electronic throttle
in [Technical]
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From: jim beam on 10 Mar 2010 23:31 On 03/10/2010 05:51 PM, Rodan wrote: > >> clare(a)snyder.on.ca wrote: >> >> Toyota throttle has 2 hall effect sensors. The output of one tracks the >> other but is offset. In other words, one starts at say, 0 volts, and the >> other at, say 1 volt - and they increase in step with each other. That way >> the CPU can tell if one has failed, and if the two outputs are shorted >> together (one bypassed) If either accelerator sensor fails, the CEL comes >> on >> and the vehicle is limited to 1/4 throttle. If both fail, the throttle >> gets set to a fast idle position and the rpm is controlled to normal idle >> speed by programmed [missfire] (injector cut) The throttle position >> sensor >> (throttle feedback) also has 2 hall effect sensors 0 and they have >> [different] "rates" - the primary gives a higher signal linear from closed >> to open, while the secondary reads full by about half throttle. >> If the CPU senses a single TPS failure the engine is reduced to a fast >> idle. >> iF BOTH tps fail, it is returned to base idle - and if the ECU determines >> that the throttle has NOT closed - the engine is shut off. The ECU has 2 >> CPUs. the main monitors all sensors and [controlls] the entire >> power-train - >> engine, transmission, cruise control, traction control, etc. The "sub" >> monitors all sensors and all outputs - and monitors the main CPU via a >> "watchdog" program. The sub ALSO controls the electronic throttle. >> Both >> cpus control an output transistor that feeds power to the throttle control >> motor - BOTH must be turned on in order to open the throttle. They are >> series connected). If either CPU senses a problem and shuts down, there >> is >> no throttle. Gets pretty darn difficult to envision any electronic error >> that could cause uncontrolled [accelleration], particularly without >> registering a code and turning on the CEL. >> _________________________________________________________________________ >> >> Once upon a time there was a cable from the gas pedal to the >> throttle that operated the throttle butterfly. The throttle >> shaft had a position sensor that told the computer how much >> power the driver was demanding. >> >> Someone figured they could save money by eliminating the >> cable and attaching a position sensor to the gas pedal to tell >> the computer the driver's gas pedal position. The throttle >> shaft still had to have a position sensor to let the computer >> know its state compared to the pedal position, so the cost >> tradeoff was one less cable and one more position sensor. >> >> But there were more costs. The throttle butterfly no longer >> had the driver's foot power to move it, so they had to add a >> servo device to the throttle to provide power to the butterfly, >> and controlling power transistors to drive the servo, plus >> a reprogrammed computer to keep track of it. >> >> More complexity, added electromechanical hardware, higher >> cost, multiple new interfaces, and more computer operations. >> The whole thing sounds like a joke invented by Rube Goldberg. >> >> Rodan. > ____________________________________________________________________ > > clare(a)snyder.on.ca wrote: > > Would be true, except it had NOTHING to do with saving money, > and the throttle position sensor doesn't tell how much power is > required - just how impatient the driver is!! > ____________________________________________________________________ > > You're right, of course. It had nothing to do with saving money. > It costs more, it's more complex, it adds more electromechanical > hardware and increases electrical, mechanical, and computer interfaces. > It introduces multiple new failure modes, while yielding no significant > improvement in gas mileage or pollution control. It is a money pit, > a maintenance nightmare and a death trap waiting for a victim. not true. electronics are much more reliable. and they /do/ offer significant improvement in mileage and pollution control. they offer significantly better control for things like cruise control and automatic transmissions too. > > So why would anyone other than Rube Goldberg build such a useless > (and dangerous) contraption? My guess is that the automakers are > trying to develop a generic accelerator pedal that would work for any > automotive power plant combination. A single pedal would indicate > the driver's intention to a gas engine, electric motor, hybrid, steam > engine, or rear-engine system, or an engine powered by tram cables. > > Unfortunately, in their zeal to prove the concept, they chose to dismantle > and scrap the simple, proven, reliable gas pedal-to-cable mechanism for > their experiment, resulting in more danger for conventional automobiles. > > Regarding the throttle position sensor - until fly-by-wire took throttle > position control away from the driver it did indicate the driver's wishes > for the power level to be applied. Stepping on a gas pedal to open > the throttle is necessary to merge into traffic, to maneuver, and to > maintain separation and safety in traffic conditions. Opening the > throttle doesn't automatically prove that a driver is impatient. > > Rodan. > > > -- nomina rutrum rutrum
From: Rodan on 11 Mar 2010 00:18 Rodan wrote: ....(adding a gas pedal position sensor) has nothing to do with saving money. It costs more, it's more complex, it adds more electromechanical hardware and increases electrical, mechanical, and computer interfaces. It introduces multiple new failure modes, while yielding no significant improvement in gas mileage or pollution control. It is a money pit, a maintenance nightmare and a death trap waiting for a victim. ________________________________________________________________________ "jim beam" wrote: not true. electronics are much more reliable. and they /do/ offer significant improvement in mileage and pollution control. they offer significantly better control for things like cruise control and automatic transmissions too. __________________________________________________________________________ I may not be seeing the tradeoff benefits you refer to. How does adding a gas pedal position sensor provide: "significant improvement in mileage and pollution control and significantly better control for things like cruise control and automatic transmissions too" ? Rodan.
From: jim beam on 11 Mar 2010 00:30 On 03/10/2010 09:18 PM, Rodan wrote: > Rodan wrote: > > ...(adding a gas pedal position sensor) has nothing to do with saving > money. It costs more, it's more complex, it adds more electromechanical > hardware and increases electrical, mechanical, and computer interfaces. > It introduces multiple new failure modes, while yielding no significant > improvement in gas mileage or pollution control. It is a money pit, > a maintenance nightmare and a death trap waiting for a victim. > ________________________________________________________________________ > > "jim beam" wrote: > > not true. electronics are much more reliable. and they /do/ offer > significant improvement in mileage and pollution control. they > offer significantly better control for things like cruise control and > automatic transmissions too. > __________________________________________________________________________ > > I may not be seeing the tradeoff benefits you refer to. > How does adding a gas pedal position sensor provide: > > "significant improvement in mileage and pollution > control and significantly better control for things > like cruise control and automatic transmissions too" ? > > Rodan. > because it provides you the means to have a proper control system between the pedal and the engine. diesels have /always/ had a control system between the driver than the engine since day one. modern "fly by wire" is simply the next step - as stated before, it best for things like ability to have better cruise, de-throttling during shifts, and to better match throttle position with load. -- nomina rutrum rutrum
From: DC on 11 Mar 2010 01:45 "jim beam" <me(a)privacy.net> wrote in message news:IeudnWYmUdD27AXWnZ2dnUVZ_tmdnZ2d(a)speakeasy.net... > On 03/09/2010 10:15 PM, Rodan wrote: >> clare(a)snyder.on.ca wrote: >> >> Toyota throttle has 2 hall effect sensors. The output of one tracks the >> other but is offset. In other words, one starts at say, 0 volts, and >> the >> other at, say 1 volt - and they increase in step with each other. > > how can that be true??? > > http://en.wikipedia.org/wiki/Hall_effect > > hall effect sensors are used for gross position detection, not small scale > linear deflections. they can be used for "wot" detection, but their > ability to work over a wide positioning range is limited. that's why > they're used in timing for things like crank position [rotational] sensors > where you're counting pulse rates, not graduation functions. > These linear Hall effect sensors do indeed exist - and being non contact are arguably highly reliable http://www.potentiometers.com/select_hall.cfm Dave
From: David Skelton on 11 Mar 2010 05:39
"dizzy" <dizzy(a)nospam.invalid> wrote in message news:bglgp518e14fmsdkehr1dalh2886g0pu0b(a)4ax.com... > David Skelton wrote: > >>I thought the main reason for ABS is to maintain steering control when the >>brakes were pressed too hard, so hazards could be avoided. > > Yes. > >>But, ABS does not >>work so well in the very wet or icy conditions. > > Sure it does. It can't perform miracles, however. > No, it doesn't work so well in slippery conditions. In slippery conditions, it is much easier to lock all four wheels at once with a stomp on the brake pedal. Then the ABS controller cannot detect wheels turning at different speeds which is required to activate the ABS system. regards David --- news://freenews.netfront.net/ - complaints: news(a)netfront.net --- |