This article is republished from autocarweekly WeChat official account
Author: Aoao Hu
Do you remember Tesla’s incredibly sci-fi yet ridiculous Yoke steering wheel?
Toyota has brought a “same style” design to its electric cars, but fortunately, it only looks the same. You may find it hard to believe, but this time it is Toyota – a company that has always been known for stability and reliability – that has become a pioneer for the future, using new technology to “tame” Tesla’s science fiction steering wheel that is both useless and ridiculous.
Akio Toyoda, who is always keen on publicly criticizing electric cars on various occasions, is considered by outsiders to be the world’s top electric car critic, but in fact, Toyota has been developing its own pure electric platform. It was initially called e-TNGA, but this name was overused for electric versions of C-HR and UX300e, and we have explained that TNGA “is not a platform, but a group of platforms”.
Finally, Toyota’s first pure electric platform was officially unveiled, and it had its own name: bZ (meaning Beyond Zero). The first work of the new platform, and Toyota’s first “native” pure electric vehicle, is called the bZ4X. This is a mid-sized pure electric SUV, similar in size to the RAV4.
The preceding paragraphs provide insignificant background information.
Whether it is the bZ platform or the bZ4X model, in my opinion, it is nothing special. It is a pure electric platform/model that was developed for electric vehicles, but still retains many traces of traditional gas-powered vehicles. However, surprisingly, Toyota has equipped this vehicle with the world’s first mass-produced steer-by-wire system – directly lifting the steering wheel from the bZ4X concept car to the production version.
The steer-by-wire system is the key to making the Yoke steering wheel truly usable and an inevitable future for achieving autonomous driving.
Let the “spinner” roll into history
Every child who died in a driving test because they didn’t know how many times they had turned the steering wheel, and every child who was scolded by their driving instructor for “grabbing the steering wheel” backwards, has reason to vote for steer-by-wire.# Tesla’s Yoke steering wheel is difficult to use
The Tesla Yoke steering wheel is notoriously difficult to use because it still requires 1-2 turns to turn fully, so once you’ve turned it once, your hands have nowhere to rest. The “Toyota version of the Yoke,” however, can turn up to 150° on one side thanks to its line-controlled steering, which is less than half a turn.
In other words, you can “stick” your hands to the left and right sides of the steering wheel and not have to change positions during the entire drive. “Backhand” and “wheel rubbing” are irrelevant to you from now on. Toyota calls it “One Motion Grip” because all you need to do is grasp the steering wheel to steer the car in any direction with a single action.
But then the question arises, why would the steering wheel have to turn several times before and not just turn the wheels based on how much the steering wheel is turned?
This is because the drive ratio of the steering wheel is usually fixed between 12:1 to 20:1 for passenger cars, meaning that the steering wheel turns 12° to 20° before the front wheels turn 1°. If the steering ratio is too small, such as 1:1, the front wheels’ actions are too sensitive to the steering wheel’s actions. Even the slightest movement in your hand will have a 100% effect on the front wheels. This is dangerous when driving at high speeds.
We can easily cruise at 120 km/h thanks to the large steering ratio that significantly reduces the steering wheel’s movements. Even if the steering wheel moves 1° accidentally, the front wheels’ action is only 0.06° at a 16:1 steering ratio, which is much easier to control.
The downside is that when making a U-turn or parking and turning the wheel, you need to turn it a few times (360° × n) to turn the front wheels all the way (generally below 40°).
Some models have variable steering ratios, which use special means to make the steering ratio larger in the center of the steering wheel and smaller at the ends. This ensures stability at high speeds and requires fewer turns to make turns during U-turns or parking.
But the variable steering ratio of mechanical steering system has limited range (generally within the range of 10:1 to 20:1, i.e. less than 2 times), which can only be partially optimized but cannot solve the problem. Even with variable steering ratio, it still needs more than one circle when the steering wheel is turned to the limit – the driver needs to change hands. The steering wheel still needs to be a complete circle.
To achieve truly arbitrary changes in steering ratios, only the big move of steer-by-wire system can be taken.
Currently, all steering systems of automobiles are mechanical ones, with the steering wheel connected to a steering column and physically linked to the steering system. As for the power assist of the steering wheel, even if it is electric power assist, it only “pushes” when you turn the steering wheel.
There is always mechanical linkage between the steering wheel and the front wheels (so the car can still be driven without assist, but the steering is very heavy), which makes it impossible (or very difficult) to have a large variable space for steering ratios. It should be said that how much you move should be matched by how much I move in mechanical connection. The variable steering ratio only allows “how much I move” to float within certain limits, but the mechanical structure is powerless when there is a need for a large range of floating.
This steering column also brings other troubles. For example, in case of a collision, it may be dangerous and an emergency disconnect mechanism needs to be designed to avoid injuring the driver.
The so-called steer-by-wire (SBW) system completely eliminates the steering column. There is no longer any physical mechanical connection between the steering wheel and the front wheels. The movement of the steering wheel is converted into electrical signals, and the steering signals are transmitted to the steering motor through the data line, and then the steering wheel is “restored” by the steering mechanism.
That is to say, theoretically, the steering wheel of steer-by-wire system can be placed anywhere in the car: front row, back row, car door, car roof, etc.
The digital steering inputs completely liberate the range of steering ratio changes. In theory, steer-by-wire can achieve any size of steering ratio, any range of variable steering ratio, any mode and any speed of steering ratio change, just by setting specific logical strategies for the system.# Toyota’s One Motion Grip Steering Wheel
The One Motion Grip steering wheel from Toyota achieves the “One Motion” effect of only requiring a single movement to turn 150°, thanks to a large variation in steering ratio controlled by wires, which is necessary for the steering wheel to function properly as a “Yoke” steering wheel.
This is because a 150° turn ratio means that the steering ratio on either end is about 4:1, but in the center it needs to be at least 14:1 or 16:1 to ensure normal high-speed performance. The range of variable steering ratios needs to be 3-4 times to achieve this. Compared with mechanical steering systems, the range of variable steering ratios is only less than 2 times.
Before the Toyota bZ4X, wired steering only appeared in concept cars and demo cars provided by suppliers such as Bosch. The first mass-produced car to use Nissan’s DAS wired steering technology was the 2014 Infiniti Q50, which was also considered a pioneer in mass-produced wired steering.
However, Nissan’s DAS is not a fully wired steering system as it still has a backup mechanical steering system. In some cases, a clutch will temporarily connect the steering wheel to the steering column, restoring mechanical steering. The Q50’s wired steering did not receive market approval and even had several recalls in the early stages, making it not only a pioneer but also a martyr.
The principle of wired steering sounds simple – mechanical signals are converted to electrical signals, and then electrical signals are restored to mechanical signals. The main reason for the delayed mass production is that the stability and safety aspects of wired steering have been insufficiently mature and reliable. The Q50’s wired steering system uses as many as three ECUs to ensure redundancy, but it still cannot completely eliminate the mechanical steering column.
One of the difficulties in wired steering is strategy design and calibration algorithms. Although it has been used in the aviation industry for many years, wired steering for cars is a new beginning. Nissan’s wired steering supplier KYB has been developing it for more than ten years but still had problems within the first one or two years of launch, leading to recalls. It shows the complexity and unknowns of the design and calibration of wired steering.
Wired steering will be an essential requirement for the future “Third Space”.Let the turning angle change greatly, make the sci-fi-style steering wheel usable, and no longer need to frequently change hands when turning, all while only relying on the function of steer-by-wire.
In the future, when true autonomous driving becomes a reality, when cars can serve as mobile meeting rooms, when you can sleep while the car drives itself, and when cars truly become the “third space,” you will need to maximize the cabin space, and the steering wheel should “find a cool place to rest” autonomously.
The steering wheel should not be allowed to sleep under the bed.
Almost all futuristic sci-fi concept cars either have no steering wheel or have a foldable steering wheel, and this requires steer-by-wire technology as support. If it is a traditional steering wheel connected by a mechanical steering column, it is difficult to be hidden without affecting space.
It can be said that if you believe that Level 5 autonomous driving on the road will one day become a reality, steer-by-wire is an inevitable trend, as it is a preparation to fully realize the significance of 100% autonomous driving.
Of course, it is still too early to discuss Level 5 at present. However, even now, Toyota has given sufficient reasons for applying the new and unique steering wheel, called “One Motion Grip” (which doesn’t seem like an official name), resembling an aircraft rudder, without the upper half-circle.
What is it useful for now?
First of all, it is well-known that car instrument panels need to avoid the upper edge of the steering wheel, so most cars design the instruments to be within the driver’s viewing angle, between the upper half-circle of the steering wheel and the central airbag cover.
However, this is not a perfect solution, because the height of the instrument can only be fixed below the upper edge of the steering wheel, and there will always be a difficult-to-shrink angle between the instrument and the road surface, causing the driver’s line of sight to leave the road surface while looking at the instrument. As for this small semicircular gap limiting the shape and size of the instrument, it is a problem that has only appeared in recent years.
The height of the instrument determines the display area and display effect. Now, with the popularity of liquid crystal displays to full liquid crystal displays, all manufacturers are striving to reduce the area of the central airbag cover of the steering wheel, in order to leave more space and allow large areas of liquid crystal displays to be “visible.”
In fact, car designers have been exploring new instrument panel solutions for decades.
For example, the mid-mounted instrument panel, which was popular twenty years ago, disappeared due to its limited actual effect. And Peugeot’s distinctive raised instrument panel, which places the instrument panel above the top edge of the steering wheel, compresses and restricts the height of the instrument panel (otherwise it affects the road view), has limited adaptability to different heights, and hasn’t become mainstream.
What? You say HUD? Let’s wait until the people of the world achieve common prosperity before we talk about that.
Tesla was the first to use a Yoke-style steering wheel on the Model S, which currently only has the benefit of better readability of the instrument panel (if we don’t count the visual effect).
Toyota did not fully use the “dividend” of “removing the top half” to increase the area of the instrument panel, but instead pushed the instrument panel in the direction away from the driver, which is more conducive to switching the line of sight between the instrument panel and the road surface, and the farther distance from people to the instrument panel also shortens the time for the eyes to switch focus. All of them are considering driving comfort and safety, rather than a sense of technology — which is very Toyota and very traditional automakers.
Toyota also offers conventional steering wheel options for the bZ4X. By comparison, you will also notice: the steering column of the Yoke steering wheel model has a sensor-like component on the upper edge, while the conventional steering wheel model does not. I guess it may be that without the obstruction of the top half, driver sensors such as fatigue monitoring will be easier to arrange.
As for the increased legroom, ease of passenger entry and exit, and filtering out unnecessary road vibrations mentioned by Toyota, you can consider them as free bonuses.
Although Toyota, known for its stability, won against the usually aggressive Tesla this time, everyone knows that Tesla is also capable and unwilling to lose. Toyota boldly adopts the latest cutting-edge technology in the bZ4X, which somewhat conceals the fact that the bZ platform lags behind in technology, but this is not the topic of this article.
Mechanical systems always mean the constraints of physical structures, and the corresponding return is higher reliability. Electronic systems always bring about great liberation in physical space and endless possibilities for imagination and application, with the cost being huge investment and potential risks to improve reliability and stability.
This article is a translation by ChatGPT of a Chinese report from 42HOW. If you have any questions about it, please email bd@42how.com.