Analysis of the functions of the car's accelerator and brake pedals

The throttle and brake are the most important parts of the human-machine interaction in a car. So how does the vehicle control unit (VCU) process the brake and throttle signals? Let's analyze it in detail.

First of all, whether it is the accelerator pedal or the brake pedal, its analysis is that the VCU collects the accelerator pedal analog quantity, and sends the pedal opening signal, effective signal and fault signal after signal processing. The pedal position opening corresponds to the voltage value and has a calibrable function.

For brake and accelerator, two analog signals are generally collected, and the voltage values ​​of the two signals differ by half. The VCU determines that the pedal sensor is normal, and then sends a pedal status signal, a pedal status validity signal, a pedal position signal, and a pedal position validity signal.

The opening method of the two-way pedal is as follows:

Pedal 1 opening (PedalPct1) calculation:

PedalPct1 = (Sig1 - Sig1Min)/ (Sig1Max - Sig1Min);

Pedal 2 opening (PedalPct2) calculation:

PedalPct2 = (Sig2 – Sigl2Min)/ (Sig2Max – Sig2Min);

Calculation of actual output pedal opening (PedalPctRec):

PedalPct=min{ PedalPct1, PedalPct2}

How should the pedal opening be calculated in the event of a fault? There are mainly the following situations:

Pedal 1 is faulty and Pedal 2 is not faulty: Use the opening of Pedal 2 to output the actual pedal opening output;

Pedal 2 is faulty and pedal 1 is not faulty: the pedal opening is used to output the actual pedal opening output;

Pedal 1 fault, pedal 2 fault: the actual output pedal opening (PedalPctRec) is 0;

Pedal 1 and Pedal 2 generate synchronization failure: PedalPct=min{ PedalPct1 , PedalPct2}.

So what are the specific faults mentioned above?

Pedal faults include pedal power supply failure, pedal 1 analog overvoltage failure, pedal 1 analog undervoltage failure; pedal 2 analog overvoltage failure, pedal 2 analog undervoltage failure; pedal 1, 2 synchronization failure;

Pedal power supply failure: If all of the following conditions are met, it is determined that the pedal power supply is faulty;

The system operation delay is 100ms; the pedal power supply is enabled; the power supply voltage feedback is not between 4.8V and 5.2V;

Pedal 1 analog overvoltage fault: If all of the following conditions are met, it is determined as a pedal 1 analog overvoltage fault;

The system operation delay is 100ms; the pedal power supply is enabled and effective; the pedal 1 analog quantity acquisition voltage is greater than Sig1Max + 0.3V;

Pedal 1 analog undervoltage fault : If all the following conditions are met, it is judged as pedal 1 analog undervoltage fault;

The system operation delay is 100ms; the pedal power supply is enabled and effective; the pedal 1 analog quantity acquisition voltage is less than Sig1Min - 0.3V;

Pedal 2 analog overvoltage fault: If all of the following conditions are met, it is determined as a pedal 2 analog overvoltage fault;

The system operation delay is 100ms; the pedal power supply is enabled and effective; the analog acquisition voltage of pedal 2 is greater than Sig1Max + 0.3V;

Pedal 2 analog undervoltage fault: If all the following conditions are met, it is judged as pedal 2 analog undervoltage fault;

The system operation delay is 100ms; the pedal power supply is enabled and effective; the pedal 2 analog quantity acquisition voltage is less than Sig1Min - 0.3V;

Pedal 1, 2 synchronization failure: If all of the following conditions are met, it is determined to be a pedal 1, 2 synchronization failure;

System operation delay 100ms; pedal power supply enable is valid; pedal voltage is not synchronized condition 3:

The analog voltage value of pedal 1 is compared with twice the analog voltage value of pedal 2 to obtain the minimum and maximum values; the maximum value – the minimum value > 0.3V;

Note: Sig1: Pedal 1 input voltage; Sig2: Pedal 2 input voltage; PedalPct1: Pedal 1 output opening; PedalPct2: Pedal 2 output opening; PedalPctRec: Actual output pedal opening; Sig1Max: Pedal 1 input voltage maximum value; Sig1Min: Pedal 1 input voltage minimum value; Sig2Max: Pedal 2 input voltage maximum value; Sig2Min: Pedal 2 input voltage minimum value;

After a fault occurs, there will be some differences in the handling of the brake pedal and the accelerator pedal. For the brake pedal, the degradation strategy after a fault is as follows:

For the accelerator pedal, its fault degradation strategy is as follows:

The above is the accelerator and brake pedal analysis function.

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