Computer on Wheels

By Mel Duvall  |  Posted 2005-08-04 Print this article Print

Strong sales of Toyota's Prius hybrid vehicles could be threatened by software malfunctions that leave drivers stuck in traffic.

At its heart, the Prius is a computer on wheels. After slipping into the driver's seat, the owner simply pushes a button on the dash-much as you might press the On button on a computer—and the vehicle powers up. This technology is often referred to as drive-by-wire, as there are no traditional cables, hydraulic lines or linkages connecting the gas pedal to the engine, the brake pedal to the brakes, or the stick shift to the transmission. If the car is in Park or Neutral and you press down on the gas pedal, the engine will not race as it would in a normal car, because the computer determines there is no purpose in doing so.

A touch-sensitive console located in the center of the dashboard provides access to a number of features, such as radio settings and climate controls, as well as updates on the vehicle's performance. The screen shows, for example, a graphic representation of the power flow from the electric motor or gas engine in the hybrid system, and the average miles per gallon achieved over the last 5 minutes and 30 minutes.

Virtually every major subsystem of the vehicle, from the electric motor to the gas engine and battery-pack system, has its own electronic control unit—a computer—to control and direct operations. The major electronic control units in turn communicate with one another over a high-bandwidth network. And orchestrating the entire operation is the hybrid ECU.

In action, it works like this: When initially pulling away, or driving at low speeds, the vehicle is powered by its electric motor. As the car picks up speed, the hybrid electronic control unit instructs the vehicle's gas engine to turn on and provide additional acceleration. The torque from the two motors is managed through a power splitting device called an electronic continuously variable transmission. At high speeds, the car runs primarily on the gas engine, which also recharges the vehicle's battery.

The combined systems give the Prius outstanding fuel mileage—60 miles per gallon in the city and 51 on the highway, as estimated by the Environmental Protection Agency. (Unlike conventional vehicles, the Prius gets better fuel mileage in the city because it can drive more often on the electric motor.)

Its complexity, however, not only prevents most owners from tinkering under the hood, but has also been a concern for the automotive repair industry in general. "One look under the hood will scare you," says Craig Van Batenburg, owner of the Automotive Career Development Center in Worcester, Mass., which specializes in training independent garages on repairing vehicles. "They're more complicated, there are more computers, more sensors, and everything's packed in so tightly."

And they can be dangerous. Power to the Prius' electric motor is supplied by a 276-volt battery pack. The average person can be killed by a 60-volt shot to the pants. Van Batenburg says safety measures are more critical than ever with the hybrids, but the independent repair industry has to learn how to handle hybrids or risk losing an increasing share of business to the dealerships.

The average car owner probably isn't aware of how software updates even get into his vehicle. On most cars, a dongle—or data port—is installed just below the lower left side of the steering wheel. When the car is brought into the repair shop, a mechanic connects to the port and runs a set of diagnostic tests. The technology is a god-send for mechanics, according to Van Batenburg. "When the check-engine light comes on, it could be one of 600 things going wrong," he says. "Without the computer systems, it could take days to pinpoint a problem."

Updating the software in the Prius, or any other vehicle, is a relatively simple process. Most shops now provide mechanics with wireless laptop computers. The mechanic uses the laptop to go to a secured Web site provided by the manufacturer, and downloads the latest software update to the laptop. From there, it gets passed through the data port to the flash memory in the vehicle.

The Prius stalling problem may turn out to be minor. In fact, Van Batenburg speculates that a number of the incidents could simply be a result of owners trying to squeeze every bit of mileage they can out of a tank of gas and eventually hitting empty. (A number of Prius owners posting in online forums have insisted their tanks were not empty; Len says her car had plenty of gas left when it stalled.) However, it is also just as possible that the problem could be widespread and will result in a recall.

In the meantime, it doesn't appear to be affecting the vehicle's sales. Toyota says it sold 9,622 Prius vehicles in the U.S. in June, at the height of attention over the software flaw, a 119% increase over the previous year. In the first six months of 2005, gas-priced-gouged consumers snapped up 53,310 of the $20,000 vehicles, compared to 21,890 in the first six months of 2004.

Owners like Len say they're not bothered by the increasing amounts of software in their vehicles and, in fact, can't wait for more innovations and software-driven features to be added to the Prius. But they want Toyota and all manufacturers to get it right.

"The computer techs, engineers and designers need to step up to the plate and fine-tune their craft," Len says. "Frankly, I hope I live long enough to own a flying car with whatever new technology is available to run it."

  • Story Guide:
    Software Bugs Threaten Toyota Hybrids
  • A Costly Problem
  • Computer on Wheels
  • Toyota Motor Sales USA at a Glance

    Next page: Base Case: Toyota Motor Sales USA at a Glance

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    Contributing Editor
    Mel Duvall is a veteran business and technology journalist, having written for a variety of daily newspapers and magazines for 17 years. Most recently he was the Business Commerce Editor for Interactive Week, and previously served as a senior business writer for The Financial Post.


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