统，由它们向驾驶室和其他地方提供信息。

新车成本中30%是电子设备：芯片、连线和网络，它们支持从自动门锁到防抱死刹车和气囊张开等功能。

由于汽车电子设备变得越来越复杂，汽车制造商借鉴网络行业，依靠共享的网络和标准协议来支持控制系统之间的内部通信。他们也转向行业标准，如蓝牙和Wi-Fi，支持与提供交通、气象、娱乐和其他信息的外部系统的连接。

今天的汽车拥有近半打的专有网络，将信息从控制系统传送到受它们控制的设备。直至最近，每家汽车制造商和每个汽车型号都有自己的网络部件。它们是加固的、特定汽车的网络，拥有极可靠的电子元器件，能经受住震动和在极端热与冷的环境中工作。

最新的趋势是标准化，从而让汽车制造商可以节省元器件和软件的开发费用。

在要解决不同速度要求的内部网络方面，各公司已集中到几个标准上。同时，汽车制造商期待着扩大这些网络的应用，替代那些支持诸如引擎发动和开灯等功能的横七竖八的连线。

更多的汽车制造商想用无线技术，支持导航、安全服务等多种新功能。

蓝牙是一项支持移动电话的技术选择。汽车行业正在开发一项特别的蓝牙标准——蓝牙Handsfree 2.0，将汽车的内装式麦克风在不需要机座的情况下与任何移动电话相连，允许不用手就能打电话。

从更长远看，汽车制造商计划利用蓝牙支持诸如远程车辆诊断、高级安全特性和车与车通信等服务。

但是，蓝牙仅是连接基于计算机的汽车与外部世界多种新兴技术中的一项。车内娱乐服务需求的高涨，使汽车制造商关注从卫星链路到专用短距离通信(RSRC)和Wi-Fi的所有技术。

即将来到的是实时的新闻、信息和娱乐服务，它们与车内娱乐系统合为一体。提供这些服务最有希望的方法是数字卫星无线电。随着压缩技术和更小天线的改进，数字卫星无线电还能提供流式视频。

另一项将能给汽车带来高速双向通信能力的技术是DSRC。DSRC是专门为运输业