Determination of the accelerator pedal position, function

W30.35-1078-75

1 Idle speed

2 Part load

3 Full load

A3 Drive control (FR) control unit

B1 Foot throttle actuator

A PWM signal at Output 1

B PWM signal at Output 2

t Time

U Voltage

1 Detecting the accelerator pedal position

The accelerator pedal position is detected by the electronic foot throttle actuator (B1):

There are two potentiometers in the foot throttle actuator (B1) which is each connected in series with an electronic unit. Both potentiometers operate in the opposite direction. This not only ensures a high degree of operating reliability but also means that breakdowns are reliably recognized. The drop in voltage at each potentiometer will vary according to how far the gas pedal is pressed and the level of the voltage which is applied at the appropriately downstream electronic circuit. The value of the voltage is also crucial for the level of the duty cycles of the respective PWM signals which are generated by each electronic circuit and sent to the drive control (FR) control unit (A3).

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 PWM (pulse-width-modulated) simply means that the transmitted information is contained in the values for the width of the impulse. The impulse changes when the gas pedal is activated. The frequency remains constant, however.

2 Transmitting the accelerator pedal position

The two PWM signals transmitted from the foot throttle actuator (B1) to the drive control (FR) control unit (A3) are in an opposite direction to each other.

This means that the PWM signal at Output 1 (A) in idling condition (1) has a low duty cycle of about 10 to 30% which increases to about 40 to 90% in the direction of full loading (3) while the PWM signal at Output 2 (B) in idling condition (1) has a high low duty cycle of about 40 to 90% which reduces to about 10 to 30% in the direction of full loading (3).

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3 Determination of the gas pedal position

Detection of the gas pedal position occurs exclusively over the drive control (FR) control unit (A3) which analyzes PWM signals from the electronic foot throttle actuator (B1) whose issued duty cycles represent the position of the gas pedal.

 No switches are required for the idling and kickdown position. These gas pedal positions are established in the drive control (FR) during the teach-in phase.