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In automatic, for the regulation of a dynamic system, the droop difference is the natural manifestation of a drift between the value of the output signal to be adjusted and the set value assigned to it. More precisely, the droop is a dimensionless quantity defined as the ratio between the relative deviation of the adjusted quantity and the corresponding relative difference of the adjustment quantity (it is therefore a notion which is similar to elasticity) .
This phenomenon occurs especially in PID controllers using only the proportional P component. Exemplify the code
For the regulation of a temperature, a proportional control system determines the heating power by fixing its value in proportion to the difference between the setpoint and the measured temperature. When there is heat loss (a building in winter), a stationary state of the system implies that the heating power is equal to the dissipated power; However, for there to be power injection, the regulator must necessarily note a difference between the setpoint and the measurement: the difference is thus a necessary condition for the injection of power.
This droop gap is significantly reduced by incorporating an integral component into the regulator. Indeed, the integration of the persistent gap gradually increments a size which, on the increase, contributes to increase the injection of power.
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