Ford F-150 Lightning Breezes Up Obstacle Where Tesla Cybertruck Struggled • Hacker News Board

Re: Ford F-150 Lightning Breezes Up Obstacle Where Tesla Cybertruck Struggled

#91

Post by HankB99 » Fri, Nov 17, 2023, 1:12 AM UTC

brucethemoose2 wrote: post #6

HankB99 wrote: post #3

To my untrained (WRT off-roading) eye, I didn't see that much difference between the two. I also wonder how much difference there would be due to driver skill. And as mentioned in TFA, Ford has been making trucks a lot longer than Tesla.

Hm? Its pretty massive to me. The Tesla has like no suspension travel. The suspension is barely compressing, and you can see the body bounce over the terrain as the wheels lift or almost lift. If you covered the top of the truck from view, I'd say it looks like a cheap crossover. And the base F-150 is not really a long travel truck, its just... you know, sprung like a truck. A little side by side UTV could run over t…

> Hm? Its pretty massive to me.

As noted - my ignorance of the nuances of off road capability. Someone who knows what they're looking at could see a lot more than I would.

Re: Ford F-150 Lightning Breezes Up Obstacle Where Tesla Cybertruck Struggled

#92

Post by satiric » Fri, Nov 17, 2023, 11:49 PM UTC

mike_d wrote: post #74

brucethemoose2 wrote: post #67

Earlier quoted context omitted.

That's a solvable software problem. The electric motors know how much they are spinning, they just need to be modulated quickly enough and intelligently enough.

Motors know nothing. The encoders know how much current is being input to the motor, but do not know the rotational output of the motor or the friction coefficient between the tires and the ground. All three are things you'd need to emulate a locking differential in software. You could fake the last two by having a reliable way to measure the travel of the vehicle from a source other than the wheels (GPS, downward ca…

Technically, you can sometimes measure the motor position without a position sensor by measuring the back EMF (although I doubt Tesla is doing this, IIRC it's hard to get good starting torque out of this setup)

Re: Ford F-150 Lightning Breezes Up Obstacle Where Tesla Cybertruck Struggled

#93

Post by satiric » Fri, Nov 17, 2023, 11:58 PM UTC

bilsbie wrote: post #20

Is the CT four wheel drive? How do locking differentials work with electric?

Through software. The Vehicle Control Unit can control the torque going to each motor independently, and can view the current speed of each motor. By looking at longitudinal acceleration vs motor speed, you can see if the wheels are slipping or not.

Alternatively, if you have a 2WD vehicle, you can just compare the motor speeds to the speeds of the undriven wheels to see if the wheels are slipping.

It's surprisingly nontrivial to detect how much the wheels are slipping, but once you can you vary the torque command based on the amount of wheelslip.