Complexity is the curse of computers. It also is their advantage. Taming complexity is the challenge that designers and programmers face. So far, they’re doing pretty well when it comes to transportation.
The problems associated with it not withstanding, the Toyota Prius (Fig. 1) represents an amazing combination of gas and electric engines, hydraulics, and electronics. Its drive-by-wire throttle system is currently under the microscope because of unintended acceleration issues, though the Prius may yet emerge from the cloud of uncertainty.
The Prius drive-by-wire system does have advantages over a purely mechanical system. For example, its smart pedal override can cut power if the driver steps on the brake and accelerator pedals at the same time. A complex mechanical version of this system would be even more prone to problems.
By-wire technology is well accepted in aviation. The F-16 Fighting Falcon and Sukhoi Su-27 Flanker fly-by-wire fighters date back to the 1960s. The Airbus A321 is just one commercial fly-by-wire aircraft that has carried millions of passengers.
These systems and even hybrids like the Prius are relatively complex. The failure modes are numerous, but good design and redundancy provide a safer vehicle. Still, reducing complexity always helps, and moving to all-electric vehicles may help more than just reducing carbon footprints.
For example, the electrical schematics for the all-electric Zap Alias (Fig. 2) and Nissan Leaf are significantly simpler than the schematics for the Prius. That isn’t surprising since all the support for the gas engine is gone, including loads of sensors, actuators, and their related electronics and wiring. Removing these components reduces weight, cost, and points of failure as well as complexity.
AUTOMOTIVE REDUNDANCY NOW
On the other hand, the level of complexity for electric vehicles is likely to rise. The increase won’t necessarily be in the schematics or engines but in the microcontrollers.
Fly-by-wire aircraft have redundancy. Cost is less of an issue, so physically replicating hardware is common. Consumer products are more cost-sensitive, meaning redundancy isn’t always at the top of a designer’s list of choices. That’s changing.
Take the Freescale MPC564xL and STMicroelectronics SPC56EL plug-compatible dual-core microcontollers with built-in FlexRay support (see “Dual-Core, Dual-Source Processor Includes FlexRay For Auto Apps”). These chips can control two brushless, three-phase electric motors.
Also, the two cores can run in a redundant, lock-step mode. Of course, this redundancy doesn’t prevent a programming snafu from causing a problem. But these chips can run more applications that are larger and more complex than their predecessors.
STEER-BY-WIRE: TODAY AND TOMORROW
Specialized vehicles like electric forklifts use steer-by-wire technology to provide a complete drive-by-wire system. Segway’s electric Human Transporter also falls into this category (see “Smart Motion Makes For A Smarter Design”). The electric power plant and drive-by-wire make the platform suitable for robotic operation.
The General Motors EN-V (Fig. 3) concept vehicle follows this electric drive-by-wire theme (see “GM Segways Into Two-Wheel Concept”). These battery-operated, two-wheeled people movers are even designed to communicate with nearby vehicles. Do you have more than two people in your group? Then have multiple EN-Vs play follow the leader. Talk about complexity.
Cars that drive themselves? They likely will be all electric simply because they will be easier and cheaper to build. And hopefully safer too.