Electronic Design

Autos Head Down Electric Avenue

The future car is going more electric for better fuel efficiency, economy, safety, convenience, and entertainment as well as for a smoother ride. The challenge auto designers face is how to store and manage all of this electricity.

Just go back 20 years to see the difference. Then, electronics primarily worked the radio, the windows, and maybe the seats—and that was it. Today, electronics have turned the car into a highly intelligent entity.

Electronics permeate every aspect of automotive functions, including engine management, pollution control, safety, convenience, entertainment, stability, security, and communication, in addition to a vast list of luxuries unheard of just a few years ago.

The trend isn't slowing down, with more intelligence being weaved into cars at every twist and turn. Eventually, electronic systems will bring autonomy to future vehicles, making them safer, more comfortable, and more efficient.

One of the more notable automotive trends is the move to hybrid electric/gasoline vehicles, prompted by economical and ecological concerns. U.S. hybrid car sales rose 81% last year over 2003, with 83,153 new hybrid cars registered, according to R.L. Polk & Co.

Most of the U.S. hybrids are actually Japanese cars (96%), like the Toyota Prius and hybrid Honda Civics, Accords, and Insights. Ford's Escape hybrid features a four-cylinder internal-combustion engine, a 70-kW electric motor in the front, and a nickel-metal-hydride battery back under the rear-load floor (Fig. 1). Nissan, General Motors, and DaimlerChrysler all plan to introduce hybrids.

Still, the reaction to hybrid cars has been somewhat tepid, because the actual mileage figures touted by the manufacturers aren't reaching expectations (but certainly better than conventional-engine cars). Hybrid sales are increasing nonetheless, with Toyota planing to build 100,000 Prius hybrids this year, up from 67,000 last year.

Concerns about gasoline consumption have piqued interest in alternate forms of energy. Powered by hydrogen, Ford's Focus fuel-cell cars have already hit the street in British Columbia under a joint five-year program between Ford, Fuel Cells Canada Co., Ballard Power Systems, the government of Canada, and the provincial government of British Columbia. According to Ford, the Focus fuel-cell vehicle (FCV) program is one of the most advanced environmental efforts in the industry, with zero emissions.

Research at the University of Florida in Gainesville has shown that biomass-to-ethanol conversion technology could be developed to help replace one-half of the gasoline fuel consumed in the U.S. E. coli bacteria in farm waste such as corn stems, cobs, and leaves produce the ethanol.

Electronics designers are looking to go beyond federally mandated passive safety systems—such as airbags and seat belts that mitigate driver and passenger injuries—to active safety systems that help drivers avoid accidents in the first place.

These systems extend past existing antilock braking systems (ABSs) and traction to prepare for emergencies and provide sensing for better situational awareness. Passive systems aren't taking a backseat, though. Federally mandated laws are pushing the use of sensors (usually MEMS) for side-impact and rollover detection.

In another development, Volvo's blindspot information system (BLIS) uses a compact imaging array camera mounted below each sideview mirror. An LED in a triangular area on the window frame alerts drivers to vehicles in the blindspots to the rear and side of their car (Fig. 2).

Active systems, such as lane-departure warning (LDW) systems, promise to help drivers who carelessly drift into the next lane due to fatigue or inattentiveness. Automotive supplier Valeo already has adopted the LaneVue LDW system from Iteris for the Nissan Infiniti FX35 and 45 sport utility vehicles (SUVs), as well as the M45 luxury sedan (Fig. 3).

The LaneVue system consists of a tiny palm-sized CMOS camera, a computer, and software. It mounts between the rearview mirror stalk and the front windshield. It then looks 25 m ahead of the vehicle to track lane markings and feeds this information into the computer. Using this data, image-processing software, and proprietary algorithms, the computer calculates the distance between the lane markings as well as the lateral to the lane marking. Consequently, it alerts the driver via a dashboard indicator light and an audible buzzer when the car is moving unsafely out of its lane.

A major issue in LDW system design is the right man-machine interface. It must provide correct, timely information so that the driver can react accordingly—without distracting and overloading the driver with too much data. That's especially challenging, considering all of the other visual and audible electronic warnings and indicators in modern cars.

To that end, Delphi Corp. plans to develop a safety "cocoon" that wraps around the car. Its Integrated Safety Systems approach uses an eye-tracking system, replete with algorithms as well as imaging devices, that are invisible to the driver. This system should be ready for the truck market by next year.

Visteon Corp. is working with the universities of Michigan and Carnegie-Mellon to develop two systems that keep drivers from veering off the road, under a program funded by the U.S. Department of Transportation (DOT). The first is a lateral drift warning system for leaving a lane or the road. The second is a warning system that alerts drivers if their vehicle is going too fast heading into a curve.

Automotive manufacturers and suppliers also are vigorously working on active electronic-stability-control (ESC) systems (some call them vehicle-system-control or VSC systems) to help prevent skidding and unstable car behavior. Sensor data and a stored database of vehicle information combine to make the intervention decisions.

In fact, General Motors' Stabilitrak version of this technology will be standard on all GM cars and trucks by 2010. Toyota has described such a system and is currently developing its version (Fig. 4).

Active electronic systems aren't limited to safety factors. They're also abetting driver comfort and ride smoothness. Bose Corp., mainly known for its high-quality audio expertise, developed an auto active adaptive suspension system based on speaker technology. It uses linear motors both as sensors and actuators. Conekt, the consultancy arm of TRW, came up with an advanced reinforced fiber composite material suspension system that provides both variable stiffness and damping, eliminating the need for separate units for both functions. In the system, when a wheel moves up or down, a motor functions as a generator and sends a control signal to keep the car level.

Unfortunately, the scads of electric-powered extras being poured into automobiles are exhausting the electricity source. Electrically driven motors are now everywhere in cars. For example, BMW uses an advanced active power-steering system (Fig. 5). Some cars contain up to 50 motors, and more may be needed as other advanced-performance systems are added.

The move to hybrid cars has placed a heavier burden on the energy plant. Some designers are investigating 42-V batteries, but this has brought technical challenges of its own. The additional costs of using 42-V batteries in a car are beginning to outweigh the advantages gained by more electrification.

As a result, some automotive system designers question whether or not 42-V systems will only appear in future high-end vehicle models and not in low-end and mid-range cars. Some designers say we need to stick to lower-voltage batteries and find a better way of managing the energy plant.

"The modern car is on a trend of electrification that's growing by about 100 W per year, and it's putting a burden on a car's conventional lead-acid battery system," says Richard Smith, executive vice president of business development at Maxwell Technologies.

His company manufactures ultracapacitors that can store lots of electrical energy in a small form factor. This ultracapacitor technology, which did not exist just a few years ago, is making it more practical to store and manage electrical energy for future hybrid and fuel-cell cars. In fact, many Japanese and European auto manufacturers are now working feverishly to incorporate ultracapacitor technology.

Electrically driven systems are just about everywhere in a car. Maxwell points out that a 16-V ultracapacitor technology, which the company is ready to introduce, can be successfully used in an automotive power plant. It's also a more practical and lower-cost solution than the higher-voltage battery route.

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