Electronic Design

Designers Tame The Harsh Environment Of The Auto

Wireless, PCs, the Internet, and multimedia will deliver living-room audio and cinema-quality video to those who can afford them.

The auto industry may have sped past its one-hundredth birthday. But as anyone who visits its research facilities and its first-tier suppliers in Detroit learns, there's no hardening of the arteries. Automotive-entertainment designers pursue innovation vigorously and enthusiastically. And despite the abundance of landmark technological breakthroughs under their belt, there's no end in sight.

After a half-dozen visits to such designers, one learns that certain themes keep repeating. For starters, they pay close attention to what's happening in the consumer industry, particularly to the technologies and specifications emerging right now—like DVD audio. Second, the early innovations in multimedia will undoubtedly be aimed at those with deeper pockets (see "Targeting The Prosperous," p. 84). Plus, designers are acutely aware of activity relating to bus specifications, such as IEEE 1394 and media-oriented system transport (MOST).

So it's not surprising that what they're designing in closely follows in the footsteps of the consumer electronics industry. Yet it also meets the rigorous automotive environmental requirements that are far more stringent than even those called for by the military.

Choosing which paths to pursue isn't easy (Fig. 1). "There are some 20 entertainment initiatives, such as MP3, Surroundsound, audio on demand, and satellite radio. I could go on, but the car will have to become compatible with them at some point," says David A. McNamara, manager of electrical/electronics systems engineering at Ford Motor Co., Dearborn, Mich. (See "Don't Touch That Dial," p. 86.)

The industry has come a long way since the time that Henry Ford took pride in the spartan features of the Model T—available only in black. Looking back, it was the high-compression engine that enabled increasing the size of vehicles. Much later on, the microprocessor ushered in the era of closed-loop engine controls and anti-skid brakes.

Now with the advent of the twenty-first century, all of the familiar scenarios that fall under the umbrella of multimedia will have a profound effect on what goes in the cockpit and rear seat, with regard to entertainment. Note that memory requirements are rising dramatically as more electronics find a permanent home in automotive vehicles (Fig. 2). In fact, The back seat is where it's happening. Automotive displays for both forward and back-seat locations illustrate this (Fig. 3).

DaimlerChrysler, Rochester Hills, Mich., has taken some large strides. The company has implemented its newest innovations in the Dodge MAXXcab, displayed at the 2000 Detroit Auto Show. (Fig. 4). "It's really a comfortable passenger truck with a very passenger-friendly interior," remarks Stephen J. Buckley, manager of electrical product innovation at DaimlerChrysler. "In the Dodge MAXXcab, we built an entire entertainment center into the rear seat of the vehicle. Actually, it's what we call an 'edutainment' system, geared toward children and young adults."

As Buckley explains, it enables passengers, regardless of age, to watch DVD movies and play CD-ROM games. There also is a touch-sensitive pad that passengers can take down from a bracket and place on their laps, enabling them to draw or do homework. Furthermore, because it's in the back seat, these monitors don't visually distract the driver.

Demand for any of these innovations begins in the home and then migrates to the world of the automobile. "People are expecting to have theater in the home. And there's no reason why they shouldn't expect it in their SUVs and vans, as well," says Cary A. Wilson, director of electrical/electronic systems engineering at Ford Motor Co.

But plenty of options still exist in the front seat. Drivers can use a telematics screen to access the Internet for weather and traffic information and road-hazard updates. Telematics means two-way, vehicle-based communications.

Additionally, those in the front have the ability to play Internet audio files because MP3 playback can be readily integrated into the radio, relying on either a Flash-memory card or a hard-disk drive. So, not only can the radio play cassettes and CDs, but MP3 as well. As for bringing MP3 into the vehicle, it can arrive on the hard disk of a PC or a PCMCIA card. Or, perhaps the program will be downloaded from the Internet via a high-speed wireless link.

Expressing pride in the company's concept car, Buckley points out that usually a designer will dream up something like this, but just put in graphics. "If you look at a lot of other concept cars, they are often fake on the inside," Buckley notes.

"We get more value out of our concept car by building these things as functional devices," Buckley adds. "So we can actually experience the design, to see if it really makes sense to provide the driver with this kind of information. And, do kids really want to play video games in the back seat? So we go the extra mile, actually building functional properties and then testing users' reactions to them."

Some 300 miles to the southwest of the motor city is Delphi Automotive Systems (formerly Delco) in Kokomo, Ind. The company first introduced entertainment systems into General Motors' vehicles in 1998 using VHS playback. Robert W. Schumacher, general director of the mobile multimedia/business line, points out that multimedia entertainment systems have already achieved high penetration in sport utilities and minivans. He expects such systems to move quickly from VHS to DVD and sees DVD taking over as the primary video playback mode. As Schumacher notes, DVD works much better in the car because the DVD playback mechanism is more compact, more rugged, and therefore, much better suited to the automotive environment.

But with all these newfangled technologies in-vading the car, who's looking after passenger safety? Part of the answer lies in bringing voice-recognition and text-to-voice capabilities to the electronic entertainment mix.

Delphi Automotive Systems has a product line known as "smart radios." By adding a pc board to a traditional analog radio, the radio can host a voice engine, thereby adding voice-recognition and a text-to-speech capability.

Dialogues between passenger and machine should become commonplace in only a few years. "Tune to 90.1 MHz," says the driver, in a hands-free instruction to the radio. "Did you say tune to 90.1 MHz?" the radio asks. "Yes, I did," the driver confirms, and then the smart radio does exactly that.

Leveling the playing field between the tortoise and the hare, DaimlerChrysler has taken a novel approach to introducing laptop computers into the vehicle. For several years, the company has been showcasing a very special "plug-and-play" concept. Rather than installing a dedicated, on-board computer system, the company will let customers install their own laptops.

The company then supplies the software so the computer interfaces seamlessly with the various on-board vehicle-entertainment systems. Underneath the front seat, a shelf for two laptops is installed—one for the front system and one for the rear system. "Why two shelves? Because a single laptop can't support both the entertainment stuff in the back and the infotronics stuff in the front," Buckley explains.

As for TV, it too will be upgraded soon. Delphi Automotive Systems makes a terrestrial TV tuner with a diversity antenna system that automatically picks the best signal. Using multiple antennas and a diversity phase-shifting technique, it eliminates much of the fading, noise, and ghosting frequently experienced with a single antenna. Ultimately, Delphi will provide satellite TV. As the car drives along, the antenna will track, staying locked onto a geosynchronous satellite. Delphi anticipates this system arriving in 2005 or 2006.

The need for a bus structure to handle the various kinds of data in the front and the rear seats is a major issue for automotive-entertainment designers. "The greatest bandwidth demands will be for the rear-seat entertainment because of digital video," says Dan Harris, manager of product planning at Delphi Automotive Systems. Increased bandwidth also is important to streaming media and DVD audio.

"What we are talking about is transferring information between modules in different geographical locations in the vehicle—the one in the front and the one, or even two, modules for the viewers in the rear," remarks Akram Mufid, a technical specialist in multimedia systems architecture at Visteon Corp., Allen Park, Mich.

Mufid acknowledges that to make it possible for two people in the back seat to watch and listen to different programs at once, a digital network using a plastic, fiber-optic media is necessary. It will provide the bus interconnection between the control unit on the instrument panel in the front and the entertainment modules in the rear seats.

As Mufid points out, plastic optical fiber is the way to go because it's extremely inexpensive. It costs five cents per foot versus 50 to 60 cents for a shielded, twisted-pair. Plus, attenuation is low, typically 0.5 dB per meter. In addition, plastic fiber optics are much lighter, exhibit a far higher bandwidth, and are immune to EMI problems.

As for the buses themselves, there are two major contenders. Initially developed by Apple Computer as FireWire for plug-and-play networking of multimedia, IEEE 1394 has become the preferred solution for the digital interconnection of consumer electronic devices. The IEEE-1394 connectors are hot-pluggable. IEEE-1394 equipment, or nodes, can autoconfigure into a network when daisy chained together with IEEE-1394 links. Regarding bit rate, IEEE 1394 defines a family spanning a wide range of approximately 100, 200, 400, and 800 Mbits/s over serial or fiber-optic (1394b) connections. For more details, go to www.1394ta.org.

The other contender, the MOST bus, was originally designed by Oasis Silicon Systems, in cooperation with BMW, Becker Radio, and DaimlerChrysler. The MOST consortium was formed in 1998 to devise a fiber-optic network that could provide an efficient and low-cost mechanism for transporting high volumes of streaming data.

The synchronous nature of MOST reduces cost by eliminating the need for buffering and signal processing at each node. It's intended for data rates from a few kbits/s to 25 Mbits/s. Supporting both synchronous and asynchronous data, it will handle up to 64 devices. For more information, see www.mostcooperation.com.

The buses most likely to be chosen are MOST, or an automotive upgrade of IEEE 1394. But the final decision on an industry-wide standard lies with the automotive multimedia interface collaboration (AMI-C). Formed more than two years ago, its announced goal is to devise a standard for a vehicle communications bus. If you want to learn more about this, check out www.ami-c.com.

When the collaboration was formed, MOST existed, but AMI-C didn't adopt it right away. The group has considered a number of specifications, including IEEE 1394, MOST, USB, Bluetooth, and home audio video (HAVI), as well as several others.

Obviously, if you want to be able to bring a DVD player or camcorder with you and plug it right into the car, IEEE 1394 is a much better choice. It's already a widely adopted standard in the computer industry and in consumer electronics. But MOST is a synchronous network. Also, one of the biggest advantages of synchronous networks versus an asynchronous network like IEEE 1394 is its ability to deliver a higher-fidelity signal to the car's speakers.

Yet some IEEE-1394 critics are quite outspoken. "Audio is synchronous in nature and requires synchronous transport. Given that we seek CD quality with a 91-dB dynamic range, this cannot be achieved with current IEEE 1394 such as it is today," Mufid says. "The reason is that you can't expect to transmit a synchronous signal over an asynchronous network. The two nodes are each working off of their own heartbeat." (A rather apt term for a clock)

"Because each node is slaved to its own local oscillator, there are likely to be dropped samples. It's analogous to any network where you could lose a packet due to an error. This slows transmission down so that you lose the real-time delivery of the audio. Higher-fidelity audio may ultimately become possible on IEEE 1394, but at a higher cost. We will work on a solution for IEEE 1394. But as far as a 91-dB dynamic range, it simply isn't here yet," Mufid says. Ford Motor Co. concurs with Mufid and Visteon Corp. on this issue.

"In the case of MOST, you have a heartbeat, and it can be anywhere between 30 and 50 kHz, running all the time," he adds. "This is one of the buses' distinguishing features. MOST is a fully synchronous network, meaning that all of the nodes are running off one heartbeat. With MOST, an effective speed rate is 24.5 Mbits/s, which is optimal for today's current LED technology. We are prepared to use either MOST, or perhaps an automotive version of IEEE 1394."

According to Buckley, MOST is DaimlerChrysler's choice for a standard. "We have been working with the MOST bus because DaimlerChrysler had joined the MOST consortium before the DaimlerChrysler merger," he says. In all likelihood, the AMI-C will adopt MOST if the legal issues can be solved.

The limiting factor for high-speed automotive networks might not be constrained by the network topology, whether it turns out to be MOST or IEEE 1394. Instead, it may come down to the key-off current. This term denotes how much current is drawn when the ignition switch is off. Today's LEDs are suitable for high-speed bus systems. But they require a biasing current during key-off that exceeds an acceptable level.

"Say you take a two-week vacation, parking your car at the airport," Mufid suggests. "When you return, you of course want your vehicle to start the instant you turn the key in the ignition switch. So assuming that there's nothing wrong with the battery, starting requires that key-off current has been low during your absence so that it hasn't significantly discharged your battery."

A typical, acceptable upper bound for key-off current is in the microampere range. "Let's now come back to entertainment system performance," Mufid says. "If you are talking about a 200- to 300-Mbit/s data rate within the car, it can't be achieved with current LED technology. This is to due to a key-off current that's in the milliampere range—which is far more than an acceptable key-off current."

In other words, you cannot turn off the LEDs employed in bus systems today. You have to bias them. If you first apply bias when the key is turned on, however, it would take seconds for systems to come up, which is too long.

"Several LED companies are working to improve LED technology so that key-off current will no longer be an obstacle for a high-speed, automotive bus system," Mufid says. "Whereas with MOST, you only synchronize once, which is when you connect up the battery. When it comes to high-speed automotive networks, the bit-error rate, the optical power budget, the bit rate, and biasing current must all be selected for optimum system performance."

Multiple programming capability is another important consideration. If the driver in the front seat wants to listen to MP3 music, while those in the rear seat have other plans for their entertainment, the outcome is annoying audio crosstalk. With a standard audio system, the driver might listen to MP3 in the front seat, while his youngsters watch Pokemon movies in the rear seat.

DaimlerChrysler is a member of a group known as the MIT Media Lab. It has developed a technology called "audio spotlight." To establish separate noninterfering zones of sound, the technique uses transducers that, like a highly directional antenna, emit highly directional sound beams (Fig. 4, again).

Using an ultrasonic transducer as the source, it emits 60-kHz ultrasonic waves that are modulated by the audio signal. As the sound wave travels through air, it becomes distorted, delivering an audible byproduct. Because the transducer produces ultrasonic waves, it collimates the waves into a narrow beam. When it's aimed at just 10° from the listener, the sound falls off and becomes inaudible.

The air itself demodulates the sound. Though the concept has been around since the 1920s, this is the first known application in a vehicle. It still has some imperfections, though. As the ultrasonic waves bounce off of the leather seating surfaces and the glass in the vehicle, there are some audible reflections.

A typical installation would comprise four transducers—one over every passenger. Each transducer has approximately a 12-in. diameter.

"DVD audio is a technology we're watching closely in the audio acoustics area for sound systems," claims Mark E. Navarre of Ford's audio acoustics engineering. "We expect that very soon, a multichannel music format will become quite popular with consumers." Although it's not currently available, Navarre predicts a significant push in the consumer electronics industry, with perhaps a large an-nouncement at the Consumer Electronics Show in Las Vegas.

Navarre says the recording industry is looking to the automotive industry to help catalyze the introduction of DVD audio. This makes sense, as most people listen to music principally in their automobiles, rather than in their homes.

"We have a huge market for audiophile, high-quality sound systems that we sell as an option. Usually the take rate is 60% to 85%," Navarre says. A take rate means a regularly purchased option. "So if it takes off with the popularity that DVD video did, there's a good chance that we'll see DVD audio replacing the compact disc in the next couple of years," according to Navarre.

"DVD stands for digital versatile disk—not digital video disk—as is often believed," Navarre notes. The DVD format is governed by a consortium of companies called the DVD Forum. These companies write standards and specifications for all DVD formats and have already published a second edition of their DVD audio specification.

All of the data contained in a DVD is digital in nature, so it can be transported over a MOST or an IEEE-1394 network. But whatever the transmission medium, the raw, digital data is read from the disk, fed to a network and then to a processor, and finally forwarded to a radio for reproduction.

Compact discs (CDs) today can provide a dynamic range of 105 dB. The dynamic range of any medium is defined as the softest sound that can be recorded and played back versus the loudest sound that can be recorded and played back without distortion.

Wow and flutter have become irrelevant because they are analog, tape-based specifications. But dynamic range, frequency response, and intermodulation distortion are still germane, because they are the properties of amplifiers and loudspeakers that inescapably are analog by nature.

The advent of the DVD is due to some pretty monumental leaps in laser technology. As a result, a DVD has a superior capacity for storing information, holding about eight times as much information as a CD.

Due to the advances in laser technology, a DVD head can read much smaller pits on a disk than a CD can. The pits have become smaller, so more of them can be put on the disk.

A disk—CD or DVD—provides a mix of reflective and defractive media. There are two states, either a reflective surface or an impregnation in that surface that forms a pit. When the light hits the pit, it scatters, instead of being reflected back to the sensor. There are binary states, with the reflection being a "zero" and the nonreflective pit sensed as a "one." The sequence of these sensed pits and nonpits comprise the stored digital bit stream retrieved by the sensor.

"What DVD audio means to us, with regard to vehicle entertainment, is that it will enable six digital audio channels to be played back all at once, when processed by an appropriate decoder," Navarre says. "So a passenger will experience the same type of music presentation that he or she hears today with a DVD video soundtrack presentation in a cinema or in the home."

The familiar CD is encoded in an uncompressed format. Its bit stream is a 16-bit, pulse-code-modulated format, sampled at 44.1 kHz. But the DVD medium in the video domain in the consumer market is Dolby digital 5.1 sound comprising five full-bandwidth channels—left, center, right, and a pair of stereosurround channels. The "0.1" stands for the additional sub-woofer band that's band-limited to an upper bound of 100 Hz.

Whatever mix of technologies winds up in a vehicle, the barriers to entry are high. "The electronics we put in cars has far better reliability, durability, and life than electronics sold in the consumer electronics field," Schumacher notes. He says components and systems must function between −40°C and 90°C in the cockpit and 125°C and 150°C under the hood, as well as endure repeated temperature cycling. And, they have to keep performing for 10 years.

Consumer electronics fall far short, as their allowed temperature excursions are narrower, typically 0°C to 60°C, and their shock and vibration requirements are more relaxed. Moreover, for automotive applications, components must be packaged differently, so that they're more rugged. The same goes for automotive-grade connectors. They have to withstand stringent shock and vibration requirements.

"We would love to see the promise of OLEDs (organic light-emitting diodes) pay off," Schumacher says. He is impressed with their high brightness and the fact that they're direct view and can function over wide temperature latitudes. Additionally, OLEDs are attracting a lot of attention because they're emissive, rather than transmissive, so they require no external light source.

Still to be solved are the problems with the full-color versions' lifespans, which aren't quite up to what the auto or any other industry would like. However, monochromatic OLEDs are beginning to appear in cell phones in Japan.

Although Delphi Automotive Systems hopes OLEDs will cut display costs, Schumacher doesn't yet count active TFT displays as down and out. "Every year they get better, their temperature range widens, the resolution goes up, and the price comes down," he says.

Automotive-entertainment designers aren't the only ones striving toward technological breakthroughs. Designers of aircraft entertainment systems are pursuing innovation paths that are quite similar to those of their colleagues in the automotive industry. Randy Robertson, the chief engineer of avionics for the Boeing Commercial Airplane Group, the Boeing Co., Seattle, Wash., says his company is developing a localized wireless communications capability, similar to Bluetooth, for use on the ground.

Along with exchanging information between the ground and the flight crew, the ground-based wireless ability will enable the loading of the latest movies on aircraft for passenger entertainment. Therefore, it will put an end to carting VHS tapes on and off the plane.

Also, the company is expanding the datalink already in use on late-model aircraft, such as the 747-400 and the 777. The latter employs a communications capability that augments the various HF, VHF, and satellite communications systems, which are standard on aircraft today. This datalink, to be utilized when the aircraft is airborne, will serve well for feeding live TV to passengers during the flight.

As for distributing movie entertainment information around the aircraft, Boeing is evaluating fiber optics. The company has fiber-optic test programs running on some airplanes in service. In particular, Boeing is evaluating the durability of fiber. Fiber optics currently operate on the 777, using fiber distributed data interface (FDDI) as a protocol along with companion interface chips. "Our runs are fairly long if you consider that a 747-400 has a length that's just over 225 feet," Robertson says. "And we do have data buses that run the entire length of the airplane."

Today, it's well known that the bandwidth of a single fiber-optic strand is extraordinary. Electromagnetic interference (EMI) has always been a major issue on aircraft with copper. Taking the critical steps necessary to properly shield both the wire and the requisite connectors is quite bothersome. That fiber-optic cable is totally immune to EMI is a big plus. So, Boeing's worries about the grounding of wires and the suppression of EMI disappear, wherever the company can switch over to fiber. And from here, the aircraft-entertainment designers look to take off.

Recommended reading:
"In This Guided Age, Gilded Model Ts," Keith Bradsher, The New York Times, business section, p. 1, Nov. 12, 2000.
Multimedia, The Complete Guide, DK Publishing Inc., New York, 1996, ISBN 0-7894-0422-2.

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