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Model S Steering Wheel Sensors

Discussion in 'Model S: Driving Dynamics' started by Zybd1201, Jul 24, 2016.

  1. Zybd1201

    Zybd1201 Member

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    Thanks in advance for your input.

    I have found that as I use autopilot, despite my hands touching the wheel, I continually get nags and the radio will turn down telling me to put my hands on the steering wheel. I have had 2 incidents now where it told me "to continue at current speed place your hands on the wheel" despite my hands being on the wheel.

    I have fixed the situation by placing both hands at 9 & 3 and squeezing the steering wheel for a 'long' period of time (about 15 seconds).

    My question is, how do the steering wheel sensors work and where are they placed? Why aren't they detecting my hands gently placed at the bottom of the wheel?

    I have a brand new 90D if that matters.
     
  2. DrComputer

    DrComputer Member

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    They don't actually "sense" your hands on the wheel. They sense torque or resistance against the wheel. So you don't need to grip anything. Just slightly turn the wheel and create resistance against autopilot and it will stop nagging (temporarily).
     
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  3. ecarfan

    ecarfan Well-Known Member

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    Tesla has stated that the steering wheel sensors work by detecting even very minor torque inputs from holding onto the wheel. There is a sensor somewhere in the steering wheel mechanism that detects the torque, but I do not know where it is located. I doubt it is located in the steering wheel rim, if that is what you are thinking.
     
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  4. Zybd1201

    Zybd1201 Member

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    Thanks guys. I think my issue is that I was assuming that by keeping my hands on the lower part of the steering wheel it would detect them but i have to actually give some gentle steering wheel torque instead of just keeping my hands there 'at the ready.'

    p.s. it is an absurdly nice feature to have. My commutes are so much nicer now. It still requires constant monitoring but as a private pilot I would very much compare it to my old 4 seater's autopilot. I had to take off, land, and closely monitor it and intervene occasionally but otherwise it just makes the traveling experience so much nicer.
     
  5. Three60guy

    Three60guy Member

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    When I placed fingers pointing toward the pedals at the location of the arrows in the picture below and providing movement (torque) the message does not go away. The only way I have been able to get rid of the message is by grasping the steering wheel by at least one hand. So, the idea that just providing torgue doesn't work with my experience.


    SteeringWheelArrows33.jpg
     
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  6. davidc18

    davidc18 Member

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    it just takes a little wiggle of the wheel to stop the "hold wheel" alert.
     
  7. Three60guy

    Three60guy Member

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    But not as I described above with the photo with fingers wiggling at the points shown with the arrows.
     
  8. Zybd1201

    Zybd1201 Member

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    My concern is this:

    DISCLAIMER: The following is my personal opinion and intellectual property. By posting it I do not give any implied or express consent for it to be published outside of this forum.

    Given the accident in Montana I see this possibly happening to me in the following way:

    I am driving on autopilot on a road with posts/barriers on the right side and I am in the far right lane. My hands ARE actually on the wheel (despite Tesla's logs saying they were not) but Tesla's logs don't show it. I know for a fact this happens because I have done it every day since I have bought the car. Then, as I am going around the turn I am getting the warnings. I move my hands around on the wheel trying to get the nag to go away. While I look down at the nag message to read it/see if it is gone the car starts veering off to the right and heads towards the polls. I look up, quickly try to override autopilot (which takes a lot of force and causes the car to jerk most of the time) but by then it is too late.

    So, I think I need to understand these nags better and not let them be such a distraction. It is, at times, unusually difficult for me to get them to go away and can become a distraction from my supervision of the autopilot.
     
  9. jmsurpri

    jmsurpri Member

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    I can turn off the nag by placing a single finger on the wheel and providing a tiny amount of torque as if I was trying to turn the wheel. The torque I apply is so small there is no way it would make any difference but it's enough to cancel the nag.
     
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  10. Zybd1201

    Zybd1201 Member

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    I will try that on my way home.
     
  11. CHG-ON

    CHG-ON Still in love after all these miles

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    All I need to do is lightly hold the wheel so that there is a bit of resistance against its automatic turning or very slightly jiggle the wheel, not even enough to alter the course. It works every time without exception. You may want to have your sensors checked.
     
  12. Zybd1201

    Zybd1201 Member

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    Yes. This is correct. I tested on the way home tonight and it seems to have just been a misunderstand on my part of how it worked. A slight left or right torque anywhere on the wheel does the trick. I thought I could just be touching it. I was wrong. :)
     
  13. Cobbler

    Cobbler Member

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    I don't think there is a sensor for detecting torque. Instead the steering motor electronics will check the required current to rotate the steering wheel (the more current > the more torque required to get to the position), but road conditions where it would be harder to steer, could influence the detection.
    Maybe for finer detection, the steering wheel has a multiturn rotary encoder on it and the feedback position vs commanded position is being monitored (aka position error detection).
     
  14. coolgj

    coolgj Member

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    I really would like Tesla to explain how it works, because I drove with my BOTH hands on the steering wheel and still get the NAGS.

    It almost shut off on me twice. The only thing that seems to work is I have to rock the steering wheel back and forth a little. But this seems more dangerous to me but it is the only solution that seems to work.

    Please Tesla explain how the NAG works and what makes it go away.
     
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  15. Zybd1201

    Zybd1201 Member

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    Glad to know I am not the only one. I was super surprised to be driving on autopilot with both hands on the wheel only to find out that Tesla doesn't think they are on the wheel. Very concerning considering their "logs" seem to be the final say in matters of how safe my driving is.
     
  16. CHG-ON

    CHG-ON Still in love after all these miles

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    Odd. I have never had that problem. If I even rest my fingers on the bottom of the wheel, a little hooked over the rim on either side of the center spoke, I never get a nag. You may want to ask them to check the sensor. Maybe it is not sensitive enough. It takes very little grip, or force, to either avoid the nag or cancel it if I have not been touching the wheel
     
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  17. scottm

    scottm Active Member

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    ..hang a little weight on the left or right spoke. No more nags.

    Gravity will provide the necessary torque, constantly.



    ...


    Or.. just keep your hands at 9 and 3 like you should while driving.
     
  18. chillaban

    chillaban Member

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    Generally, I apply mild resistance to the direction I expect the car to err (or the direction I don't want the car to go). For example, if you're driving with a concrete barrier on your left, I would apply mild steering resistance in the rightward direction. If you're taking a curve to the right, I would apply slight resistance to the right in case the car doesn't track the curve all the way. Similarly, steer away from cars next to you, etc.

    That kind of resistance is what the car's steering sensors are looking for. Rapidly wiggling the wheel or gripping it harder won't do anything.

    And plus, bracing the wheel in the above way leaves you more prepared in case the car does something wrong.
     
  19. scottm

    scottm Active Member

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    I'm thinking Tesla can probably detect a constant torque drag, like a weight hanging on the wheel. It's TOO constant for a human to emulate that.

    Maybe Tesla needs to add more Captcha-like tests to detect a real driver interaction, and "not a robot" (ironically reversed doubt paradigm) but real meatware is at least pretending to drive..

    I can see it now... a pop-up that make you do a "random thing" while checking for your response time meanwhile discarding the input for its other (normal) purpose or function..

    Random things can include:
    "Press the left dial on steering wheel now!"
    "Press volume down button now!"
    "Spin right dial up now!"
    "Press both down buttons now!"
    ...

    ..tests your cognitive abilities / sobriety / attentiveness too...
    Not only "hands on wheel" but ... "brain engaged" tests

    Fail to respond fast enough.. and "DING! disengaging AP"
     
  20. chillaban

    chillaban Member

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    I've joked before about autopilot plane crashes and how the plane needs to periodically disconnect the controls and simulate an in-flight emergency as a pilot competency check.


    But maybe semi-autonomous cars really need to do something like that. For example, detect nobody is next to you, then pretend to slowly drift into the lane and wait for the driver to correct you. There really needs to be a way to identify if the user is paying attention, because I'll be first to admit: I had an Audi A6 with a simple lane departure warning / assist system, and 50,000 miles later I could center my car in the lane without looking at the road just by blindly wiggling the steering wheel and sensing the least point of resistance from the LDW system.

    Just because your hands are on the wheel does not mean you're paying any attention.
     
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