Originally Posted by mtberman

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...The basic arrangement was developed by Aisin and Toyota. Toyota moved it in-house, leaving Aisin with the architecture but no buyer. Most accounts I've seen indicate that Toyota didn't think anything would come of it. Aisin, however, knew the system was a torque-monster so they brought in Volvo to develop it for big trucks. Enter Ford, who acquired Volvo. They decided to apply it to the Mazda platform on which the Escape was based. Meanwhile, Toyota introduced the Prius in Japan in '96. Ford took apart a Prius in (I think) '97, saw enough to be concerned, and approached Toyota about sharing it. Toyota would not license it, and did not want to share any of the controller stuff (software) at all. But they were desperately behind in Europe because they had no diesel play. In the end, Toyota granted hybrid licenses to Ford, who agreed to license certain diesel patents to Toyota.

The systems were developed separately so there are significant differences. But both are based on the same original idea for a planetary gear arrangement of multiple inputs & outputs, some of which alternate between driving and being driven. IIRC, one of the Motor Generators is off to the side on the Ford unit instead of in-line as on Toyota's. Regardless, if you understand how the PSD works in a Prius, you (basically) understand Ford's.

There are some specific differences, but none worth dwelling on IMO aside from the different position of one of the MGs.