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Fly-by-wire gas pedal — Parallax Forums

Fly-by-wire gas pedal

Shack_in_kyShack_in_ky Posts: 2
edited 2008-11-13 18:44 in BASIC Stamp
I have a tug that is used in off-the-road applications.· It has a "K" car carbed engine.· I'm looking at making a fly-by-wire gas pedal for it.· The tug is used so frequently that I've had continued problems with the linkage between the existing pedal and the carb.· The electronics would solve my problem.· This project is in the planning stages.· So far, I'm thinking of using the stamp and a pot for the brains and a hobby servo for the actuator.· I'll also add an e-stop for those "just in case" voices in my head.· I'm just a novice at the stamp so I'm looking for some advice from the more experienced.· Any thoughts or similar projects?

Comments

  • SRLMSRLM Posts: 5,045
    edited 2008-11-12 15:40
    If you decide to use the servo, make sure that it has enough torque to do the job. Otherwise, you may find that it gets stuck. Also, it should probably be mechanically set to turn off(by a spring maybe) whenever electic power is lost.
  • Carl HayesCarl Hayes Posts: 841
    edited 2008-11-12 15:41
    Me, I'd see what I could do about improving the mechanical linkage. A high-quality Bowden cable between pedal and carb would be extremely reliable and easy to adjust.

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    · -- Carl, nn5i
  • Shack_in_kyShack_in_ky Posts: 2
    edited 2008-11-12 20:39
    SRLM said...
    If you decide to use the servo, make sure that it has enough torque to do the job. Otherwise, you may find that it gets stuck. Also, it should probably be mechanically set to turn off(by a spring maybe) whenever electic power is lost.
    Excellent points.· I've thought about both of these too.· The servo is rated at 47 oz-in.· Not alot of torque to play with.· The mechanical closing spring will need to be small.· Do you know of a cheap servo that easily interfaces to the stamp that has more torque?
  • Lab RatLab Rat Posts: 289
    edited 2008-11-12 21:50
    i think all servos interface with the stamp

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    Parallax posesses power beyond belief.

    Believe in it.
  • SRLMSRLM Posts: 5,045
    edited 2008-11-13 00:09
    Any standard servo will work with any uC that can output a simple PWM. I'd recomend looking at your local hobby store for servos. The RC helicopter and can industry really turns them out in high strength. Here is a website that also sells lots of servos.

    Servos

    Also, you might want to get rid of the "cheap" part in your servo. You don't want it to get stuck at full on... Rather, reliable is the best option.
  • ercoerco Posts: 20,261
    edited 2008-11-13 00:46
    Yikes. I'm all for tech-ing something up, and love nothing better than a great rig job, but I would not consider using a servo in this application. Of course it can be done, and will work for a while, but you must responsibly consider what might happen during any electrical glitch or mechanical failure. You're introducing a lot of new light-duty parts in a servo to·a fairly hostile·underhood environment with heat, vibration, water/humidity, dirt, gas, & oil. Probably in an area you where you won't do a thorough preflight inspection before each use. Unless you are a real thrillseeker with great insurance, any possibility of unintentional ·part- or full-throttle acceleration is a bad possibility. I'm with Carl, use a good, bulletproof mechanical cable and be done with it. Thousands of reliable old Cessnas can't be wrong.

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    ·"If you build it, they will come."
  • icepuckicepuck Posts: 466
    edited 2008-11-13 03:25
    Is it the 2.2 liter 4cyl with a belt driven mechanical governor and a zenith carb? The ones that I've delt with were so worn out it was next to impossible to get the speed you want. The advantage with fly-by-wire is that your top vehicle speed or rpm can set electronically. If you were to use a key pad you could set the top speed based on what code the user entered-sort of like the cat wp4500 with the key pad option. Below are links to fly-by-wire systems that I've delt with on a regular basis. Hope this helps.It will be interesting to see what you come up with..
    -dan
    http://www.zenithfuelsystems.com/
    http://www.impco.ws/products.htm
  • remmi870remmi870 Posts: 79
    edited 2008-11-13 09:56
    i wouldnt recommend using a servo, unfortunetly you may run into a problem with the ignition system feeding efi via the signal on the servo, i actualy had two servos run by a basic stamp homwork board that would cross couple and i would have them running at the same time, not verry desirable if you have a engine running. its just not worth the chance that the servo fail or if the stamp fails the servo may go erratic.
  • Carl HayesCarl Hayes Posts: 841
    edited 2008-11-13 13:49
    Lab Rat said...
    i think all servos interface with the stamp

    I assure you that this is not so.· Some servos are not even electric.· Can you interface a Stamp with a hydraulic·servo that operates at 3000 psi·without using electricity anywhere in its control system?·-- and some electric ones are large devices massing several tens of kilograms and having control systems that are totally analog and rather more complex than the tiny ones used with Stamps.

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    · -- Carl, nn5i
  • MSDTechMSDTech Posts: 342
    edited 2008-11-13 18:44
    If you look at many recent automobiles, you may find they are going to servo driven throttles. In order for stability control to work, the computer must be able to decrease the throttle. I just hope I don't have a computer failure on my car, as the pedal is only connected to a variable resistor - the computer just makes it go if it thinks that what I really want.
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