Strange cruise control behavior?

Discussion in 'Gen 2 Prius Main Forum' started by Indy, May 12, 2005.

  1. Indy

    Indy New Member

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    When I am using the cruise, and I tap the brake pedal, the first small increment of pedal movement causes the brakes to be engaged, but the cruise does not shut off. Then if I depress the brake further, the cruise drops out of its set speed.

    This cannot be right, can it, since the brakes are "dragging" while the cruise speed is being maintained?
     
  2. Frank Hudon

    Frank Hudon Senior Member

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    the first small amount of brake pedal movement just starts the regen, no brake application the next small movement activates the brake light circuit that dissengages the CC. If the pedal travel is more than I'd say 1 1/2" the brake light switch might need adjustment.
     
  3. xevious

    xevious New Member

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    You might want to have your brake switch inspected. This could be a sign of misadjustment or impending failure.

    Were you eligible for the brake switch recall? If so, did you have the switch replaced?
     
  4. KTPhil

    KTPhil Active Member

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    If it's an '04, have you done the brake switch recall?
     
  5. DanMan32

    DanMan32 Senior Member

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    Not all '04s get the brake switch recall. Looked last night, even though I bought the car in August, it was mfd in June.
     
  6. Indy

    Indy New Member

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    It's an '05 and it has done this since I got it.

    I will have them look at it when I take it in for its next service.

    I have learned to pull the cruise switch toward me to fall out of a set speed, which should be more efficient if I am not planning on braking otherwise. I have also learned that on anything other then a very flat, straight stretch of road, I can do better with MPG than the cruise can. But, sometimes I use it anyway for convenience or to ease foot fatigue.

    It is a concern if it is related to the brake light switch, as I depend on brake taps to warn tailgaters of impending stops.
     
  7. Brian K

    Brian K New Member

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    Hi Indy,

    I've found the same thing re: cruise control. I can do better re: mpg than it can by my maintianing semi "constant throttle" than it can by maintaining constant speed.

    No surprise there, pretty much any vehicle does better with constant throttle. A simple software upgrade should accomplish this for us all and save our throttle foot. Fuzzy logic would make the "constant throttle" liveable since true constant throttle would get one run over by a semi'.

    Brian K
     
  8. Indy

    Indy New Member

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    Brian,

    I have given a lot of thought to a system or set of directions that would maximize mileage and have decided it cannot be done.

    Only you know what you are planning to do, and only you can interpret the myriad cues and signals you get on the road. Only you can make those critical safety decisions, like whether a constant throttle would be dangerous on a particular stretch of road at a particular time.

    The bottom line is that you must make those decisions all the time, and your throttle position is the way you control the machinery to best accomodate those decisions. I like the cruise control because I am lazy, but I can get better mileage with my own brain than any fuzzy logic could manage.
     
  9. Brian K

    Brian K New Member

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    Good for you, that you're so certain. I don't agree.

    The reason criuse control doesn't get max efficiency is because of it's slavish desire to maintain a given speed regardless of cosequences. In this case gas mileage. Another gent called it "too agressive a control" I agree with that phrase.

    We have computers on board and an LCD. It's just a matter of programming and a (maybe but doubt it) different cruise control to allow the user to select an acceptable speed/acceleration range for the CC to maintain. Assuming of course the computers can accept the additional lines of code. It might even allow user input to the minimum MPG that is acceptable. Re: speed; Minus and plus tolerances, nothing more. When calling for power it's OK to accept a lower speed/acceleration profile to maintain mpg efficiency. That's what I mean by an acceptable speed/acceleration range. The default is a zero value, the driver sets the deviation. Pretty simple really, everything else works the same.

    It might even be as simple as accepting factory defaults in CC; speed maximization or MPG maximizing, that'd work too. Probably be less code too.

    Control systems like this are everywhere in industry, so your agreement isn't really needed, they already exist.

    Obviously driver input is still needed, that's a given, I never gave any hint that that wasn't the case, that came from elsewhere. You misunderstood what I meant, but then, I didn't give a full explanation, I just thought common sense would apply. I probably still haven't fully explained for some. Just understand I'm not talking AI, just cruise control, one still must drive ones vehicle. It works now, my version would work better. From a driver standpoint there would be no operational change to the CC other than setpoints of some sort. Toyota could just implement it and update the software in our vehicles and not pay me and that would work just fine (hint, hint).

    I still love our Prius and don't mind having my foot on the throttle. I'm certainly not ready to have AI pilot my vehicle for me.
     
  10. DanMan32

    DanMan32 Senior Member

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    The purpose of any cruise control is to maintain speed. You are better off maintaining a speed rather than deviating back and forth from it.

    Also, don't forget, you do not have direct control of the throttle. You tell the HV ECU what acceleration you desire, and it does the calculations of throttle (ICE power), MG1/MG2 involvement, and how much power to inject from the battery.
     
  11. longjohn931

    longjohn931 New Member

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    I just completed a 450 mile trip with my new Prius in Florida. I used the Florida turnpike from Orlando to Hollywood and back. I set it at 70 mph, stopped approximately 5 times, during the trip and averaged 45.2 mph using cruise on all the turnpike mileage. I noticed it never deviated from my set speed. This vehicle is phenomenal. I have never driven a vehicle that can maintain this kind of cruise control accuracy, even in flat Florida.
    Cruise control is a tool to relieve leg and foot fatigue and maintain a constant speed. I will gladly use mu cruise at the expense of efficiency.
     
  12. u4iia

    u4iia New Member

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    Indy,

    I have the same pedal travel as you. It takes more than a tap to disengage. I may be hallucinating but i could swear I was in EV at a full stop today until I pressed down the brake pedal another inch or so. Hmmm. Mine was manufactured in 04 of 05.
     
  13. DanMan32

    DanMan32 Senior Member

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    <div class='quotetop'>QUOTE(longjohn931\";p=\"90719)</div>
    Did you mean 45.2MPG? 45.2 MPH seems awfully slow for the turnpike unless there was huge traffic.
     
  14. Mystery Squid

    Mystery Squid Junior Member

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    I was thinking about this. I think it has more to do with the analysis of forward topography. I'm an avid sportbiker, and oddly enough, being a sportbiker has allowed me to "fit right in" simply because I'm used to the concept of using topography, neutral, negative throttle, etc. Heck, I haven't even owned it 24 hours and I was able to milk 58.2 mpg over my 30 mile commute this morning, and I know I could have done better (and that's with a couple of periods of "heavy" accleration).

    Thing is, cruise control has no way of knowing, or using to it's advantage, let's say a long downhill run, whereas at the end of which, let's imagine a small hill, you know you can make it over by sacrificing maybe 2 or 3 mph. And that's just one example...

    :D
     
  15. DanMan32

    DanMan32 Senior Member

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    Is it energy dispensed that makes us feel strained, or power output? I believe it is latter. Slowing down going uphill and accelerating downhill is keeping the power more uniform.

    Some people can walk all day, but can't run very far.
     
  16. longjohn931

    longjohn931 New Member

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    <div class='quotetop'>QUOTE(DanMan32\";p=\"90816)</div>
    Did you mean 45.2MPG? 45.2 MPH seems awfully slow for the turnpike unless there was huge traffic.
    [/b][/quote]


    DanMan32, knew you'd be there typo thanks
     
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