Proportional plus Derivative PD control

Proportional plus Derivative eontrol aetion is expressed as 

The inelusion of a derivative term in the eontroller generally gives improved damping and stability. This is diseussed in more detail in Chapters 5 and 6. 

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We have just described proportional (P) control and proportional plus derivative (PD) control. Integration can be added to a controller, which not only gives it reset action, but also can exacerbate instability. There are proportional plus integral (PI) and proportional-integral-derivative (PID) controllers. These classical types are used where the system dynamics (the Plant) are well defined. 

In order to demonstrate the effect of derivative action we will formulate a proportional plus derivative (PD) controller. This probably has no practical application but including integral action would make the trends very difficult to interpret. Combining Equations (3.5)... 

This control mode is called proportional plus rate (PD) control because the derivative section responds to the rate of change of the error signal. 

Controller modes—settings and functions that include proportional (P), proportional plus integral (PI), proportional plus derivative (PD), and proportbnal-integral-derivative (PID). Proportional control is primarily used to provide gain where little or no load change typically occurs in the process. Proportional plus integral is used to eliminate offset between the setpoint and process variables PI works best where... 

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