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Hyundai's "E-corner" system
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This is a most excellent place for technology news and articles.
Lots of added tech makes these more likely to fail. And I don't think they'll be cheap to replace.
Now you'll have to worry about front wheel alignment and rear wheel alignements more often. The rear steering components will add cost to the initial purchase of the vehicle as well as more maintaince costs. All to cram more cars into on street parking.
The primary reasons that multiple attempts have failed for over 100 years! Motors in each wheel could possibly cross the barrier of complexity, but I'm still not expecting this to make it to mass production anytime soon.