electronic throttle
in [Technical]
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From: clare on 9 Mar 2010 19:13 On Tue, 09 Mar 2010 13:21:18 -0500, clare(a)snyder.on.ca wrote: >> >>Quite pssibly how they do it - I was just showing a "simple" example. > > >I got a LOT more information on how Toyota REALLY does it. I'll share >later tonight. OK - Here's what I've found. 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 differnt "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.
From: Bill Putney on 9 Mar 2010 20:20 clare(a)snyder.on.ca wrote: > On Tue, 09 Mar 2010 13:21:18 -0500, clare(a)snyder.on.ca wrote: > >>> Quite pssibly how they do it - I was just showing a "simple" example. >> >> I got a LOT more information on how Toyota REALLY does it. I'll share >> later tonight. > > > OK - Here's what I've found. > 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 differnt "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. Interesting - I always thought of Hall effect sensors as switches (on/off, proximity, etc.). I wasn't aware that they could be used for analog pruposes, but a little research shows that they can indeed. -- Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
From: cuhulin on 9 Mar 2010 22:10 Runaway Toyotas. http://www.libertypost.org/cgi-bin/readart.cgi?ArtNum=285260 cuhulin
From: cuhulin on 9 Mar 2010 23:30 On the web, When cars had vacuum powered windshield wipers Ahhh yes, how well do I remember those.They would let you down when you needed them the most! cuhulin
From: Rodan on 10 Mar 2010 01:15
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. |