Soon your car’s steering wheel will no longer be connected to the wheels

Basically, nothing has changed since the birth of the automobile: cars have been steered for more than a century with a steering wheel (or handlebars) connected to the wheels via a metal column. But a new revolution will change the game. The marketing of systems fully electronic steering, where the steering wheel no longer has a physical link with the wheels, is imminent. The benefits are many. The most obvious concerns the disappearance of the steering column, which frees up space on board to reorganize the cabin. This also makes it possible to dispense with a metallic element, and therefore to save weight. Above all, this leaves much greater adjustment latitude than a traditional system, while isolating the steering wheel from road vibrations.

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Conventional steering assistance, whether electric or hydraulic, does nothing more than reduce the effort required to turn the steering wheel, variably depending on the speed. This greatly facilitates the task in town, but there remains a physical limit: the gear ratio between the pinion and the rack is fixed. And this one is based on a compromise. At low speed, we would like the most direct and most assisted steering possible, so as not to have to “mill” with the steering wheel, for example during a parallel maneuver. On the highway, on the contrary, we prefer a significant reduction, so that the small imperceptible movements of the hands do not result in deviations from the trajectory.

There are already tricks to vary the gear ratio

To vary the gear ratio angle depending on the driving situation, there are already several solutions. The simplest is a variable pitch rack. This type of component, used in particular by Volkswagen on its Golf GTI, consists of increasingly tight teeth on the rack as the steering wheel is turned. In short, the response is less lively around the midpoint, on the low steering angles used at high speed. On the contrary, as you turn the steering wheel, the effect is amplified. This gives a feeling of increased responsiveness in tight turns.

At the house of Ford, it’s a worm gear electric motor system mounted on the steering wheel hub which is offered on some high-end models, such as the Edge, S-Max and Galaxy. At low speed, this comes into play at the same time as the driver turns the steering wheel, to amplify the steering. Which amounts in this precise case to reducing the angle of reduction perceived.

^{BMW Active Steering}

BMW offers with its parametric active steering a system philosophically close to that of Ford, but more advanced in its management. Here, an epicyclic gear train controlled by an electric motor divides the steering column into two segments, making it possible to amplify the steering as at Ford, depending on the speed. In addition to this advantage of facilitating maneuvers, there are other functions from the Bavarian manufacturer. The device can thus provide micro-corrections to compensate for crosswind effectsor even countersteer to help the car get back on line in the event of a skid.

Infiniti, steering pioneer “bywire” on the Q50

If all these systems tend to overcome the constraints, they still require compromises related to the mechanical connection between the steering column and the rack. The real solution, for total freedom in steering management, is enabled by electronics. The steering wheel is linked to sensors measuring the effort, the steering angle and its rotation speed, while the rack is driven directly by an electric motor, whose response is programmed according to the data of the sensors. This system is called in English “steer by wire“. Thus, all the fantasies are possible, with for example a very direct angle at low speed in maneuvers and, on the contrary, a very “locked” steering wheel on the motorway, to ensure the stability of the trajectory. In addition, the freedoms allowed to calibrate the feeling are infinite, allowing for example to differentiate the sensitivity on models nevertheless using the same components.

The first manufacturer to have marketed a steering “bywire” is Infiniti, on its Q50 sedan launched in 2013. At the time, however, it was impossible to homologate a model without a steering column. So Nissan’s premium brand engineers designed a clutch system on the column, which automatically locked in the event of an electronic system failure. This was highly unlikely, since the electrical circuit was equipped with triple redundancy, aligning with aeronautical standards. That is to say that if the main circuit encounters a problem, a second takes over, itself doubled by a third “spare wheel”… Electronic failure is highly improbable: we can bet without great risk that the All Infiniti Q50s equipped with this option have never needed their emergency steering column.

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The magnitude of the gear ratios chosen by Infiniti engineers testifies to the flexibility of the system. Below 40 km/h, this was fixed at 9:1 (meaning that when the steering wheel turns 9 degrees, the wheels turn 1 degree), and could vary up to 24.7:1 on the highway. This is respectively more direct than on the lowest cut and less direct than on a 4×4 with a high center of gravity. But a high adjustment range is not enough to achieve a successful steering bywire. Infiniti learned this the hard way, with sometimes confusing variations, pointed out by testers. When registering the auto in tight turns, the steering angle increased as the speed decreased, causing the auto to turn sharply while the angle at the steering wheel remained constant. This could cause quite brutal loss of adhesion of the rear axle. In 2016, the Japanese brand recalled the cars in circulation to review its copy, with less excessive tuning.

The Lexus RZ 450e, the first production car without a steering column

Since Infiniti in 2013, no manufacturer has marketed a car equipped with a steering system bywire. But the situation is about to change. In the fall, another high-end Japanese brand will follow suit: Lexus. The RZ 450e electric SUVtechnical cousin of the Toyota bZ4X will thus have, on certain finishes, the One Motion Grip electronic steering. This is accompanied by a “yoke” steering wheel, that is to say without a hoop in the upper part, designed so that the hands never move from the lateral gripping zones. To make parking maneuvers easier, this means that the steering wheel should not make more than half a turn from lock to lock at low speed. And, indeed, the engineers at Lexus went much further than those at Infiniti on this point: indeed, at low speeds, the gear ratio can go down to 1:1. This means that if you turn the steering wheel 10 degrees, the wheels do the same. Unheard of on a car, since it gives more direct steering than a kart! Conversely, the maximum gear ratio is 16:1, corresponding to the average of a classic direction. Despite these unusual features, this is not to confuse the customer too much. “The gear ratio varies in real time depending on driving conditions. The variation is progressive, stepless, and transparent to the driver,” says Lexus.

^{Lexus RZ450e}

Unlike Infiniti, Lexus did not retain a physical steering column to compensate for any electronic failure. “European regulations require having a complete backup system”, assure us the brand’s engineers. “But this one is not necessarily mechanical. The Lexus RZ has a complete redundant circuit, including its own battery and its own inverter”. In short, the electric SUV will be the first mass-produced model to do without a steering column. For the moment, the brand does not communicate the additional cost linked to this option.

^{Lexus RZ450e}

Lexus claims to have developed its steering system bywire internally. However, he should not remain a pioneer for very long. In effect, several equipment manufacturers are already working on the subject. This is particularly the case of Schaeffler, which has partnered for this type of development with Paravan. This last company has worked on the subject for the adaptation of vehicles intended for disabled people, for whom a derogation is allowed. By recovering Paravan’s experience, Schaeffler was able to get a head start, testing its system in competition, particularly in the GT3 category, which gave satisfaction to the drivers. The equipment manufacturer hopes to deliver directions in small series bywirefirst to high-end manufacturers.

Directions bywire could become the norm in 2035

But it is another German equipment manufacturer, ZF, which should be the first to supply. This indeed announces serial applications from 2023, with “significant volumes”, from several major manufacturers whose names are still unknown. During an event organized on the Trappes circuit in the Paris region, we were able to test a prototype of Volkswagen ID.3 thus equipped with a direction bywire. So as not to confuse the testers too much, the ZF engineers chose a rather wise setting for this demonstrator, which also retains a traditional steering wheel. Indeed, the gear ratio only varies here between 9:1 and 19:1. On trial, the feeling is quite natural, the transitions between the various fluid speeds. The benefit in terms of maneuverability is noticeable: to highlight it, ZF took us on a tour of the karting circuit with particularly tight turns. The effect is convincing, but the adjustment of the prototype leaves us on our hunger. Knowing the possibilities of this technology, one can only hope for a more extreme setting. Still, ZF has proven with this ID.3 that taking control of a direction bywire could be immediate and intuitive. We can’t wait to try the Lexus RZ 450e, whose promise of a change of scenery is superior.

Electronic steering promises endless freedom to developers. It will be interesting, in the near future, to see how each brand will adapt this device according to its needs and the perception of its customers. What is certain is that the technology is a priori promised a bright future: ZF estimates that the management market share bywire will be important from 2030. As for Schaeffler, he believes that this type of leadership will be the norm in 2035.