A product that enables agility, safety, and comfort in numerous driving situations, German multinational supplier ZF’s active rear axle steering system AKC (Active Kinematics Control) has reached a critical milestone, with one million units produced since the start of production in 2013.
With the AKC, the toe angle of the rear wheels can be changed, and this results in enhanced steering functions. It further increases manoeuvrability during parking and in city traffic by steering the rear wheels in the opposite direction at low speeds. The technology also allows the vehicle's turning radius to be reduced by up to 10%, making it easier to manoeuvre passenger cars.
In turn, steering the rear wheels in the same direction stabilises the vehicle at higher speeds from approximately 60 kmph, especially during evasive and lane change manoeuvres, said the company.
Dr Peter Holdmann, Head of the Car Chassis Technology Division, ZF said, “We continue to see a sharp increase in demand for our active rear axle steering systems because the technology provides decisive advantages in terms of the challenges of modern mobility.”
In fact, demand for rear axle steering is further expected to grow considering the transformation of the industry towards electromobility, as battery-electric vehicles (BEV) will also benefit from the technology.
Since the battery is usually placed between the axles in electrified passenger cars, they usually have a longer wheelbase. This has a negative effect on the agility and turning radius of the vehicle, explained ZF.
“This effect is particularly noticeable in urban surroundings and parking situations. Here, our rear axle steering is an excellent solution to allow these vehicles to be easy to manoeuvre. In addition, customers benefit from increased stability and safety thanks to steering in the same direction at higher speeds,” Holdmann said.
Second-Generation AKC
ZF launched the second-generation AKC in 2020. This new-gen product helps SUVs and luxury sedans achieve similar manoeuvrability to that of significantly more compact vehicles. An actuating force of 11 kN enables vehicles of up to 3.5 tonnes of weight to use this technology, said ZF. This, along with the product’s ‘steer-by-wire’ system properties, makes it ideally suited to the requirements of automated and electrified mobility.
ZF manufacturers the AKC system at its Lebring, Austria facility in two variants: in a dual and a central actuator architecture. The dual actuator variant is ideal for sports cars because it saves valuable installation space in the central part of the rear axle. When installing dual actuators, each wheel is individually steered by a separate actuator.
The central actuator variant, on the other hand, is positioned in the centre of the axle with a larger actuator. This is primarily installed in sedans, pick-ups, or SUVs.
ZF has also announced that production of a central actuator variant for an EV pick-up by a North American customer is currently launching into the market.