It’s called K-turn mode, and Rivian has recently filed a patent for this driving assistance system. Now, while Tank Turn allows Rivian's R1T electric truck and R1S SUV to rotate into place by shifting torque to the wheels, it’s not a feature you want to use on soft surfaces. That’s because it will cause the wheels to dig into the ground, eventually sinking the vehicle instead of turning it.
That’s where K-turn mode comes in, as it’s designed to offer improved maneuverability by enabling turns with decreased radius without the wheels sinking into the ground.
According to the patent filing and the accompanying images and diagrams on PatentScope, K-turn mode works in a similar fashion to Tank Turn, but there are some key differences, as the patent listing explains.
“The K-turn mode is engaged in response to determining that an amount that at least one of the front wheels of the vehicle is turned exceeds a turn threshold. While operating in the K-turn mode, forward torque is provided to the front wheels of the vehicle. Further, backward torque is provided to the rear wheels of the vehicle. Yet further, the rear wheels of the vehicle remain substantially in static contact with a ground while the front wheels slip in relation to the ground.”
Gallery: Rivian K-turn mode patent
Basically, the rear wheels (or only one of them) can be kept static in K-turn mode or locked, “anchoring” the rear of the EV so that the torque of the front wheels can turn it. This could prove useful not only off-road to avoid digging, but also in tight places, for example when maneuvering in the city (hence the K-turn name).
Looking at the diagrams, the feature seems to be activated at the “turn threshold,” as patent Fig. 5 describes. This suggests the driver needs to turn the wheel beyond lock for the K-turn to kick in.
It’s not hard to imagine Rivian further developing this technology to work on EVs with various motor configurations. Obviously, K-turn is currently under development, so the first Rivian EVs set to reach customers this month won’t have it. Still, it sounds like something an over-the-air update can easily solve further down the line.