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ความคิดเห็นที่ 109 |
Before drive by wire technology was introduced, if a throttle stuck open you could generally put your toe under the accelerator and lift up. Occasionally after servicing or repair, the wire or cable between the accelerator and throttle would not be correctly reinstalled causing sudden acceleration. However, with the ETC, the movement is all done by electronic controls moving an electric motor. But just moving the throttle by sending a signal to the motor is an open loop condition and leads to poor control. Most if not all current ETC systems have a closed loop system whereby the ECU tells the throttle to open a certain amount according to an algorithm based on the geometry of the throttle. Then, if due to dirt build up in the throttle bore or a damaged TPS a signal is sent from the TPS to the ECU, the ECU can make appropriate adjustments to compensate, though it might result in surging, hesitation or uneven idle.
There are two primary types of throttle position sensors: a potentiometer or a Hall Effect sensor (magnetic device). The potentiometer is a satisfactory way for non-critical applications such as volume control on a radio, but as it has a wiper contact rubbing against a resistance element, and dirt and wear between the wiper and the resistor can cause erratic readings. The more reliable solution is the magnetic coupling that makes no physical contact, so will never be subject to failing by wear.
This is an insidious failure as it may not provide any symptoms until there is total failure. All cars having a TPS have what is know as a 'limp-home-mode'. When the car goes into the limp-home-mode it is because the accelerator and engine control computer and the throttle are not talking to each other in a way that they can understand. The engine control computer shuts down the signal to the throttle position motor and a set of springs in the throttle set it to a fast idle, fast enough to get the transmission in gear but not so fast that the car cannot be stopped by the brakes.
Recently, ETC has been suspected by some to be responsible for some incidents of unintended acceleration in Toyota and Lexus vehicles. This is fiercely disputed by Toyota, which blames unintended acceleration on owners, weather mats, and most recently defective gas pedals.
ลองแปลกันดูนะครับ จาก : http://en.wikipedia.org/wiki/Electronic_throttle_control
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Golden Axe
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5 ก.พ. 53 03:03:16
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