Products for Passenger Cars

Agile in Every Situation – AKC Active Rear-Axle Steering

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Comfort, space, safety and a great driving experience – these are all advantages of larger, modern vehicles. But what about agility?
Lars Weitbrecht,
Lars Weitbrecht originally comes from the music and gaming industry, but in addition to holding a game pad or guitar in his hand, he also enjoys the power of the pen and the feel of the steering wheel.
It’s excellent, if AKC – ZF’s active rear-axle steering – is included. The ZF system enables trucks, SUVs and larger cars to maneuver with the agility of a compact vehicle. In addition, AKC reduces sway in pickups and SUVs, allowing for a more comfortable ride and more stable towing of trailers.

Pickups and SUVs are huge –both in size and popularity. Many four-wheel-drive vehicles are now larger than ever, reaching dimensions of nearly six meters in length, over two meters wide and nearly as high. Weights can reach a whopping 6,000 pounds with occupants. Despite their mammoth size – or maybe because of it – trucks and SUVs are extremely popular, . from business use to family vehicles, especially in the USA, due to their almost endless versatility and long range.
Such a "heavyweight" is currently on ZF’s test tracks in Germany and the US. Recently a group of ZF developers gathered at the site near Vienna to test the truck’s maneuverability on a small, demanding parkour. The course incorporates sharpturns and curves between pylons, as well as parking in a standard commercial size parking space. “You’ll never get that vehicle in there in one try,” you think. Well, think again. Agile as a go-kart, the off-road titan maneuvers into the open space – in one move, without readjustment.

This is possible because the rear wheels also turn, in this case in the opposite direction as the front wheels, making the steering radius significantly smaller. The technology that achieves this is the AKC active rear-axle steering system from ZF. The recently-released second generation turns the rear wheels 12 degrees, significantly greater than the six degrees available in the original version. With this technology, even pickups, SUVs and the longest sedans become as agile as compact cars. This improves the driving experience, and also brings safety and comfort advantages, especially in very narrow urban areas.
The latest generation AKC offers rear steering angle of up to twelve degrees.

Active Kinematics Control (AKC): The Agility Ace for Passenger Cars

Active Kinematics Control (AKC): The Agility Ace for Passenger Cars

"Passenger cars are getting bigger and heavier," comments Ingo Hermansa, Head of the Mechatronic Chassis Actuators product line, at the edge of the test site. The latest technologies and laws are increasing the dimensions of vehicles. In pure battery-electric vehicles, a long wheelbase is added to make room for the batteries.
"This may lead to more comfort, safety and sustainability, but it is at the expense of maneuvrability," Hermansa continues. This is particularly evident in the urban environment. "At a narrow intersection or in the parking garage, this can be a bit exciting." Our AKC counteracts this. In the second generation, the actuators installed on the rear axle can cause the rear wheels to turn up to 10 degrees. With this agility ace, even crossovers or SUVs have the turning circle of a compact car.
The AKC also offers advantages on the main road or highway. Because when the rear wheels steer, the vehicle becomes noticeably more stable, especially during evasive or lane change maneuvers.

"The benefits of AKC are particularly evident when we run tests with a trailer – preferably on uneven roads," explains Hermansa. Anyone who has ever completed such a trip knows what unwanted momentum arises from the combination of speed and inertia. Our AKC can balance these forces – goodbye to wavering tandem, hello gentle exit.

Another key safety factor: ZF’s AKC can significantly shorten braking distance – especially in situations where the road surface is not smooth. AKC contributes to greater and more consistent contact between the tires and the road, and therefore increases safety, It also adds to a better driving experience as changes in direction, both gradual and sudden, are smoother, with drivers and passengers feeling significantly less impact.

If You Want Agility, Choose AKC

If You Want Agility, Choose AKC

Demand shows that ZF has taken the right path with the AKC. Currently, 1.3 million vehicles worldwide are already equipped with our AKC. A fifth assembly line was opened at our Lebring plant in Austria. And our customers include well-known automotive brands from all over the world. "By the end of 2023, there will be more than 1.7 million vehicles operating with AKC," Hermansa asserts.
ZF has equipped a total of
vehicles with AKC by the end of 2023.

Active Kinematics Control (AKC)

AKC is used in two variants, depending on the requirements and available installation space: as a central and dual controller system.

The central controller (also called single actuator) is installed in the middle of the axle and steers both wheels via track control arms. With the dual control principle, each wheel is individually steered by a separate Stella actuator.

Central controler

More about the AKC

The capability to steer the rear axle has advantages in every driving situation. Increased agility in urban areas, higher stability when it matters. In conjunction with vehicle stability control, AKC can even reduce brake distance and improve trailer stability when towing.

Dual control principle