Exploring the flaws in Tesla’s yoke-shaped steering wheel execution and the ways in which Lexus’s steer-by-wire concept is fixing it.
Tesla recently introduced the yoke steering wheel on the Tesla Model S Plaid. The yoke’s design subtracts the top and bottom arcs of the wheel, meant to mimic the steering wheels of Formula 1 cars for a sportier feel and, in theory, a more comfortable driving experience. Customers were ecstatic at first but quickly realised that utilising this wheel is extremely complicated and, in some cases, dangerous. Lexus recognised this as an opportunity to innovate and introduced a fully electric steering mechanism called ‘steer-by-wire’ which addressed all of the key downsides of Tesla’s design drawbacks.
What Tesla Got Wrong
Tesla introduced the yoke steering wheel in 2021 but stuck to a traditional mechanical steering system which has a full revolution of around 1000 degrees end-to-end. But with portions of the upper and lower hemispheres missing in the yoke, drivers cannot safely do a hand-over-hand manoeuvre. Every automobile journalist who reviewed Tesla’s yoke said this was a huge oversight, and the delivery felt hurried and poorly executed. Tesla, which has had many ‘firsts’ in the industry, wanted to bag an early mover’s advantage on a wheel redesign but completely ignored the necessary modifications to the rest of the car to complement it. This did not, however, dampen car enthusiasts’ excitement as news about Lexus introducing a yoke of their own was already circulating in the community.
What Lexus Got Right
Lexus engineers thoroughly researched the yoke and concluded that the typical mechanical steering system is not best suited for its design. So, in 2022, it created a steer-by-wire system, in which the mechanical link between the steering wheel and the front wheels was replaced with an entirely electronic system connected by wires that send electronic signals that turn the wheel. Wired systems in cars are not entirely new concepts and have been used in throttles for some time now. The drive-by-wire throttle system eliminates the need for physical throttle wires to engage the engine and instead relies on actuators that receive electronic signals from the driver’s throttle input. Lexus innovated by applying this proven concept to a new application – steering.
The steer-by-wire system addresses the issue of making tighter turns by eliminating the need for overhand steering entirely. As opposed to 1000 degrees of end-to-end rotation, Lexus limited the steering angle to 150 degrees and used clever computing algorithms to determine steering ratio. The steering ratio refers to the ratio of angles turned in the steering wheel to angles turned in the front tires. This is made possible through the use of onboard electronics which adjusts the steering ratios depending on driving conditions such as speed, road occupancy and the vicinity of other vehicles.
Lexus’ approach has been well received by car journalists and they have applauded its engineers for getting it ‘right.’ To accommodate this reinvented wheel, the solutions presented open doors to new possibilities which could significantly improve the driving experience.
Lexus engineers thoroughly researched the yoke and concluded that the typical mechanical steering system is not best suited for its design. So, in 2022, it created a steer-by-wire system, in which the mechanical link between the steering wheel and the front wheels was replaced with an entirely electronic system connected by wires that send electronic signals that turn the wheel.
Is a Yoke and Steer-by-Wire Better?
If car companies want to adopt the yoke, then steer-by-wire is the way to go. Without an electronic system, it will be incredibly complicated to have self-adjusting steering ratios. But the questions on most people’s minds are whether this redesign was needed in the first place, and does it actually solve a problem inherent in mechanical systems.
Given the rapid pace at which new electric vehicles are being introduced to the market, it is evident that the future is electric. Virtually all mechanical components in cars are being replaced by electronic or electrical systems – locking mechanisms, mirror adjustment, proximity sensors, windshield wipers, consoles, suspension, braking, engines, and motors to name a few. Steer-by-wire is the natural progression to making electric vehicles fully electric.
Mechanical steering is bulky, clunky, and heavy and requires regular servicing and maintenance. On the other hand, a steer-by-wire system is small, responsive, and light. For electric vehicles, using steer-by-wire would allow manufacturers to reduce their cars’ curb weight resulting in significantly higher mileage and significantly lower maintenance costs.
Lexus’ Steer-by-wire is arguably safer as well. Because electric vehicles risk running out of charge, Lexus has incorporated two-fold redundancy in its backup power system. If the car battery dies, a backup power supply kicks in to let the car driver pull over safely. If there is a critical failure, a second backup power supply ensures continued power delivery to the wheels.
Additionally, the self-adjusting steering ratio can be complemented with object-detecting computer vision making the car fully aware of its surroundings. In scenarios where fast-moving traffic makes an abrupt stop, this system can react within a fraction of a second to amplify the steering ratio and simultaneously adjust the suspension to prepare for an evasive manoeuvre. Engineers are also presented with further innovation opportunities by integrating an automatic system override to the car’s onboard computer so the evasive manoeuvre is performed by the car and not the driver. Effectively, there is nothing inherently wrong with mechanical steering systems, but steer-by-wire presents opportunities for making driving more intuitive and safer.
The Catch
Being a completely new idea, steer-by-wire is not quite road-ready yet. For instance, Lexus has reported irregularities in steering ratios when dry-turning (when the car is not moving), and at high speeds on empty highways, the system may not recognise emergency manoeuvres as legitimate steering inputs, resulting in a slow lane change as opposed to a quick evasion.
Over a certain range of low speeds, the steering response is overly sensitive. For instance, when driving down residential neighbourhoods with narrow, winding roads, the car tends to oversteer. Given most residential areas require drivers to maintain a low speed, this is a big cause for concern as it takes away from the intuition of the car’s behaviour. Cars should be built to be predictive and intuitive, so unless these bumps can be confidently smoothed out, steer-by-wire requires further development before being introduced to the masses.
Being the first mover in any new revolution can bear great rewards but also carries with it great risks. Tesla tried to bank on the first mover advantage in changing the design of the wheel but if they had given more time and thought to fully solve all the new problems that came to light with the yoke design, consumers would not have been left wanting more. Lexus on the other hand has become a fast follower by innovating on the concept and a first mover in terms of introducing the steer-by-wire system.
