San Jose, Calif. A teardown of the Toyota Prius stole the spotlight last week at the Embedded Systems Conference here, with the culmination of a multistage project that exposed the electronics and design techniques used to create one of the most advanced alternative-energy vehicles to date. Attendees were treated to a dissection of six of the vehicle's most critical electronic subsystems--from the inverter to the entertainment system--to give designers insight into what makes the Prius tick and how its engineers overcame challenges related to energy conversion, heat dissipation, safety, cost, weight, efficiency and navigation.
The project started in early February with the stripping down of the Prius at the Troy, Mich., facilities of engineering and manufacturing analyst firm Munro and Associates. That project was led by Munro associate Al Steier. From there, six of the Prius' most critical subsystems were shipped to David Carey, president of Portelligent (Austin, Texas), for closer analysis. While Steier gained insight into the car's general design and layout, Carey leveraged his expertise in electronic systems to explore innovation at the board and chip levels and shared that knowledge in six presentations at ESC last week.
AutomotiveDesignline. com editor Rick DeMeis, who tracked the teardown process, said Toyota followed standard practice, "with modules, bits and pieces--from electronics to doors and other components--that readily fit in place, enabling building the same vehicle, with the same quality, anywhere in the world." Of note was the sheer weight of the inverter/converter--what DeMeis called "the electrical switching yard"--which provides voltage control, switching of dc to dc and dc to ac for the motor drive, and ac to dc to charge the battery with the gasoline engine and during regenerative braking. Heat dissipation concerns required "massive" aluminum casting that brought the weight to 30 pounds. DeMeis also cited the engine control module, which was shielded from EMI and placed away from heat and moisture.
The six subsystems torn down by Carey at the show were the inverter, skid-control module, airbag, navigation system, entertainment system and main dashboard module. Carey said Toyota chose to stick with standard, well-established parts in many instances.
"The Prius teardown highlights the growing distributed-system electronics" used in autos, he said. "Mission-critical subsystems rely on relatively conservative design choices in both IC packaging and IC components--some microprocessor designs were up to 12 years old--while infotainment systems are implemented in a form closer to state of the art." Carey called the hybrid drive electronics "a fantastic piece of analog design and power-flow management to provide seamless hand-off between electric and gas power along with regenerative power recovery."
The Prius teardown will be featured in the May 14 issue of Under the Hood, an EE Times supplement presented by EE Times and Techonline. Subsystem teardowns can be seen on AutomotiveDesignline. com and Techonline.com/underthehood.