Tesla Model S
How does the Tesla Model S Traction Control system work?
I was pulling out of the parking lot at work the other day and happened to experience some wheel spin as I drove over a patch of sand near a construction site. One wheel spun with limited grip while the other wheel pushed me through the slippery patch. The wheel modulation happened automatically and trouble free which led me to think – How does the Model S traction control work?
Before I dive into it all, one caveat: I’m an electrical/software engineer and not a mechanical engineer. I can change a tire, I used to change my own oil many years ago, but otherwise I let a trusted shop (usually a dealer) do all of the work. The information below is based on my own research and opinions.
Open Differential
I had a very basic knowledge of how the AC induction motor drives the wheels on my Model S. I thought it was just a direct current motor with a positive and negative terminal that spun one way or the other depending on polarity which in turn spun the wheels. This kind of thinking comes from my days dealing with radio control hobby kits coming out of Radio Shack. I hadn’t thought about how that may translate into driving of two wheels, nor how it would handle situations where traction is limited due to sand and ice.
It turns out, the shaft of the Model S electric motor inserts into an open differential gear box that then drives the two wheels. This gearing allows the outside drive wheel to rotate faster than the inner drive wheel during turns. Without this gearing either the inside wheel will rotate too fast or the outside wheel will drag. Any imbalance may lead to poor handling, damage to your tires and introduce a lot of stress to the drivetrain. HowStuffWorks has great animated images showing how it operates in action.
Tesla describes the gearing as follows (for the Roadster):
“The motor is directly coupled to a single speed gearbox, above the rear axle. The simplicity of a single gear ratio reduces weight and eliminates the need for complicated shifting and clutch work. The elegant motor does not need a complicated reverse gear – the motor simply spins in the opposite direction.”
The downside of the open differential approach is that torque is evenly applied to both wheels. The traction control system limits the maximum amount of torque that can be applied to each wheel without making it slip.
Turning traction control off essentially allows the motor to not back down even when one of the tires is spinning. This can often result in a lot of tire spinning and will not necessarily remove you from being stuck. In fact you may end up digging a deeper hole than the one you’re already in.
Limited Slip
Traditionally a limited slip differential allows for torque to be applied independently of each wheel. This involves complicated gearing which involves more components, adds additional weight and overall may not be as reliable on a Model S that produces such astronomical torque. For that reason Tesla chose to utilize a much simpler and sturdier open differential. But they needed to solve the slip problem.
Tesla solved the problem on the Model S by selectively applying rear brakes in order to transfer torque to the wheel that grips. These commands are fed into the electronic stability control system which is capable of braking the rear wheels independently as a way to improve the handling of the car under various conditions.
Tesla describes both traction and stability control as follows:
“Model S Traction Control is designed to ensure maximum contact between the road and the tires. Whether you are accelerating off the line, zooming along the winding roads of the Rockies or find yourself in a Gulf Coast rainstorm, Traction Control prevents loss of traction and maintains control. Stability Control reacts in moments of under-steer or over-steer by reducing torque and applying the brakes to individual wheels for enhanced control when cornering.”
Summary
Tesla Motors is about disrupting the norm and re-thinking how things should be done. If you start from scratch and question every design decision, every part, every ounce of weight, every approach and leverage the best minds on the planet, what kind of car will you end up with? The Model S is Tesla’s current answer and certainly not their final answer.
Tesla’s traction control and emulated limited slip functionality is another case of Tesla replacing complex and inefficient hardware with something lighter, simpler and more state of the art – augmenting functionality through software and algorithmic science utilizing today’s advanced computing power.
The next time you slam that “go” pedal and take off like a space ship, think about all the technology that’s helping you launch into the future.
This morning’s reports of a Tesla Cybertruck recall only went to shed more light on how the production ramp of the pickup is going.
With delivery figures for the third quarter revealed yesterday, it also shows a grim reality for the Model S and Model X, two vehicles that have become more of a novelty in Tesla’s lineup as the Model 3, Model Y, and Cybertruck have truly taken charge.
The NHTSA documents released this morning show the Cybertruck is being recalled for a delayed rearview image, which will be resolved with an Over-the-Air update.
Tesla addresses Cybertruck rearview camera “recall” with free software update
However, they also show that 27,185 units are potentially impacted by the issue, giving us a rough guess of how many Cybertrucks have been produced thus far.
The breakdown seems to show that from the last Cybertruck recall in June, when 11,688 units were potentially impacted, we have seen roughly 15,497 additional pickups make their way to customers.
In a perfect world, that would mean 910 Cybertruck are delivered every week, or 130 per day, and since the first recall occurred with three weeks left in June and in Q2, we can subtract 2,730 Cybertrucks from the 15,497 that have been delivered since then.
We know that as of now there are 27,185 Cybertrucks delivered, and as of June 6, there were 11,688 Cybertrucks delivered.
That means 15,497 were delivered between June 6 and today (maybe yesterday?), which is about 910 per week or 130 per day.
EDIT: since this recall includes…
— ⚙️ Mike, cyberowners.com (@TeslaTruckClub) October 3, 2024
These figures are very rough estimates. That would leave 13,157 Cybertrucks delivered in Q3, roughly.
Tesla said 22,915 Model S, Model X, and Cybertruck were delivered in Q3. This would leave just 9,758 Model S and Model X to be delivered, less than 10,000 units for an entire quarter, if the Cybertruck delivery figures are close to accurate.
“We’re Continuing to Make Them for Sentimental Reasons”
Elon Musk said during the Q3 2019 Earnings Call that the Model S and Model X are truly vehicles that are “niche products,” and they knew it wouldn’t take the company to a mass-market status:
“I mean, they’re very expensive, made in low volume. To be totally frank, we’re continuing to make them more for sentimental reasons than anything else. They’re really of minor importance to the future.”
Tesla’s Q1 ’21 Deliveries prove Elon Musk was right about the Model S and X in 2019
Interestingly, the vehicles have had their moments through the past few years. In Q4 2023, the Model S and Model X saw their highest delivery count in five years, accounting for 22,969 deliveries that quarter.
Now, they’re around the 10,000 mark.
It will be interesting to see what Tesla’s plans are for these two cars, especially as Robotaxi unveiling is scheduled for next week, and there could be the potential for more vehicles to be released in the coming years with the next-gen platform taking focus.
It would be a real gut punch to the long-time Tesla fans who saw the Model S and Model X launch the company into the Model 3. But all good things must come to an end.
I’d love to hear from you! If you have any comments, concerns, or questions, please email me at joey@teslarati.com. You can also reach me on Twitter @KlenderJoey, or if you have news tips, you can email us at tips@teslarati.com.
Tesla has launched a 3-year subscription bundle for the Model S and Model X. The $5,000 bundle includes access to Full Self Driving (FSD) (Supervised), free Supercharging, and Premium Connectivity.
Tesla’s official website shows that the 3-year subscription bundle is only available for the Model S and Model X for now. Model 3 and Model Y orders are only allowed to purchase FSD for its full 8,000 price. This is understandable as Tesla is likely testing the waters for the 3-year subscription bundle.
So let's break this down for Model X and S owners:
— Ale𝕏andra Merz 🇺🇲 (@TeslaBoomerMama) August 9, 2024
Monthly subscription
– to FSD $99
– to Premium Connectivity $9.99
then add $30 of free supercharging per month
and after three years, it adds up to … 🥁 … $5,000 https://t.co/UleF6mIrIo
The 3-year FSD (Supervised), free Supercharging, and Premium Connectivity bundle have mostly received support from the electric vehicle community, some of whom noted that the service would probably be popular among those who lease their cars for three years. It should be noted, however, that vehicles that are for commercial use are not eligible for the 3-year bundle.
The price of the 3-year bundle is quite reasonable considering the individual prices of the services that are included. Full Self Driving’s monthly subscription costs $99, so three years of the service would be worth $3,564. Premium Connectivity, at $10 a month, would cost $360 over three years. Free Supercharging could not be purchased individually, but a reasonable value for the service could be around $30 a month or $1,080 over three years. Together, the three services amount to $5,004 over a three-year period.
Tesla Bundle subscription agreement pic.twitter.com/01Z4QHDI9O
— Whole Mars Catalog (@WholeMarsBlog) August 9, 2024
Tesla’s 3-year bundle has the makings of a popular service, but the fact that it is currently limited to the Model S and Model X means that only a small group of customers would be able to take advantage of the offer. As per Tesla’s Q2 vehicle delivery and production report, Tesla only delivered a total of 21,551 non-Model 3/Y vehicles in the second quarter. From that number, Cox Automotive estimated that 8,755 were Tesla Cybertrucks. This means that just over 12,700 Model S and Model X were sold in the second quarter.
Don’t hesitate to contact us with news tips. Just send a message to simon@teslarati.com to give us a heads up.
Tesla has started shipping the Model S Plaid flagship sedan with newly-redesigned Sport seats.
The Model S Plaid has been available for customers for a few years now, and while it is a mainstay in Tesla’s lineup, its look and feel are not quite old or outdated enough to justify a complete redesign.
However, Tesla has a knack for updating certain things within the vehicle, especially interior options, including steering wheels or a simplified interior altogether, as it did with the Model 3 “Highland.”
It has done this with the Model S Plaid, the premier version of its flagship sedan.
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- Credit: Tesla
After leaked images of a newly designed Model S Plaid seat appeared last October, it was clear that Tesla had some plans to update the seats for a new look and advantages that would fit the high-performance EV.
Tesla has brought some new features with these Sport Seats:
- Track-inspired bolstering that provides lateral support
- Suede bolsters for increased grip, exclusive Plaid composite design in the backrest
- Same comfort and 12-way power adjust, heating, and ventilation as original Model S Plaid seats
For what it is worth, the seats appear to be similar to the ones that leaked in the images in October.
However, the leaked images showed some minor quality issues with loose paneling, so we’re hopeful they have refined this with the units it will ship:
Credit: u/s3pirion on r/TeslaMotors
Tesla launched the new Sport Seats in the Plaid Model S in both the North American and Chinese markets this evening. All Model S Plaid vehicles built from April 1, 2024, and beyond will now come standard with these seats, so there is no additional upcharge for them.
I’d love to hear from you! If you have any comments, concerns, or questions, please email me at joey@teslarati.com. You can also reach me on Twitter @KlenderJoey, or if you have news tips, you can email us at tips@teslarati.com.
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