Through the snow as if on rails(newsroom.porsche.com)
newsroom.porsche.com
Through the snow as if on rails
https://newsroom.porsche.com/en/2019/technology/porsche-engineering-e-suv-torque-control-software-18800.html
11 comments
> What people fail to realize, particularly in slippery conditions, is that it's often much easier to gain speed than to shed it. Modern traction control systems make it more (too) easy to gain speed without equally making it easy to shed speed.
Which raises an interesting question: if a traction control system can detect poor traction conditions and compensate, couldn't it just as easily warn the driver to slow down, just like the backup radar on recent cars warns about pedestrians and cross traffic?
I used to own a VW which would turn on a light indicating a high chance of black ice when the temperature conditions lent themselves to that (black ice can form at several degrees above freezing temperature).
I suspect that a car could warn of low traction and recommend slowing down, but no car offers it because consumers won't buy a car that nags them to slow down, Even if it's for their own safety.
Which raises an interesting question: if a traction control system can detect poor traction conditions and compensate, couldn't it just as easily warn the driver to slow down, just like the backup radar on recent cars warns about pedestrians and cross traffic?
I used to own a VW which would turn on a light indicating a high chance of black ice when the temperature conditions lent themselves to that (black ice can form at several degrees above freezing temperature).
I suspect that a car could warn of low traction and recommend slowing down, but no car offers it because consumers won't buy a car that nags them to slow down, Even if it's for their own safety.
I have experienced that VW ice warning. It was awful.
First of all, the possibility of ice is obvious. No warning is needed. That is just silly.
Second of all, it wasn't just a light. It was a loud noise.
Third of all, the warning was delayed. It wouldn't occur right when starting the car. It often jolted me for attention right as I was pulling out into very busy traffic. The warning was a hazardous distraction.
First of all, the possibility of ice is obvious. No warning is needed. That is just silly.
Second of all, it wasn't just a light. It was a loud noise.
Third of all, the warning was delayed. It wouldn't occur right when starting the car. It often jolted me for attention right as I was pulling out into very busy traffic. The warning was a hazardous distraction.
> First of all, the possibility of ice is obvious. No warning is needed. That is just silly.
Partly correct. Yes, the possibility may be in part obvious by conditions such as temperature. But I think most people who are used to driving on icy conditions can tell you that the ice may still come as a surprise. A system that could _reliably_ warn about slippery conditions would be good.
Partly correct. Yes, the possibility may be in part obvious by conditions such as temperature. But I think most people who are used to driving on icy conditions can tell you that the ice may still come as a surprise. A system that could _reliably_ warn about slippery conditions would be good.
my car does the exact same thing and it's easily dumbest feature a modern car has ever had. It's Canada in January, of course ice is possible. The alert goes off at a random time up to 15 minutes into a journey. Since it's audible you think something really serious has happened and now focus is not on the road but trying to figure out which tire has punctured or if a connecting rod is protruding from the engine block. Then you remember the stupid ice warning and are reminded how much you hate the alert, meanwhile in your distracted state you have driven into the ditch.
Somewhere where it snows once every 3 years it might be helpful. When you live in a place with real winter it actually makes you less safe since your brain has to spend time processing the alert for a condition that's obvious since the entire horizon is covered in a blanket of snow.
Somewhere where it snows once every 3 years it might be helpful. When you live in a place with real winter it actually makes you less safe since your brain has to spend time processing the alert for a condition that's obvious since the entire horizon is covered in a blanket of snow.
It’s not just braking. Porsche says:
> An uncontrolled vehicle would quickly understeer in this situation. In other words, the driver initiates the turn, but the vehicle slides in a straight line without slowing down. The control software in the e-SUV immediately puts an end to understeering. In a left-hand turn, it would brake the rear left wheel and accelerate the right one until a neutral driving situation was restored.
Braking the left rear wheel won’t do much if there isn’t enough traction to correct the understeer.
Even if you imagine the car has a magic gyroscope that can arbitrarily control yaw, if you try to make an 0.2g turn when none of your tires have 0.2g of traction, it’s not happening. You won’t oversteer, and you won’t understeer. You will, however, steer less than you wanted, and you’ll go off the road.
> An uncontrolled vehicle would quickly understeer in this situation. In other words, the driver initiates the turn, but the vehicle slides in a straight line without slowing down. The control software in the e-SUV immediately puts an end to understeering. In a left-hand turn, it would brake the rear left wheel and accelerate the right one until a neutral driving situation was restored.
Braking the left rear wheel won’t do much if there isn’t enough traction to correct the understeer.
Even if you imagine the car has a magic gyroscope that can arbitrarily control yaw, if you try to make an 0.2g turn when none of your tires have 0.2g of traction, it’s not happening. You won’t oversteer, and you won’t understeer. You will, however, steer less than you wanted, and you’ll go off the road.
What I want is something like a tail-hook that I can deploy from underneath the car in an emergency situation that will just drag along the ground grabbing on to whatever it can get a grip on, whether that's snow, dirt, or asphalt. If I change my main point of contact with the supporting surface from rolling rubber to a metal spike (or something like that) I'm gonna slow down a hell of a lot faster than I would otherwise.
I’m not seeing how this could work on most driving surfaces. On asphalt you would have to penetrate the surface, which would require extreme force, or somehow apply additional downforce to a friction device, which would reduce braking friction to the other wheels.
> you would have to penetrate the surface
No, you just have to push down hard enough to take some of the pressure off the tires. (In an extreme case you would lift the tires entirely off the ground. A nice side effect is that you would no longer need a tire jack. Hm, I am beginning to understand why car manufacturers don't implement this :-)
No, you just have to push down hard enough to take some of the pressure off the tires. (In an extreme case you would lift the tires entirely off the ground. A nice side effect is that you would no longer need a tire jack. Hm, I am beginning to understand why car manufacturers don't implement this :-)
Sounds like a good way to destroy our roads.
I remember my dad ranting in our 88 oldsmobile about how stupid all of those 4WD SUVs were, running around so fast in the snow. He would always say that 4WD could help you accelerate, but not help you brake. But whenever he bought tires, he would always get all-seasons. He found out the hard way (by rear ending an SUV) that a lot of those 4WD vehicles that drive so confidently in the snow are doing so not because they rely on their 4WD, but because they can rely on their tires.
Tires matter. A lot. For the past 25 years, snow tires have gotten continuously better. I recently tried out a set of hakkapeliittas, and the difference in driving confidence was dramatic. I could actually count on my car to reasonably stop in a way that I've never felt before, even with chains.
Tires matter. A lot. For the past 25 years, snow tires have gotten continuously better. I recently tried out a set of hakkapeliittas, and the difference in driving confidence was dramatic. I could actually count on my car to reasonably stop in a way that I've never felt before, even with chains.
Re: Hakkapeliittas: They are amazing in the snow and ice, agreed, but terrible on the dry at interstate speeds. Coming off the highway on an off-ramp at 70 on Hakkas is one of the most butt-puckering experiences I've had.
After a couple pairs of Hakkas, I switched to Blizzaks, which are not quite as good in snow and ice, but WAY better in the dry.
Front Range CO gets some good snow, but not enough days for the Hakkas to be my preference. YMMV depending on snow days in your location.
After a couple pairs of Hakkas, I switched to Blizzaks, which are not quite as good in snow and ice, but WAY better in the dry.
Front Range CO gets some good snow, but not enough days for the Hakkas to be my preference. YMMV depending on snow days in your location.
I had a friend who used to like to say "4WD can help you accelerate but it can't help you stop". I took him out in my '80 Subaru in the snow one day. It had a lever to activate 4WD, and I demonstrated how it would slow significantly faster with 4WD engaged.
The reason is that there was no ABS, and the brake proportioning valve would send most of the stopping power to the front wheels, since most of your stopping power comes from them on the dry roads. But in snow, the fronts lock up before the rears are slowing you down much. With 4WD active, the front brakes were connected to the back as well as the front and would use their stopping power as well.
Today is a different world though, with ABS.
You're right, it's all about the tires. I used to drive an Audi S4 which I would put Blizzaks on in the winter. I would take people out in the snow and blast around, it was amazingly predictable and controllable.
The reason is that there was no ABS, and the brake proportioning valve would send most of the stopping power to the front wheels, since most of your stopping power comes from them on the dry roads. But in snow, the fronts lock up before the rears are slowing you down much. With 4WD active, the front brakes were connected to the back as well as the front and would use their stopping power as well.
Today is a different world though, with ABS.
You're right, it's all about the tires. I used to drive an Audi S4 which I would put Blizzaks on in the winter. I would take people out in the snow and blast around, it was amazingly predictable and controllable.
In your case the engine braking made up for, what sounds to be, a poorly calibrated braking system. Yes, front brakes take the majority of braking load and they are designed that way from a braking distribution standpoint. But you have zero advantage with engine braking in a 4WD system vs properly calibrated brakes because on snow it doesn't matter - it simply comes down to the point where you lose tire tire friction greater than the inertia of the vehicle. ABS works to prevent a lockup of the wheel which reduces the opportunity to use friction even friction has been lost.
You are right that some 4WD systems (generally not AWD systems) can have an advantage of engine braking in wet or snowy conditions by not having to use brakes as much. Most drivers overcompensate on braking application in snow or a loss of control situation, which is why ABS works so well against the natural human response. But if you have a driver that is aware of the vehicle mass and the road conditions a proper braking system wouldn't lose out to control of a vehicle being stopped to engine braking in a 4WD system. Most people don't have the driving skill to know when engine braking would even be advantageous over wheel braking. And engine braking done too aggressively is hard to quickly disengage comparative to letting up on too much wheel brake application which can lead to longer periods of loss of control.
Ultimately what Porsche lays claim to is outlandish in extreme situations. They can't beat the laws of physics. And unless their car has active tire studding it wouldn't stand a chance against a quarter mile stretch of wet ice at 4 degree decline. Doesn't matter what vehicle, tires or software you've got. That vehicle is sliding to the bottom with no control.
You are right that some 4WD systems (generally not AWD systems) can have an advantage of engine braking in wet or snowy conditions by not having to use brakes as much. Most drivers overcompensate on braking application in snow or a loss of control situation, which is why ABS works so well against the natural human response. But if you have a driver that is aware of the vehicle mass and the road conditions a proper braking system wouldn't lose out to control of a vehicle being stopped to engine braking in a 4WD system. Most people don't have the driving skill to know when engine braking would even be advantageous over wheel braking. And engine braking done too aggressively is hard to quickly disengage comparative to letting up on too much wheel brake application which can lead to longer periods of loss of control.
Ultimately what Porsche lays claim to is outlandish in extreme situations. They can't beat the laws of physics. And unless their car has active tire studding it wouldn't stand a chance against a quarter mile stretch of wet ice at 4 degree decline. Doesn't matter what vehicle, tires or software you've got. That vehicle is sliding to the bottom with no control.
I well remember the first winter with my new company 4WD pickup. Sure I could go much faster in poor conditions. But once I lost control there was no correcting out of it. You were powerless and just had to wait until you slid to a stop or hit something!
Exactly.
I remember a few years ago I came across an article on a major car website that ranked four wheel drive as more important in winter conditions than proper winter tires. I personally don’t care if accelerating takes a little longer as long as I’m able to steer and stop, but I guess everyone has their own preference.
I remember a few years ago I came across an article on a major car website that ranked four wheel drive as more important in winter conditions than proper winter tires. I personally don’t care if accelerating takes a little longer as long as I’m able to steer and stop, but I guess everyone has their own preference.
I think it's because you can add better tires to car with 4WD if you determine you need it. You can't add 4WD/AWD to a car with winter tires.
Tires are the dominant factor in my experience. (In deep snow ground clearance is also a significant factor.) Many videos [1], [2] on youtube corrobrate this.
For the non-professional drivers on public roads, AWD is not a safety feature. It's arguably dangerous as it gives false confidence as you exceed the limits of your equipment.
It does provide a convenience at low speeds (e.g. parking lots and driveways) as it makes it more difficult to get stuck but even there tires and ground clearance are the dominant factors.
[1]: https://www.youtube.com/watch?v=EC1E2eDt1JY [2]: https://www.youtube.com/watch?v=iXjzYbpt9Ow
For the non-professional drivers on public roads, AWD is not a safety feature. It's arguably dangerous as it gives false confidence as you exceed the limits of your equipment.
It does provide a convenience at low speeds (e.g. parking lots and driveways) as it makes it more difficult to get stuck but even there tires and ground clearance are the dominant factors.
[1]: https://www.youtube.com/watch?v=EC1E2eDt1JY [2]: https://www.youtube.com/watch?v=iXjzYbpt9Ow
This is why Colorado now requires chains in severe conditions for passenger vehicles. AWD gets you up to speed, it does not get you back down to 0.
Chains in CO are NOT required for passenger vehicles. CO only requires chains for commercial vehicles.
There is a new "traction law" for passenger vehicles, which, when in effect, requires M+S tires OR AWD, and at least 3/16" tread. If you don't satisfy those requirements, you can put on chains.
https://www.codot.gov/travel/winter-driving/tractionlaw
There is a new "traction law" for passenger vehicles, which, when in effect, requires M+S tires OR AWD, and at least 3/16" tread. If you don't satisfy those requirements, you can put on chains.
https://www.codot.gov/travel/winter-driving/tractionlaw
“During severe winter storms, CDOT will implement a Passenger Vehicle Chain Law (also known as a Code 16). This is the final safety measure before the highway is closed.
When the Passenger Vehicle Chain Law is in effect, every vehicle on the roadway must have chains or an alternative traction device (like AutoSock).“ (emphasis mine)
When the Passenger Vehicle Chain Law is in effect, every vehicle on the roadway must have chains or an alternative traction device (like AutoSock).“ (emphasis mine)
You're right, I was misreading your original post, and thought you were referring to the new traction laws. I sit corrected. :-)
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Sounds like a good move. California has done this for years, but it’s much more necessary there because the drivers aren’t used to snow.
Pretty tough to overcome momentum absent friction.
Easy. Just generate a small, but dense planet-sized mass opposite the direction of momentum, then terminate its existence once momentum has ceased. Don't break earth or the space-time continuum in the process though - you might agitate stockholders.
Seriously though, physics is physics. Software can do a lot, but it can't do magic.
Seriously though, physics is physics. Software can do a lot, but it can't do magic.
I suspect some readers didn't get your accurate but brief comment. I'll expand it :).
Regardless of technology, once the limits of friction are surpassed, there's no current technology to save you from your momentum. And furthermore, moving the max capable speed upward with technology just means that when something unforeseen or accidental occurs, it now has a multiplied effect.
Regardless of technology, once the limits of friction are surpassed, there's no current technology to save you from your momentum. And furthermore, moving the max capable speed upward with technology just means that when something unforeseen or accidental occurs, it now has a multiplied effect.
Taking a corner at 80 km/h on a snowy road seems like an interesting proposition overall.
In the '70's, Porsche unabashedly made cars that earned the nickname "widowmaker."
Now it's bragging that in the near future a driver (user?) will be able to mash their car's throttle mid-corner with total impunity.
Off the top of my head I can't think of another car company that's had such a weird trajectory.
It's disappointing the new technology is unlikely to help Porsche users stop any faster, because the need for them to do so could be a side affect of their finally feeling secure when turning.
Now it's bragging that in the near future a driver (user?) will be able to mash their car's throttle mid-corner with total impunity.
Off the top of my head I can't think of another car company that's had such a weird trajectory.
It's disappointing the new technology is unlikely to help Porsche users stop any faster, because the need for them to do so could be a side affect of their finally feeling secure when turning.
When the Porsche 959 came out, it was likely the most technologically advanced performance road car available (well, not likely... certainly).
The performance numbers and vehicle stats were fantastic, and the look was arguably good for that time. But there was one common complaint: it was boring. The car was so well engineered that it could be a very manageable daily driver, or it could go set lap records with an average driver. In other words, there was little risk, and equally little reward.
Now you have Teslas with straight line performance that even stupid Dodge "muscle" cars can't match, at least for speeds even remotely within some legal limit. Since most drivers are ill equipped to drive a slow car well, it's quite scary to imagine them driving cars with the current performance characteristics.
So yeah, give them more go fast tech and watch what happens! Unless we develop some new stop-faster tech that greatly improves on the current situation, there will just be more accidents.
The performance numbers and vehicle stats were fantastic, and the look was arguably good for that time. But there was one common complaint: it was boring. The car was so well engineered that it could be a very manageable daily driver, or it could go set lap records with an average driver. In other words, there was little risk, and equally little reward.
Now you have Teslas with straight line performance that even stupid Dodge "muscle" cars can't match, at least for speeds even remotely within some legal limit. Since most drivers are ill equipped to drive a slow car well, it's quite scary to imagine them driving cars with the current performance characteristics.
So yeah, give them more go fast tech and watch what happens! Unless we develop some new stop-faster tech that greatly improves on the current situation, there will just be more accidents.
> Now it's bragging that in the near future a driver (user?) will be able to mash their car's throttle mid-corner with total impunity.
Funnily enough, that's exactly what you're supposed to do in a Porsche (assuming it is a rear engine 911). Unlike most cars, 911s will understeer (or correct an oversteer) when you mash the throttle, and oversteer when you lift off the throttle. The reason they're called widowmakers is that the oversteer/understeer dynamics are the exact opposite from what you would expect. Think you're going too fast into that turn? If you slow down, you're dead, but if you speed up, you'll survive.
It's also why crazy adrenaline junkies love them so much...in some senses, they're actually safer when you push them hard than they are when you try to be careful.
Funnily enough, that's exactly what you're supposed to do in a Porsche (assuming it is a rear engine 911). Unlike most cars, 911s will understeer (or correct an oversteer) when you mash the throttle, and oversteer when you lift off the throttle. The reason they're called widowmakers is that the oversteer/understeer dynamics are the exact opposite from what you would expect. Think you're going too fast into that turn? If you slow down, you're dead, but if you speed up, you'll survive.
It's also why crazy adrenaline junkies love them so much...in some senses, they're actually safer when you push them hard than they are when you try to be careful.
> Funnily enough, that's exactly what you're supposed to do in a Porsche (assuming it is a rear engine 911). Unlike most cars, 911s will understeer (or correct an oversteer) when you mash the throttle, and oversteer when you lift off the throttle.
That is only true for pre-1994 911s. The 928 never showed that behaviour due to having a Weissach axle from the very beginning of production in 1977.
That is only true for pre-1994 911s. The 928 never showed that behaviour due to having a Weissach axle from the very beginning of production in 1977.
It's also true of later 911s as well. I did carbon fiber bodywork for a PCA club racing team in college, and I definitely experienced it in some of the water cooled 996s. Some of the traction control methods reduced it a bit, but Porsche knows that they can't get rid of it entirely without changing the balance of the car (or alienating fans).
The 928 and the 944 were also front engine with a rear transaxle, which evened out the weight distribution quite a bit, and that alone mitigated a lot of the lift throttle oversteer. I loved the handling of both of those cars...you get the 50/50 weight distribution of a mid engine car, but the handling is so much more stable and predictable because the weight is at the ends of the car. Too bad they were about as reliable as octogenarian flatulence.
The 928 and the 944 were also front engine with a rear transaxle, which evened out the weight distribution quite a bit, and that alone mitigated a lot of the lift throttle oversteer. I loved the handling of both of those cars...you get the 50/50 weight distribution of a mid engine car, but the handling is so much more stable and predictable because the weight is at the ends of the car. Too bad they were about as reliable as octogenarian flatulence.
> The 928 never showed that behaviour due to having a Weissach axle from the very beginning of production in 1977.
I used to drive a 928. Perfect 50/50 weight distribution, beautiful throaty engine, and the most god-awful gearbox ever made. I had to rev match to shift up! in 2nd gear. They had a design flaw where the synchromesh just fundamentally would not work, and if you fixed it it would just break itself again.
I had to learn heel-toe shifting just to be able to drive that car at all. I fucking loved it, and it really got me into cars.
Also that car was great for whipping around a turn, just push on the throttle, slide around the back, then take off (I realize this is not the fastest way, but it is the most fun).
I apologize for the tangent, it's just not often people talk about 928s anymore.
I used to drive a 928. Perfect 50/50 weight distribution, beautiful throaty engine, and the most god-awful gearbox ever made. I had to rev match to shift up! in 2nd gear. They had a design flaw where the synchromesh just fundamentally would not work, and if you fixed it it would just break itself again.
I had to learn heel-toe shifting just to be able to drive that car at all. I fucking loved it, and it really got me into cars.
Also that car was great for whipping around a turn, just push on the throttle, slide around the back, then take off (I realize this is not the fastest way, but it is the most fun).
I apologize for the tangent, it's just not often people talk about 928s anymore.
Jeremy Clarkson also is an unabashed fan:
https://www.youtube.com/watch?v=XiLc7GvmS_A
A 20 year old 944 was my first sports car. Simultaneously the best and worst decision I had ever made.
https://www.youtube.com/watch?v=XiLc7GvmS_A
A 20 year old 944 was my first sports car. Simultaneously the best and worst decision I had ever made.
Don't forget its role in the movie Risky Business:
https://www.youtube.com/watch?v=8O8_FMhW9dY
"Porsche. There is no substitute."
I wonder what they paid for that line.
https://www.youtube.com/watch?v=8O8_FMhW9dY
"Porsche. There is no substitute."
I wonder what they paid for that line.
Partially it's different markets: In SUVs these things are seen differently.
Partially I think it's a general change in attitude, and one I think is mirrored in other sports car makers too: They all have various kinds of stability features, and options to control how it balances between strict control and "fun" behavior (you can't necessarily turn it of entirely anymore, and for a vehicle with individually driven wheels the concept of "non-assisted" doesn't even make sense)
Partially I think it's a general change in attitude, and one I think is mirrored in other sports car makers too: They all have various kinds of stability features, and options to control how it balances between strict control and "fun" behavior (you can't necessarily turn it of entirely anymore, and for a vehicle with individually driven wheels the concept of "non-assisted" doesn't even make sense)
It's basically ABS, but with more "vroom".
Congratulations!
Porsche has discovered the concept of putting an electronic motor into each wheel, and what that can do for them with regards to stability control.
Porsche has discovered the concept of putting an electronic motor into each wheel, and what that can do for them with regards to stability control.
It’s more than that. They’ve implemented a system that’s is capable of responding in real time.
And without any additional sensors.
This is a control theory problem: creating an observer, a model of the state of an unmeasurable quantity that you want to control, from limited data indirectly related to what you want, and using that to make control outputs, in a stable manner.
This is a control theory problem: creating an observer, a model of the state of an unmeasurable quantity that you want to control, from limited data indirectly related to what you want, and using that to make control outputs, in a stable manner.
I'm not sure that not adding additional sensors counts as impressive. Cars are already laden with all sorts of telemetry gathering sensors: ABS/speed at each individual wheel, steering angle sensor, accelerometers, temp and moisture sensors, etc.
Once you reach the limits of friction, and then some external factor surprises you (such as a little bump in the pavement which briefly lightens your car, resulting in newly greatly reduced friction), what will the great technology do to compensate? I can tell you - for a brief period, its compensation will have minimal benefit. But meanwhile, your momentum will happily carry you on in the direction you were traveling when you hit that bump.
"Real time" in a mechanical system is pretty generous compared to electrical systems. Changes are in the timescale of 1 to 100 hz compared to the kHz (or even MHz) switching speeds of many electrical systems. Once you switch away from the large rotating mass of an engine (+ drivetrain), you get pretty much instantaneous torque response on an electric motor for free.
I'd say it's more interesting that they were able to figure out the delta between driver intent and physical response without adding any sensors. Having that much flexibility in the firmware of multiple control units (probably collaborating between several vendors) was likely a more complex challenge.
I'd say it's more interesting that they were able to figure out the delta between driver intent and physical response without adding any sensors. Having that much flexibility in the firmware of multiple control units (probably collaborating between several vendors) was likely a more complex challenge.
This is a basic property of any 3-phase AC VFD motor, it's hard to see what's special here compared to a traditional electric drivetrain.
Like ABS?
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Hub or in-wheel motors have significant engineering challenges from the increase unsprung weight inside the wheels.
I'm curious which company hired Porsche Engineering for this. Porsche wouldn't hesitate adding more sensors for their own vehicles.
C’mon! Video please, Porsche.
Pics or it didn't happen.
>There was also an additional challenge: The driving characteristics had to be optimized exclusively through software. The Porsche engineers could not install any additional sensors and had to use the existing control devices. The task, in short, was essentially driving stability by app.
sounds almost like 737 MAX. Though of course it is just a common chewing sound of "software eating the world".
sounds almost like 737 MAX. Though of course it is just a common chewing sound of "software eating the world".
Not at all. The 737 Max added new, larger engines which had to be located more forward of the wing, leading to very different thrust balance characteristics compared to the previous models. The new software was made to try to prevent a pitch up change caused by too much thrust forward of the center of gravity.
Congrats, Porsche has discovered the 3-phase AC VFD. The same technology that has been used for decades in diesel electric locomotives.
It's well known that it has fantastic anti-slip properties. I'll have to dig up the source but in the transition from DC->AC in rail engines there was a massive increase in traction. The inherent principal of a 3-phase motor means that it will naturally resist overspeed(in the same way EV regen works) unless the VFD drives it faster.
[edit] I remembered right, the improvement is on the order of 100% over DC[1]
[1] https://www.republiclocomotive.com/ac-traction-vs-dc-tractio...
It's well known that it has fantastic anti-slip properties. I'll have to dig up the source but in the transition from DC->AC in rail engines there was a massive increase in traction. The inherent principal of a 3-phase motor means that it will naturally resist overspeed(in the same way EV regen works) unless the VFD drives it faster.
[edit] I remembered right, the improvement is on the order of 100% over DC[1]
[1] https://www.republiclocomotive.com/ac-traction-vs-dc-tractio...
What people fail to realize, particularly in slippery conditions, is that it's often much easier to gain speed than to shed it. Modern traction control systems make it more (too) easy to gain speed without equally making it easy to shed speed.