When Tesla swapped the steering wheels on some cars for an airplane-style yoke, there was a lot of controversy. Some of it was exaggerated, and in response, some of the support for Tesla was exaggerated as well. As usual, the truth lies somewhere between the two extremes. There are some legitimate reasons to be concerned about the yoke, and many people just wouldn’t like it for reasons of personal taste.
A justified criticism of the yoke was its performance at low speeds. On the highway, where you’d hardly ever turn the steering wheel more than 90 degrees or so, the yoke is fine. The same goes for most urban driving situations. But when you need to move the wheel quickly to navigate parking lots, reversing trailers, and other similar scenarios, the need to hand over when there’s no place to lay your hand has been a problem for some drivers, and likely a problem. . inconvenience to the people who insist it’s not a problem (if they were honest).
A recent video on Technique explained let us see how Lexus solved this problem and made its yoke a much more pleasant experience.
Long story short, Lexus has eliminated the mechanical connection between the steering wheel and the front wheels, or in other words, it’s a steer-by-wire system. And it gives Lexus the ability to do some very interesting things that wouldn’t be easy or even possible with a mechanical system.
In Jason’s video, he addresses five big questions about the Lexus system:
- How does it work?
- Why are you doing this?
- Is it safe?
- How does it make a Lexus yoke better than a Tesla yoke?
- What are some drawbacks of the system?
How it works
Cars on the road today use a mechanical system to turn the front wheels and steer the car. There are assist systems to make this job easier for the driver, such as hydraulic power steering or electric power steering, but they only help you turn the steering wheel and do not remove the wheel-to-wheel connection.
But in the Lexus system there is no steering. There is only a sensor in the steering column that detects the position of the steering wheel and this information is sent to the steering motor, which puts the wheels in the correct position. The process is different, but in the end you still get the same kind of control over the wheels.
There are some obvious objections to this system, the most important of which is security. No one wants to be one software or hardware failure away from having no steering control over their vehicle. So Jason will come back to that later. Another obvious problem is that the steering wheel can feel “lifeless”, but this wheel works like the one in a decent driving simulator and gives appropriate feedback, but in response to real forces and not a simulation.
Why even do this?
Lexus told Jason that electric motors are much more responsive than gas-powered cars. With that better throttle response comes regenerative braking, which is also much more responsive than the usual mechanical braking systems. Lexus wanted its upcoming EVs and plug-in hybrids to have the same steering responsiveness, with minimal lag and system stretch.
Another way this system can be extra responsive is by using different ratios in the control, without having to use complex systems to provide variable ratios. This gives Toyota (Lexus’ parent company) the ability to have much more control over the ratio between steering wheel rotation and wheel rotation in different situations.
Another advantage is in the packaging. If you don’t have a full steering column, the steering wheel can go almost anywhere and you can move it a lot more to suit the driver’s needs and preferences. This comfort is enhanced even more when you consider that not all road feedback has to be passed to the wheel (something enthusiasts want, but other people don’t).
Is it safe?
I must admit that as an old-school driver I was not initially thrilled with this idea. What happens if the computer system fails without a mechanical link? Losing something like power steering or throttle probably won’t kill you, but the thought of not being able to control your car is terrifying.
The system is actually built with a lot of redundancy to prevent loss of steering control
First, it has three batteries to prevent power loss from turning off the control. There is the main EV or hybrid traction battery, the regular 12v battery, and an auxiliary 12-volt battery to keep the system running in the event that both the inverter and the regular 12v battery fail.
The control actuator also has redundancy. It has two motors, two sets of sensors, two computers, two sets of wires, and even two feedback motors. If something goes wrong, there’s a whole second system that can keep the system running and give you a warning that you need to get the system repaired.
Why this is better than Tesla’s yoke
For yokes, this system is particularly great as it can eliminate the need for hand-over-hand control. At high speeds, the ratio can be very long and loose for stability. At lower speeds, the ratio can be very tight, so you don’t have to move the yoke much to get the wheels fully turned. This makes it a lot easier to drive into parking lots and reverse with trailers, for example, and makes a round wheel superfluous.
This makes the advantages of the yoke (better visibility, less space requirement) much more important. When these advantages do not have to compete with disadvantages (difficult steering at low speeds), they can really shine. The steering is sensitive when needed at low speeds, and looser at high speeds for maximum control and comfort at all speeds.
Jason also points out that Toyota still offers physical knobs and buttons, something people who don’t want everything to be touchscreen will appreciate.
cons
Finally, Jason gives us some information about the drawbacks of the system.
One of the big ones is that it could give more security than a normal steering system, but it doesn’t. The system can be set to not always do what the driver says. For example, at high speeds, if you slam the wheel to one side too quickly, it may decide that the wheel movement was unsafe and ignore or dampen it to prevent loss of control. For people not trying to do things like PIT maneuvers or J-turns, this would be OK and maybe even good for safety. For enthusiasts and pros, this system wouldn’t be great, but it could probably be turned off the way traction control can be turned off. But Lexus isn’t taking advantage of that opportunity.
There is also some lag in the system, which can be clearly seen in Jason’s video. This means that the steering wheel does not always match the driver’s input like a mechanical system. The final version of the system could be better, but the prototype system has this problem.
Featured image provided by Lexus.
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