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CHAPTER 2 : TERMINOLOGY

PID : Proportionnel Intégral Dérivé :

The principle of the PID algorithm consists on 3 actions that are dependant to the difference

between the setpoint (SV) and the measured process value (PV).

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A proportional action ne action proportionnelle, the error is multiplied by a gain GR

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A complete action, the error is integrated on an interval of time TI

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Derivated action, the error is derivated according to time TD

PID principle schematic

The parameters of the PID influence the answer of the system in the following way:

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When the proportional gain GR increases, the time of rise is shorter but there is a more

important overshoot of the setpoint. The time of stabilization varies little and the static error is

improved.

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When 1 / TI increase, the time of rise is shorter, but there is a more important overtaking of the

setpoint. The time of stabilization stretches out but we assure a static no error.

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When TD increases, the time of rise changes little, but the overshoot decreases. The time of

stabilization is better and there is no influence on the static error.

Introduction

EDMS xxxxxxxxx 03 2009

The use of 24/48/96 controllers is going to allow through a parameter setting of variables to appeal

to automatic functions or manual regulations.

These variables are going to allow:

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To choose the type of sensor used (probe thermocouple or PT100, analogical sensor),

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To choose the type of output used according to the actuator(s) (relay, solid state relay,

analogical),

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To choose the function of regulation (heating or cooling or heating and cooling),

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To reduce the time of establishment (the value of measure reaches as quickly as possible the

setpoint),

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Avoid overshoot (fuzzy logic and PID2),

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To maintain the temperature very close to the setpoint (réduction of the hysteresis and the dead

band),

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Avoid influence of perturbation,

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To activate alarms (high, low, delayed…),

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Setup ramps (up to 16 depending the model) to chain cycles of regulations,

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To have information of defects (overflowing measures, defect sensors),

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To lock or authorize the modification of the parameters from the front face of the product.

Gr

1/Ti

Td

Process

+

-

Consigne

Mesure

SetPoint (SP)

Process value (PV)