P only controller/PID - overshoot

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SUMMARY

The discussion focuses on the behavior of a Proportional (P) controller in a cruise control system for a car, specifically addressing the phenomenon of overshoot. When the error becomes negative, indicating that the vehicle has exceeded the desired speed, the output of the controller also turns negative, which theoretically suggests negative thrust. However, in practical terms, this results in the vehicle braking, as the motor operates in generator mode to recharge the battery, thus contributing to a "green energy drive." Understanding this dynamic is crucial for effectively implementing P controllers in automotive applications.

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  • Proportional control theory
  • Basic principles of cruise control systems
  • Understanding of electric motor operation
  • Knowledge of energy recovery systems in vehicles
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Automotive engineers, control systems designers, and students studying vehicle dynamics and energy efficiency in electric vehicles.

Herman Oen
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Homework Statement


I am trying to understand the Proportinal controller, used as a cruise controll for a car. I do understand how it works as long as there are no overshoot.

Homework Equations

The Attempt at a Solution


The reason why I do not understand overshoot is because the error then gets negative and then the output also gets negative (out=Kp*error). This means negative thrust? You can never give less thrust than 0, so what is actually happening when the error gets negative?
 
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Herman Oen said:
You can never give less thrust than 0, so what is actually happening when the error gets negative?
The car will brake.

The motor will act as a generator, and will charge the battery ( having a "green energy drive" and an electric motor ).
 
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