How Does Autopilot Sense "Hands on Wheel"?

[Shinteetah]

I'm not asking this question to get around the system. I'm asking because the system seems to ignore me.

I frequently prop my arm on my knee and hold the steering wheel. This results in little weight/pressure on the wheel but I do have a full grip on it.

When I use Autopilot -- which is a lot, I just finished a 1300 mile run -- I will keep a hand on the wheel but often propped up as described. Autopilot regularly yells at me to hold the wheel, even though I am. I've found I usually have to jig the wheel a little, wiggling the car in the lane, to turn off the warning.

This isn't critical, but with all the Autopilot freak-out news (when I was leaving on this run my Dad told me goodbye and not to rely on Autopilot) and reports that Tesla's data showed the driver wasn't holding the wheel, it makes me worry a bit. If someone hit me, but then Tesla's data showed I wasn't holding the wheel, would I be more liable than if I were in a car without Autopilot and someone hit me? And even though I WAS holding the wheel?

My very informal experiments MIGHT indicate that two hands on the top half of the wheel stave off the warning, but results are inconclusive. Can anyone tell me how to keep my car happy and convinced that I'm paying attention? Thanks!

 

[mblakele]

It's a torque sensor. You have to resist the car a little, but not enough to deactivate the feature. Try a slightly firmer grip on the wheel. I had the same problem at first. Now I usually keep my hands toward the bottom of the wheel, to minimize fatigue.

The nag message is, in my opinion, bad design: poorly worded and much too small.

 

[Kristoffer Helle]

It's not torque sensor. It's a position sensor. Very accurate.

 

[Skione65]

It's not torque sensor. It's a position sensor. Very accurate.

@Kristoffer Helle,

Can you explain in more detail? To anyone else....I believe what the OP is asking is 'where' on the wheel does the hand need to be? Also....does it need to be 'constant' pressure, or a 'touch' pressure every so often or certain amount of time to cancel out the nag. What exactly is the parameter the sensor is searching for to meet the requirements of the nag (touch, pressure, heat sensor for the hand)?

Ski

 

[omarsultan]

I believe @mblakele is correct - the car sense torque on the steering wheel.

==UPDATE==

Quick Googling found this quote:

One method is to detect torque on the steering wheel, hinted Musk. “So we might issue a visual and auditory alert to make sure you’re okay.”

 

[TaoJones]

Pressing/squeezing the area directly adjacent the left thumb controls makes the nag go away*







* There's a joke there somewhere...

 

[msnow]

It's not torque sensor. It's a position sensor. Very accurate.

No, it's torque.

 

[Sir Guacamolaf]

It detects your weight on the steering wheel, i.e. torque sensor.

1. When it gives you a warning "Hold steering wheel" just try and put a little pressure with your hands, not enough to disengage autopilot, but enough to get rid of the warning.
2. Also, if you hold the steering very lightly (i.e. full contact, but not putting any weight), it still gives you the "Hold steering wheel" message.

Autopilot when used properly is BETTER and SAFER than no autopilot. But it is also too easy to not use it properly and not understand it's limitations. So, I feel there is a true danger of Autopilot giving a false sense of security, and the driver may rely on autopilot without understanding it's limitations. Sadly there are plenty of idiots abusing autopilot, and I fear that they will ruin it for all of us.

Personally speaking, unless it's a more or less straight freeway, I don't let go of the steering wheel. And when when I do, I always keep my eyes on the road. But given that I am not doing the mundane task of watching the lines ahead of me, I feel my brain has more free cycles so I have more situational awareness of the idiots around me, which keeps me safer.

 

[ecarfan]

Pressing/squeezing the area directly adjacent the left thumb controls makes the nag go away

I suspect that when you do that you inadvertently apply enough torque to the steering wheel to alert the system that you are in contact with the wheel.

 

[Todd Burch]

If you want more details, in particular a servomotor is used:

Servomotor - Wikipedia, the free encyclopedia

 

[rscott0]

No, it's torque.

OK, we've got people who insist it is positioning (e.g. a slight movement of the steering wheel by your hand, the same thing that it detects to know to move the wheels when AP is not used), torque (very similar I believe, seeing how fast the steering wheel is turned), and pressure sensors (your hand is physically pushing slightly on the wheel, such as a tight grip, even if the wheel isn't turning).

This could be tested by [1] holding tightly on the wheel but not turning it, and [2] not even touching the wheel, but occasionally turning it (preferably in a place where no sensor would likely be). It might take some time to figure it out, though.

 

[msnow]

OK, we've got people who insist it is positioning (e.g. a slight movement of the steering wheel by your hand, the same thing that it detects to know to move the wheels when AP is not used), torque (very similar I believe, seeing how fast the steering wheel is turned), and pressure sensors (your hand is physically pushing slightly on the wheel, such as a tight grip, even if the wheel isn't turning).

This could be tested by [1] holding tightly on the wheel but not turning it, and [2] not even touching the wheel, but occasionally turning it (preferably in a place where no sensor would likely be). It might take some time to figure it out, though.

There's no dispute here. Everyone except one post says its torque. What's the issue?

 

[Cosmacelf]

I make the nag go away and/or never get the nag by periodically jiggling the steering wheel a bit. I jiggle left and then right against the resistance of the AP controlled steering wheel and then let it fall back into neutral. It doesn't move the car (much), but it is enough to tell the car I'm here. Gripping the steering wheel doesn't do it for me, I have to move it slightly.

If you do this every few minutes, you'll never get a visual nag, let alone an audio one.

 

[mikeash]

If the car is alerting when you have a hand on the wheel, try adjusting your position a bit so that the weight of your hand pulls the wheel a bit. Rather than holding the bottom, hold the side, for example. This will apply some constant torque and make sure the car knows you're there.

 

[ohmman]

I make the nag go away and/or never get the nag by periodically jiggling the steering wheel a bit. I jiggle left and then right against the resistance of the AP controlled steering wheel and then let it fall back into neutral. It doesn't move the car (much), but it is enough to tell the car I'm here. Gripping the steering wheel doesn't do it for me, I have to move it slightly.

If you do this every few minutes, you'll never get a visual nag, let alone an audio one.

This is what I do as well. Leaving my hand on the side isn't enough, I guess I "follow" the wheel movement enough that it doesn't detect me. Mine nags me all the time, despite having my hands on the wheel all the time. So I have to do this jiggle dance to make sure it knows I'm around.

 

[ecarfan]

we've got people who insist it is positioning (e.g. a slight movement of the steering wheel by your hand, the same thing that it detects to know to move the wheels when AP is not used), torque (very similar I believe, seeing how fast the steering wheel is turned)

Yes those are the same thing. And torque is the force applied to the wheel that causes the wheel to rotate.

 

[Max*]

So now that we all agree that it's a torque sensor.

I keep my left elbow on the arm rest, and my left hands fingers rest lightly/not-really-grip the area with the volume controls. That weight is enough for the torque sensor to never give me a keep-hands-on-wheel message.

 

[Zybd1201]

Autopilot when used properly is BETTER and SAFER than no autopilot. But it is also too easy to not use it properly and not understand it's limitations.

I only agree with us saying that autopilot is "better and safer" than no autopilot if we include the caveat that autopilot does some crazy dangerous things that you as the human have to react to immediately or risk harming yourself and others.

To me, better and safer, requires that it be something which at minimum does not do harm. I think I am experiencing in my first few thousand miles on autopilot what the news stories are showing. Autopilot can be very dangerous and even when used properly as an aid the only reason it is not dangerous is because of human intervention.

I want it to be better. I do. It just isn't. I think you agree but I just would argue with the "better and safer" comment.

 

[Sir Guacamolaf]

^^ I agree, Auto-steering especially can unexpectedly do some really crazy things, and there is a real danger of the driver getting desensitized into a false sense of security. At 65mph, milliseconds matter. Auto-steering is just not safe enough at the moment, to allow it unsupervised for more than a few milliseconds, which sort of defeats a great portion of the purpose.

 

[RDoc]

I just grip the wheel comfortably at the bottom, next to the spoke and let the wheel move my hand. I never get a nag.

However, there have been several occasions when the car has done something crazed, e.g. steering towards a truck in the lane to the right, when the movement of the wheel instantly alerted me and I pretty much instinctively twisted the wheel, both correcting the car and disabling autopilot.

IMHO, it is dangerous and irresponsible to not have a hand on the wheel. I also don't see what the point is.